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• Silverlight Cream for February 26, 2011 -- #1052

  - by Dave Campbell

  In this Issue: Mark Monster, Gill Cleeren, Pencho Popadiyn, Kevin Dockx, Joost van Schaik, Jesse Liberty, John Papa, Jeremy Likness, Arik Poznanski(-2-), Page Brooks, Deborah Kurata, Mike Snow, Alfred Astort, Samuel Jack, XAMLNinja, and Shawn Wildermuth. Above the Fold: Silverlight: "Asynchronous Callbacks with Rx" Jesse Liberty WP7: "Phoney Windows Phone 7 Project Now Available!" Shawn Wildermuth MVVM: "Validating our ViewModel" Mark Monster Shoutouts: Shawn Wildermuth has a video up of his FadingMessage class to show it off: Introducing Phoney's FadingMessage Class From SilverlightCream.com: Validating our ViewModel Mark Monster discusses Validation in his latest post... using INotifyDataErrorInfo and his own implementation of a ViewModel base that supports it and INPC. Getting ready for Microsoft Silverlight Exam 70-506 (Part 7) Gill Cleeren hits part 7 of his series at SilverlightShow on a great walk through Silverlight and getting ready for the exam. This is the final part and concentrates on deploying apps. Windows Phone 7–Creating Custom Keyboard Pencho Popadiyn has a post at SilverlightShow discussing problems with WP7 keyboards in his native Bulgaria, and his solution to the problem... create his own. 360 Degrees Feedback by Kevin Dockx Kevin Dockx produced a white paper for his company about an employee review solution they did in Silverlight. The white paper is available, and SilverlightShow interviewd Kevin to answer questions about the app. Extended Windows Phone 7 page for handling rotation, focused element updates and back key press Looks like Joost van Schaik has a few posts I've missed... and I'm not going to get to them all today! ... this one is about the base class he uses for WP7 apps... a bunch of utilities he uses... definitely worth a look (and a take). Asynchronous Callbacks with Rx Jesse Liberty has his 8th post in the Rx series up and this one's on Asynchronous Callbacks... if you haven't seen this before, you should definitely look into it... cool stuff, Jesse! Silverlight TV 63: Exploring National Instruments' App Using Data and Business Features John Papa has Silverlight TV number 63 up and is talking to Steve Lasker about National Instruments and their Lab View product. Great demo and discussion. Jounce Part 11: Debugging MEF Jeremy Likness's latest (number 11) in his series on his MVVM framework Jounce is out, and he's discussing how to debug MEF, which Jounce handles nicely through the logging he provides... and you can use it externally to Jounce. Get Twitter Trends on Windows Phone 7 Arik Poznanski has a couple Twitter for WP7 posts up... first is one for pulling Twitter trends from whatthetrend.com... plus the code to do it. Searching Twitter on Windows Phone 7 In his next post, Arik Poznanski shows how to search twitter from your WP7 ... again with code. Tiled Background Control in Silverlight Page Brooks shows how to get a tiled background control in Silverlight ... did you know there was one in the JetPack them? Silverlight Charting: Displaying Data Above the Column Deborah Kurata continues her charting posts with this one displaying the column value above the column. I like this... it has a clean look and all the data is available at a glance. Silverlight: Tasks on the Win7 Mobile Phone Mike Snow has a list of the WP7 tasks available and an example of using them... looks like a pretty good reference! 10 of 10 - Aesthetics and alignment matter Alfred Astort discusses aesthetics and WP7 dev... looks like it's the same as any app development, but if you're not doing it, you should be. Simon Squared – We have Multi-player: Days 4, 5 and (ahem!) 6 Samuel Jack details the completion of his multi-player game for WP7 utilizing Azure, in the hour-by-hour detail he's done the rest... plus a video of the final product! Who ate all the pies!! XAMLNinja has a very good discussion/link set of Charting posts all leading up to a portrait-only version of charting for WP7 with labels that looks looks great Phoney Windows Phone 7 Project Now Available! Shawn Wildermuth has a collection of classes he always uses with WP7 dev, and he's sharing them with all of us a "Phoney" Tools project on Codeplex... and now has a NuGet project also. Stay in the 'Light! Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCream Join me @ SilverlightCream | Phoenix Silverlight User Group Technorati Tags: Silverlight    Silverlight 3    Silverlight 4    Windows Phone MIX10

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• Retrieve Performance Data from SOA Infrastructure Database

  - by fip

  My earlier blog posting shows how to enable, retrieve and interpret BPEL engine performance statistics to aid performance troubleshooting. The strength of BPEL engine statistics at EM is its break down per request. But there are some limitations with the BPEL performance statistics mentioned in that blog posting: The statistics were stored in memory instead of being persisted. To avoid memory overflow, the data are stored to a buffer with limited size. When the statistic entries exceed the limitation, old data will be flushed out to give ways to new statistics. Therefore it can only keep the last X number of entries of data. The statistics 5 hour ago may not be there anymore. The BPEL engine performance statistics only includes latencies. It does not provide throughputs. Fortunately, Oracle SOA Suite runs with the SOA Infrastructure database and a lot of performance data are naturally persisted there. It is at a more coarse grain than the in-memory BPEL Statistics, but it does have its own strengths as it is persisted. Here I would like offer examples of some basic SQL queries you can run against the infrastructure database of Oracle SOA Suite 11G to acquire the performance statistics for a given period of time. You can run it immediately after you modify the date range to match your actual system. 1. Asynchronous/one-way messages incoming rates The following query will show number of messages sent to one-way/async BPEL processes during a given time period, organized by process names and states select composite_name composite, state, count(*) Count from dlv_message where receive_date >= to_timestamp('2012-10-24 21:00:00','YYYY-MM-DD HH24:MI:SS') and receive_date <= to_timestamp('2012-10-24 21:59:59','YYYY-MM-DD HH24:MI:SS') group by composite_name, state order by Count; 2. Throughput of BPEL process instances The following query shows the number of synchronous and asynchronous process instances created during a given time period. It list instances of all states, including the unfinished and faulted ones. The results will include all composites cross all SOA partitions select state, count(*) Count, composite_name composite, component_name,componenttype from cube_instance where creation_date >= to_timestamp('2012-10-24 21:00:00','YYYY-MM-DD HH24:MI:SS') and creation_date <= to_timestamp('2012-10-24 21:59:59','YYYY-MM-DD HH24:MI:SS') group by composite_name, component_name, componenttype order by count(*) desc; 3. Throughput and latencies of BPEL process instances This query is augmented on the previous one, providing more comprehensive information. It gives not only throughput but also the maximum, minimum and average elapse time BPEL process instances. select composite_name Composite, component_name Process, componenttype, state, count(*) Count, trunc(Max(extract(day from (modify_date-creation_date))*24*60*60 + extract(hour from (modify_date-creation_date))*60*60 + extract(minute from (modify_date-creation_date))*60 + extract(second from (modify_date-creation_date))),4) MaxTime, trunc(Min(extract(day from (modify_date-creation_date))*24*60*60 + extract(hour from (modify_date-creation_date))*60*60 + extract(minute from (modify_date-creation_date))*60 + extract(second from (modify_date-creation_date))),4) MinTime, trunc(AVG(extract(day from (modify_date-creation_date))*24*60*60 + extract(hour from (modify_date-creation_date))*60*60 + extract(minute from (modify_date-creation_date))*60 + extract(second from (modify_date-creation_date))),4) AvgTime from cube_instance where creation_date >= to_timestamp('2012-10-24 21:00:00','YYYY-MM-DD HH24:MI:SS') and creation_date <= to_timestamp('2012-10-24 21:59:59','YYYY-MM-DD HH24:MI:SS') group by composite_name, component_name, componenttype, state order by count(*) desc;   4. Combine all together Now let's combine all of these 3 queries together, and parameterize the start and end time stamps to make the script a bit more robust. The following script will prompt for the start and end time before querying against the database: accept startTime prompt 'Enter start time (YYYY-MM-DD HH24:MI:SS)' accept endTime prompt 'Enter end time (YYYY-MM-DD HH24:MI:SS)' Prompt "==== Rejected Messages ===="; REM 2012-10-24 21:00:00 REM 2012-10-24 21:59:59 select count(*), composite_dn from rejected_message where created_time >= to_timestamp('&&StartTime','YYYY-MM-DD HH24:MI:SS') and created_time <= to_timestamp('&&EndTime','YYYY-MM-DD HH24:MI:SS') group by composite_dn; Prompt " "; Prompt "==== Throughput of one-way/asynchronous messages ===="; select state, count(*) Count, composite_name composite from dlv_message where receive_date >= to_timestamp('&StartTime','YYYY-MM-DD HH24:MI:SS') and receive_date <= to_timestamp('&EndTime','YYYY-MM-DD HH24:MI:SS') group by composite_name, state order by Count; Prompt " "; Prompt "==== Throughput and latency of BPEL process instances ====" select state, count(*) Count, trunc(Max(extract(day from (modify_date-creation_date))*24*60*60 + extract(hour from (modify_date-creation_date))*60*60 + extract(minute from (modify_date-creation_date))*60 + extract(second from (modify_date-creation_date))),4) MaxTime, trunc(Min(extract(day from (modify_date-creation_date))*24*60*60 + extract(hour from (modify_date-creation_date))*60*60 + extract(minute from (modify_date-creation_date))*60 + extract(second from (modify_date-creation_date))),4) MinTime, trunc(AVG(extract(day from (modify_date-creation_date))*24*60*60 + extract(hour from (modify_date-creation_date))*60*60 + extract(minute from (modify_date-creation_date))*60 + extract(second from (modify_date-creation_date))),4) AvgTime, composite_name Composite, component_name Process, componenttype from cube_instance where creation_date >= to_timestamp('&StartTime','YYYY-MM-DD HH24:MI:SS') and creation_date <= to_timestamp('&EndTime','YYYY-MM-DD HH24:MI:SS') group by composite_name, component_name, componenttype, state order by count(*) desc;  

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• Explaining Explain Plan Notes for Auto DOP

  - by jean-pierre.dijcks

  I've recently gotten some questions around "why do I not see a parallel plan" while Auto DOP is on (I think)...? It is probably worthwhile to quickly go over some of the ways to find out what Auto DOP was thinking. In general, there is no need to go tracing sessions and look under the hood. The thing to start with is to do an explain plan on your statement and to look at the parameter settings on the system. Parameter Settings to Look At First and foremost, make sure that parallel_degree_policy = AUTO. If you have that parameter set to LIMITED you will not have queuing and we will only do the auto magic if your objects are set to default parallel (so no degree specified). Next you want to look at the value of parallel_degree_limit. It is typically set to CPU, which in default settings equates to the Default DOP of the system. If you are testing Auto DOP itself and the impact it has on performance you may want to leave it at this CPU setting. If you are running concurrent statements you may want to give this some more thoughts. See here for more information. In general, do stick with either CPU or with a specific number. For now avoid the IO setting as I've seen some mixed results with that... In 11.2.0.2 you should also check that IO Calibrate has been run. Best to simply do a: SQL> select * from V$IO_CALIBRATION_STATUS; STATUS        CALIBRATION_TIME ------------- ---------------------------------------------------------------- READY         04-JAN-11 10.04.13.104 AM You should see that your IO Calibrate is READY and therefore Auto DOP is ready. In any case, if you did not run the IO Calibrate step you will get the following note in the explain plan: Note -----    - automatic DOP: skipped because of IO calibrate statistics are missing One more note on calibrate_io, if you do not have asynchronous IO enabled you will see:  ERROR at line 1: ORA-56708: Could not find any datafiles with asynchronous i/o capability ORA-06512: at "SYS.DBMS_RMIN", line 463 ORA-06512: at "SYS.DBMS_RESOURCE_MANAGER", line 1296 ORA-06512: at line 7 While this is changed in some fixes to the calibrate procedure, you should really consider switching asynchronous IO on for your data warehouse. Explain Plan Explanation To see the notes that are shown and explained here (and the above little snippet ) you can use a simple explain plan mechanism. There should  be no need to add +parallel etc. explain plan for <statement> SELECT PLAN_TABLE_OUTPUT FROM TABLE(DBMS_XPLAN.DISPLAY()); Auto DOP The note structure displaying why Auto DOP did not work (with the exception noted above on IO Calibrate) is like this: Automatic degree of parallelism is disabled: <reason> These are the reason codes: Parameter -  parallel_degree_policy = manual which will not allow Auto DOP to kick in  Hint - One of the following hints are used NOPARALLEL, PARALLEL(1), PARALLEL(MANUAL) Outline - A SQL outline of an older version (before 11.2) is used SQL property restriction - The statement type does not allow for parallel processing Rule-based mode - Instead of the Cost Based Optimizer the system is using the RBO Recursive SQL statement - The statement type does not allow for parallel processing pq disabled/pdml disabled/pddl disabled - For some reason (alter session?) parallelism is disabled Limited mode but no parallel objects referenced - your parallel_degree_policy = LIMITED and no objects in the statement are decorated with the default PARALLEL degree. In most cases all objects have a specific degree in which case Auto DOP will honor that degree. Parallel Degree Limited When Auto DOP does it works you may see the cap you imposed with parallel_degree_limit showing up in the note section of the explain plan: Note -----    - automatic DOP: Computed Degree of Parallelism is 16 because of degree limit This is an obvious indication that your are being capped for this statement. There is one quite interesting one that happens when you are being capped at DOP = 1. First of you get a serial plan and the note changes slightly in that it does not indicate it is being capped (we hope to update the note at some point in time to be more specific). It right now looks like this: Note -----    - automatic DOP: Computed Degree of Parallelism is 1 Dynamic Sampling With 11.2.0.2 you will start seeing another interesting change in parallel plans, and since we are talking about the note section here, I figured we throw this in for good measure. If we deem the parallel (!) statement complex enough, we will enact dynamic sampling on your query. This happens as long as you did not change the default for dynamic sampling on the system. The note looks like this: Note ----- - dynamic sampling used for this statement (level=5)

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• Load balancing with multiple gateways

  - by ttouch

  I have to different ISPs, each on each own network. The main connects via ethernet and the secondary via wifi. The two networks have no relation at all. I just connect to them simultaneously. The reason I want to load balance between them is to achieve higher Internet speeds. Note: I have no advanced network hardware. Just my pc and the two routers that I have no access... main network: if: eth0 gw: 192.168.178.1 my ip: 192.168.178.95 speed: 400 kbit/s secondary network: if: wlan0 gw: 192.168.1.1 my ip: 192.168.1.95 speed: 300 kbit/s A diagram to explain the situation: http://i.imgur.com/NZdsv.jpg I'm on Arch Linux x64. I use netcfg to configure the interfaces Configs: # /etc/network.d/main CONNECTION='ethernet' DESCRIPTION='A basic static ethernet connection using iproute' INTERFACE='eth0' IP='static' ADDR='192.168.178.95' # /etc/network.d/second CONNECTION='wireless' DESCRIPTION='A simple WEP encrypted wireless connection' INTERFACE='wlan0' SECURITY='wep' ESSID='wifi_essid' KEY='the_password' IP="static" ADDR='192.168.1.95' And I use iptables to load balance, rules: #!/bin/bash /usr/sbin/ip route flush table ISP1 2>/dev/null /usr/sbin/ip rule del fwmark 101 table ISP1 2>/dev/null /usr/sbin/ip route add table ISP1 192.168.178.0/24 dev eth0 proto kernel scope link src 192.168.178.95 metric 202 /usr/sbin/ip route add table ISP1 default via 192.168.178.1 dev eth0 /usr/sbin/ip rule add fwmark 101 table ISP1 /usr/sbin/ip route flush table ISP2 2>/dev/null /usr/sbin/ip rule del fwmark 102 table ISP2 2>/dev/null /usr/sbin/ip route add table ISP2 192.168.1.0/24 dev wlan0 proto kernel scope link src 192.168.1.95 metric 202 /usr/sbin/ip route add table ISP2 default via 192.168.1.1 dev wlan0 /usr/sbin/ip rule add fwmark 102 table ISP2 /usr/sbin/iptables -t mangle -F /usr/sbin/iptables -t mangle -X /usr/sbin/iptables -t mangle -N MARK-gw1 /usr/sbin/iptables -t mangle -A MARK-gw1 -m comment --comment 'send via 192.168.178.1' -j MARK --set-mark 101 /usr/sbin/iptables -t mangle -A MARK-gw1 -j CONNMARK --save-mark /usr/sbin/iptables -t mangle -A MARK-gw1 -j RETURN /usr/sbin/iptables -t mangle -N MARK-gw2 /usr/sbin/iptables -t mangle -A MARK-gw2 -m comment --comment 'send via 192.168.1.1' -j MARK --set-mark 102 /usr/sbin/iptables -t mangle -A MARK-gw2 -j CONNMARK --save-mark /usr/sbin/iptables -t mangle -A MARK-gw2 -j RETURN /usr/sbin/iptables -t mangle -A PREROUTING -j CONNMARK --restore-mark /usr/sbin/iptables -t mangle -A PREROUTING -m comment --comment "this stream is already marked; escape early" -m mark ! --mark 0 -j ACCEPT /usr/sbin/iptables -t mangle -A PREROUTING -m comment --comment 'prevent asynchronous routing' -i eth0 -m conntrack --ctstate NEW -j MARK-gw1 /usr/sbin/iptables -t mangle -A PREROUTING -m comment --comment 'prevent asynchronous routing' -i wlan0 -m conntrack --ctstate NEW -j MARK-gw2 /usr/sbin/iptables -t mangle -N DEF_POL /usr/sbin/iptables -t mangle -A DEF_POL -m comment --comment 'default balancing' -p tcp -m conntrack --ctstate ESTABLISHED,RELATED -j CONNMARK --restore-mark /usr/sbin/iptables -t mangle -A DEF_POL -m comment --comment 'default balancing' -p udp -m conntrack --ctstate ESTABLISHED,RELATED -j CONNMARK --restore-mark /usr/sbin/iptables -t mangle -A DEF_POL -m comment --comment 'balance gw1 tcp' -p tcp -m conntrack --ctstate NEW -m statistic --mode nth --every 2 --packet 0 -j MARK-gw1 /usr/sbin/iptables -t mangle -A DEF_POL -m comment --comment 'balance gw1 tcp' -p tcp -m conntrack --ctstate NEW -m statistic --mode nth --every 2 --packet 0 -j ACCEPT /usr/sbin/iptables -t mangle -A DEF_POL -m comment --comment 'balance gw2 tcp' -p tcp -m conntrack --ctstate NEW -m statistic --mode nth --every 2 --packet 1 -j MARK-gw2 /usr/sbin/iptables -t mangle -A DEF_POL -m comment --comment 'balance gw2 tcp' -p tcp -m conntrack --ctstate NEW -m statistic --mode nth --every 2 --packet 1 -j ACCEPT /usr/sbin/iptables -t mangle -A DEF_POL -m comment --comment 'balance gw1 udp' -p udp -m conntrack --ctstate NEW -m statistic --mode nth --every 2 --packet 0 -j MARK-gw1 /usr/sbin/iptables -t mangle -A DEF_POL -m comment --comment 'balance gw1 udp' -p udp -m conntrack --ctstate NEW -m statistic --mode nth --every 2 --packet 0 -j ACCEPT /usr/sbin/iptables -t mangle -A DEF_POL -m comment --comment 'balance gw2 udp' -p udp -m conntrack --ctstate NEW -m statistic --mode nth --every 2 --packet 1 -j MARK-gw2 /usr/sbin/iptables -t mangle -A DEF_POL -m comment --comment 'balance gw2 udp' -p udp -m conntrack --ctstate NEW -m statistic --mode nth --every 2 --packet 1 -j ACCEPT /usr/sbin/iptables -t mangle -A PREROUTING -j DEF_POL /usr/sbin/iptables -t nat -A POSTROUTING -m comment --comment 'snat outbound eth0' -o eth0 -s 192.168.0.0/16 -m mark --mark 101 -j SNAT --to-source 192.168.178.95 /usr/sbin/iptables -t nat -A POSTROUTING -m comment --comment 'snat outbound wlan0' -o wlan0 -s 192.168.0.0/16 -m mark --mark 102 -j SNAT --to-source 192.168.1.95 /usr/sbin/ip route flush cache (this script was made by fukawi2, I don't know how to use iptables) but I have no Internet connection... output of iptables -t mangle -nvL Chain PREROUTING (policy ACCEPT 1254K packets, 1519M bytes) pkts bytes target prot opt in out source destination 1278K 1535M CONNMARK all -- * * 0.0.0.0/0 0.0.0.0/0 CONNMARK restore 21532 15M ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0 /* this stream is already marked; escape early */ mark match ! 0x0 582 72579 MARK-gw1 all -- eth0 * 0.0.0.0/0 0.0.0.0/0 /* prevent asynchronous routing */ ctstate NEW 2376 696K MARK-gw2 all -- wlan0 * 0.0.0.0/0 0.0.0.0/0 /* prevent asynchronous routing */ ctstate NEW 1257K 1520M DEF_POL all -- * * 0.0.0.0/0 0.0.0.0/0 Chain INPUT (policy ACCEPT 1276K packets, 1535M bytes) pkts bytes target prot opt in out source destination Chain FORWARD (policy ACCEPT 0 packets, 0 bytes) pkts bytes target prot opt in out source destination Chain OUTPUT (policy ACCEPT 870K packets, 97M bytes) pkts bytes target prot opt in out source destination Chain POSTROUTING (policy ACCEPT 870K packets, 97M bytes) pkts bytes target prot opt in out source destination Chain DEF_POL (1 references) pkts bytes target prot opt in out source destination 1236K 1517M CONNMARK tcp -- * * 0.0.0.0/0 0.0.0.0/0 /* default balancing */ ctstate RELATED,ESTABLISHED CONNMARK restore 15163 2041K CONNMARK udp -- * * 0.0.0.0/0 0.0.0.0/0 /* default balancing */ ctstate RELATED,ESTABLISHED CONNMARK restore 555 33176 MARK-gw1 tcp -- * * 0.0.0.0/0 0.0.0.0/0 /* balance gw1 tcp */ ctstate NEW statistic mode nth every 2 555 33176 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 /* balance gw1 tcp */ ctstate NEW statistic mode nth every 2 277 16516 MARK-gw2 tcp -- * * 0.0.0.0/0 0.0.0.0/0 /* balance gw2 tcp */ ctstate NEW statistic mode nth every 2 packet 1 277 16516 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 /* balance gw2 tcp */ ctstate NEW statistic mode nth every 2 packet 1 1442 384K MARK-gw1 udp -- * * 0.0.0.0/0 0.0.0.0/0 /* balance gw1 udp */ ctstate NEW statistic mode nth every 2 1442 384K ACCEPT udp -- * * 0.0.0.0/0 0.0.0.0/0 /* balance gw1 udp */ ctstate NEW statistic mode nth every 2 720 189K MARK-gw2 udp -- * * 0.0.0.0/0 0.0.0.0/0 /* balance gw2 udp */ ctstate NEW statistic mode nth every 2 packet 1 720 189K ACCEPT udp -- * * 0.0.0.0/0 0.0.0.0/0 /* balance gw2 udp */ ctstate NEW statistic mode nth every 2 packet 1 Chain MARK-gw1 (3 references) pkts bytes target prot opt in out source destination 2579 490K MARK all -- * * 0.0.0.0/0 0.0.0.0/0 /* send via 192.168.178.1 */ MARK set 0x65 2579 490K CONNMARK all -- * * 0.0.0.0/0 0.0.0.0/0 CONNMARK save 2579 490K RETURN all -- * * 0.0.0.0/0 0.0.0.0/0 Chain MARK-gw2 (3 references) pkts bytes target prot opt in out source destination 3373 901K MARK all -- * * 0.0.0.0/0 0.0.0.0/0 /* send via 192.168.1.1 */ MARK set 0x66 3373 901K CONNMARK all -- * * 0.0.0.0/0 0.0.0.0/0 CONNMARK save 3373 901K RETURN all -- * * 0.0.0.0/0 0.0.0.0/0

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• Eventlet or gevent or Stackless + Twisted, Pylons, Django and SQL Alchemy

  - by Khorkrak

  We're using Twisted extensively for apps requiring a great deal of asynchronous io. There are some cases where stuff is cpu bound instead and for that we spawn a pool of processes to do the work and have a system for managing these across multiple servers as well - all done in Twisted. Works great. The problem is that it's hard to bring new team members up to speed. Writing asynchronous code in Twisted requires a near vertical learning curve. It's as if humans just don't think that way naturally. We're considering a mixed approach perhaps. Maybe do the xmlrpc server part and process management in Twisted still but the other stuff in code that at least looks synchronous while not being as such. Then again I like explicit over implicit so hmmm. Anyway onto greenlets - how well does that stuff work? So there's Stackless and as you can see from my Gallentean avatar I'm well aware of the tremendous success in it's use for CCP's flagship EVE Online game first hand. What about Eventlet or gevent? Well for now only Eventlet works with Twisted. However gevent claims to be faster since it's not a pure python implementation it instead uses libevent. It also has fewer idiosyncrasies and defects supposedly. The documentation there is minimal in comparison to Eventlet and it's maintained by 1 guy as far as I can tell. This makes me leery but all great projects start this way so... Then there's PyPy - I haven't even finished reading about that one yet - just saw it in this thread: Drawbacks of Stackless. So confusing - I'm wondering what the heck to do - sounds like Eventlet is probably the best bet but is it really stable enough? Anyone out there have any experience with it? Should we go with Stackless instead as it's been around and is proven technology - just like Twisted is as well - and they do work together nicely. But still I hate having to have a separate version of Python to do this. what to do.... This somewhat obnoxious blog entry hit the nail on the head for me though: Asynchronous IO for Grownups We're stuck using MySQL as well - I never knew how great PostgreSQL was until having had to work on a production OLTP system in MySQL instead - but that's another story. But if that monkey patch thing really works then wow. Just wow.

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• Developing ASP.NET MVC UI Extensions - best approach

  - by user252160

  What are the best practices in developing rich UI extensions for ASP.NET MVC (I mean asynchronous / partial loading, slick effects, skinning etc) ? I saw that Telerik has an MVC suite of extensions, but haven't tried them yet, so I cannot comment on them. My biggest concern as of the moment is how to structure the code of my extensions so that C#, ASP markup, and JQuery remain separate from each other, yet encapsulated in a way that the extension must be easy to distribute and reuse. I know that the user control approach had many flaws, yet it sort of allowed application developers to just reference a control, set some parameters and get it going in a few minutes. I'd like to achieve the same kind of portability/reusability as I still keep the code easy to extend and build upon. Now, some ideas that come to mind as topics for discussion are: template helpers vs. extension method helpers or a possible integration efficient use of jQuery - naming conventions - - asynchronous action loading - etc you can add whatever comes to your mind

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• BLOB Reading via IHttpAsyncHandler

  - by shaniirfan

  Hi, I am storing images in SQL Server 2000 database (BLOB type). There is a web page in my ASP.NET application which need to show a lot images to the end user and i want to handle browser's requests for images through a IHttpAsyncHandler. I found a similer post on codeproject "Asynchronous HTTP Handler for Asynchronous BLOB DataReader." But for some reasons, page get freeze upon completion of "BeginProcessRequest" method and "EndProcessRequest" method never get call. Can anyone look at this post and let me know whats wrong in that post? OR what i need to do to complete this task (BLOB Reading via IHttpAsyncHandler)?

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• Threading in java

  - by Mohd Adnan

  THREAD make the run time environment asynchronous. kindly elaborate the above line?

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• Accessing a master page from httphandler

  - by vondip

  Hi All, I am developing a small application in asp.net (writing in c#). In my application I am using jquery to perform asynchronous call to the server. I have an http handler that listens in to the requests and does what it needs to do. Problems start when in the handler I need to access information stored in the page , from where the asynchronous call started. When I try this: Page page = HttpContext.Current.Handler as Page; I don't get a page. How else can I access the page itself? Thank you

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• "Microsoft DNS Client" vs. getaddrinfo?

  - by Josh K

  Right now, my application is using the c-ares asynchronous DNS resolver library on Windows below cURL, and I have users complaining that it behaves differently from other windows apps. One particular user said that "other applications are using the Microsoft DNS client" and experiences no problems. cURL itself has an asynchronous DNS implementation that uses getaddrinfo() in a thread. My guess is that would be equivalent behavior to using the "DNS Client" and its host of functions (e.g. DnsQuery?) So, dear Lazyweb, I ask if there is a tangible difference between the behavior of getaddrinfo() vs. using the actual Dns* APIs from the Win32 API.

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• slsvcutil.exe Proxy and Interfaces

  - by JPM

  Is it possible when using slsvcutil.exe to generate a proxy through the command line not to have the proxy file output the Interface in an Asynchronous fashion. For example, if I have a function "foo()" on the serverside in the Interface, when I generate the proxy using Slsvcutil.exe, it makes two functions in the interface definition in the proxy named "BeginFoo()" and "EndFoo()". All I want is "Foo()", I don't need the other two methods. Is this possible? I'm using the proxy with Monotouch which is why I need to use Slsvcutil.exe but don't need the Asynchronous methods. Thanks!

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• Handling credit cards and IOS

  - by Susan Jackie

  I am using NSUrlConnection asyncronous request to transmit credit card information to a secure third party server. I do the following: I get the credit card number, cvv, etc from the uitextfields. Encode the credit card information into a json format. Set as httpd body of the nsurlconnection request as follows: NSURL * url = [[NSURL URLWithString: "https://www.example.com"]; NSMutableURLRequest * request = [[NSMutableURLRequest alloc] initWithURL: url]; [request setHTTPMethod: @"POST"]; [request setValue:@"application/json" forHTTPHeaderField:@"Accept"]; [request setValue:@"application/json" forHTTPHeaderField:@"Content-Type"]; [request setHTTPBody: [NSJSONSerialization dataWithJSONObject: params options: kNilOptions error: &parseError]]; Send this information via asynchronous request to a secure third party server: [NSURLConnection sendAsynchronousRequest:request queue: queue completionHandler:^(NSURLResponse *response, NSData *data, NSError * requestError) { What should I be considering to send user credit card information to a third party server using nsurlconnection asynchronous request?

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• How do you update a TextField from a grails remoteLink?

  - by Randyaa

  Existing markup: <g:textField name="identifier"/> <g:remoteLink action="newId" update="identifier">generate new id</g:remoteLink> Corresponding HTML markup: <input type="text" id="identifier" name="identifier"> <a onclick="new Ajax.Updater('guid','/webapp/domain/newId',{asynchronous:true,evalScripts:true});return false;" href="/webapp/domain/newId">generate</a> The HTML markup it generates when the link is clicked: <input type="text" id="identifier" name="identifier">THE-NEW-ID-HERE</input> <a onclick="new Ajax.Updater('guid','/webapp/domain/newId',{asynchronous:true,evalScripts:true});return false;" href="/webapp/domain/newId">generate</a>

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• multiple occurences of HandleCreated for a single control

  - by Asher

  I’m using control that needs to be register to asynchronous events. The events will be raised in the UI thread using the ISynchronizeInvoke interface implemented by WinForms controls I can’t register to the event at the constructor because it will allow calling the event handler before the control is fully created. during which calls to ISynchronizeInvoke are not allowed. Solution to that problem is to use the perform the asynchronous event registration from an event handler to the HandleCreated instead of registering from the constructor. however, this poses another issue, in some scenations the HandleCreated event is raised multiple times as result of change at the control state. For example, each changing of the “RightToLeft” property causes a WMCreate message that cause raising the “HandleCreated” event. How can I prevent the multiply times of event rising? Is there is another way to know when the control is created and display for the first time? I can keep a boolean flag in the HandleCreated, however it feels like a hack and I am wondering if there is a better way to handle this issue.

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• How can you tell the source of the data when using the Stream.BeginRead Method?

  - by xarzu

  When using the Stream.BeginRead Method, and you are reading from a stream into a memory, how is it determined where you are reading the data from? See: http://msdn.microsoft.com/en-us/library/system.io.stream.beginread.aspx In the list of parameters, I do not see one that tells where the data is being read from: Parameters buffer Type: System.Byte[] The buffer to read the data into. offset Type: System.Int32 The byte offset in buffer at which to begin writing data read from the stream. count Type: System.Int32 The maximum number of bytes to read. callback Type: System.AsyncCallback An optional asynchronous callback, to be called when the read is complete. state Type: System.Object A user-provided object that distinguishes this particular asynchronous read request from other requests.

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• What technologies are appropriate for a human workflow system?

  - by CCw

  I'm researching various workflow architectures and it is overwhelming. The workflow system I am creating will be almost completely human-driven. Very little, if any, asynchronous activity will be taking place. One possibility is to simply use a RDBMS and have a task table, from which stored procedures would be used to enforce synchronous access to each task. This seems very simple, but I'm having a hard time coming up with reasons why I might need to involve a heavier solution. If my system has ~500 concurrent users, and there is very little in the way of automated or asynchronous tasks, should I even consider the various workflow patterns/packages out there like Mule, BPEL/SOA, Spring Work Flow, etc?

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• link_to_remote in rails, problem pass :id

  - by nakada

  i have problem use link_to_remote link_to_remote document example say link_to_remote "Delete this post", :update => "posts", :url => { :action => "destroy", :id => post.id } this code make below html code <a href="#" onclick="new Ajax.Updater('posts', '/blog/destroy/3', {asynchronous:true, evalScripts:true}); return false;">Delete this post</a> but my app don't. my html is <a href="#" onclick="new Ajax.Updater('posts', '/blog/6', {asynchronous:true, evalScripts:true, parameters:'authenticity_token=' + encodeURIComponent('2C4Yo8OIDN+dm9oieL37uRg++PuWa8LCz18gW5Cu+Vg=')}); return false;">Delete this post</a> where is destroy in url? i expected '/blog/destroy/6' but actually 'blog/6' what's the problem? my rails version is 2.3.5

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• How to keep a .NET console app running?

  - by intoorbit

  Consider a Console application that starts up some services in a separate thread. All it needs to do is wait for the user to press Ctrl+C to shut it down. Which of the following is the better way to do this? static ManualResetEvent _quitEvent = new ManualResetEvent(false); static void Main() { Console.CancelKeyPress += delegate { _quitEvent.Set(); }; // kick off asynchronous stuff _quitEvent.WaitOne(); // cleanup/shutdown and quit } Or this, using Thread.Sleep(1): static bool _quitFlag = false; static void Main() { Console.CancelKeyPress += delegate { _quitFlag = true; }; // kick off asynchronous stuff while (!_quitFlag) { Thread.Sleep(1); } // cleanup/shutdown and quit }

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• Soapi.CS : A fully relational fluent .NET Stack Exchange API client library

  - by Sky Sanders

  Soapi.CS for .Net / Silverlight / Windows Phone 7 / Mono as easy as breathing...: var context = new ApiContext(apiKey).Initialize(false); Question thisPost = context.Official .StackApps .Questions.ById(386) .WithComments(true) .First(); Console.WriteLine(thisPost.Title); thisPost .Owner .Questions .PageSize(5) .Sort(PostSort.Votes) .ToList() .ForEach(q=> { Console.WriteLine("\t" + q.Score + "\t" + q.Title); q.Timeline.ToList().ForEach(t=> Console.WriteLine("\t\t" + t.TimelineType + "\t" + t.Owner.DisplayName)); Console.WriteLine(); }); // if you can think it, you can get it. Output Soapi.CS : A fully relational fluent .NET Stack Exchange API client library 21 Soapi.CS : A fully relational fluent .NET Stack Exchange API client library Revision code poet Revision code poet Votes code poet Votes code poet Revision code poet Revision code poet Revision code poet Votes code poet Votes code poet Votes code poet Revision code poet Revision code poet Revision code poet Revision code poet Revision code poet Revision code poet Revision code poet Revision code poet Revision code poet Revision code poet Votes code poet Comment code poet Revision code poet Votes code poet Revision code poet Revision code poet Revision code poet Answer code poet Revision code poet Revision code poet 14 SOAPI-WATCH: A realtime service that notifies subscribers via twitter when the API changes in any way. Votes code poet Revision code poet Votes code poet Comment code poet Comment code poet Comment code poet Votes lfoust Votes code poet Comment code poet Comment code poet Comment code poet Comment code poet Revision code poet Comment lfoust Votes code poet Revision code poet Votes code poet Votes lfoust Votes code poet Revision code poet Comment Dave DeLong Revision code poet Revision code poet Votes code poet Comment lfoust Comment Dave DeLong Comment lfoust Comment lfoust Comment Dave DeLong Revision code poet 11 SOAPI-EXPLORE: Self-updating single page JavaSript API test harness Votes code poet Votes code poet Votes code poet Votes code poet Votes code poet Comment code poet Revision code poet Votes code poet Revision code poet Revision code poet Revision code poet Comment code poet Revision code poet Votes code poet Comment code poet Question code poet Votes code poet 11 Soapi.JS V1.0: fluent JavaScript wrapper for the StackOverflow API Comment George Edison Comment George Edison Comment George Edison Comment George Edison Comment George Edison Comment George Edison Answer George Edison Votes code poet Votes code poet Votes code poet Votes code poet Revision code poet Revision code poet Answer code poet Comment code poet Revision code poet Comment code poet Comment code poet Comment code poet Revision code poet Revision code poet Votes code poet Votes code poet Votes code poet Votes code poet Comment code poet Comment code poet Comment code poet Comment code poet Comment code poet 9 SOAPI-DIFF: Your app broke? Check SOAPI-DIFF to find out what changed in the API Votes code poet Revision code poet Comment Dennis Williamson Answer Dennis Williamson Votes code poet Votes Dennis Williamson Comment code poet Question code poet Votes code poet About A robust, fully relational, easy to use, strongly typed, end-to-end StackOverflow API Client Library. Out of the box, Soapi provides you with a robust client library that abstracts away most all of the messy details of consuming the API and lets you concentrate on implementing your ideas. A few features include: A fully relational model of the API data set exposed via a fully 'dot navigable' IEnumerable (LINQ) implementation. Simply tell Soapi what you want and it will get it for you. e.g. "On my first question, from the author of the first comment, get the first page of comments by that person on any post" my.Questions.First().Comments.First().Owner.Comments.ToList(); (yes this is a real expression that returns the data as expressed!) Full coverage of the API, all routes and all parameters with an intuitive syntax. Strongly typed Domain Data Objects for all API data structures. Eager and Lazy Loading of 'stub' objects. Eager\Lazy loading may be disabled. When finer grained control of requests is desired, the core RouteMap objects may be leveraged to request data from any of the API paths using all available parameters as documented on the help pages. A rich Asynchronous implementation. A configurable request cache to reduce unnecessary network traffic and to simplify your usage logic. There is no need to go out of your way to be frugal. You may set a distinct cache duration for any particular route. A configurable request throttle to ensure compliance with the api terms of usage and to simplify your code in that you do not have to worry about and respond to 50X errors. The RequestCache and Throttled Queue are thread-safe, so can make as many requests as you like from as many threads as you like as fast as you like and not worry about abusing the api or having to write reams of management/compensation code. Configurable retry threshold that will, by default, make up to 3 attempts to retrieve a request before failing. Every request made by Soapi is properly formed and directed so most any http error will be the result of a timeout or other network infrastructure. A retry buffer provides a level of fault tolerance that you can rely on. An almost identical javascript library, Soapi.JS, and it's full figured big brother, Soapi.JS2, that will enable you to leverage your server cycles and bandwidth for only those tasks that require it and offload things like status updates to the client's browser. License Licensed GPL Version 2 license. Why is Soapi.CS GPL? Can I get an LGPL license for Soapi.CS? (hint: probably) Platforms .NET 3.5 .NET 4.0 Silverlight 3 Silverlight 4 Windows Phone 7 Mono Download Source code lives @ http://soapics.codeplex.com. Binary releases are forthcoming. codeplex is acting up again. get the source and binaries @ http://bitbucket.org/bitpusher/soapi.cs/downloads The source is C# 3.5. and includes projects and solutions for the following IDEs Visual Studio 2008 Visual Studio 2010 ModoDevelop 2.4 Documentation Full documentation is available at http://soapi.info/help/cs/index.aspx Sample Code / Usage Examples Sample code and usage examples will be added as answers to this question. Full API Coverage all API routes are covered Full Parameter Parity If the API exposes it, Soapi giftwraps it for you. Building a simple app with Soapi.CS - a simple app that gathers all traces of a user in the whole stackiverse. Fluent Configuration - Setting up a Soapi.ApiContext could not be easier Bulk Data Import - A tiny app that quickly loads a SQLite data file with all users in the stackiverse. Paged Results - Soapi.CS transparently handles multi-page operations. Asynchronous Requests - Soapi.CS provides a rich asynchronous model that is especially useful when writing api apps in Silverlight or Windows Phone 7. Caching and Throttling - how and why Apps that use Soapi.CS Soapi.FindUser - .net utility for locating a user anywhere in the stackiverse Soapi.Explore - The entire API at your command Soapi.LastSeen - List users by last access time Add your app/site here - I know you are out there ;-) if you are not comfortable editing this post, simply add a comment and I will add it. The CS/SL/WP7/MONO libraries all compile the same code and with the exception of environmental considerations of Silverlight, the code samples are valid for all libraries. You may also find guidance in the test suites. More information on the SOAPI eco-system. Contact This library is currently the effort of me, Sky Sanders (code poet) and can be reached at gmail - sky.sanders Any who are interested in improving this library are welcome. Support Soapi You can help support this project by voting for Soapi's Open Source Ad post For more information about the origins of Soapi.CS and the rest of the Soapi eco-system see What is Soapi and why should I care?

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• How to add event receiver to SharePoint2010 content type programmatically

  - by ybbest

  Today , I’d like to show how to add event receiver to How to add event receiver to SharePoint2010 content type programmatically. 1. Create empty SharePoint Project and add a class called ItemContentTypeEventReceiver and make it inherit from SPItemEventReceiver and implement your logic as below public class ItemContentTypeEventReceiver : SPItemEventReceiver { private bool eventFiringEnabledStatus; public override void ItemAdded(SPItemEventProperties properties) { base.ItemAdded(properties); UpdateTitle(properties); } private void UpdateTitle(SPItemEventProperties properties) { SPListItem addedItem = properties.ListItem; string enteredTitle = addedItem["Title"] as string; addedItem["Title"] = enteredTitle + " Updated"; DisableItemEventsScope(); addedItem.Update(); EnableItemEventsScope(); } public override void ItemUpdated(SPItemEventProperties properties) { base.ItemUpdated(properties); UpdateTitle(properties); } private void DisableItemEventsScope() { eventFiringEnabledStatus = EventFiringEnabled; EventFiringEnabled = false; } private void EnableItemEventsScope() { eventFiringEnabledStatus = EventFiringEnabled; EventFiringEnabled = true; } } 2.Create a Site or Web(depending or your requirements) scoped feature and implement your feature event handler as below: public override void FeatureActivated(SPFeatureReceiverProperties properties) { SPWeb web = GetFeatureWeb(properties); //http://karinebosch.wordpress.com/walkthroughs/event-receivers-theory/ string assemblyName =  System.Reflection.Assembly.GetExecutingAssembly().FullName; const string className = "YBBEST.AddEventReceiverToContentType.ItemContentTypeEventReceiver"; SPContentType contentType= web.ContentTypes["Item"]; AddEventReceiverToContentType(className, contentType, assemblyName, SPEventReceiverType.ItemAdded, SPEventReceiverSynchronization.Asynchronous); AddEventReceiverToContentType(className, contentType, assemblyName, SPEventReceiverType.ItemUpdated, SPEventReceiverSynchronization.Asynchronous); contentType.Update(); } protected static void AddEventReceiverToContentType(string className, SPContentType contentType, string assemblyName, SPEventReceiverType eventReceiverType, SPEventReceiverSynchronization eventReceiverSynchronization) { if (className == null) throw new ArgumentNullException("className"); if (contentType == null) throw new ArgumentNullException("contentType"); if (assemblyName == null) throw new ArgumentNullException("assemblyName"); SPEventReceiverDefinition eventReceiver = contentType.EventReceivers.Add(); eventReceiver.Synchronization = eventReceiverSynchronization; eventReceiver.Type = eventReceiverType; eventReceiver.Assembly = assemblyName; eventReceiver.Class = className; eventReceiver.Update(); } 3.Deploy your solution and now you have a event receiver that attached to the Item contentType. You can download the complete source code here.You can also check how to add event receiver to a list using SharePoint event receiver item in Visual Studio2010 in my previous blog.

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• Easy remote communication without WCF

  - by Ralf Westphal

  If you´ve read my previous posts about why I deem WCF more of a problem than a solution and how I think we should switch to asynchronous only communication in distributed application, you might be wondering, how this could be done in an easy way. Since a truely simple example to get started with WCF still is drawing quite some traffic to this blog, let me pick up on that and show you, how to accomplish the same but much easier with an async communication API. For simplicities sake let me put all...(read more)

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• How do you keep code with continuations/callbacks readable?

  - by Heinzi

  Summary: Are there some well-established best-practice patterns that I can follow to keep my code readable in spite of using asynchronous code and callbacks? I'm using a JavaScript library that does a lot of stuff asynchronously and heavily relies on callbacks. It seems that writing a simple "load A, load B, ..." method becomes quite complicated and hard to follow using this pattern. Let me give a (contrived) example. Let's say I want to load a bunch of images (asynchronously) from a remote web server. In C#/async, I'd write something like this: disableStartButton(); foreach (myData in myRepository) { var result = await LoadImageAsync("http://my/server/GetImage?" + myData.Id); if (result.Success) { myData.Image = result.Data; } else { write("error loading Image " + myData.Id); return; } } write("success"); enableStartButton(); The code layout follows the "flow of events": First, the start button is disabled, then the images are loaded (await ensures that the UI stays responsive) and then the start button is enabled again. In JavaScript, using callbacks, I came up with this: disableStartButton(); var count = myRepository.length; function loadImage(i) { if (i >= count) { write("success"); enableStartButton(); return; } myData = myRepository[i]; LoadImageAsync("http://my/server/GetImage?" + myData.Id, function(success, data) { if (success) { myData.Image = data; } else { write("error loading image " + myData.Id); return; } loadImage(i+1); } ); } loadImage(0); I think the drawbacks are obvious: I had to rework the loop into a recursive call, the code that's supposed to be executed in the end is somewhere in the middle of the function, the code starting the download (loadImage(0)) is at the very bottom, and it's generally much harder to read and follow. It's ugly and I don't like it. I'm sure that I'm not the first one to encounter this problem, so my question is: Are there some well-established best-practice patterns that I can follow to keep my code readable in spite of using asynchronous code and callbacks?

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• links for 2011-02-16

  - by Bob Rhubart

  On the Software Architect Trail Software architect is the #1 job, according to a 2010 CNN-Money poll. In this article in Oracle Magazine, several members of the OTN architect community talk about the career paths that led them to this lucrative role.  (tags: oracle oraclemagazine softwarearchitect) Oracle Technology Network Architect Day: Denver Registration opens soon for this event to be held in Denver on March 23, 2011.  (tags: oracle otn entarch) How the Internet Gets Inside Us : The New Yorker "It isn’t just that we’ve lived one technological revolution among many; it’s that our technological revolution is the big social revolution that we live with." - Adam Gopnik (tags: internet progress technology innovation) The Insider Threat: Understand and Mitigate Your Risks: CSO Webcast February 23, 2011 at 1:00 PM EST/ 10:00 AM PST .  Speakers: Randy Trzeciak, lead for the CERT Insider Threat research team, and  Roxana Bradescu, Director of Database Security at Oracle. (tags: oracle CERT security) The Tom Kyte Blog: An Interesting Read... Tom looks at "an internet security firm brought down by not following the most *basic* of security principals." (tags: security oracle) Jason Williamson: Oracle as a Service in the Cloud "It is not trivial to migrate large amounts of pre-relational or 'devolved' relational data. To do this, we again must revert back to a tight roadmap to migration and leverage the growing tools and services that we have." - Jason Williamson (tags: oracle cloud soa) Edwin Biemond: Java / Oracle SOA blog: Building an asynchronous web service with JAX-WS "Building an asynchronous web service can be complex especially when you are used to synchronous Web services where you can wait for the response in your favorite tool." - Oracle ACE Edwin Biemond (tags: oracle oracleace java soa) Shared Database Servers (The SaaS Report) "Outside the virtualization world, there are capabilities of Oracle Database which can be used to prevent resource contention and guarantee SLA." - Shivanshu Upadhyay (tags: oracle database cloud SaaS) White Paper: Experiencing the New Social Enterprise "Increasingly organizations recognize the mandate to create a modern user experience that transforms existing business processes and increases business efficiency and agility." (tags: e20 enterprise2.0 socialcomputing oracle) Clusterware 11gR2 - Setting up an Active/Passive failover configuration Gilles Haro illustrates the steps necessary to achieve "a fully operational 11gR2 database protected by automatic failover capabilities." (tags: oracle clusterware) Oracle ERP: How to overcome local hurdles in a global implementation "The corporate world becomes a global village as many companies expand their business and offices around different countries and even continents. And this number keeps increasing. This globalization raises interesting questions..." - Jan Verhallen (tags: oracle capgemini entarch erp) Webcast: Successful Strategies for Optimizing Your Data Warehouse. March 3. 10 a.m. PT/1 p.m. ET Thursday, March 3, 2011. 10 a.m. PT/1 p.m. ET. Speakers: Mala Narasimharajan (Senior Product Marketing Manager, Oracle Data Integration) and Denis Gray (Principal Product Manager, Oracle Data Integration) (tags: oracle dataintegration datawarehousing)

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• Monitor Linux file system events with inotify

  <b>IBM Developerworks:</b> "Summary: Use inotify when you need efficient, fine-grained, asynchronous monitoring of Linux file system events. Use it for user-space monitoring for security, performance, or other purposes."

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• Consuming the Amazon S3 service from a Win8 Metro Application

  - by cibrax

  As many of the existing Http APIs for Cloud Services, AWS also provides a set of different platform SDKs for hiding many of complexities present in the APIs. While there is a platform SDK for .NET, which is open source and available in C#, that SDK does not work in Win8 Metro Applications for the changes introduced in WinRT. WinRT offers a complete different set of APIs for doing I/O operations such as doing http calls or using cryptography for signing or encrypting data, two aspects that are absolutely necessary for consuming AWS. All the I/O APIs available as part of WinRT are asynchronous, and uses the TPL model for .NET applications (HTML and JavaScript Metro applications use a model based in promises, which is similar concept).  In the case of S3, the http Authorization header is used for two purposes, authenticating clients and make sure the messages were not altered while they were in transit. For doing that, it uses a signature or hash of the message content and some of the headers using a symmetric key (That's just one of the available mechanisms). Windows Azure for example also uses the same mechanism in many of its APIs. There are three challenges that any developer working for first time in Metro will have to face to consume S3, the new WinRT APIs, the asynchronous nature of them and the complexity introduced for generating the Authorization header. Having said that, I decided to write this post with some of the gotchas I found myself trying to consume this Amazon service. 1. Generating the signature for the Authorization header All the cryptography APIs in WinRT are available under Windows.Security.Cryptography namespace. Many of operations available in these APIs uses the concept of buffers (IBuffer) for representing a chunk of binary data. As you will see in the example below, these buffers are mainly generated with the use of static methods in a WinRT class CryptographicBuffer available as part of the namespace previously mentioned. private string DeriveAuthToken(string resource, string httpMethod, string timestamp) { var stringToSign = string.Format("{0}\n" + "\n" + "\n" + "\n" + "x-amz-date:{1}\n" + "/{2}/", httpMethod, timestamp, resource); var algorithm = MacAlgorithmProvider.OpenAlgorithm("HMAC_SHA1"); var keyMaterial = CryptographicBuffer.CreateFromByteArray(Encoding.UTF8.GetBytes(this.secret)); var hmacKey = algorithm.CreateKey(keyMaterial); var signature = CryptographicEngine.Sign( hmacKey, CryptographicBuffer.CreateFromByteArray(Encoding.UTF8.GetBytes(stringToSign)) ); return CryptographicBuffer.EncodeToBase64String(signature); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The algorithm that determines the information or content you need to use for generating the signature is very well described as part of the AWS documentation. In this case, this method is generating a signature required for creating a new bucket. A HmacSha1 hash is computed using a secret or symetric key provided by AWS in the management console. 2. Sending an Http Request to the S3 service WinRT also ships with the System.Net.Http.HttpClient that was first introduced some months ago with ASP.NET Web API. This client provides a rich interface on top the traditional WebHttpRequest class, and also solves some of limitations found in this last one. There are a few things that don't work with a raw WebHttpRequest such as setting the Host header, which is something absolutely required for consuming S3. Also, HttpClient is more friendly for doing unit tests, as it receives a HttpMessageHandler as part of the constructor that can fake to emulate a real http call. This is how the code for consuming the service with HttpClient looks like, public async Task<S3Response> CreateBucket(string name, string region = null, params string[] acl) { var timestamp = string.Format("{0:r}", DateTime.UtcNow); var auth = DeriveAuthToken(name, "PUT", timestamp); var request = new HttpRequestMessage(HttpMethod.Put, "http://s3.amazonaws.com/"); request.Headers.Host = string.Format("{0}.s3.amazonaws.com", name); request.Headers.TryAddWithoutValidation("Authorization", "AWS " + this.key + ":" + auth); request.Headers.Add("x-amz-date", timestamp); var client = new HttpClient(); var response = await client.SendAsync(request); return new S3Response { Succeed = response.StatusCode == HttpStatusCode.OK, Message = (response.Content != null) ? await response.Content.ReadAsStringAsync() : null }; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } You will notice a few additional things in this code. By default, HttpClient validates the values for some well-know headers, and Authorization is one of them. It won't allow you to set a value with ":" on it, which is something that S3 expects. However, that's not a problem at all, as you can skip the validation by using the TryAddWithoutValidation method. Also, the code is heavily relying on the new async and await keywords to transform all the asynchronous calls into synchronous ones. In case you would want to unit test this code and faking the call to the real S3 service, you should have to modify it to inject a custom HttpMessageHandler into the HttpClient. The following implementation illustrates this concept, In case you would want to unit test this code and faking the call to the real S3 service, you should have to modify it to inject a custom HttpMessageHandler into the HttpClient. The following implementation illustrates this concept, public class FakeHttpMessageHandler : HttpMessageHandler { HttpResponseMessage response; public FakeHttpMessageHandler(HttpResponseMessage response) { this.response = response; } protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, System.Threading.CancellationToken cancellationToken) { var tcs = new TaskCompletionSource<HttpResponseMessage>(); tcs.SetResult(response); return tcs.Task; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } You can use this handler for injecting any response while you are unit testing the code.

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