Lockfile test to see NFS CB_NOTIFY_LOCK behaviour between Linux/BSD NFS server implementations.

locktest.c

/*
 * locktest.c
 *
 *    Lock a file (block until we have a lock), write a message to the file, and
 *    sleep for a while. If we run multiple of these at once in a loop, we can show
 *    that file system locking is working correctly.
 *
 * USAGE:
 *    locktest.exe FILENAME SECONDS MESSAGE NUMRUNS
 *
 * PARAMETERS:
 *    FILENAME: This program will attempt to lock FILENAME.lck, and once completed
 *              will write the parameter MESSAGE to FILENAME.
 *    SECONDS:  Period to sleep for after obtaining a lock and writing a message
 *              to FILENAME. We use this to show clearly that other process is
 *              waiting.
 *    MESSAGE:  Message to write to FILENAME on each loop. A good value to use
 *              is $HOSTNAME, so if we run from multiple PODs, it will show how many
 *              successful writes there have been, and if the locking is really
 *              working properly - if it isn't we won't see a full set of entries in
 *              the file.
 *    NUMRUNS:  Run this many executions of our full process. Useful when wanting to
 *              show that locking behaves over many executions.
 *
 * DESCRIPTION:
 *
 *  Created on: Jan 23, 2019
 *
 */

#include <stdio.h>
#include <fcntl.h>
#include <errno.h>
#include <unistd.h>
#include <iostream>
#include <string.h>
#include <string>
#include <sstream>
#include <stdlib.h>

using namespace std;

int main(int argc, const char *argv[])
{
	if (argc != 5)
	{
		cerr << "Usage:" << argv[0] << " FILENAME SECONDS MESSAGE NUMRUNS" << endl;
		exit(1);
	}

	const char *filename = argv[1];
	int seconds;
	stringstream ss1(argv[2]);
	ss1 >> seconds;
	const char *message = argv[3];
	int numruns;
	stringstream ss2(argv[4]);
	ss2 >> numruns;

	if ( !filename || !strcmp(filename,"") )
	{
		filename = "lock.txt";
		cout << "Using default value for file (" << filename << ")" << endl;
	}

	for (int i=1; i<=numruns; i++)
	{
		if (numruns > 0)
		{
			cout << "Execution #" << i << endl;
		}

		char lockfilename[100];
		sprintf(lockfilename, "%s.lck", filename);
		cout << "Opening " << lockfilename << endl;

		int lockfd = open(lockfilename, O_WRONLY | O_CREAT, 0664);
		if (lockfd < 0)
		{
			cerr << "ERROR: Could not open " << lockfilename << " (" << strerror(errno) << ")" << endl;
			exit(1);
		}

		cout << "Locking " << lockfilename << endl;
		if (lockf(lockfd, F_LOCK, 0) != 0)
		{
			cerr << "ERROR: Could not lock " << lockfilename << " (" << strerror(errno) << ")" << endl;
			close(lockfd);
			exit(1);
		}
		cout << "Locked " << lockfilename << std::endl;

		cout << "Opening " << filename << endl;
		FILE *fp = fopen(filename, "a");
		if (!fp)
		{
			cerr << "ERROR: Could not open " << filename << " (" << strerror(errno) << ")" << endl;
			exit(1);
		}

		cout << "Writing message to " << filename << endl;
		fprintf(fp, "%s\n", message);
		fflush(fp);

		if (seconds)
		{
			cout << "Sleeping for " << seconds << " seconds..." << endl;
			sleep(seconds);
		}
		cout << "Closing " << filename << std::endl;
		fclose(fp);
		cout << "Closing " << lockfilename << std::endl;
		close(lockfd);
	}
	exit(0);
}