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• Road Warrior VPN Setup

  - by wobblycogs

  I apologise up front for the rather open ended nature of this question but I've got well out of my depth and could really do with some pointers. I need to set up a road warrior VPN solution which will allow our customers to securely access a number of services we provide for them. Customer machines will be running a variety of Windows versions from XP onwards with a variety of patch levels. Typically they will connect from the clients main offices but not always. It is safe to assume that all clients will be behind NATs but we may occasionally see a connection that isn't NAT'ed. Typical connection situation is therefore: Customer Laptop -- Router (NAT) -- Internet -- VPN Server + Firewall -- Server (Win 2008 R2, Non-routable IP) There will initially be a dozen or so people that could connect but that will grow quickly to around 100. It's unlikely that we'll see that many concurrent connections though, I imagine our total VPN throughput would be <50Mbps peak. What are my options for setting this up? I've been trying to set up a system like this using a MikroTik router for a few days but have struggled to get it working correctly, particularly with NAT'ed clients. I've had a quick look at OpenVPN and liked what I saw but I think it's unlikely our customers IT departments would allow the client to be installed. Finally I've looked at the Cisco ASA range but I'm on a fairly tight budget so this is less preferable but it looks like it would work pretty much out of the box. My fall back position is to connect the server directly and use the provided VPN + Firewall facilities but that is far from ideal as the number of servers is likely to grow over time.

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• how to go about scaling a web-application ?

  - by phoenix24

  for someone whoes been primarily a web-application developer, and know not much about scaling/scalability techniques. I'll start by stating my application is written in Python, using Django; a fairly standard setup. I currently use Apache 2.2 for my webserver, and MySql for my database server; both running on the same vps server. Up until now, it was basically a prototype and merely 15-30 concurrent users at any given time; so I had no issues, but now since we'll be adding more users we'll have severe performance issues. So my question is how do i go about scaling my web-application? and my plan is as follows. Now I have just one vps server running, apache + mysql. Next, I plan to add another vps server, to run only MySql; so i'll have one web-server and one db server. Next, I'll add Memcache to the webserver for caching data; and taking some load off mysql. Next, another web-server for serving all the static content; Next, a vps server for load-balancing (nginx/varnish) behind which would be my two web-servers and then db-server. Does that sound like a workable strategy, please guide me around here.

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• How to correctly calculate address spaces?

  - by user337308

  Below is an example of a question given on my last test in a Computer Engineering course. Anyone mind explaining to me how to get the start/end addresses of each? I have listed the correct answers at the bottom... The MSP430F2410 device has an address space of 64 KB (the basic MSP430 architecture). Fill in the table below if we know the following. The first 16 bytes of the address space (starting at the address 0x0000) is reserved for special function registers (IE1, IE2, IFG1, IFG2, etc.), the next 240 bytes is reserved for 8-bit peripheral devices, and the next 256 bytes is reserved for 16-bit peripheral devices. The RAM memory capacity is 2 Kbytes and it starts at the address 0x1100. At the top of the address space is 56KB of flash memory reserved for code and interrupt vector table. What Start Address End Address Special Function Registers (16 bytes) 0x0000 0x000F 8-bit peripheral devices (240 bytes) 0x0010 0x00FF 16-bit peripheral devices (256 bytes) 0x0100 0x01FF RAM memory (2 Kbytes) 0x1100 0x18FF Flash Memory (56 Kbytes) 0x2000 0xFFFF

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• Nginx + PHP-FPM Too Many Resources

  - by user3393046

  My Server has the following Specs CPU: 6 Cores Intel(R) Xeon(R) CPU E5-2650 v2 @ 2.60GHz RAM: 32 GB I have a problem with nginx+php-fpm. They are taking too many resources for an unknown reason. Even if i restart the nginx + php-fpm the start up processes will use many resources. My nginx Config is the following: user nginx; worker_processes auto; error_log /var/log/nginx/error.log warn; pid /var/run/nginx.pid; worker_rlimit_nofile 300000; events { worker_connections 6000; use epoll; } http { include /etc/nginx/mime.types; default_type application/octet-stream; log_format main '$remote_addr - $remote_user [$time_local] "$request" ' '$status $body_bytes_sent "$http_referer" ' '"$http_user_agent" "$http_x_forwarded_for"'; access_log /var/log/nginx/access.log main; sendfile on; #tcp_nopush on; keepalive_timeout 65; #gzip on; include /etc/nginx/conf.d/*.conf; } My php-fpm pool config is the following [www] user = nginx group = nginx listen = /var/run/php5-fpm.sock listen.owner = nginx listen.group = nginx listen.allowed_clients = 127.0.0.1 pm = ondemand pm.max_children = 1500; pm.process_idle_timeout = 5; chdir = / security.limit_extensions = .php I'm using on pm.ondemand since my website has to support many concurrent connections at the same time and i was unable to to it with dynamic/static. I guess this isnt the problem because as i said earlier when i restart nginx+php-fpm at the same time, they are taking too much resources without any request. Here is the screenshot with the CPU Usage http://s28.postimg.org/v54q25zod/Untitled.png

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• Requests per second slower when using nginx for load balancing

  - by Ed Eliot

  I've set up nginx as a load balancer that reverse proxies requests to 2 Apache servers. I've benchmarked the setup with ab and am getting approx 35 requests per second with requests distributed between the 2 backend servers (not using ip_hash). What is confusing me is that if I query either of the backend servers directly via ab I get around 50 requests per second. I've experimented with a number of different values in ab the most common being 1000 requests with 100 concurrent connections. Any idea why traffic distributed across 2 servers would result in fewer requests per second than hitting either directly? Additional info: I've experimented with worker_processes values of between 1 and 8, worker_connections between 1024 and 8092 and have also tried keepalive 0 and 65. My main conf currently looks like this: user www-data; worker_processes 1; error_log /var/log/nginx/error.log; pid /var/run/nginx.pid; worker_rlimit_nofile 8192; events { worker_connections 2048; use epoll; } http { include /etc/nginx/mime.types; sendfile on; keepalive_timeout 0; tcp_nodelay on; gzip on; gzip_disable "MSIE [1-6]\.(?!.*SV1)"; include /etc/nginx/conf.d/*.conf; include /etc/nginx/sites-enabled/*; } I've got one virtual host (in sites available) that redirects everything under / to 2 backends across a local network.

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• recursive function's summation in MATLAB

  - by lucky

  B=[1 1 1 1 1 1....1] % vector of length N elements Xk= sin(2*pi/16) i need to find function alpha(l,k) which is having two variables l and k and a condition given that alpha(l,0)=alpha(l,-1)=alpha(l,-2)......=alpha(l,-(N-1))=0 i.e no matter what value of l ,alpha = 0 for past values A= input('no of iterations'); % no. of iterations user want N=input('N values of alpha:') alpha1=[]; for k=0:A-1 l=0:N-1 % need 10 separate alpha values for every k, which goes from 0 to A-1 alpha(l,k)= Xk + summation( B(j)*alpha(l,k-j)) % as summation goes from j=1 to N alpha1=[alpha1 alpha] end; could anyone please help me to solve this recursive function, i am new to matlab. alpha

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• dose not name a type error in c++

  - by user985316

  #include <math.h> #include <stdlib.h> #include <stdio.h> #include <vector> #define IE 40 #define JE 40 #define KE 40 #define ia 7 #define ja 7 #define ka 7 #define NFREQS 3 using namespace std; main() float l,m,n,i,j,k,ic,jc,kc,nsteps,n_pml; float ddx,dt,T,epsz,muz,pi,eaf,npml; int ib,jb,kb; . . . . ic=IE*0.5 ; jc=JE*0.5 ; ....'ic'dose not name a type. ....'jc'dose not name a type.

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• How to override ggplot2's axis formatting?

  - by Richie Cotton

  When you choose a log scale, ggplot2 formats the breaks like 10^x. I'd like it to not do that. For example, the code below should display a graph with ticks at 1, 2, 5 etc, not 10^0, 10^0.3, 10^0.69 etc. library(ggplot2) dfr <- data.frame(x = 1:100, y = rlnorm(100)) breaks <- as.vector(c(1, 2, 5) %o% 10^(-1:1)) p1 <- ggplot(dfr, aes(x, y)) + geom_point() + scale_y_log10(breaks = breaks) print(p1) I guess that adding a formatter argument to scale_y_log10 would do the trick, but I'm not sure what to put in the argument, or where the options might be documented.

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• In using Samsung acclerometer

  - by cheesebunz

  Hi everyone , i have this sample code i want to use. I'm not sure where to place it. I'm using Visual studio 2008 , windows mobile 6 sdk. I wish to test the accelerometer but i'm not sure where i should code it. The start is e.g. form1. Do i create new existing item new program.cs a new C# file and do this(as of below)? #include "smiAccelerometer.h" SmiAccelerometerVector accel; // get the acceleration vector containing X, Y, Z components if (SmiAccelerometerGetVector(&accel) == SMI_SUCCESS) { // Successfully got acceleration. // Use accel.x, accel.y and accel.z in your application } else { // failed to get the acceleration }

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• matlab noninteger step indexing

  - by rlbond

  So, I have a vector: k = 1:100; And I want to take 19 elements from it, which are roughly equally-spaced. So I write this: m = k(1:(99/18):end); This works great, except for a tiny problem: Warning: Integer operands are required for colon operator when used as index m = 1 7 12 18 23 29 34 40 45 51 56 62 67 73 78 84 89 95 100 Now, I understand why this comes up, but I'd like to get rid of that warning. Is there a "right" way to do this without a warning?

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• 3 hash functions to best hash sliding window strings for a bloom filter with minimum collisions

  - by Duaa

  Hi all: I need 3 hash functions to hash strings of a sliding window moving over a text, to be used later to search within a bloom vector. I'm using C# in my programming I read something about rolling hash functions and cyclic polynomials, they are used for sliding window applications. But really, I did not find any codes, they are just descriptions So please, if anyone have any idea about 3 best C# hash functions to use with sliding window strings of fixed size (5-char), that consume less time and have minimum number of collisions, either they are rolling hash functions or others, please help me with some C# codes or links to hash functions names Duaa

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• How to find all clusters of forest on map?

  - by Damir

  How to find all clusters of forest on map ? I have simple class cell like (Type is enum {RIVER, FOREST,GRASS,HILL} class Cell{ public: Type type; int x; int y }; and map like vector<Cell> grid. Can anyone suggest me algorithm to create list<list<Cell>> clusters where list contains FOREST cells in same cluster (cluster are set of connected cells - connection can be in eight direction:up,down,left,right,up_right,up_left,down_left,down_right)? I need to find all clusters of forest on map and put every single cluster in list<Cell>.

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• Using Python tuples as vectors

  - by Etaoin

  I need to represent immutable vectors in Python ("vectors" as in linear algebra, not as in programming). The tuple seems like an obvious choice. The trouble is when I need to implement things like addition and scalar multiplication. If a and b are vectors, and c is a number, the best I can think of is this: tuple(map(lambda x,y: x + y, a, b)) # add vectors 'a' and 'b' tuple(map(lambda x: x * c, a)) # multiply vector 'a' by scalar 'c' which seems inelegant; there should be a clearer, simpler way to get this done -- not to mention avoiding the call to tuple, since map returns a list. Is there a better option?

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• C++ - dynamic pointer of array

  - by Eagle

  Hi to all, first i would like to say i am Newbie in C++. As part of my master thesis i am writing a program in C++ which also get as parameters the variables m and d (both integers). Were d is the power of 2 (this means 2^d elements). Parameter m define the number of possible interactions between one element and the total group (2^d elements). The number of possible interactions is computed as following: \kappa = \sum_{i=0}^m\binom{d}{i} (at present i generate vector of vectors for 2^d x \kappa, but my Prof. would like me to create different statistics to different m's. My first though was to to generate a dynamic array of m arrays of different sizes... Then i though of defining a 3-dim array with the biggest needed 2d array, but also program speed is important (e.g d = 20). i would like to ask for your advice how to define such kind of dynamic array that will also be fast. Regards

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• Rotate a feature Image in Open Layers

  - by Ozaki

  I have an open layers map. It adds and removes my "imageFeature" every 10secs or so. I have a JSON feed that gives me the rotation that I need, I have a request to get that rotation and set it as a variable of rotationv. Everything works but the fact when the image is recreated it does not update the rotation. My code is as follows: JSON request: var rotationv = (function () { rotationv = null; $.ajax({ 'async': false, 'global': true, 'url': urldefault, 'dataType': "json", 'success': function (data) { rotationv = data.rotation; } }); return rotationv })(); Creating image feature: imageFeature = new OpenLayers.Feature.Vector( new OpenLayers.Geometry.Point(mylon, mylat), { rotation: rotationv } ); The image is set in the styling elsewhere. Why does this not rotate my image?

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• Make Map Key Sorted According To Insert Sequence

  - by Yan Cheng CHEOK

  Without help from additional container (like vector), is it possible that I can make map's key sorted same sequence as insertion sequence? #include <map> #include <iostream> using namespace std; int main() { map<const char*, int> m; m["c"] = 2; m["b"] = 2; m["a"] = 2; m["d"] = 2; for (map<const char*, int>::iterator begin = m.begin(); begin != m.end(); begin++) { // How can I get the loop sequence same as my insert sequence. // c, b, a, d std::cout << begin->first << std::endl; } getchar(); }

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• The Cleanest Reset for ARM Processor

  - by waffleman

  Lately, I've been cleaning up some some C code that runs on an ARM7 controller. In some situations (upgrade, fatal error, etc...) the program will perform a reset. Presently it just jumps to 0 and assumes that the start-up code will reinitialize everything correctly. It got me to thinking about what would be the best procedure a la "Leave No Trace" for an ARM reset. Here is my first crack at it: void Reset(void) { /* Disable interrupts */ __disable_interrupts(); /* Reset peripherals, externals and processor */ AT91C_BASE_RSTC->RSTC_RCR = AT91C_RSTC_KEY | AT91C_RSTC_PERRST | AT91C_RSTC_EXTRST| AT91C_RSTC_PROCRST; while(AT91C_BASE_RSTC->RSTC_RSR & AT91C_RSTC_SRCMP); /* Jump to the reset vector */ (*(void(*)())0)(); } Anything I haven't considered?

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• IIS 7.5 truncating POST body containing JSON data with ASP.NET MVC 3

  - by Guneet Sahai

  I'm facing a problem which I hope is a configuration thing with IIS but is right now giving a lot of trouble. Basically I have a controller that accepts a JSON and does some processing. While it generally works fine, but every now and then when the system has some load I get an error. After some painful debugging, we figured the incoming JSON gets truncated which causes the deserialzer to fail. To narrow down the problem - we wrote a simple controller that accepts a JSON and tries to deserialize it. In case it fails it just logs it. This works fine but when I hit it using a load testing tool (JMeter) it throws the same error (truncation) for a few requests. The # of failures increased when I increase parallel connections. It starts showing with 150 concurrent requests. We are running IIS 7 on windows 2008 server with ASP.Net MVC 3 with more or less default configuration of IIS. More information available in my question below http://stackoverflow.com/questions/12662282/content-length-of-http-request-body-size

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• Online chart editor

  - by Alexander Gladysh

  I love to use Google Documents as MS Word and MS Excel replacements for online collaboration. However, now I need to discuss architecture layout for my software. Nothing too fancy, perhaps a little (pseudo-)UML, but mostly basic shapes (rectangles, ellipses etc.) with labels, connected by thin lines or arrows. In olden Windows times I'd go for Visio, and be happy. But now I want to use online tool. Preferably free. No need for code reverse engineering etc., just plain assisted vector drawing. Any advice? What do you use?

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• code throws std::bad_alloc, not enough memory or can it be a bug?

  - by Andreas

  I am parsing using a pretty large grammar (1.1 GB, it's data-oriented parsing). The parser I use (bitpar) is said to be optimized for highly ambiguous grammars. I'm getting this error: 1terminate called after throwing an instance of 'std::bad_alloc' what(): St9bad_alloc dotest.sh: line 11: 16686 Aborted bitpar -p -b 1 -s top -u unknownwordsm -w pos.dfsa /tmp/gsyntax.pcfg /tmp/gsyntax.lex arbobanko.test arbobanko.results Is there hope? Does it mean that it has ran out of memory? It uses about 15 GB before it crashes. The machine I'm using has 32 GB of RAM, plus swap as well. It crashes before outputting a single parse tree. The parser is an efficient CYK chart parser using bit vector representations; I presume it is already near the limit of memory efficiency. If it really requires too much memory I could sample from the grammar rules, but this will decrease parse accuracy of course.

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• log4j: Change format of loggers configured in another library.

  - by Ignacio Thayer

  Using clojure, I've been able to successfully setup log4j very simply by using this log4j.properties file, and including log4j in my classpath. # BEGIN log4j.properties log4j.appender.STDOUT=org.apache.log4j.ConsoleAppender log4j.appender.STDOUT.layout=org.apache.log4j.PatternLayout log4j.appender.STDOUT.layout.ConversionPattern=%d{MMdd HHmmss SSS} %5p %c [%t] %m\n log4j.rootLogger=DEBUG, STDOUT Then after :use'ing clojure.contrib.logging, I'm able to print a statement with the desired formatting as expected like so: (info "About to print this") (debug "This is debug-level") My question is how to achieve a consistent formatting for logging statements made from loggers configured in other libraries. I thought I could find existing loggers using org.apache.log4j.LogManager.getCurrentLoggers() and change the PatternLayouts there, but I'm not able to iterate over that enumeration in clojure, as I get the following error: Dont know how to create ISeq from: java.util.Vector$1 I assume this is possible somehow, and probably very simply. How? Thanks much.

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• Under what conditions will sendmail try to immediately resend a message instead of waiting for the standard requeue interval?

  - by Mike B

  CentOS 5.8 | Sendmail 8.14.4 I used to think that if SendMail experienced a temporary (400-class) error during delivery, it would place the message in a deferred queue (e.g. /var/spool/mqueue) and retry an hour later. For the most part, that appears to be the case. But every now and then, I'll notice log entries like this (email/domains renamed to protect the innocent :-) ) : Dec 5 01:43:03 foobox-out sendmail [11078]: qBE3l7js123022: to=<[email protected]>, delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=124588, relay=exbox.foo.com. [10.10.10.10], dsn=4.0.0, stat=Deferred: 421 4.3.2 The maximum number of concurrent connections has exceeded a limit, closing transmission channel Dec 5 01:53:34 foobox-out sendmail [12763]: qBE3l7js123022: to=<[email protected]>, delay=00:10:31, xdelay=00:00:00, mailer=relay, pri=214588, relay=exbox.foo.com., dsn=4.0.0, stat=Deferred: 452 4.3.1 Insufficient system resources Dec 5 02:53:35 foobox-out sendmail [23255]: qBE3l7js123022: to=<[email protected]>, delay=01:10:32, xdelay=00:00:01, mailer=relay, pri=304588, relay=exbox.foo.com. [10.10.10.10], dsn=2.0.0, stat=Sent (<[email protected]> Queued mail for delivery) Why did Sendmail try again just 10 minutes after the first attempt and then wait another hour before trying again? If this is expected behavior, what scenarios will cause this faster requeue interval to occur?

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• Is it safe to use the same parameters for input and output in D3DX functions?

  - by JB

  Using the D3DX library that is a part of directX, specifically directx9 in this case, I'm wondering if it's safe to use the same matrix (or vector etc) for input and ouput D3DXMATRIX mat; D3DXMatrixInverse(&mat, NULL, &mat); I've been avoiding doing so, assuming that it would result in bad things happening when parts of the array got partly overwritten as results are calculated but I see an awful lot of code around that does exactly this. A brief test indicates that it seems to work ok, so I'm assuming that the D3DX functions take a copy where necessary of the input data, or some other method to ensure that this works ok, but I can't find it documented anywhere so I'm reluctant to rely on it working. Is there any official statement on using the functions like this?

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• Calculating 2D angles for 3D objects in perspective

  - by Will

  Imagine a photo, with the face of a building marked out. Its given that the face of the building is a rectangle, with 90 degree corners. However, because its a photo, perspective will be involved and the parallel edges of the face will converge on the horizon. With such a rectangle, is it possible to calculate the angle in 2D of the edges of a face that is 90 degrees to it? In the image below, the blue is the face marked on the photo, and I'm wondering how to calculate the 2D vector of the red lines of the other face:

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• E4X in ActionScript

  - by Brian Genisio

  Hey all, Looking at the E4X implementation in ActionScript, it occurs to me that they had to figure out how to do three things that I am not sure can be done within ActionScript regularly: Properties/Getters prefixed with @: var myAttribute = xmlPerson.@name; Nameless functions for filtering: xmlData.person.(/* predicate */) lambda syntax for predicates: xmlData.person.(@name == "Brian") So here is my question: Are these just one-off capabilities (much like Vector.<>) they put in just for E4X, therefore keeping out of reach for us? Or do we, as ActionScript developers, have access to these features? More specifically, I'd love to get access to the expression tree of that lambda predicate for my own code (not tied to the XML classes in any way). I figured out that this is called the "filter operator"... but I am not sure how to harness it. Not sure I can... since ActionScript does not allow for operator overloading :(

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