Modules: allow to check for AOF loading client.

src/aof.c

@@ -652,10 +652,11 @@ void feedAppendOnlyFile(struct redisCommand *cmd, int dictid, robj **argv, int a
 
 /* In Redis commands are always executed in the context of a client, so in
  * order to load the append only file we need to create a fake client. */
-struct client *createFakeClient(void) {
+struct client *createAOFClient(void) {
     struct client *c = zmalloc(sizeof(*c));
 
     selectDb(c,0);
+    c->id = CLIENT_ID_AOF; /* So modules can identify it's the AOF client. */
     c->conn = NULL;
     c->name = NULL;
     c->querybuf = sdsempty();
@@ -729,7 +730,7 @@ int loadAppendOnlyFile(char *filename) {
      * to the same file we're about to read. */
     server.aof_state = AOF_OFF;
 
-    fakeClient = createFakeClient();
+    fakeClient = createAOFClient();
     startLoadingFile(fp, filename);
 
     /* Check if this AOF file has an RDB preamble. In that case we need to

src/module.c

@@ -1504,7 +1504,15 @@ int RM_ReplicateVerbatim(RedisModuleCtx *ctx) {
  *    are guaranteed to get IDs greater than any past ID previously seen.
  *
  * Valid IDs are from 1 to 2^64-1. If 0 is returned it means there is no way
- * to fetch the ID in the context the function was currently called. */
+ * to fetch the ID in the context the function was currently called.
+ *
+ * After obtaining the ID, it is possible to check if the command execution
+ * is actually happening in the context of AOF loading, using this macro:
+ *
+ *      if (RedisModule_IsAOFClient(RedisModule_GetClientId(ctx)) {
+ *          // Handle it differently.
+ *      }
+ */
 unsigned long long RM_GetClientId(RedisModuleCtx *ctx) {
     if (ctx->client == NULL) return 0;
     return ctx->client->id;

src/redismodule.h

@@ -404,6 +404,8 @@ int REDISMODULE_API_FUNC(RedisModule_ExitFromChild)(int retcode);
 int REDISMODULE_API_FUNC(RedisModule_KillForkChild)(int child_pid);
 #endif
 
+#define RedisModule_IsAOFClient(id) ((id) == UINT64_MAX)
+
 /* This is included inline inside each Redis module. */
 static int RedisModule_Init(RedisModuleCtx *ctx, const char *name, int ver, int apiver) __attribute__((unused));
 static int RedisModule_Init(RedisModuleCtx *ctx, const char *name, int ver, int apiver) {

src/server.h

@@ -827,6 +827,11 @@ typedef struct user {
 
 /* With multiplexing we need to take per-client state.
  * Clients are taken in a linked list. */
+
+#define CLIENT_ID_AOF (UINT64_MAX) /* Reserved ID for the AOF client. If you
+                                      need more reserved IDs use UINT64_MAX-1,
+                                      -2, ... and so forth. */
+
 typedef struct client {
     uint64_t id;            /* Client incremental unique ID. */
     connection *conn;