processor_content_modifier: add support for OTel metrics

The following patch, extends the processor capabilities to operate
on top of metrics, specifically on resource and scope metadata such as
attributes, name, version, etc.

Signed-off-by: Eduardo Silva <[email protected]>

Author: edsiper

plugins/processor_content_modifier/CMakeLists.txt

@@ -1,7 +1,10 @@
 set(src
   cm_config.c
   cm_logs.c
+  cm_metrics.c
   cm_traces.c
+  cm_opentelemetry.c
+  cm_utils.c
   cm.c
   )
 

plugins/processor_content_modifier/cm.c

@@ -98,6 +98,24 @@ static int cb_process_traces(struct flb_processor_instance *ins,
 
 }
 
+static int cb_process_metrics(struct flb_processor_instance *ins,
+                              struct cmt *in_cmt,
+                              struct cmt **out_cmt,
+                              const char *tag,
+                              int tag_len)
+{
+    int ret;
+    struct content_modifier_ctx *ctx;
+
+    if (!ins->context) {
+        return FLB_PROCESSOR_FAILURE;
+    }
+    ctx = ins->context;
+
+    ret = cm_metrics_process(ins, ctx, in_cmt, out_cmt, tag, tag_len);
+    return ret;
+}
+
 static struct flb_config_map config_map[] = {
     {
         FLB_CONFIG_MAP_STR, "context", NULL,
@@ -144,7 +162,7 @@ struct flb_processor_plugin processor_content_modifier_plugin = {
     .description        = "Modify the content of Logs, Metrics and Traces",
     .cb_init            = cb_init,
     .cb_process_logs    = cb_process_logs,
-    .cb_process_metrics = NULL,
+    .cb_process_metrics = cb_process_metrics,
     .cb_process_traces  = cb_process_traces,
     .cb_exit            = cb_exit,
     .config_map         = config_map,

plugins/processor_content_modifier/cm.h

@@ -116,5 +116,10 @@ int cm_traces_process(struct flb_processor_instance *ins,
                       struct ctrace *traces_context,
                       const char *tag, int tag_len);
 
+int cm_metrics_process(struct flb_processor_instance *ins,
+                       struct content_modifier_ctx *ctx,
+                       struct cmt *in_cmt,
+                       struct cmt **out_cmt,
+                       const char *tag, int tag_len);
 
 #endif

plugins/processor_content_modifier/cm_config.c

@@ -218,6 +218,53 @@ static int set_context(struct content_modifier_ctx *ctx)
                  strcasecmp(ctx->context_str, "attributes") == 0) {
             context = CM_CONTEXT_METRIC_LABELS;
         }
+
+        /*
+         * OpenTelemetry contexts
+         * ----------------------
+         */
+        else if (strcasecmp(ctx->context_str, "otel_resource_attributes") == 0) {
+            context = CM_CONTEXT_OTEL_RESOURCE_ATTR;
+        }
+        else if (strcasecmp(ctx->context_str, "otel_scope_attributes") == 0) {
+            context = CM_CONTEXT_OTEL_SCOPE_ATTR;
+        }
+        else if (strcasecmp(ctx->context_str, "otel_scope_name") == 0) {
+            /*
+             * scope name is restricted to specific actions, make sure the user
+             * cannot messed it up
+             *
+             *   action              allowed ?
+             *   -----------------------------
+             *   CM_ACTION_INSERT       Yes
+             *   CM_ACTION_UPSERT       Yes
+             *   CM_ACTION_DELETE       Yes
+             *   CM_ACTION_RENAME        No
+             *   CM_ACTION_HASH         Yes
+             *   CM_ACTION_EXTRACT       No
+             *   CM_ACTION_CONVERT       No
+             */
+
+            if (ctx->action_type == CM_ACTION_RENAME ||
+                ctx->action_type == CM_ACTION_EXTRACT ||
+                ctx->action_type == CM_ACTION_CONVERT) {
+                flb_plg_error(ctx->ins, "action '%s' is not allowed for context '%s'",
+                              ctx->action_str, ctx->context_str);
+                return -1;
+            }
+
+            /* check that 'name' is the key set */
+            if (!ctx->key) {
+                ctx->key = flb_sds_create("name");
+            }
+            else if (strcasecmp(ctx->key, "name") != 0) {
+                flb_plg_error(ctx->ins, "context '%s' requires the name of the key to be 'name', no '%s'",
+                              ctx->context_str, ctx->key);
+                return -1;
+            }
+
+            context = CM_CONTEXT_OTEL_SCOPE_NAME;
+        }
         else {
             flb_plg_error(ctx->ins, "unknown metrics context '%s'", ctx->context_str);
             return -1;