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, 5 insertions, 5 deletions

diff --git a/src/rdb.h b/src/rdb.h
index 5942c4333..f2a5a28fe 100644
--- a/src/rdb.h
+++ b/src/rdb.h
@@ -148,10 +148,10 @@ int rdbLoadLenByRef(rio *rdb, int *isencoded, uint64_t *lenptr);
 int rdbSaveObjectType(rio *rdb, robj *o);
 int rdbLoadObjectType(rio *rdb);
 int rdbLoad(char *filename, rdbSaveInfo *rsi, int rdbflags);
-int rdbSaveBackground(char *filename, rdbSaveInfo *rsi);
-int rdbSaveToSlavesSockets(rdbSaveInfo *rsi);
+int rdbSaveBackground(int req, char *filename, rdbSaveInfo *rsi);
+int rdbSaveToSlavesSockets(int req, rdbSaveInfo *rsi);
 void rdbRemoveTempFile(pid_t childpid, int from_signal);
-int rdbSave(char *filename, rdbSaveInfo *rsi);
+int rdbSave(int req, char *filename, rdbSaveInfo *rsi);
 ssize_t rdbSaveObject(rio *rdb, robj *o, robj *key, int dbid);
 size_t rdbSavedObjectLen(robj *o, robj *key, int dbid);
 robj *rdbLoadObject(int type, rio *rdb, sds key, int dbid, int *error);
@@ -170,8 +170,8 @@ int rdbLoadBinaryFloatValue(rio *rdb, float *val);
 int rdbLoadRio(rio *rdb, int rdbflags, rdbSaveInfo *rsi);
 int rdbLoadRioWithLoadingCtx(rio *rdb, int rdbflags, rdbSaveInfo *rsi, rdbLoadingCtx *rdb_loading_ctx);
 int rdbFunctionLoad(rio *rdb, int ver, functionsCtx* functions_ctx, int rdbflags, sds *err);
-int rdbSaveRio(rio *rdb, int *error, int rdbflags, rdbSaveInfo *rsi);
-int functionsSaveRio(rio *rdb);
+int rdbSaveRio(int req, rio *rdb, int *error, int rdbflags, rdbSaveInfo *rsi);
+ssize_t rdbSaveFunctions(rio *rdb);
 rdbSaveInfo *rdbPopulateSaveInfo(rdbSaveInfo *rsi);
 
 #endif