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• Solutions for redundant server and client code?

  - by Fragsworth

  In our system, the code which exists on the client side (in Flash and Javascript) mirrors the code that exists on the server side (e.g. in Python or PHP), normally with respect to the models, the methods available for those models, and the unit tests written for them. This becomes a problem in systems where you want to minimize data transfer (e.g. multiplayer games). I do not want to write the same code and unit tests redundantly for both the client and server, but I don't know of any standard solutions to deal with this. Basically, I want a language/compiler which can produce models and methods for three main languages: Actionscript, Javascript, and any server language. Does something like this exist?

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• How to disable or tune filesystem cache sharing for OpenVZ?

  - by gertvdijk

  For OpenVZ, an example of container-based virtualization, it seems that host and all guests are sharing the filesystem cache. This sounds paradoxical when talking about virtualization, but this is actually a feature of OpenVZ. It makes sense too. Because only one kernel is running, it's possible to benefit from sharing the same pages of filesystem cache in memory. And while it sounds beneficial, I think a set up here actually suffers in performance from it. Here's why I think why: my machines aren't actually sharing any files on disk so I can't benefit from this feature in OpenVZ. Several OpenVZ machines are running MySQL with MyISAM tables. MyISAM relies on the system's filesystem cache for caching of data files, unlike InnoDB's buffer pool. Also some virtual machines are known to do heavy and large I/O operations on the same filesystem in the host. For example, when running cat *.MYD > /dev/null on some large database in one machine, I saw the filesystem cache lowering in another, monitored by htop. This essentially flushes all the useful filesystem cache in guests (FIFO) and so it flushes the MySQL caches in the guests. Now users are complaining that MySQL is very slow. And it is. Some simple SELECT queries take several seconds on times disk I/O is heavily used by other machines. So, simply put: Is there a way to avoid filesystem cache being wiped out by other virtual machines in container-based virtualization? Some thoughts: Choosing algorithm for flushing filesystem cache in the kernel. (possible? how?) Reserving a certain amount of pages for a single VM. (seems no option for filesystem cache type of pages that reading man vzctl) Will running MySQL on another filesystem get me anywhere? If not, I think my alternatives are: Use KVM for MySQL-MyISAM running VMs. KVM actually assigns memory to the VM and does not allow swapping out caches unless using a balloon driver. Move to InnoDB and tune the buffer pools, dirty pages, etc. This is now considered to be 'nice to have' on the long-term as not everyone responsible for administration of the system understands InnoDB. more suggestions welcome. System software: Proxmox (now 1.9, could be upgraded to 2.x). One big LV assigned for the VMs.

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• Flashing and closing PyS60 SIS

  - by Matrich

  I created a py script for S60 2nd Edition FP3 with a background image, database, sound files which are stored in a folder on c drive. After several hours, I have managed to convert it into sis which I sent to my mobile phone. First, I installed the sis on the external memory and it failed to work. I read online that it should be on the same drive as python runtime. So I installed it on phone memory but it just flashes and then closes. I made another sis with a database and it worked so I suspect it could be because it cant find the background image and sound files in the folder. How can I know the cause of this? Also, how can I include the background image and sound files with the sis so that they are automatically installed when installing the sis file?

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• Django + Pydev/Eclipse + Google App Engine - possible?

  - by Lee Tang

  Has anyone been able to get Google App Engine/Django working in Pydev/Eclipse? I tried this but had difficulty getting Pydev to recognize all of the externally linked folders (django plugins) that I was referencing. I ended up copying all of those folders into the project en masse, rather than referencing them, resulting in a massively bloated project folder - it was really an unworkable solution that eventually made me give up the whole project. So, I'm wondering if anyone has tried this or has any idea what I might have been doing wrong. (Keep in mind this was my first attempt at using Pydev, Django, App Engine and Python!!)

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• Should I start a General Software Developer User Group? [closed]

  - by Jeb

  I'm moving to a small town (Panama City, Florida) at some point in the future. I've found a Linux user group, and a .Net user group, but I'd like to spend my time outside of the office learning about Python, Android, JQuery -- mostly things that aren't owned by .Net. I'm debating trying to start another user group of some sort there, primarily to attract programmers who use technologies other than .Net. What are some of the more general programming user groups in existence already? I'm looking for something I could franchise.

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• Ubuntu and Postfix Configuration Issues

  - by Obi Hill

  I recently installed postfix on Ubuntu Natty. I'm having a problem with the configuration. Firstly here is my postfix configuration file: # Debian specific: Specifying a file name will cause the first # line of that file to be used as the name. The Debian default # is /etc/mailname. myorigin = /etc/mailname smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu) biff = no # appending .domain is the MUA's job. append_dot_mydomain = no # Uncomment the next line to generate "delayed mail" warnings delay_warning_time = 4h readme_directory = no # TLS parameters smtpd_tls_cert_file=/etc/ssl/certs/ssl-cert-snakeoil.pem smtpd_tls_key_file=/etc/ssl/private/ssl-cert-snakeoil.key smtpd_use_tls=yes smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache # See /usr/share/doc/postfix/TLS_README.gz in the postfix-doc package for # information on enabling SSL in the smtp client. mydomain = $myorigin myhostname = mail.nairanode.com alias_maps = hash:/etc/postfix/aliases alias_database = hash:/etc/postfix/aliases # this specifies where the virtual mailbox folders will be located virtual_mailbox_base = /var/spool/mail/virtual # this specifies where the virtual mailbox folders will be located virtual_mailbox_base = /var/spool/mail/virtual # this is for the mailbox location for each user virtual_mailbox_maps = mysql:/etc/postfix/mysql_mailbox.cf # and this is for aliases virtual_alias_maps = mysql:/etc/postfix/mysql_alias.cf # and this is for domain lookups virtual_mailbox_domains = mysql:/etc/postfix/mysql_domains.cf # this is how to connect to the domains (all virtual, but the option is there) # not used yet # transport_maps = mysql:/etc/postfix/mysql_transport.cf virtual_uid_maps = static:5000 virtual_gid_maps = static:5000 mydestination = $myorigin, $myhostname, localhost.localdomain, , localhost relayhost = mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128 mailbox_size_limit = 0 recipient_delimiter = + inet_interfaces = all #mynetworks_style = host # ADDITIONAL unknown_local_recipient_reject_code = 550 maximal_queue_lifetime = 7d minimal_backoff_time = 1000s maximal_backoff_time = 8000s smtp_helo_timeout = 60s smtpd_recipient_limit = 16 smtpd_soft_error_limit = 3 smtpd_hard_error_limit = 12 # Requirements for the HELO statement smtpd_helo_restrictions = permit_mynetworks, warn_if_reject reject_non_fqdn_hostname, reject_invalid_hostname, permit # Requirements for the sender details smtpd_sender_restrictions = permit_mynetworks, warn_if_reject reject_non_fqdn_sender, reject_unknown_sender_domain, reject_unauth_$ # Requirements for the connecting server smtpd_client_restrictions = reject_rbl_client sbl.spamhaus.org, reject_rbl_client blackholes.easynet.nl, reject_rbl_client dnsbl.n$ # Requirement for the recipient address smtpd_recipient_restrictions = reject_unauth_pipelining, permit_mynetworks, reject_non_fqdn_recipient, reject_unknown_recipient_do$ # require proper helo at connections smtpd_helo_required = yes # waste spammers time before rejecting them smtpd_delay_reject = yes disable_vrfy_command = yes Here is also my /etc/postfix/aliases: # See man 5 aliases for format postmaster: root Here is also my /etc/mailname: nairanode.com I've also updated my hostname to nairanode.com However, when I run postalias /etc/postfix/aliases I get the following : postalias: warning: valid_hostname: invalid character 47(decimal): /etc/mailname postalias: fatal: file /etc/postfix/main.cf: parameter mydomain: bad parameter value: /etc/mailname Is there something I'm doing wrong?! I noticed that when I replace myorigin = /etc/mailname with myorigin = nairanode.com in my postfix config, I don't see any errors anymore after calling postalias. Is this a bug or something?!

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• How can this closure test be written in other languages?

  - by Jian Lin

  I wonder how the following closure test can be written in other languages, such as C and Java. Can the same result be expected also in Perl, Python, and PHP? Ideally, we don't need to make a new local variable such as x and assign it the value of i inside the loop, but just so that i has a new copy in the new scope each time. (if possible). (some discussion is in this question.) The following is in Ruby, the "1.8.6" on the first line of result is the Ruby version which can be ignored. p RUBY_VERSION $foo = [] (1..5).each do |i| $foo[i] = lambda { p i } end (1..5).each do |j| $foo[j].call() end the print out is: [MacBook01:~] $ ruby scope.rb "1.8.6" 1 2 3 4 5 [MacBook01:~] $ Contrast that with another test, with i defined outside: p RUBY_VERSION $foo = [] i = 0 (1..5).each do |i| $foo[i] = lambda { p i } end (1..5).each do |j| $foo[j].call() end the print out: [MacBook01:~] $ ruby scope2.rb "1.8.6" 5 5 5 5 5 [MacBook01:~] $

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• How to set a local image in pynotify?

  - by George Edison

  If I run the following in python in Ubuntu 10.04: >>> import pynotify >>> p = pynotify.Notification ("Notice","","/home/george/Pictures/test.png") >>> p.show() true The message displays as expected, except the image does not appear in the OSD. How can I display a local image? In fact, for what I need, it would be better if I could display a remote image. (via HTTP) How can I do that?

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• What is a Web Framework ? How does it compare with LAMP

  - by Nishant

  I started web development in LAMP/WAMP and it was logical to me . There is a Web Server program called Apache which does the networking part of setting up a service on port 80 ( common port ) . If the request is regular HTML it uses the HTTP headers to transport files .And if the request for the file is a PHP one , it has a mod_php with which Apache invokes the PHP interpreter to process the file and it gives back HTML which is again transferred as usual HTML . Now the question is what is a Web Framework ? I came across Python based website creation and there is Flask . What is a flask , how does it compare with LAMP . Further are DJango / Ruby on Rails different from flask ? Can someone answer me and also give some good places to read on these .Thanks for your answers in advance . Further is things like LAMP slower than the common FRAMEWORKS because they claimn easy deplyment fo web apps .

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• Calculating spam probability

  - by Hobhouse

  I am building a website in python/django and want to predict wether a user submission is valid or wether it is spam. Users have an accept rate on their submissions, like this website has. Users can moderate other users' submissions; and these moderations are later metamoderated by an admin. Given this: user A with an submission accept rate of 60% submits something. user B moderates A's post as a valid submission. However, his moderations are often wrong, and his moderations' accept rate is a mere 30%. user C moderates A's post as spam. User C is usually right. His moderations' accept rate is 80%. How can I predict the chance of A's post being spam?

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• Django - Tips to avoid repeating code in views

  - by D Roddis

  I'm moving from a PHP background into Django development via python, mostly for the sake of tackling a MVC (or MVT) that I feel makes the most sense, although in this pattern I've started to notice a lot of repeated code in my views. For example, when logged in I have information regarding the user that I would like to appear on every page, although when using render_to_response and in every view this is required I have to grab the information and pass it to the render_to_response function. I'm wondering what would be the most efficient way to cut down on the duplicate code which would in essence be required in all views in a particular app. Thanks in advance.

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• How to instantly termainate an un-supervised script on demand?

  - by errr

  I have a GUI which resembles an interpreter. It allows the user to write a script in Jython (implementation of Python in Java) and run it whenever he wants. Apart from that, I also wish to allow the user to instantly terminate the run whenever he wants. Thing is, I don't really know how to do it. The script is being run on a different Thread, but I don't know of any secure way to stop/interrupt/terminate a thread in the middle of its run, let alone not knowing what is being run by the thread/script (it could be a simple task or maybe some sort of a heavy SQL query against a DB, and a DB is something which requires careful resource handling). How can I instantly terminate such run on demand?

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• REST API for driving distance?

  - by Mark

  Is there a service that will give me the driving distance between two addresses? Apparently Google Maps API requires you to display a map, which I don't want to do (on that particular page), and I'd like to just snag the data and save it to my DB after a user submits a form, rather than waiting for JS to do it's thing. If it's relevant, this is going into a Django app. I discovered that CloudMade offers a Python API, which is nice, except their latest dev release has a bug in it (can't use the API object), but more importantly, it's support for Canada is awful/worthless (couldn't find directions from any major city around here!).

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• Java vs Flash for webcam access

  - by Alfredo Palhares

  I will make a video chat website, but coming from PHP and Python for the web i have no experience with video steaming. What do you recommend? Java or Flash? What's more flexible ? I am thinking of even making a C++ server application for stream controlling with a PHP fronted. Since is going to be a high traffic website and performance is a must. Can you point to some direction? Any documentation? Framework?

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• How to extract all IDs accessed from a mysql general log using the linux commandline?

  - by shlomoid

  This should be a trivial question for anyone who's good with bash/sed/awk. Unfortunately, I'm not, yet :) I've got a general log from MySQL which contains some queries that have a common parameter, they query on a specific id field. The queries look like update tbl set col='binary_values' where id=X; I need to process the log and extract all the IDs that these queries touched, each in it's own line. The purpose of this is to figure out how many times each ID is accessed. Eventually I'd group and count the values. The binary values are indeed binary junk, so they kinda messed up some things I've been trying to do. Eventually we solved the problem temporarily using a python script, but I'm sure the linux command line tool set can do it too. How would you do it?

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• When compiling programs to run inside a VM, what should march and mtune be set to?

  - by Russ

  With VMs being slave to whatever the host machine is providing, what compiler flags should be provided to gcc? I would normally think that -march=native would be what you would use when compiling for a dedicated box, but the fine detail that -march=native is going to as indicated in this article makes me extremely wary of using it. So... what to set -march and -mtune to inside a VM? For a specific example... My specific case right now is compiling python (and more) in a linux guest inside a KVM-based "cloud" host that I have no real control over the host hardware (aside from 'simple' stuff like CPU GHz m CPU count, and available RAM). Currently, cpuinfo tells me I've got an "AMD Opteron(tm) Processor 6176" but I honestly don't know (yet) if that is reliable and whether the guest can get moved around to different architectures on me to meet the host's infrastructure shuffling needs (sounds hairy/unlikely). All I can really guarantee is my OS, which is a 64-bit linux kernel where uname -m yields x86_64.

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• Custom User Management for Google App Engine Java

  - by Gopi

  I am using GAE Java for a multi-user application. There are multiple users with different roles. Each user can login, do some operations and logout. The business restricts me from using Google User Service and I need to implement my own for authentication and session management. Can anyone please share with me how should I go about implementing my own user management? I have read its very tricky to implement own user management. Any pointers in terms of best approaches/ design / existing frameworks if any ? I could see some similar posts but they are for python.

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• Devising a test strategy

  - by Simon Callan

  As part of a new job, I have to devise and implement a complete test strategy for the companies new product. So far, all I really know about it is that it is written in C++, uses an SQL database and has a web API which is used by a browser client written using GWT. As far as I know, there isn't much of an existing strategy, except for using Python scripts to test the web API. I need to develop and implement a suitable strategy for unit, system, regression and release testing, preferably a fully automated one. I'm looking for good references for : Devising the complete test strategy. Testing the web API. Testing the GWT based application. Unit testing C++ code. In addition, any suitable tools would be appreciate

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• How can I mark a file as descended from 2 other files in Mercurial?

  - by Matt Joiner

  I had 2 Python similar scripts, that I've since merged into one (and now takes some parameters to differ the behaviour appropriately). Both of the previous files are in the tip of my Mercurial repository. How can I indicate that the new file, is a combination of the 2 older files that I intend to remove? Also note, that 1 file has been chosen in favor of the other, and some code moved across, so if it's not possible to create a version controlled file with a new name, then assimilating one file's history into the other will suffice.

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• Postfix issues sending mail to addresses under domain located on server

  - by iamthewit

  I recently installed virtualmin on my nice shiny new rackspace cloud. Everything went seemlessly but I've been having some issues getting emails to send properly. The problem seems to be that the server can not send mail to email addresses where the domain is owned by my server. For example, on my server I run multiple virtual domains, lets call this one test.com. When I run the mail command from shell (mail [email protected]) I get the following back from my maillog: Oct 6 14:55:18 test postfix/pickup[8737]: DC1131612CC: uid=0 from= Oct 6 14:55:18 test postfix/cleanup[8769]: DC1131612CC: [email protected] Oct 6 14:55:18 test postfix/qmgr[8738]: DC1131612CC: [email protected], size=353, nrcpt=1 (queue active) Oct 6 14:55:18 test postfix/error[8771]: DC1131612CC: [email protected], relay=none, delay=0, delays=0/0/0/0, dsn=5.0.0, status=bounced (User unknown in virtual alias table) Oct 6 14:55:18 test postfix/cleanup[8769]: DD07D1612D1: [email protected] Oct 6 14:55:18 test postfix/bounce[8772]: DC1131612CC: sender non-delivery notification: DD07D1612D1 Oct 6 14:55:18 test postfix/qmgr[8738]: DD07D1612D1: from=<, size=2268, nrcpt=1 (queue active) Oct 6 14:55:18 test postfix/qmgr[8738]: DC1131612CC: removed Oct 6 14:55:18 test postfix/local[8773]: DD07D1612D1: [email protected], relay=local, delay=0.03, delays=0/0/0/0.03, dsn=2.0.0, status=sent (delivered to command: /usr/bin/procmail-wrapper -o -a $DOMAIN -d $LOGNAME) Oct 6 14:55:18 test postfix/qmgr[8738]: DD07D1612D1: removed when I run mail [email protected] the message is sent and received perfectly fine. I'm a bit of a noob when it comes to servers, but I pick things up fairly quickly, so please excuse any incorrect terminology and my general noobiness. Any help would be greatly appreciated, I've been googling for quite a while but I haven't found a solution yet, I'll add a copy of my main.cf file in a response below cheers guys here is the reformatted postconf, do you want the reformatted main.cf file too, or is this enough? alias_database = hash:/etc/postfix/aliases alias_maps = hash:/etc/postfix/aliases broken_sasl_auth_clients = yes command_directory = /usr/sbin config_directory = /etc/postfix daemon_directory = /usr/libexec/postfix debug_peer_level = 2 home_mailbox = Maildir/ html_directory = no mailbox_command = /usr/bin/procmail-wrapper -o -a $DOMAIN -d $LOGNAME mailq_path = /usr/bin/mailq.postfix manpage_directory = /usr/share/man myhostname = server.test.com newaliases_path = /usr/bin/newaliases.postfix readme_directory = /usr/share/doc/postfix-2.3.3/README_FILES sample_directory = /usr/share/doc/postfix-2.3.3/samples sender_bcc_maps = hash:/etc/postfix/bcc sendmail_path = /usr/sbin/sendmail.postfix setgid_group = postdrop smtpd_recipient_restrictions = permit_mynetworks permit_sasl_authenticated reject_unauth_destination smtpd_sasl_auth_enable = yes smtpd_sasl_security_options = noanonymous unknown_local_recipient_reject_code = 550 virtual_alias_maps = hash:/etc/postfix/virtual

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• What is a good Very-High level UI framework for JavaScript?

  - by Robert Gould

  I need to write a temporary Web-based graphical front-end for a custom server system. In this case performance and scalability aren't issues, since at most 10 people may check the system simultaneously. Also it should be PHP or Python (server) & JavaScript (client) (can't use Flex or Silverlight for very specific non-programming related issues). So I know I could use YUI or jQuery, but was wondering if there is something even more high-level that would say allow me to write such a little project within a few hours of work, and get done with it. Basically I want to be as lazy as possible (this is throw-away code anyways) and get the job done in as little time as possible. Any suggestions?

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• PHP - Frameworks, ORM, Encapsulation.

  - by Ian

  Programming languages/environments aside, are there many developers who are using a framework in PHP, ORM and still abide by encapsulation for the DAL/BLL? I'm managing a team of a few developers and am finding that most of the frameworks require me to do daily code inspection because my developers are using the built in ORM. Right now, I've been using a tool to generate the classes and CRUD myself, with an area for them to write additional queries/functions. What's been happening though, is they are creating vulnerabilities by not doing proper checks on data permission, or allowing the key fields to be manipulated in the form. Any suggestions, other than get a new team and a new language (I've seen Python/Ruby frameworks have the same issues).

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• inews failed: "No colon-space in "X-MS-TNEF-Correlator:"

  - by wolfgangsz

  We run a news server for our engineering teams, which is also linked to the code repositories (so that all engineers can subscribe to any changes in the repos or just the projects they are interested in). On quite a regular basis (several times a day) I (as the sysadmin for that server) receive bounces from innd with the above as the first line. The news server simply rejects these messages and the articles don't get posted. Here is an example: inews failed: inews: cannot send article to server: 441 437 No colon-space in "X-MS-TNEF-Correlator:" header inews: article not posted -------- Article Contents Path: aminocom.com!ctaylor From: [email protected] (Cameron Taylor) Newsgroups: amino.qa.reports Content-Language: en-US Content-Type: multipart/alternative; boundary="_000_A2AB95742ADD524795C13EDE8F8CCD201A798C0Eukswaex01_" MIME-Version: 1.0 Subject: [QA REPORT] MDK 400 release 3.4.33 **PRE-RELEASE** Message-ID: Date: Thu, 9 Sep 2010 16:15:16 +0000 X-Received: from uk-swa-ex02.aminocom.com (uk-swa-ex02.aminocom.com [10.171.3.10]) by theoline.aminocom.com (8.14.3/8.13.8) with ESMTP id o89GF8tx019494 for ; Thu, 9 Sep 2010 17:15:08 +0100 X-Received: from uk-swa-ex01.aminocom.com ([10.171.3.9]) by uk-swa-ex02 ([10.171.3.10]) with mapi; Thu, 9 Sep 2010 17:15:18 +0100 X-To: QA Reports X-Thread-Topic: [QA REPORT] MDK 400 release 3.4.33 **PRE-RELEASE** X-Thread-Index: ActQOjBdms0CSJsORNSxRIMSZ4H3Ow== X-Accept-Language: en-US, en-GB X-MS-Has-Attach: X-MS-TNEF-Correlator: X-Auto-Response-Suppress: DR, OOF, AutoReply --_000_A2AB95742ADD524795C13EDE8F8CCD201A798C0Eukswaex01_ Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable SQA Test Report [QA REPORT] MDK 400 release 3.4.33 **PRE-RELEASE** Status .... (rest of the message is not important) And yes, quite clearly this header doesn't have anything after the colon. The man page for innd doesn't specify why it rejects these messages, it just says it rejects them. So far I have found out these headers are linked to messages in RTF format (coming from Outlook clients), where normally the formatting information would be stored in a winmail.dat attachment. The clients all use MS Exchange 2010 servers to send their mail (identified above as uk-swa-ex02.aminocom.com) which forwards the message to the news server. Does anybody know what advice I need to give these users to avoid their articles getting bounced? Or can I change the behaviour of innd? Or do I need to filter these headers out before innd processes the articles?

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• How can I implement incremental (find-as-you-type) search on command line?

  - by florianbw

  I'd like to write small scripts which feature incremental search (find-as-you-type) on the command line. Use case: I have my mobile phone connected via USB, Using gammu --sendsms TEXT I can write text messages. I have the phonebook as CSV, and want to search-as-i-type on that. What's the easiest/best way to do it? It might be in bash/zsh/Perl/Python or any other scripting language. Edit: Solution: Modifying Term::Complete (http://search.cpan.org/~jesse/perl-5.12.0/lib/Term/Complete.pm) did what I want. See below for the answer.

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• How to tune system settings for mongoDB on Linux?

  - by jsh

  Trying to squeeze a lot out of one question here -- please bear with me. Although the MongoDB man pages make several useful recommendations about system settings like ulimit (http://docs.mongodb.org/manual/reference/ulimit/), and other production factors (http://docs.mongodb.org/manual/administration/production-notes/) they seem mysteriously silent on things like virtual memory and swap settings. The closest we get to a hint is that "...the operating system’s virtual memory subsystem manages MongoDB’s memory..." (http://docs.mongodb.org/manual/faq/fundamentals/#does-mongodb-require-a-lot-of-ram). Running the same job - high writes and high reads on about 10,000,000 records in a single collection -- on my 4-processor, 4GB RAM macbook and an 8-core ubuntu box with 64GB RAM I saw dramatically WORSE read performance on the linux box with factory settings, and could hear the disk constantly spinning, indicating high I/O and presumably swapping. Yes, other things were happening on the box, but there was plenty of free RAM, disk space, etc.; furthermore, I did not see evidence that Mongo was expanding to take advantage of all that free RAM as it is touted to do. Linux box default settings were as follows: vm.swappiness =60 vm.dirty_background_ratio = 10 vm.dirty_ratio = 20 vm.dirty_expire_centisecs =3000 vm.dirty_writeback_centisecs=500 I hazarded some guesses looking at docs and blogs for other types of databases (Oracle, MYSQL, etc.), experimented, and adjusted as below. vm.swappiness=10 vm.dirty_background_ratio=5 vm.dirty_ratio=5 vm.dirty_writeback_centisecs=250 vm.dirty_expire_centisecs=500 I saw some immediate apparent improvements in read time. However, when I ran my test jobs again, read performance continued to be painfully sluggish during heavy writes. Then, I REBUILT the collection from an available data source - and suddenly I can read at 1ms or less per record WHILE doing the write job! So the question is really two-fold: 1) What are appropriate VM settings for MongoDB on Linux? 2) (bonus) Does Mongo do some checking or optimization with the OS while data is being built? In other words, if I have built a large data set with suboptimal VM or I/O settings, does Mongo make assumptions during the memory-mapping process that will fail to take advantage of optimizations down the road? Obviously I don't fully grok memory mapping under the hood (I was hoping I wouldn't have to). Any help appreciated...thanks! -j

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