text: /* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
  
  /*  Fluent Bit
   *  ==========
   *  Copyright (C) 2019-2021 The Fluent Bit Authors
   *  Copyright (C) 2015-2018 Treasure Data Inc.
   *
   *  Licensed under the Apache License, Version 2.0 (the "License");
   *  you may not use this file except in compliance with the License.
   *  You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   *  Unless required by applicable law or agreed to in writing, software
   *  distributed under the License is distributed on an "AS IS" BASIS,
   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   *  See the License for the specific language governing permissions and
   *  limitations under the License.
   */
  
  #include <fluent-bit/flb_output_plugin.h>
  
  #include "prom.h"
  #include "prom_http.h"
  
  pthread_key_t ph_metrics_key;
  
  /* Return the newest storage metrics buffer */
  static struct prom_http_buf *metrics_get_latest()
  {
      struct prom_http_buf *buf;
      struct mk_list *metrics_list;
  
      metrics_list = pthread_getspecific(ph_metrics_key);
      if (!metrics_list) {
          return NULL;
      }
  
      if (mk_list_size(metrics_list) == 0) {
          return NULL;
      }
  
      buf = mk_list_entry_last(metrics_list, struct prom_http_buf, _head);
      return buf;
  }
  
  /* Delete unused metrics, note that we only care about the latest node */
  static int cleanup_metrics()
  {
      int c = 0;
      struct mk_list *tmp;
      struct mk_list *head;
      struct mk_list *metrics_list;
      struct prom_http_buf *last;
      struct prom_http_buf *entry;
  
      metrics_list = pthread_getspecific(ph_metrics_key);
      if (!metrics_list) {
          return -1;
      }
  
      last = metrics_get_latest();
      if (!last) {
          return -1;
      }
  
      mk_list_foreach_safe(head, tmp, metrics_list) {
          entry = mk_list_entry(head, struct prom_http_buf, _head);
          if (entry != last && entry->users == 0) {
              mk_list_del(&entry->_head);
              flb_free(entry->buf_data);
              flb_free(entry);
              c++;
          }
      }
  
      return c;
  }
  
  /*
   * Callback invoked every time a new payload of Metrics is received from
   * Fluent Bit engine through Message Queue channel.
   *
   * This function runs in a Monkey HTTP thread worker and it purpose is
   * to take the metrics data and store it locally for every thread, so then
   * it can be available on 'cb_metrics()' to serve it as a response.
   */
  static void cb_mq_metrics(mk_mq_t *queue, void *data, size_t size)
  {
      struct prom_http_buf *buf;
      struct mk_list *metrics_list = NULL;
  
      metrics_list = pthread_getspecific(ph_metrics_key);
      if (!metrics_list) {
          metrics_list = flb_malloc(sizeof(struct mk_list));
          if (!metrics_list) {
              flb_errno();
              return;
          }
          mk_list_init(metrics_list);
          pthread_setspecific(ph_metrics_key, metrics_list);
      }
  
      /* FIXME: convert data ? */
      buf = flb_malloc(sizeof(struct prom_http_buf));
      if (!buf) {
          flb_errno();
          return;
      }
      buf->users = 0;
      buf->buf_data = flb_malloc(size);
      if (!buf->buf_data) {
          flb_errno();
          flb_free(buf);
          return;
      }
      memcpy(buf->buf_data, data, size);
      buf->buf_size = size;
  
      mk_list_add(&buf->_head, metrics_list);
      cleanup_metrics();
  }
  
  /* Create message queue to receive Metrics payload from the engine */
  static int http_server_mq_create(struct prom_http *ph)
  {
      int ret;
  
      pthread_key_create(&ph_metrics_key, NULL);
  
      ret = mk_mq_create(ph->ctx, "/metrics", cb_mq_metrics, NULL);
      if (ret == -1) {
          return -1;
      }
      ph->qid_metrics = ret;
      return 0;
  }
  
  /* HTTP endpoint: /metrics */
  static void cb_metrics(mk_request_t *request, void *data)
  {
      struct prom_http_buf *buf;
      (void) data;
  
      buf = metrics_get_latest();
      if (!buf) {
          mk_http_status(request, 404);
          mk_http_done(request);
          return;
      }
  
      buf->users++;
  
      mk_http_status(request, 200);
      mk_http_send(request, buf->buf_data, buf->buf_size, NULL);
      mk_http_done(request);
  
      buf->users--;
  }
  
  /* HTTP endpoint: / (root) */
  static void cb_root(mk_request_t *request, void *data)
  {
      (void) data;
  
      mk_http_status(request, 200);
      mk_http_send(request, "Fluent Bit Prometheus Exporter\n", 31, NULL);
      mk_http_done(request);
  }
  
  struct prom_http *prom_http_server_create(struct prom_exporter *ctx,
                                            const char *listen,
                                            const char *tcp_port,
                                            struct flb_config *config)
  {
      int ret;
      int vid;
      char tmp[32];
      struct prom_http *ph;
  
      ph = flb_malloc(sizeof(struct prom_http));
      if (!ph) {
          flb_errno();
          return NULL;
      }
      ph->config = config;
  
      /* HTTP Server context */
      ph->ctx = mk_create();
      if (!ph->ctx) {
          flb_free(ph);
          return NULL;
      }
  
      /* Compose listen address */
      snprintf(tmp, sizeof(tmp) -1, "%s:%s", listen, tcp_port);
      mk_config_set(ph->ctx,
                    "Listen", tmp,
                    "Workers", "1",
                    NULL);
  
      /* Virtual host */
      vid = mk_vhost_create(ph->ctx, NULL);
      ph->vid = vid;
  
      /* Set HTTP URI callbacks */
      mk_vhost_handler(ph->ctx, vid, "/metrics", cb_metrics, NULL);
      mk_vhost_handler(ph->ctx, vid, "/", cb_root, NULL);
  
      /* Create a Message Queue to push 'metrics' to HTTP workers */
      ret = http_server_mq_create(ph);
      if (ret == -1) {
          mk_destroy(ph->ctx);
          flb_free(ph);
          return NULL;
      }
  
      return ph;
  }
  
  void prom_http_server_destroy(struct prom_http *ph)
  {
  
  }
  
  int prom_http_server_start(struct prom_http *ph)
  {
      return mk_start(ph->ctx);
  }
  
  
  int prom_http_server_stop(struct prom_http *ph)
  {
      return mk_stop(ph->ctx);
  }
  
  
  int prom_http_server_mq_push_metrics(struct prom_http *ph,
                                       void *data, size_t size)
  {
      return mk_mq_send(ph->ctx, ph->qid_metrics, data, size);
  }
  