signals

Is there any way to run some code after transaction commit in Django? I need to send some messages to a rabbitmq server for offline processing, but the message gets to the consumer before the Django transaction is commited. My message is sent in the post_save signal of the model. What I'm looking for is a similar mechanism, using signals or something else, that would execute code after the commit (and do nothing if the transaction fails). I haven't found any generic way of doing it in Django. Do you have any ideas? UPDATE 2 : django-transaction-hooks was merged into Django core and released in

How do signals work in unix? I went through W.R. Stevens but was unable to understand. Please help me. The explanation below is not exact, and several aspects of how this works differ between different systems (and maybe even the same OS on different hardware for some portions), but I think that it is generally good enough for you to satisfy your curiosity enough to use them. Most people start using signals in programming without even this level of understanding, but before I got comfortable using them I wanted to understand them. signal delivery The OS kernel has a data structure called a

I am currently working on a wrapper for a dedicated server running in the shell. The wrapper spawns the server process via subprocess and observes and reacts to its output. The dedicated server must be explicitly given a command to shut down gracefully. Thus, CTRL-C must not reach the server process. If I capture the KeyboardInterrupt exception or overwrite the SIGINT-handler in python, the server process still receives the CTRL-C and stops immediately. So my question is: How to prevent subprocesses from receiving CTRL-C / Control-C / SIGINT? robert Somebody in the #python IRC-Channel

I am trying to set up an exception handler using sigaction. It works well for the first exception. But the sigaction handler is not called after the 1st exception and the program ends abruptly when the second signal happens. #include <iostream> #include <signal.h> #include <exception> #include <string.h> typedef void (*SigactionHandlerPointer)(int iSignal, siginfo_t * psSiginfo, void * psContext); using namespace std; void SigactionHookHandler( int iSignal, siginfo_t * psSiginfo, void * psContext ) { cout << "Signal Handler Exception Caught: std::exception -- signal : " << iSignal << " from

I'd like to enter the debugger upon typing ctrl-C (or sending a SIGINT). I have installed the debugger (I'm running Ruby 1.9.3) and verified that it works. I've added this to my setup files (this is for Padrino, but I assume it would be similar for Rails): # file: config/boot.rb Padrino.before_load do trap("SIGINT") { debugger } if Padrino.env == :development end ... but typing Ctrl-C does not invoke the debugger. In fact, if I replace debugger with puts "saw an interrupt!" , typing Ctrl-C doesn't cause a print to happen either. update Following this suggestion from Mike Dunlavey , I tried

I am trying to receive a signal when I/O is possible on a file descriptor. The program needs to be doing something else when it is not doing I/O, so using select(2) is not an option. When I run the sample code is below, it is printing the message from inside the handler as fast as it can, even when there is no data on stdin. Even weirder is that the file descriptor reported in the siginfo_t structure varies from run to run. I only set it up for stdin (fd 0); why would the handler report any other value? Sometimes I see 0, sometimes, I see 1, most of the time I see '?', which indicates a value

I was trying this program from Advance Programming in Unix Environment. #include<stdio.h> #include<signal.h> static void handler(int sig){ if(sig == SIGUSR1) printf("handled user1 signal"); else if(sig == SIGUSR2) printf("handles user2 signal"); else printf("unkown signal"); } int main(){ if(signal(SIGUSR1, handler) == SIG_ERR) printf("can't handle signal SIGUSR1"); if(signal(SIGUSR2, handler) == SIG_ERR) printf("can't handle signal SIGUSR2"); for(;;) pause(); return 0; } I am using Ubuntu 11.10. I compile the program with gcc and then run a.out as indicated in the book. $./a.out& [1]+ 1345 $