prom: basic builtin prometheus stats exporter

This is a vpp builtin alternative, not a replacement, for the existing
vpp_prometheus_exporter.

The plugin works by registering with http_static as a url handler for
stats.prom and handles requests by scraping the stats segment in the
main thread. It will therefore consume vpp process cpu cycles.

By default the plugin is disabled. To enable, first start the http
static server an then use "prom enable" cli.

Type: feature

Signed-off-by: Florin Coras <fcoras@cisco.com>
Change-Id: If6888e965d1b2361f6a5546586068213d37079d1

MAINTAINERS

@@ -779,6 +779,11 @@ I:	http
 M:	Florin Coras <fcoras@cisco.com>
 F:	src/plugins/http
 
+Plugin - Prom
+I:	prom
+M:	Florin Coras <fcoras@cisco.com>
+F:	src/plugins/prom
+
 cJSON
 I:	cjson
 M:	Ole Troan <ot@cisco.com>

src/plugins/http_static/static_server.c

@@ -300,6 +300,10 @@ hss_session_send_data (hss_url_handler_args_t *args)
   hss_session_t *hs;
 
   hs = hss_session_get (args->sh.thread_index, args->sh.session_index);
+
+  if (hs->data && hs->free_data)
+    vec_free (hs->data);
+
   hs->data = args->data;
   hs->data_len = args->data_len;
   hs->free_data = args->free_vec_data;

src/plugins/prom/CMakeLists.txt

@@ -0,0 +1,21 @@
+# Copyright (c) 2022 Cisco and/or its affiliates.
+# 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.
+
+add_vpp_plugin(prom
+  SOURCES
+  prom.c
+  prom_cli.c
+
+  LINK_LIBRARIES
+  vppapiclient
+)

src/plugins/prom/FEATURE.yaml

@@ -0,0 +1,10 @@
+---
+name: Prom (Prometheus Exporter)
+maintainer: Florin Coras <fcoras@cisco.com>
+features:
+  - Stats scraper
+  - Prometheus exporter
+description: "HTTP static server url handler that scrapes stats and exports
+              them in Prometheus format"
+state: experimental
+properties: [MULTITHREAD]

src/plugins/prom/prom.h

@@ -0,0 +1,58 @@
+/*
+ * Copyright (c) 2022 Cisco and/or its affiliates.
+ * 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.
+ */
+
+#ifndef SRC_PLUGINS_PROM_PROM_H_
+#define SRC_PLUGINS_PROM_PROM_H_
+
+#include <vnet/session/session.h>
+#include <http_static/http_static.h>
+
+typedef struct prom_main_
+{
+  u8 *stats;
+  f64 last_scrape;
+  hss_register_url_fn register_url;
+  hss_session_send_fn send_data;
+  u32 scraper_node_index;
+  u8 is_enabled;
+
+  u8 **stats_patterns;
+  f64 min_scrape_interval;
+  u8 used_only;
+  vlib_main_t *vm;
+} prom_main_t;
+
+typedef enum prom_process_evt_codes_
+{
+  PROM_SCRAPER_EVT_RUN,
+} prom_process_evt_codes_t;
+
+void prom_enable (vlib_main_t *vm);
+prom_main_t *prom_get_main (void);
+
+void prom_stat_patterns_set (u8 **patterns);
+void prom_stat_patterns_add (u8 **patterns);
+u8 **prom_stat_patterns_get (void);
+void prom_stat_patterns_free (void);
+
+#endif /* SRC_PLUGINS_PROM_PROM_H_ */
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */

src/plugins/prom/prom_cli.c

@@ -0,0 +1,147 @@
+/*
+ * Copyright (c) 2022 Cisco and/or its affiliates.
+ * 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 <prom/prom.h>
+
+static uword
+unformat_stats_patterns (unformat_input_t *input, va_list *args)
+{
+  u8 ***patterns = va_arg (*args, u8 ***);
+  u8 *pattern;
+
+  while (unformat_check_input (input) != UNFORMAT_END_OF_INPUT)
+    {
+      if (unformat (input, "%s", &pattern))
+	vec_add1 (*patterns, pattern);
+      else
+	return 0;
+    }
+  return 1;
+}
+
+static clib_error_t *
+prom_patterns_command_fn (vlib_main_t *vm, unformat_input_t *input,
+			  vlib_cli_command_t *cmd)
+{
+  unformat_input_t _line_input, *line_input = &_line_input;
+  u8 is_clear = 0, is_show = 0, **pattern = 0;
+  clib_error_t *error = 0;
+
+  if (!unformat_user (input, unformat_line_input, line_input))
+    return 0;
+
+  while (unformat_check_input (line_input) != UNFORMAT_END_OF_INPUT)
+    {
+      if (unformat (line_input, "show"))
+	is_show = 1;
+      else if (unformat (line_input, "clear"))
+	is_clear = 1;
+      else if (unformat (line_input, "add %U", unformat_stats_patterns,
+			 &pattern))
+	{
+	  prom_stat_patterns_add (pattern);
+	  vec_free (pattern);
+	}
+      else
+	{
+	  error = clib_error_return (0, "unknown input `%U'",
+				     format_unformat_error, line_input);
+	  break;
+	}
+    }
+  unformat_free (line_input);
+
+  if (error)
+    return error;
+
+  if (is_clear)
+    prom_stat_patterns_free ();
+
+  if (is_show)
+    {
+      u8 **patterns = prom_stat_patterns_get ();
+      vec_foreach (pattern, patterns)
+	vlib_cli_output (vm, " %v\n", *pattern);
+    }
+
+  return 0;
+}
+
+VLIB_CLI_COMMAND (prom_patterns_command, static) = {
+  .path = "prom patterns",
+  .short_help = "prom patterns [show] [clear] [add <patterns>...]",
+  .function = prom_patterns_command_fn,
+};
+
+static clib_error_t *
+prom_command_fn (vlib_main_t *vm, unformat_input_t *input,
+		 vlib_cli_command_t *cmd)
+{
+  unformat_input_t _line_input, *line_input = &_line_input;
+  prom_main_t *pm = prom_get_main ();
+  clib_error_t *error = 0;
+  u8 **patterns = 0;
+  u8 is_enable = 0;
+
+  if (!unformat_user (input, unformat_line_input, line_input))
+    goto no_input;
+
+  while (unformat_check_input (line_input) != UNFORMAT_END_OF_INPUT)
+    {
+      if (unformat (line_input, "enable"))
+	is_enable = 1;
+      else if (unformat (line_input, "min-scrape-interval %f",
+			 &pm->min_scrape_interval))
+	;
+      else if (unformat (line_input, "used-only"))
+	pm->used_only = 1;
+      else if (unformat (line_input, "stat-patterns %U",
+			 unformat_stats_patterns, &patterns))
+	prom_stat_patterns_set (patterns);
+      else
+	{
+	  error = clib_error_return (0, "unknown input `%U'",
+				     format_unformat_error, line_input);
+	  break;
+	}
+    }
+
+  unformat_free (line_input);
+
+  if (error)
+    return error;
+
+no_input:
+
+  if (is_enable && !pm->is_enabled)
+    prom_enable (vm);
+
+  return 0;
+}
+
+VLIB_CLI_COMMAND (prom_enable_command, static) = {
+  .path = "prom",
+  .short_help = "prom [enable] [min-scrape-interval <n>] [used-only]"
+		"[stat-patterns <patterns>...]",
+  .function = prom_command_fn,
+};
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */