+static void prom_logger(__attribute__((unused)) void *arg, char const *fmt,
+ va_list ap) {
+ /* {{{ */
+ char errbuf[1024];
+ vsnprintf(errbuf, sizeof(errbuf), fmt, ap);
+
+ ERROR("write_prometheus plugin: %s", errbuf);
+} /* }}} prom_logger */
+
+#if MHD_VERSION >= 0x00090000
+static int prom_open_socket(int addrfamily) {
+ /* {{{ */
+ char service[NI_MAXSERV];
+ snprintf(service, sizeof(service), "%hu", httpd_port);
+
+ struct addrinfo *res;
+ int status = getaddrinfo(httpd_host, service,
+ &(struct addrinfo){
+ .ai_flags = AI_PASSIVE | AI_ADDRCONFIG,
+ .ai_family = addrfamily,
+ .ai_socktype = SOCK_STREAM,
+ },
+ &res);
+ if (status != 0) {
+ return -1;
+ }
+
+ int fd = -1;
+ for (struct addrinfo *ai = res; ai != NULL; ai = ai->ai_next) {
+ fd = socket(ai->ai_family, ai->ai_socktype | SOCK_CLOEXEC, 0);
+ if (fd == -1)
+ continue;
+
+ if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &(int){1}, sizeof(int)) != 0) {
+ WARNING("write_prometheus plugin: setsockopt(SO_REUSEADDR) failed: %s",
+ STRERRNO);
+ close(fd);
+ fd = -1;
+ continue;
+ }
+
+ if (bind(fd, ai->ai_addr, ai->ai_addrlen) != 0) {
+ close(fd);
+ fd = -1;
+ continue;
+ }
+
+ if (listen(fd, /* backlog = */ 16) != 0) {
+ close(fd);
+ fd = -1;
+ continue;
+ }
+
+ char str_node[NI_MAXHOST];
+ char str_service[NI_MAXSERV];
+
+ getnameinfo(ai->ai_addr, ai->ai_addrlen, str_node, sizeof(str_node),
+ str_service, sizeof(str_service),
+ NI_NUMERICHOST | NI_NUMERICSERV);
+
+ INFO("write_prometheus plugin: Listening on [%s]:%s.", str_node,
+ str_service);
+ break;
+ }
+
+ freeaddrinfo(res);
+
+ return fd;
+} /* }}} int prom_open_socket */
+
+static struct MHD_Daemon *prom_start_daemon() {
+ /* {{{ */
+ int fd = prom_open_socket(PF_INET6);
+ if (fd == -1)
+ fd = prom_open_socket(PF_INET);
+ if (fd == -1) {
+ ERROR("write_prometheus plugin: Opening a listening socket for [%s]:%hu "
+ "failed.",
+ (httpd_host != NULL) ? httpd_host : "::", httpd_port);
+ return NULL;
+ }
+
+ unsigned int flags = MHD_USE_THREAD_PER_CONNECTION | MHD_USE_DEBUG;
+#if MHD_VERSION >= 0x00095300
+ flags |= MHD_USE_INTERNAL_POLLING_THREAD;
+#endif
+
+ struct MHD_Daemon *d = MHD_start_daemon(
+ flags, httpd_port,
+ /* MHD_AcceptPolicyCallback = */ NULL,
+ /* MHD_AcceptPolicyCallback arg = */ NULL, http_handler, NULL,
+ MHD_OPTION_LISTEN_SOCKET, fd, MHD_OPTION_EXTERNAL_LOGGER, prom_logger,
+ NULL, MHD_OPTION_END);
+ if (d == NULL) {
+ ERROR("write_prometheus plugin: MHD_start_daemon() failed.");
+ close(fd);
+ return NULL;
+ }
+
+ return d;
+} /* }}} struct MHD_Daemon *prom_start_daemon */
+#else /* if MHD_VERSION < 0x00090000 */
+static struct MHD_Daemon *prom_start_daemon() {
+ /* {{{ */
+ struct MHD_Daemon *d = MHD_start_daemon(
+ MHD_USE_THREAD_PER_CONNECTION | MHD_USE_DEBUG, httpd_port,
+ /* MHD_AcceptPolicyCallback = */ NULL,
+ /* MHD_AcceptPolicyCallback arg = */ NULL, http_handler, NULL,
+ MHD_OPTION_EXTERNAL_LOGGER, prom_logger, NULL, MHD_OPTION_END);
+ if (d == NULL) {
+ ERROR("write_prometheus plugin: MHD_start_daemon() failed.");
+ return NULL;
+ }
+
+ return d;
+} /* }}} struct MHD_Daemon *prom_start_daemon */
+#endif
+