[KIP-848] Fixes related to Offset Commit previous error and ConsumerGroupHeartbeat not updating member epoch in a case (#4672)

[KIP-848] Fixed a condition where error was being raised in commit due to old error in the topic partition
[KIP-848] Fix discarding heartbeat response without epoch update when leaving during inflight HB

Author: pranavrth

CHANGELOG.md

@@ -8,6 +8,10 @@ librdkafka v2.12.0 is a feature release:
 
 ## Fixes
 
+### General fixes
+* Fix for discarding the member epoch in a consumer group heartbeat response when leaving with an inflight HB (#4672).
+* Fix for an error being raised after a commit due to an existing error in the topic partition (#4672).
+
 ### Telemetry fixes
 
 * Issues: #5179 .

src/rdkafka_cgrp.c

@@ -3085,8 +3085,6 @@ void rd_kafka_cgrp_handle_ConsumerGroupHeartbeat(rd_kafka_t *rk,
 
         rd_dassert(rkcg->rkcg_flags & RD_KAFKA_CGRP_F_HEARTBEAT_IN_TRANSIT);
 
-        if (rd_kafka_cgrp_will_leave(rkcg))
-                err = RD_KAFKA_RESP_ERR__OUTDATED;
         if (err)
                 goto err;
 
@@ -3106,15 +3104,25 @@ void rd_kafka_cgrp_handle_ConsumerGroupHeartbeat(rd_kafka_t *rk,
         }
 
         rd_kafka_buf_read_i32(rkbuf, &member_epoch);
-        rd_kafka_buf_read_i32(rkbuf, &heartbeat_interval_ms);
-
-        int8_t are_assignments_present;
-        rd_kafka_buf_read_i8(rkbuf, &are_assignments_present);
         rkcg->rkcg_generation_id = member_epoch;
+
+        rd_kafka_dbg(rk, CGRP, "HEARTBEAT",
+                     "ConsumerGroupHeartbeat response received for "
+                     "member id \"%.*s\" with epoch %d",
+                     RD_KAFKAP_STR_PR(&member_id), member_epoch);
+
+        if (rd_kafka_cgrp_will_leave(rkcg)) {
+                err = RD_KAFKA_RESP_ERR__OUTDATED;
+                goto err;
+        }
+
+        rd_kafka_buf_read_i32(rkbuf, &heartbeat_interval_ms);
         if (heartbeat_interval_ms > 0) {
                 rkcg->rkcg_heartbeat_intvl_ms = heartbeat_interval_ms;
         }
 
+        int8_t are_assignments_present;
+        rd_kafka_buf_read_i8(rkbuf, &are_assignments_present);
         if (are_assignments_present == 1) {
                 rd_kafka_topic_partition_list_t *assigned_topic_partitions;
                 const rd_kafka_topic_partition_field_t assignments_fields[] = {
@@ -3134,11 +3142,10 @@ void rd_kafka_cgrp_handle_ConsumerGroupHeartbeat(rd_kafka_t *rk,
                                     sizeof(assigned_topic_partitions_str), 0);
                         }
 
-                        rd_kafka_dbg(
-                            rk, CGRP, "HEARTBEAT",
-                            "ConsumerGroupHeartbeat response received target "
-                            "assignment \"%s\"",
-                            assigned_topic_partitions_str);
+                        rd_kafka_dbg(rk, CGRP, "HEARTBEAT",
+                                     "ConsumerGroupHeartbeat received target "
+                                     "assignment \"%s\"",
+                                     assigned_topic_partitions_str);
                 }
 
                 if (assigned_topic_partitions) {

src/rdkafka_request.c

@@ -1726,9 +1726,9 @@ rd_kafka_handle_OffsetCommit(rd_kafka_t *rk,
                         continue;
                 }
 
+                rktpar->err = partition->err;
                 if (partition->err) {
-                        rktpar->err = partition->err;
-                        err         = partition->err;
+                        err = partition->err;
                         errcnt++;
                         /* Accumulate actions for per-partition
                          * errors. */