Function clusterBeforeSleep

app/redis-6.2.6/src/cluster.c:3765–3795

This function is called before the event handler returns to sleep for * events. It is useful to perform operations that must be done ASAP in * reaction to events fired but that are not safe to perform inside event * handlers, or to perform potentially expansive tasks that we need to do * a single time before replying to clients. */

 * handlers, or to perform potentially expansive tasks that we need to do
 * a single time before replying to clients. */
void clusterBeforeSleep(void) {
    int flags = server.cluster->todo_before_sleep;

    /* Reset our flags (not strictly needed since every single function
     * called for flags set should be able to clear its flag). */
    server.cluster->todo_before_sleep = 0;

    if (flags & CLUSTER_TODO_HANDLE_MANUALFAILOVER) {
        /* Handle manual failover as soon as possible so that won't have a 100ms
         * as it was handled only in clusterCron */
        if(nodeIsSlave(myself)) {
            clusterHandleManualFailover();
            if (!(server.cluster_module_flags & CLUSTER_MODULE_FLAG_NO_FAILOVER))
                clusterHandleSlaveFailover();
        }
    } else if (flags & CLUSTER_TODO_HANDLE_FAILOVER) {
        /* Handle failover, this is needed when it is likely that there is already
         * the quorum from masters in order to react fast. */
        clusterHandleSlaveFailover();
    }

    /* Update the cluster state. */
    if (flags & CLUSTER_TODO_UPDATE_STATE)
        clusterUpdateState();

    /* Save the config, possibly using fsync. */
    if (flags & CLUSTER_TODO_SAVE_CONFIG) {
        int fsync = flags & CLUSTER_TODO_FSYNC_CONFIG;
        clusterSaveConfigOrDie(fsync);
    }
}

void clusterDoBeforeSleep(int flags) {
    server.cluster->todo_before_sleep |= flags;