logs_to_metrics: Support optional value_field for counters

Support incrementing counters by a specified value.

If a `value_field` is specified for a counter, the counter is incremented by the given value instead of just counting the number of records.

This allows tracking different metrics, such as the total number of bytes sent or received in an access log.

Signed-off-by: Fabian Ruff <[email protected]>

Author: databus23

plugins/filter_log_to_metrics/log_to_metrics.c

@@ -639,13 +639,14 @@ static int cb_log_to_metrics_init(struct flb_filter_instance *f_ins,
     snprintf(metric_description, sizeof(metric_description) - 1, "%s",
              ctx->metric_description);
 
-    /* Value field only needed for modes gauge and histogram */
-    if (ctx->mode > 0) {
-        if (ctx->value_field == NULL || strlen(ctx->value_field) == 0) {
-            flb_plg_error(f_ins, "value_field is not set");
-            log_to_metrics_destroy(ctx);
-            return -1;
+    if (ctx->value_field == NULL || strlen(ctx->value_field) == 0) {
+        /* require value field for modes gauge and histogram */
+        if (ctx->mode > 0) {
+                flb_plg_error(f_ins, "value_field is not set");
+                log_to_metrics_destroy(ctx);
+                return -1;
         }
+    } else {
         snprintf(value_field, sizeof(value_field) - 1, "%s",
                     ctx->value_field);
     }
@@ -825,6 +826,7 @@ static int cb_log_to_metrics_filter(const void *data, size_t bytes,
     char **label_values = NULL;
     int label_count = 0;
     int i;
+    double counter_value = 0;
     double gauge_value = 0;
     double histogram_value = 0;
     char kubernetes_label_values
@@ -901,8 +903,50 @@ static int cb_log_to_metrics_filter(const void *data, size_t bytes,
             /* Calculating and setting metric depending on the mode */
             switch (ctx->mode) {
                 case FLB_LOG_TO_METRICS_COUNTER:
-                    ret = cmt_counter_inc(ctx->c, ts, label_count,
-                                    label_values);
+
+                    // If value_field is not set, increment counter by 1
+                    if (ctx->value_field == NULL || strlen(ctx->value_field) == 0) {
+                        ret = cmt_counter_inc(ctx->c, ts, label_count,
+                                        label_values);
+                        break;
+                    }
+                    // If value_field is set, increment counter by value
+                    ra = flb_ra_create(ctx->value_field, FLB_TRUE);
+                    if (!ra) {
+                        flb_plg_error(ctx->ins, "invalid record accessor key, aborting");
+                        break;
+                    }
+
+                    rval = flb_ra_get_value_object(ra, map);
+
+                    if (!rval) {
+                        flb_warn("given value field is empty or not existent");
+                        break;
+                    }
+                    if (rval->type == FLB_RA_STRING) {
+                        sscanf(rval->val.string, "%lf", &counter_value);
+                    }
+                    else if (rval->type == FLB_RA_FLOAT) {
+                        counter_value = rval->val.f64;
+                    }
+                    else if (rval->type == FLB_RA_INT) {
+                        counter_value = (double)rval->val.i64;
+                    }
+                    else {
+                        flb_plg_error(f_ins,
+                                    "cannot convert given value to metric");
+                        break;
+                    }
+                    ret = cmt_counter_add(ctx->c, ts, counter_value,
+                                        label_count, label_values);
+                    if (rval) {
+                        flb_ra_key_value_destroy(rval);
+                        rval = NULL;
+                    }
+                    if (ra) {
+                        flb_ra_destroy(ra);
+                        ra = NULL;
+                    }
                     break;
 
                 case FLB_LOG_TO_METRICS_GAUGE:
@@ -1066,7 +1110,7 @@ static struct flb_config_map config_map[] = {
     {
      FLB_CONFIG_MAP_STR, "value_field", NULL,
      0, FLB_TRUE, offsetof(struct log_to_metrics_ctx, value_field),
-     "Numeric field to use for gauge or histogram"
+     "Numeric field to use for gauge, histogram or counter"
     },
     {
      FLB_CONFIG_MAP_STR, "metric_name", "a",