out_prometheus_exporter: Handle multiply concatenated metrics type of events (#9122)

* out_prometheus_exporter: Handle multiply concatenated metrics type of events

Signed-off-by: Hiroshi Hatake <hiroshi@chronosphere.io>

* out_prometheus_exporter: Plug a memory leak

Signed-off-by: Hiroshi Hatake <hiroshi@chronosphere.io>

* out_prometheus_exporter: Plug a leak on error

Signed-off-by: Hiroshi Hatake <hiroshi@chronosphere.io>

---------

Signed-off-by: Hiroshi Hatake <hiroshi@chronosphere.io>

Author: cosmo0920

plugins/out_prometheus_exporter/prom.c

@@ -175,44 +175,68 @@ static void cb_prom_flush(struct flb_event_chunk *event_chunk,
     int add_ts;
     size_t off = 0;
     flb_sds_t metrics;
-    cfl_sds_t text;
+    cfl_sds_t text = NULL;
+    cfl_sds_t tmp = NULL;
     struct cmt *cmt;
     struct prom_exporter *ctx = out_context;
+    int ok = CMT_DECODE_MSGPACK_SUCCESS;
+
+    text = flb_sds_create_size(128);
+    if (text == NULL) {
+        flb_plg_debug(ctx->ins, "failed to allocate buffer for text representation of metrics");
+        FLB_OUTPUT_RETURN(FLB_ERROR);
+    }
 
     /*
      * A new set of metrics has arrived, perform decoding, apply labels,
      * convert to Prometheus text format and store the output in the
      * hash table for metrics.
+     * Note that metrics might be concatenated. So, we need to consume
+     * until the end of event_chunk.
      */
-    ret = cmt_decode_msgpack_create(&cmt,
-                                    (char *) event_chunk->data,
-                                    event_chunk->size, &off);
-    if (ret != 0) {
-        FLB_OUTPUT_RETURN(FLB_ERROR);
-    }
+    while ((ret = cmt_decode_msgpack_create(&cmt,
+                                            (char *) event_chunk->data,
+                                            event_chunk->size, &off)) == ok) {
 
-    /* append labels set by config */
-    append_labels(ctx, cmt);
+        if (ret != 0) {
+            flb_sds_destroy(text);
+            FLB_OUTPUT_RETURN(FLB_ERROR);
+        }
 
-    /* add timestamp in the output format ? */
-    if (ctx->add_timestamp) {
-        add_ts = CMT_TRUE;
-    }
-    else {
-        add_ts = CMT_FALSE;
-    }
+        /* append labels set by config */
+        append_labels(ctx, cmt);
+
+        /* add timestamp in the output format ? */
+        if (ctx->add_timestamp) {
+            add_ts = CMT_TRUE;
+        }
+        else {
+            add_ts = CMT_FALSE;
+        }
 
-    /* convert to text representation */
-    text = cmt_encode_prometheus_create(cmt, add_ts);
-    if (!text) {
+        /* convert to text representation */
+        tmp = cmt_encode_prometheus_create(cmt, add_ts);
+        if (!tmp) {
+            cmt_destroy(cmt);
+            flb_sds_destroy(text);
+            FLB_OUTPUT_RETURN(FLB_ERROR);
+        }
+        ret = flb_sds_cat_safe(&text, tmp, flb_sds_len(tmp));
+        if (ret != 0) {
+            flb_plg_error(ctx->ins, "could not concatenate text representant coming from: %s",
+                          flb_input_name(ins));
+            cmt_encode_prometheus_destroy(tmp);
+            flb_sds_destroy(text);
+            cmt_destroy(cmt);
+            FLB_OUTPUT_RETURN(FLB_ERROR);
+        }
+        cmt_encode_prometheus_destroy(tmp);
         cmt_destroy(cmt);
-        FLB_OUTPUT_RETURN(FLB_ERROR);
     }
-    cmt_destroy(cmt);
 
     if (cfl_sds_len(text) == 0) {
         flb_plg_debug(ctx->ins, "context without metrics (empty)");
-        cmt_encode_text_destroy(text);
+        flb_sds_destroy(text);
         FLB_OUTPUT_RETURN(FLB_OK);
     }
 
@@ -221,11 +245,11 @@ static void cb_prom_flush(struct flb_event_chunk *event_chunk,
     if (ret == -1) {
         flb_plg_error(ctx->ins, "could not store metrics coming from: %s",
                       flb_input_name(ins));
-        cmt_encode_prometheus_destroy(text);
+        flb_sds_destroy(text);
         cmt_destroy(cmt);
         FLB_OUTPUT_RETURN(FLB_ERROR);
     }
-    cmt_encode_prometheus_destroy(text);
+    flb_sds_destroy(text);
 
     /* retrieve a full copy of all metrics */
     metrics = hash_format_metrics(ctx);