out_kafka: emit a metric when librdkafka signals an error

The async nature of the kafka output makes the fluentbit_output_dropped_records_total insufficient to determine whether there are problems sending messages to kafka. fluent-bit considers a message delivered when it has been added to the librdkafka buffers. If librdkafka subsequently fails to deliver the message, the only feedback is a log message such as: ``` [2024/11/12 07:56:45] [ warn] [output:kafka:azure] message delivery failed: Local: Message timed out ``` So let's add a metric that exposes how often librdkafka signals that it has problems talking to kafka. Signed-off-by: Dennis Kaarsemaker <[email protected]>
fluent · Nov 12, 2024 · 2ef65d1 · 2ef65d1
1 parent 58cc2d5
commit 2ef65d1
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diff --git a/plugins/out_kafka/kafka.c b/plugins/out_kafka/kafka.c
@@ -34,6 +34,9 @@ void cb_kafka_msg(rd_kafka_t *rk, const rd_kafka_message_t *rkmessage,
     if (rkmessage->err) {
         flb_plg_warn(ctx->ins, "message delivery failed: %s",
                      rd_kafka_err2str(rkmessage->err));
+#ifdef FLB_HAVE_METRICS
+        cmt_counter_inc(ctx->cmt_kafka_errors, cfl_time_now(), 1, (char *[]){ctx->ins->alias});
+#endif
     }
     else {
         flb_plg_debug(ctx->ins, "message delivered (%zd bytes, "

diff --git a/plugins/out_kafka/kafka_config.c b/plugins/out_kafka/kafka_config.c
@@ -211,6 +211,12 @@ struct flb_out_kafka *flb_out_kafka_create(struct flb_output_instance *ins,
         }
     }
 
+    /* Metrics */
+#ifdef FLB_HAVE_METRICS
+    ctx->cmt_kafka_errors = cmt_counter_create(ctx->ins->cmt, "fluentbit", "output", "kafka_errors_total", "Number of kafka errors processing queued messages", 1, (char*[]) {"name"});
+    cmt_counter_set(ctx->cmt_kafka_errors, cfl_time_now(), 0, 1, (char *[]){ctx->ins->alias});
+#endif
+
     flb_plg_info(ctx->ins, "brokers='%s' topics='%s'", ctx->kafka.brokers, tmp);
 #ifdef FLB_HAVE_AVRO_ENCODER
     flb_plg_info(ctx->ins, "schemaID='%s' schema='%s'", ctx->avro_fields.schema_id, ctx->avro_fields.schema_str);

diff --git a/plugins/out_kafka/kafka_config.h b/plugins/out_kafka/kafka_config.h
@@ -124,6 +124,7 @@ struct flb_out_kafka {
     struct flb_avro_fields avro_fields;
 #endif
 
+    struct cmt_counter *cmt_kafka_errors;
 };
 
 struct flb_out_kafka *flb_out_kafka_create(struct flb_output_instance *ins,