Fix and improve module error reply statistics (#10278)

This PR handles several aspects
1. Calls to RM_ReplyWithError from thread safe contexts don't violate thread safety.
2. Errors returning from RM_Call to the module aren't counted in the statistics (they
  might be handled silently by the module)
3. When a module propagates a reply it got from RM_Call to it's client, then the error
  statistics are counted.

This is done by:
1. When appending an error reply to the output buffer, we avoid updating the global
  error statistics, instead we cache that error in a deferred list in the client struct.
2. When creating a RedisModuleCallReply object, the deferred error list is moved from
  the client into that object.
3. when a module calls RM_ReplyWithCallReply we copy the deferred replies to the dest
  client (if that's a real client, then that's when the error statistics are updated to the server)

Note about RM_ReplyWithCallReply: if the original reply had an array with errors, and the module
replied with just a portion of the original reply, and not the entire reply, the errors are currently not
propagated and the errors stats will not get propagated.

Fix #10180

1 files changed, 2 insertions, 1 deletions

diff --git a/src/call_reply.h b/src/call_reply.h
index 5b07dc437..ff98f7f5a 100644
--- a/src/call_reply.h
+++ b/src/call_reply.h
@@ -34,7 +34,7 @@
 
 typedef struct CallReply CallReply;
 
-CallReply *callReplyCreate(sds reply, void *private_data);
+CallReply *callReplyCreate(sds reply, list *deferred_error_list, void *private_data);
 int callReplyType(CallReply *rep);
 const char *callReplyGetString(CallReply *rep, size_t *len);
 long long callReplyGetLongLong(CallReply *rep);
@@ -51,6 +51,7 @@ const char *callReplyGetVerbatim(CallReply *rep, size_t *len, const char **forma
 const char *callReplyGetProto(CallReply *rep, size_t *len);
 void *callReplyGetPrivateData(CallReply *rep);
 int callReplyIsResp3(CallReply *rep);
+list *callReplyDeferredErrorList(CallReply *rep);
 void freeCallReply(CallReply *rep);
 
 #endif /* SRC_CALL_REPLY_H_ */