IntervalCheck

IntervalCheck is a utility that calls runtime specified user created functions at a specified interval

Install

IntervalCheck includes a Smithy formula to automate deployment, for centers not using Smithy the build looks as follow:

# If on Titan
$ module switch PrgEnv-pgi PrgEnv-gnu
#

$ mkdir build
$ CC=gcc CXX=g++ cmake -DCMAKE_INSTALL_PREFIX=/path/to/install ..
$ make
$ make install

The artificact libIntervalCheck.so will be created under {PREFIX}/lib

Run

IntervalCheck works best with dynamically linked applications, in this case all that is needed to enable the timer is to set LD_PRELOAD to the path of libIntervalCheck.so.

To specify a function for IntervalCheck to call a dynamic library containing the function, with signature void (void), must be created. LD_PRELOAD must preload this library, and the function name must be provided to IntervalCheck. An example of how to achieve this is given below:

Step 1: Create a function

$ cat code.c

#include "stdio.h"

void foo() {
  printf("Hi from foo()\n");
}

void bar() {
  printf("Hi from bar()\n");
}

Step 2: Compile the function into a dynamic library, libcode.so

$ gcc -shared -fpic code.c -o libcode.so

Step 3: LD_PRELOAD the interval check library as well as our custom library, provide the path as needed

$ export LD_PRELOAD=./libIntervalCheck.so:./libcode.so

Step 4: Tell IntervalCheck to call foo() and bar(), which is contained in the LD_PRELOAD library libcode.so

$ export IC_FUNCTIONS="foo:bar"

Step 4: Run your dynamically linked application as normal!

$ cat a.c
int main() {
  do{} while(1);
  return 0;
}

$ gcc a.c

$ ./a.out
Hi from foo()
Hi from bar()

... 300 seconds ...

Hi from foo()
Hi from bar()
...

Tuning

The following environment variables can be used to fine time IntervalTimer

TMPDIR : Set the path to create temporary lock files in(default /tmp)

IC_INTERVAL : The interval in seconds between running the specified functions(default 300)

IC_UNSET_PRELOAD : Unset the LD_PRELOAD variable on IntervalCheck initialization if set(default unset)

IC_DEBUG : Enable debug information if set(default unset)

IC_PER_NODE : Only run one instance of IntervalCheck per node if set(default set)

IC_CALLBACKS : Colon seperated list of function names to be called by IntervalCheck