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

1 files changed, 147 insertions, 0 deletions

diff --git a/src/plugins/prom/prom_cli.c b/src/plugins/prom/prom_cli.c
new file mode 100644
index 00000000000..453e8a066fc
--- /dev/null
+++ b/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:
+ */