out_kafka: Introduce the raw_log_key option raw format

Allow to write the value of a single key instead of the entire message to kafka. This allows to use a part of the message as the message_key and another part as the payload. This is similar to other output plugins. The value of the key must be a string and the format must be set to raw. Signed-off-by: Holger Hans Peter Freyther <[email protected]>
fluent · May 25, 2024 · a1d260d · a1d260d
1 parent c4d6803
commit a1d260d
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diff --git a/plugins/out_kafka/kafka.c b/plugins/out_kafka/kafka.c
@@ -100,6 +100,8 @@ int produce_message(struct flb_time *tm, msgpack_object *map,
     char *dynamic_topic;
     char *message_key = NULL;
     size_t message_key_len = 0;
+    char *raw_key = NULL;
+    size_t raw_key_len = 0;
     struct flb_kafka_topic *topic = NULL;
     msgpack_sbuffer mp_sbuf;
     msgpack_packer mp_pck;
@@ -211,6 +213,15 @@ int produce_message(struct flb_time *tm, msgpack_object *map,
             }
         }
 
+        /* Lookup raw_log_key */
+        if (ctx->raw_log_key && !raw_key && val.type == MSGPACK_OBJECT_STR) {
+            if (key.via.str.size == ctx->raw_log_key_len &&
+                    strncmp(key.via.str.ptr, ctx->raw_log_key, ctx->raw_log_key_len) == 0) {
+                raw_key = (char *) val.via.str.ptr;
+                raw_key_len = val.via.str.size;
+            }
+        }
+
         /* Lookup key/topic */
         if (ctx->topic_key && !topic && val.type == MSGPACK_OBJECT_STR) {
             if (key.via.str.size == ctx->topic_key_len &&
@@ -346,6 +357,15 @@ int produce_message(struct flb_time *tm, msgpack_object *map,
 
     }
 #endif
+    else if (ctx->format == FLB_KAFKA_FMT_RAW) {
+        if (raw_key == NULL) {
+            flb_plg_error(ctx->ins, "missing raw_log_key");
+            msgpack_sbuffer_destroy(&mp_sbuf);
+            return FLB_ERROR;
+        }
+        out_buf = raw_key;
+        out_size = raw_key_len;
+    }
 
     if (!message_key) {
         message_key = ctx->message_key;
@@ -643,6 +663,13 @@ static struct flb_config_map config_map[] = {
     0,  FLB_FALSE, 0,
     "Set the kafka group_id."
    },
+   {
+    FLB_CONFIG_MAP_STR, "raw_log_key", NULL,
+    0, FLB_TRUE, offsetof(struct flb_out_kafka, raw_log_key),
+    "By default, the whole log record will be sent to Kafka. "
+    "If you specify a key name with this option, then only the value of "
+    "that key will be sent to Kafka."
+   },
    /* EOF */
    {0}
 };

diff --git a/plugins/out_kafka/kafka_config.c b/plugins/out_kafka/kafka_config.c
@@ -93,6 +93,9 @@ struct flb_out_kafka *flb_out_kafka_create(struct flb_output_instance *ins,
             ctx->format = FLB_KAFKA_FMT_AVRO;
         }
 #endif
+        else if (strcasecmp(ctx->format_str, "raw") == 0) {
+            ctx->format = FLB_KAFKA_FMT_RAW;
+        }
     }
     else {
         ctx->format = FLB_KAFKA_FMT_JSON;
@@ -114,6 +117,14 @@ struct flb_out_kafka *flb_out_kafka_create(struct flb_output_instance *ins,
         ctx->message_key_field_len = 0;
     }
 
+    /* Config: Log_Key */
+    if (ctx->raw_log_key) {
+        ctx->raw_log_key_len = strlen(ctx->raw_log_key);
+    }
+    else {
+        ctx->raw_log_key_len = 0;
+    }
+
     /* Config: Timestamp_Key */
     if (ctx->timestamp_key) {
         ctx->timestamp_key_len = strlen(ctx->timestamp_key);

diff --git a/plugins/out_kafka/kafka_config.h b/plugins/out_kafka/kafka_config.h
@@ -34,6 +34,7 @@
 #ifdef FLB_HAVE_AVRO_ENCODER
 #define FLB_KAFKA_FMT_AVRO            3
 #endif
+#define FLB_KAFKA_FMT_RAW             4
 #define FLB_KAFKA_TS_KEY              "@timestamp"
 #define FLB_KAFKA_QUEUE_FULL_RETRIES  "10"
 
@@ -80,6 +81,9 @@ struct flb_out_kafka {
     int message_key_field_len;
     char *message_key_field;
 
+    int raw_log_key_len;
+    char *raw_log_key;
+
     /* Gelf Keys */
     struct flb_gelf_fields gelf_fields;