Function RM_RegisterClusterMessageReceiver

src/module.cpp:6208–6243

Register a callback receiver for cluster messages of type 'type'. If there * was already a registered callback, this will replace the callback function * with the one provided, otherwise if the callback is set to NULL and there * is already a callback for this function, the callback is unregistered * (so this API call is also used in order to delete the receiver). */

 * is already a callback for this function, the callback is unregistered
 * (so this API call is also used in order to delete the receiver). */
void RM_RegisterClusterMessageReceiver(RedisModuleCtx *ctx, uint8_t type, RedisModuleClusterMessageReceiver callback) {
    if (!g_pserver->cluster_enabled) return;

    uint64_t module_id = moduleTypeEncodeId(ctx->module->name,0);
    moduleClusterReceiver *r = clusterReceivers[type], *prev = NULL;
    while(r) {
        if (r->module_id == module_id) {
            /* Found! Set or delete. */
            if (callback) {
                r->callback = callback;
            } else {
                /* Delete the receiver entry if the user is setting
                 * it to NULL. Just unlink the receiver node from the
                 * linked list. */
                if (prev)
                    prev->next = r->next;
                else
                    clusterReceivers[type]->next = r->next;
                zfree(r);
            }
            return;
        }
        prev = r;
        r = r->next;
    }

    /* Not found, let's add it. */
    if (callback) {
        r = (moduleClusterReceiver*)zmalloc(sizeof(*r), MALLOC_LOCAL);
        r->module_id = module_id;
        r->module = ctx->module;
        r->callback = callback;
        r->next = clusterReceivers[type];
        clusterReceivers[type] = r;
    }
}

/* Send a message to all the nodes in the cluster if `target` is NULL, otherwise
 * at the specified target, which is a REDISMODULE_NODE_ID_LEN bytes node ID, as