Check fd number - Githubissues

AlexStocks commented 2 months ago

Which PikiwiDB functionalities are relevant/related to the feature request?

No response

Description

PikiwiDB starts failed：

After modify fd number, it starts sucessfully.

Proposed solution

Check fd number when PikiwiDB starts as Redis.

#define RLIMIT_NOFILE   5       /* max number of open files */

struct rlimit {
    rlim_t  rlim_cur;
    rlim_t  rlim_max;
};
struct rlimit limit;

/* This function will try to raise the max number of open files accordingly to
 * the configured max number of clients. It also reserves a number of file
 * descriptors (CONFIG_MIN_RESERVED_FDS) for extra operations of
 * persistence, listening sockets, log files and so forth.
 *
 * If it will not be possible to set the limit accordingly to the configured
 * max number of clients, the function will do the reverse setting
 * server.maxclients to the value that we can actually handle. */
void adjustOpenFilesLimit(server_t *server) { //come from /redis/server.c/adjustOpenFilesLimit()
    rlim_t maxfiles = server->maxclients+CONFIG_MIN_RESERVED_FDS;
    struct rlimit limit;

    if (getrlimit(RLIMIT_NOFILE,&limit) == -1) {
        printf("Unable to obtain the current NOFILE limit (%s), assuming 1024 and setting the max clients configuration accordingly.",
               strerror(errno));
        server->maxclients = 1024-CONFIG_MIN_RESERVED_FDS;
    } else {
        rlim_t oldlimit = limit.rlim_cur;

        /* Set the max number of files if the current limit is not enough
         * for our needs. */
        if (oldlimit < maxfiles) {
            rlim_t bestlimit;
            int setrlimit_error = 0;

            /* Try to set the file limit to match 'maxfiles' or at least
             * to the higher value supported less than maxfiles. */
            bestlimit = maxfiles;
            while(bestlimit > oldlimit) {
                rlim_t decr_step = 16;

                limit.rlim_cur = bestlimit;
                limit.rlim_max = bestlimit;
                if (setrlimit(RLIMIT_NOFILE,&limit) != -1) break;
                setrlimit_error = errno;

                /* We failed to set file limit to 'bestlimit'. Try with a
                 * smaller limit decrementing by a few FDs per iteration. */
                if (bestlimit < decr_step) break;
                bestlimit -= decr_step;
            }

            /* Assume that the limit we get initially is still valid if
             * our last try was even lower. */
            if (bestlimit < oldlimit) bestlimit = oldlimit;

            if (bestlimit < maxfiles) {
                unsigned int old_maxclients = server->maxclients;
                server->maxclients = bestlimit-CONFIG_MIN_RESERVED_FDS;
                /* maxclients is unsigned so may overflow: in order
                 * to check if maxclients is now logically less than 1
                 * we test indirectly via bestlimit. */
                if (bestlimit <= CONFIG_MIN_RESERVED_FDS) {
                    printf("Your current 'ulimit -n' "
                           "of %llu is not enough for the server to start. "
                           "Please increase your open file limit to at least "
                           "%llu. Exiting.",
                           (unsigned long long) oldlimit,
                           (unsigned long long) maxfiles);
                    exit(1);
                }
                printf("You requested maxclients of %d "
                       "requiring at least %llu max file descriptors.",
                       old_maxclients,
                       (unsigned long long) maxfiles);
                printf("Server can't set maximum open files "
                       "to %llu because of OS error: %s.",
                       (unsigned long long) maxfiles, strerror(setrlimit_error));
                printf("Current maximum open files is %llu. "
                       "maxclients has been reduced to %d to compensate for "
                       "low ulimit. "
                       "If you need higher maxclients increase 'ulimit -n'.",
                       (unsigned long long) bestlimit, server->maxclients);
            } else {
                printf("Increased maximum number of open files "
                       "to %llu (it was originally set to %llu).",
                       (unsigned long long) maxfiles,
                       (unsigned long long) oldlimit);
            }
        }
    }
}