tor

The Tor anonymity network
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prometheus.c (3637B)

      1 /* Copyright (c) 2020-2021, The Tor Project, Inc. */
      2 /* See LICENSE for licensing information */
      3 
      4 /**
      5 * @file prometheus.c
      6 * @brief Metrics format driver for Prometheus data model.
      7 **/
      8 
      9 #define METRICS_STORE_ENTRY_PRIVATE
     10 
     11 #include "orconfig.h"
     12 
     13 #include "lib/container/smartlist.h"
     14 #include "lib/log/util_bug.h"
     15 #include "lib/malloc/malloc.h"
     16 #include "lib/string/printf.h"
     17 
     18 #include "lib/metrics/prometheus.h"
     19 
     20 #include <string.h>
     21 
     22 /** Return a static buffer containing all the labels properly formatted
     23 * for the output as a string.
     24 *
     25 * Subsequent calls to this invalidates the previous result. */
     26 static const char *
     27 format_labels(smartlist_t *labels)
     28 {
     29  static char buf[1024];
     30  char *line = NULL;
     31 
     32  if (smartlist_len(labels) == 0) {
     33    buf[0] = '\0';
     34    goto end;
     35  }
     36 
     37  line = smartlist_join_strings(labels, ",", 0, NULL);
     38  tor_snprintf(buf, sizeof(buf), "%s", line);
     39 
     40 end:
     41  tor_free(line);
     42  return buf;
     43 }
     44 
     45 /** Write the string representation of the histogram entry to the specified
     46 * buffer.
     47 *
     48 * Note: entry **must** be a histogram.
     49 */
     50 static void
     51 format_histogram(const metrics_store_entry_t *entry, buf_t *data)
     52 {
     53  tor_assert(entry->type == METRICS_TYPE_HISTOGRAM);
     54 
     55  const char *labels = format_labels(entry->labels);
     56 
     57  for (size_t i = 0; i < entry->u.histogram.bucket_count; ++i) {
     58    metrics_histogram_bucket_t hb = entry->u.histogram.buckets[i];
     59    if (strlen(labels) > 0) {
     60      buf_add_printf(data, "%s_bucket{%s,le=\"%.2f\"} %" PRIi64 "\n",
     61                     entry->name, labels, (double)hb.bucket, hb.value);
     62    } else {
     63      buf_add_printf(data, "%s_bucket{le=\"%.2f\"} %" PRIi64 "\n",
     64                     entry->name, (double)hb.bucket, hb.value);
     65    }
     66  }
     67 
     68  if (strlen(labels) > 0) {
     69    buf_add_printf(data, "%s_bucket{%s,le=\"+Inf\"} %" PRIi64 "\n",
     70                   entry->name, labels,
     71                   metrics_store_hist_entry_get_count(entry));
     72    buf_add_printf(data, "%s_sum{%s} %" PRIi64 "\n", entry->name, labels,
     73                   metrics_store_hist_entry_get_sum(entry));
     74    buf_add_printf(data, "%s_count{%s} %" PRIi64 "\n", entry->name, labels,
     75                   metrics_store_hist_entry_get_count(entry));
     76  } else {
     77    buf_add_printf(data, "%s_bucket{le=\"+Inf\"} %" PRIi64 "\n", entry->name,
     78                   metrics_store_hist_entry_get_count(entry));
     79    buf_add_printf(data, "%s_sum %" PRIi64 "\n", entry->name,
     80                   metrics_store_hist_entry_get_sum(entry));
     81    buf_add_printf(data, "%s_count %" PRIi64 "\n", entry->name,
     82                   metrics_store_hist_entry_get_count(entry));
     83  }
     84 }
     85 
     86 /** Format the given entry in to the buffer data. */
     87 void
     88 prometheus_format_store_entry(const metrics_store_entry_t *entry, buf_t *data,
     89                              bool no_comment)
     90 {
     91  tor_assert(entry);
     92  tor_assert(data);
     93 
     94  if (!no_comment) {
     95    buf_add_printf(data, "# HELP %s %s\n", entry->name, entry->help);
     96    buf_add_printf(data, "# TYPE %s %s\n", entry->name,
     97                   metrics_type_to_str(entry->type));
     98  }
     99 
    100  switch (entry->type) {
    101  case METRICS_TYPE_COUNTER: FALLTHROUGH;
    102  case METRICS_TYPE_GAUGE:
    103  {
    104    const char *labels = format_labels(entry->labels);
    105    if (strlen(labels) > 0) {
    106      buf_add_printf(data, "%s{%s} %" PRIi64 "\n", entry->name,
    107                     labels,
    108                     metrics_store_entry_get_value(entry));
    109    } else {
    110      buf_add_printf(data, "%s %" PRIi64 "\n", entry->name,
    111                     metrics_store_entry_get_value(entry));
    112    }
    113    break;
    114  }
    115  case METRICS_TYPE_HISTOGRAM:
    116    format_histogram(entry, data);
    117    break;
    118  default:
    119    tor_assert_unreached();
    120  }
    121 }