Generate RDB with Functions only via redis-cli --functions-rdb (#9968)

This is needed in order to ease the deployment of functions for ephemeral cases, where user
needs to spin up a server with functions pre-loaded.

#### Details:

* Added `--functions-rdb` option to _redis-cli_.
* Functions only rdb via `REPLCONF rdb-filter-only functions`. This is a placeholder for a space
  separated inclusion filter for the RDB. In the future can be `REPLCONF rdb-filter-only
  "functions db:3 key-patten:user*"` and a complementing `rdb-filter-exclude` `REPLCONF`
  can also be added.
* Handle "slave requirements" specification to RDB saving code so we can use the same RDB
  when different slaves express the same requirements (like functions-only) and not share the
  RDB when their requirements differ. This is currently just a flags `int`, but can be extended to
  a more complex structure with various filter fields.
* make sure to support filters only in diskless replication mode (not to override the persistence file),
  we do that by forcing diskless (even if disabled by config)

other changes:
* some refactoring in rdb.c (extract portion of a big function to a sub-function)
* rdb_key_save_delay used in AOFRW too
* sendChildInfo takes the number of updated keys (incremental, rather than absolute)

Co-authored-by: Oran Agra <oran@redislabs.com>

1 files changed, 23 insertions, 4 deletions

diff --git a/src/redis-cli.c b/src/redis-cli.c
index 2fb7d9ef0..397e3bfa8 100644
--- a/src/redis-cli.c
+++ b/src/redis-cli.c
@@ -226,6 +226,7 @@ static struct config {
     int pipe_mode;
     int pipe_timeout;
     int getrdb_mode;
+    int get_functions_rdb_mode;
     int stat_mode;
     int scan_mode;
     int intrinsic_latency_mode;
@@ -1643,6 +1644,9 @@ static int parseOptions(int argc, char **argv) {
         } else if (!strcmp(argv[i],"--rdb") && !lastarg) {
             config.getrdb_mode = 1;
             config.rdb_filename = argv[++i];
+        } else if (!strcmp(argv[i],"--functions-rdb") && !lastarg) {
+            config.get_functions_rdb_mode = 1;
+            config.rdb_filename = argv[++i];
         } else if (!strcmp(argv[i],"--pipe")) {
             config.pipe_mode = 1;
         } else if (!strcmp(argv[i],"--pipe-timeout") && !lastarg) {
@@ -1848,6 +1852,11 @@ static int parseOptions(int argc, char **argv) {
               " line interface may not be safe.\n", stderr);
     }
 
+    if (config.get_functions_rdb_mode && config.getrdb_mode) {
+        fprintf(stderr,"Option --functions-rdb and --rdb are mutually exclusive.\n");
+        exit(1);
+    }
+ 
     if (config.stdin_lastarg && config.stdin_tag_arg) {
         fprintf(stderr, "Options -x and -X are mutually exclusive.\n");
         exit(1);
@@ -1949,6 +1958,8 @@ static void usage(int err) {
 "  --replica          Simulate a replica showing commands received from the master.\n"
 "  --rdb <filename>   Transfer an RDB dump from remote server to local file.\n"
 "                     Use filename of \"-\" to write to stdout.\n"
+" --functions-rdb <filename> Like --rdb but only get the functions (not the keys)\n"
+"                     when getting the RDB dump file.\n"
 "  --pipe             Transfer raw Redis protocol from stdin to server.\n"
 "  --pipe-timeout <n> In --pipe mode, abort with error if after sending all data.\n"
 "                     no reply is received within <n> seconds.\n"
@@ -7158,7 +7169,8 @@ static void latencyDistMode(void) {
 
 #define RDB_EOF_MARK_SIZE 40
 
-void sendReplconf(const char* arg1, const char* arg2) {
+int sendReplconf(const char* arg1, const char* arg2) {
+    int res = 1;
     fprintf(stderr, "sending REPLCONF %s %s\n", arg1, arg2);
     redisReply *reply = redisCommand(context, "REPLCONF %s %s", arg1, arg2);
 
@@ -7167,10 +7179,12 @@ void sendReplconf(const char* arg1, const char* arg2) {
         fprintf(stderr, "\nI/O error\n");
         exit(1);
     } else if(reply->type == REDIS_REPLY_ERROR) {
-        fprintf(stderr, "REPLCONF %s error: %s\n", arg1, reply->str);
         /* non fatal, old versions may not support it */
+        fprintf(stderr, "REPLCONF %s error: %s\n", arg1, reply->str);
+        res = 0;
     }
     freeReplyObject(reply);
+    return res;
 }
 
 void sendCapa() {
@@ -8411,6 +8425,7 @@ int main(int argc, char **argv) {
     config.cluster_send_asking = 0;
     config.slave_mode = 0;
     config.getrdb_mode = 0;
+    config.get_functions_rdb_mode = 0;
     config.stat_mode = 0;
     config.scan_mode = 0;
     config.intrinsic_latency_mode = 0;
@@ -8522,11 +8537,15 @@ int main(int argc, char **argv) {
         slaveMode();
     }
 
-    /* Get RDB mode. */
-    if (config.getrdb_mode) {
+    /* Get RDB/functions mode. */
+    if (config.getrdb_mode || config.get_functions_rdb_mode) {
         if (cliConnect(0) == REDIS_ERR) exit(1);
         sendCapa();
         sendRdbOnly();
+        if (config.get_functions_rdb_mode && !sendReplconf("rdb-filter-only", "functions")) {
+            fprintf(stderr, "Failed requesting functions only RDB from server, aborting\n");
+            exit(1);
+        }
         getRDB(NULL);
     }