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allow counter metrics to use value_field instead of increment by 1 only #11344

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allow counter metrics to use value_field instead of increment by 1 only #11344

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5ac79a0
filter_log_to_metrics: allow counter metrics to use value_field inste…
Lusitaniae Jan 6, 2026
0789d49
filter_log_to_metrics: add handling for negative/missing values
Lusitaniae Jan 6, 2026
07039bc
filter_log_to_metrics: initialize var
Lusitaniae Jan 6, 2026
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85 changes: 79 additions & 6 deletions plugins/filter_log_to_metrics/log_to_metrics.c
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Original file line number Diff line number Diff line change
Expand Up @@ -643,10 +643,10 @@ 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) {
/* Value field is required for gauge and histogram modes, optional for counter */
if (ctx->mode == FLB_LOG_TO_METRICS_GAUGE || ctx->mode == FLB_LOG_TO_METRICS_HISTOGRAM) {
if (ctx->value_field == NULL || strlen(ctx->value_field) == 0) {
flb_plg_error(f_ins, "value_field is not set");
flb_plg_error(f_ins, "value_field is required for gauge and histogram modes");
log_to_metrics_destroy(ctx);
return -1;
}
Expand All @@ -660,6 +660,19 @@ static int cb_log_to_metrics_init(struct flb_filter_instance *f_ins,
return -1;
}
}
else if (ctx->mode == FLB_LOG_TO_METRICS_COUNTER &&
ctx->value_field != NULL && strlen(ctx->value_field) > 0) {
/* value_field is optional for counter mode */
snprintf(value_field, sizeof(value_field) - 1, "%s",
ctx->value_field);

ctx->value_ra = flb_ra_create(ctx->value_field, FLB_TRUE);
if (ctx->value_ra == NULL) {
flb_plg_error(f_ins, "invalid record accessor key for value_field");
log_to_metrics_destroy(ctx);
return -1;
}
}


/* Check if buckets are defined for histogram, if not assume defaults */
Expand Down Expand Up @@ -836,8 +849,10 @@ static int cb_log_to_metrics_filter(const void *data, size_t bytes,
char **label_values = NULL;
int label_count = 0;
int i;
int sscanf_ret = 0;
double gauge_value = 0;
double histogram_value = 0;
double counter_value = 0;
char kubernetes_label_values
[NUMBER_OF_KUBERNETES_LABELS][MAX_LABEL_LENGTH];

Expand Down Expand Up @@ -912,8 +927,66 @@ 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 set, use it; otherwise increment by 1 */
if (ctx->value_ra != NULL) {
rval = flb_ra_get_value_object(ctx->value_ra, map);
if (!rval) {
/* No value field, increment by 1 */
ret = cmt_counter_inc(ctx->c, ts, label_count,
label_values);
}
else {
/* Read value from field */
if (rval->type == FLB_RA_STRING) {
sscanf_ret = sscanf(rval->val.string, "%lf", &counter_value);
if (sscanf_ret != 1) {
flb_plg_error(f_ins,
"cannot parse value_field '%s' as numeric, falling back to increment by 1",
rval->val.string);
flb_ra_key_value_destroy(rval);
rval = NULL;
ret = cmt_counter_inc(ctx->c, ts, label_count,
label_values);
break;
}
}
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");
flb_ra_key_value_destroy(rval);
rval = NULL;
break;
}

/* Validate counter value is non-negative */
if (counter_value < 0) {
flb_plg_error(f_ins,
"counter value_field contains negative value %.2f, falling back to increment by 1",
counter_value);
flb_ra_key_value_destroy(rval);
rval = NULL;
ret = cmt_counter_inc(ctx->c, ts, label_count,
label_values);
break;
}

ret = cmt_counter_add(ctx->c, ts, counter_value,
label_count, label_values);
flb_ra_key_value_destroy(rval);
rval = NULL;
}
}
else {
/* No value_field configured, increment by 1 */
ret = cmt_counter_inc(ctx->c, ts, label_count,
label_values);
}
break;

case FLB_LOG_TO_METRICS_GAUGE:
Expand Down Expand Up @@ -1057,7 +1130,7 @@ 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 (optional for counter)"
},
{
FLB_CONFIG_MAP_STR, "metric_name", "a",
Expand Down