format_json: Reimplement format_json_metric().

This new implementation uses the new format of the metric_t type.
It produces output that is compatible with the prometheus/prom2json
project.

Makefile.am

@@ -495,7 +495,7 @@ libformat_json_la_SOURCES = \
 	src/utils/format_json/format_json.h
 libformat_json_la_CPPFLAGS  = $(AM_CPPFLAGS)
 libformat_json_la_LDFLAGS   = $(AM_LDFLAGS)
-libformat_json_la_LIBADD    =
+libformat_json_la_LIBADD    = libmetric.la
 if BUILD_WITH_LIBYAJL
 libformat_json_la_CPPFLAGS += $(BUILD_WITH_LIBYAJL_CPPFLAGS)
 libformat_json_la_LDFLAGS  += $(BUILD_WITH_LIBYAJL_LDFLAGS)

src/daemon/plugin_mock.c

@@ -244,3 +244,21 @@ int plugin_thread_create(__attribute__((unused)) pthread_t *thread,
  * would be to hard-code the top-level config keys in daemon/collectd.c to avoid
  * having these references in daemon/configfile.c. */
 int fc_configure(const oconfig_item_t *ci) { return ENOTSUP; }
+
+int plugin_convert_values_to_metrics(__attribute__((unused))
+                                     value_list_t const *vl,
+                                     __attribute__((unused))
+                                     metrics_list_t **ml) {
+  return ENOTSUP;
+}
+
+void destroy_metrics_list(metrics_list_t *ml) {
+  while (ml != NULL) {
+    identity_destroy(ml->metric.identity);
+    meta_data_destroy(ml->metric.meta);
+
+    metrics_list_t *next = ml->next_p;
+    free(ml);
+    ml = next;
+  }
+}

src/utils/format_json/format_json.c

@@ -376,131 +376,6 @@ static int value_list_to_json(char *buffer, size_t buffer_size, /* {{{ */
   return 0;
 } /* }}} int value_list_to_json */
 
-
-int format_json_metric(char *buffer_p, size_t *ret_buffer_fill, /* {{{ */
-                       size_t *ret_buffer_free, const metric_t *metric_p,
-                       int store_rates) {
-  char temp[1024];
-  gauge_t rate = -1;
-  int status = 0;
-
-  if ((buffer_p == NULL) || (ret_buffer_fill == NULL) ||
-      (ret_buffer_free == NULL) || (metric_p == NULL) ||
-      (metric_p->identity == NULL) || (metric_p->ds == NULL))
-    return -EINVAL;
-
-  if (*ret_buffer_free < 3)
-    return -ENOMEM;
-
-  /* Respect high water marks and fere size */
-  char *buffer = buffer_p + (*ret_buffer_fill);
-  size_t buffer_size = *ret_buffer_free;
-  size_t offset = 0;
-
-#define BUFFER_ADD(...)                                                        \
-  do {                                                                         \
-    status = snprintf(buffer + offset, buffer_size - offset, __VA_ARGS__);     \
-    if (status < 1)                                                            \
-      return -1;                                                               \
-    else if (((size_t)status) >= (buffer_size - offset))                       \
-      return -ENOMEM;                                                          \
-    else                                                                       \
-      offset += ((size_t)status);                                              \
-  } while (0)
-
-#define BUFFER_ADD_KEYVAL(key, value)                                          \
-  do {                                                                         \
-    status = json_escape_string(temp, sizeof(temp), (value));                  \
-    if (status != 0)                                                           \
-      return status;                                                           \
-    BUFFER_ADD(",\"%s\":%s", (key), temp);                                     \
-  } while (0)
-
-  /* Designed to be called multiple times, as when adding metrics from a
-     metrics_lisat_t object. When finalizing, the initial leading comma
-     will be replaced by a [ */
-  BUFFER_ADD(",{");
-  BUFFER_ADD_KEYVAL("name", metric_p->identity->name);
-  if (metric_p->value_type == DS_TYPE_GAUGE) {
-    if (isfinite(metric_p->value.gauge))
-      BUFFER_ADD(JSON_GAUGE_FORMAT, metric_p->value.gauge);
-    else
-      BUFFER_ADD("null");
-  } else if (store_rates) {
-    if (rate == -1)
-      status = uc_get_rate(metric_p, &rate);
-    if (status != 0) {
-      WARNING("utils_format_json: uc_get_rate failed.");
-      buffer_p[*ret_buffer_fill] = '0';
-      return -1;
-    }
-
-    if (isfinite(rate))
-      BUFFER_ADD(JSON_GAUGE_FORMAT, rate);
-    else
-      BUFFER_ADD("null");
-  } else if (metric_p->value_type == DS_TYPE_COUNTER)
-    BUFFER_ADD("%" PRIu64, (uint64_t)metric_p->value.counter);
-  else if (metric_p->value_type == DS_TYPE_DERIVE)
-    BUFFER_ADD("%" PRIi64, metric_p->value.derive);
-  else if (metric_p->value_type == DS_TYPE_ABSOLUTE)
-    BUFFER_ADD("%" PRIu64, metric_p->value.absolute);
-  else {
-    ERROR("format_json: Unknown data source type: %i", metric_p->value_type);
-    buffer_p[*ret_buffer_fill] = '0';
-    return -1;
-  }
-
-  BUFFER_ADD(",\"time\":%.3f", CDTIME_T_TO_DOUBLE(metric_p->time));
-  BUFFER_ADD(",\"interval\":%.3f", CDTIME_T_TO_DOUBLE(metric_p->interval));
-  BUFFER_ADD_KEYVAL("plugin", metric_p->plugin);
-  BUFFER_ADD_KEYVAL("type", metric_p->type);
-  BUFFER_ADD_KEYVAL("dsname", metric_p->ds->name);
-  BUFFER_ADD_KEYVAL("dstype", DS_TYPE_TO_STRING(metric_p->value_type));
-
-  if (metric_p->identity->root_p != NULL) {
-    c_avl_iterator_t *iter_p = c_avl_get_iterator(metric_p->identity->root_p);
-    if (iter_p != NULL) {
-      char *key_p = NULL;
-      char *value_p = NULL;
-      BUFFER_ADD("\"labels\":{");
-      while ((c_avl_iterator_next(iter_p, (void **)&key_p,
-                                  (void **)&value_p)) == 0) {
-        if ((key_p != NULL) && (value_p != NULL)) {
-          BUFFER_ADD_KEYVAL(key_p, value_p);
-        }
-      }
-      BUFFER_ADD("},");
-      c_avl_iterator_destroy(iter_p);
-    }
-  }
-
-  if (metric_p->meta != NULL) {
-    char meta_buffer[buffer_size];
-    memset(meta_buffer, 0, sizeof(meta_buffer));
-    status = meta_data_to_json(meta_buffer, sizeof(meta_buffer),
-                               metric_p->meta->meta);
-    if (status != 0) {
-      buffer_p[*ret_buffer_fill] = '0';
-      return status;
-    }
-
-    BUFFER_ADD(",\"meta\":%s", meta_buffer);
-  } /* if (vl->meta != NULL) */
-
-  BUFFER_ADD("}");
-
-#undef BUFFER_ADD_KEYVAL
-#undef BUFFER_ADD
-
-  /* Update hihg water mark and free size */
-  (*ret_buffer_fill) += offset;
-  (*ret_buffer_free) -= offset;
-
-  return 0;
-} /* }}} */
-
-
 static int format_json_value_list_nocheck(char *buffer, /* {{{ */
                                           size_t *ret_buffer_fill,
                                           size_t *ret_buffer_free,
@@ -668,6 +543,142 @@ static int format_time(yajl_gen g, cdtime_t t) /* {{{ */
   return 0;
 } /* }}} int format_time */
 
+/* TODO(octo): format_metric should export the interval, too. */
+/* TODO(octo): Decide whether format_metric should export meta data. */
+static int format_metric(yajl_gen g, metric_t const *m) {
+  CHECK_SUCCESS(yajl_gen_map_open(g)); /* BEGIN metric */
+
+  if (c_avl_size(m->identity->labels) != 0) {
+    JSON_ADD(g, "labels");
+    CHECK_SUCCESS(yajl_gen_map_open(g)); /* BEGIN labels */
+
+    c_avl_iterator_t *iter = c_avl_get_iterator(m->identity->labels);
+    char *k = NULL, *v = NULL;
+    while (c_avl_iterator_next(iter, (void *)&k, (void *)&v) == 0) {
+      JSON_ADD(g, k);
+      JSON_ADD(g, v);
+    }
+    c_avl_iterator_destroy(iter);
+
+    CHECK_SUCCESS(yajl_gen_map_close(g)); /* END labels */
+  }
+
+  if (m->time != 0) {
+    JSON_ADD(g, "timestamp_ms");
+    JSON_ADDF(g, "%" PRIu64, CDTIME_T_TO_MS(m->time));
+  }
+
+  strbuf_t buf = STRBUF_CREATE;
+  int status = value_marshal_text(&buf, m->value, m->value_type);
+  if (status != 0) {
+    STRBUF_DESTROY(buf);
+    return status;
+  }
+  JSON_ADD(g, "value");
+  JSON_ADD(g, buf.ptr);
+  STRBUF_DESTROY(buf);
+
+  CHECK_SUCCESS(yajl_gen_map_close(g)); /* END metric */
+
+  return 0;
+}
+
+/* format_metrics_list that all metrics in ml have the same name and value_type.
+ */
+static int format_metrics_list(yajl_gen g, metrics_list_t const *ml) {
+  CHECK_SUCCESS(yajl_gen_map_open(g)); /* BEGIN metric family */
+
+  metric_t const *m = &ml->metric;
+
+  JSON_ADD(g, "name");
+  JSON_ADD(g, m->identity->name);
+
+  char const *type = NULL;
+  switch (m->value_type) {
+  /* TODO(octo): handle store_rates. */
+  case VALUE_TYPE_GAUGE:
+    type = "GAUGE";
+    break;
+  case VALUE_TYPE_DERIVE:
+  case DS_TYPE_COUNTER:
+    type = "COUNTER";
+    break;
+  default:
+    ERROR("format_json_metric: Unknown value type: %d", m->value_type);
+    return EINVAL;
+  }
+  JSON_ADD(g, "type");
+  JSON_ADD(g, type);
+
+  JSON_ADD(g, "metrics");
+  CHECK_SUCCESS(yajl_gen_array_open(g));
+  for (metrics_list_t const *ptr = ml; ptr != NULL; ptr = ptr->next_p) {
+    int status = format_metric(g, &ptr->metric);
+    if (status != 0) {
+      return status;
+    }
+  }
+  CHECK_SUCCESS(yajl_gen_array_close(g));
+
+  CHECK_SUCCESS(yajl_gen_map_close(g)); /* END metric family */
+
+  return 0;
+}
+
+int format_json_metric(strbuf_t *buf, metric_t const *m, bool store_rates) {
+  if ((buf == NULL) || (m == NULL))
+    return EINVAL;
+
+#if HAVE_YAJL_V2
+  yajl_gen g = yajl_gen_alloc(NULL);
+  if (g == NULL)
+    return -1;
+#if COLLECT_DEBUG
+  yajl_gen_config(g, yajl_gen_beautify, 1);
+  yajl_gen_config(g, yajl_gen_validate_utf8, 1);
+#endif
+
+#else /* !HAVE_YAJL_V2 */
+  yajl_gen_config conf = {0};
+#if COLLECT_DEBUG
+  conf.beautify = 1;
+  conf.indentString = "  ";
+#endif
+  yajl_gen g = yajl_gen_alloc(&conf, NULL);
+  if (g == NULL)
+    return -1;
+#endif
+
+  yajl_gen_array_open(g);
+
+  int status = format_metrics_list(g, &(metrics_list_t){.metric = *m});
+  if (status != 0) {
+    yajl_gen_clear(g);
+    yajl_gen_free(g);
+    return status;
+  }
+
+  yajl_gen_array_close(g);
+
+  /* copy to output buffer */
+  unsigned char const *out = NULL;
+#if HAVE_YAJL_V2
+  size_t unused_out_len = 0;
+#else
+  unsigned int unused_out_len = 0;
+#endif
+  if (yajl_gen_get_buf(g, &out, &unused_out_len) != yajl_gen_status_ok) {
+    yajl_gen_clear(g);
+    yajl_gen_free(g);
+    return -1;
+  }
+  status = strbuf_print(buf, (void *)out);
+
+  yajl_gen_clear(g);
+  yajl_gen_free(g);
+  return status;
+} /* }}} format_json_metric */
+
 static int format_alert(yajl_gen g, notification_t const *n) /* {{{ */
 {
   CHECK_SUCCESS(yajl_gen_array_open(g)); /* BEGIN array */

src/utils/format_json/format_json.h

@@ -30,6 +30,7 @@
 #include "collectd.h"
 
 #include "plugin.h"
+#include "utils/strbuf/strbuf.h"
 
 #ifndef JSON_GAUGE_FORMAT
 #define JSON_GAUGE_FORMAT GAUGE_FORMAT
@@ -40,11 +41,13 @@ int format_json_initialize(char *buffer, size_t *ret_buffer_fill,
 int format_json_value_list(char *buffer, size_t *ret_buffer_fill,
                            size_t *ret_buffer_free, const data_set_t *ds,
                            const value_list_t *vl, int store_rates);
-int format_json_metric(char *buffer_p, size_t *ret_buffer_fill,
-                       size_t *ret_buffer_free, const metric_t *metric_p,
-                       int store_rates);
 int format_json_finalize(char *buffer, size_t *ret_buffer_fill,
                          size_t *ret_buffer_free);
+
+/* format_json_metric writes m to buf in JSON format. The format produces is
+ * compatible to the "prometheus/prom2json" project. */
+int format_json_metric(strbuf_t *buf, metric_t const *m, bool store_rates);
+
 int format_json_notification(char *buffer, size_t buffer_size,
                              notification_t const *n);