tracer: Add new tracer to list loaded elements and other features

This new tracer will list loaded elements and plugins. This should
make it easier to generate minimal builds of GStreamer.

This also traces other features such as typefind functions, device
providers and dynamic types.

The format of the output of gst-stats should match the parameters
expected by the meson based gst-build system.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/782>

6 files changed, 390 insertions, 0 deletions

diff --git a/docs/plugins/gst_plugins_cache.json b/docs/plugins/gst_plugins_cache.json
index 66f5bd1f6c..67927f5652 100644
--- a/docs/plugins/gst_plugins_cache.json
+++ b/docs/plugins/gst_plugins_cache.json
@@ -2868,6 +2868,7 @@
         "package": "GStreamer",
         "source": "gstreamer",
         "tracers": {
+            "factories": {},
             "latency": {},
             "leaks": {},
             "log": {},
diff --git a/plugins/tracers/gstfactories.c b/plugins/tracers/gstfactories.c
new file mode 100644
index 0000000000..fbb2505e20
--- /dev/null
+++ b/plugins/tracers/gstfactories.c
@@ -0,0 +1,187 @@
+/* GStreamer
+ * Copyright (C) 2021 Collabora Ltd.
+ *  @author: Olivier Crete <olivier.crete@collabora.com>
+ *
+ * gstfactories.c: A trace to log which plugin & factories are being used
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ */
+/**
+ * SECTION:tracer-factories
+ * @short_description: log plugin and factories
+ *
+ * A tracing module that logs which plugins and factories are being used.
+ *
+ * This tracing module is particularly useful in conjuction with the `gst-stats`
+ * program to generate a list of plugins and elements that are loaded by a
+ * particular application to generate a minimal custom build of GStreamer.
+ *
+ * As a very simple example, you can run your application like this:
+ * ```
+ * $ GST_TRACERS=factories GST_DEBUG=GST_TRACER:7 gst-launch-1.0 audiotestsrc num-buffers=10 ! fakesink 2> log.txt
+ * ...
+ * $ gst-stats-1.0 log.txt
+ * Plugins used: audiotestsrc;coreelements
+ * Elements: audiotestsrc:audiotestsrc;coreelements:fakesink
+ * Device-providers:
+ * Typefinds:
+ * Dynamic-types:
+ * ```
+ *
+ * Based on this information, one can build a minimal, yet sufficient
+ * build of GStreamer using gst-build with a configuration like this one:
+ * ```
+ * meson setup builddir -Dgst-full-elements="audiotestsrc:audiotestsrc;coreelements:fakesink"
+ * ```
+ *
+ * Since: 1.20
+ */
+
+#ifdef HAVE_CONFIG_H
+#  include "config.h"
+#endif
+
+#include "gstfactories.h"
+
+G_DEFINE_TYPE (GstFactoriesTracer, gst_factories_tracer, GST_TYPE_TRACER);
+
+static GstTracerRecord *tr_factory_used;
+
+static void
+do_element_new (GstFactoriesTracer * self, GstClockTime ts,
+    GstElement * element)
+{
+  const gchar *plugin_name;
+  const gchar *factory_name;
+  GstPluginFeature *feature;
+  GstElementFactory *factory = gst_element_get_factory (element);
+  const gchar *source_module_name = "Unknown";
+  GstPlugin *plugin;
+
+  if (factory == NULL)
+    return;
+
+  feature = GST_PLUGIN_FEATURE (factory);
+
+  factory_name = gst_plugin_feature_get_name (feature);
+  plugin_name = gst_plugin_feature_get_plugin_name (feature);
+
+  if (factory_name == NULL)
+    factory_name = "";
+  if (plugin_name == NULL)
+    plugin_name = "";
+
+  plugin = gst_plugin_feature_get_plugin (feature);
+  if (plugin)
+    source_module_name = gst_plugin_get_source (plugin);
+
+  gst_tracer_record_log (tr_factory_used,
+      (guint64) (guintptr) g_thread_self (), ts, "element", factory_name,
+      plugin_name, source_module_name);
+
+  g_clear_object (&plugin);
+}
+
+static void
+do_plugin_feature_loaded (GstFactoriesTracer * self, GstClockTime ts,
+    GstPluginFeature * feature)
+{
+  const gchar *plugin_name;
+  const gchar *factory_name;
+  const gchar *factory_type;
+  const gchar *source_module_name = "Unknown";
+  GstPlugin *plugin;
+
+  /* Only care about elements when one is created */
+  if (GST_IS_ELEMENT_FACTORY (feature))
+    return;
+
+  if (GST_IS_TYPE_FIND_FACTORY (feature))
+    factory_type = "typefind";
+  else if (GST_IS_DEVICE_PROVIDER_FACTORY (feature))
+    factory_type = "device-provider";
+  else if (GST_IS_DYNAMIC_TYPE_FACTORY (feature))
+    factory_type = "dynamic-type";
+  else
+    g_assert_not_reached ();
+
+  factory_name = gst_plugin_feature_get_name (feature);
+  plugin_name = gst_plugin_feature_get_plugin_name (feature);
+
+  if (factory_name == NULL)
+    factory_name = "";
+  if (plugin_name == NULL)
+    plugin_name = "";
+
+  plugin = gst_plugin_feature_get_plugin (feature);
+  if (plugin)
+    source_module_name = gst_plugin_get_source (plugin);
+  if (source_module_name == NULL)
+    source_module_name = "";
+
+  gst_tracer_record_log (tr_factory_used,
+      (guint64) (guintptr) g_thread_self (), ts, factory_type, factory_name,
+      plugin_name, source_module_name);
+
+  g_clear_object (&plugin);
+}
+
+static void
+gst_factories_tracer_class_init (GstFactoriesTracerClass * klass)
+{
+  /* announce trace formats */
+  /* *INDENT-OFF* */
+  tr_factory_used = gst_tracer_record_new ("factory-used.class",
+      "thread-id", GST_TYPE_STRUCTURE, gst_structure_new ("scope",
+          "type", G_TYPE_GTYPE, G_TYPE_UINT64,
+          "related-to", GST_TYPE_TRACER_VALUE_SCOPE, GST_TRACER_VALUE_SCOPE_THREAD,
+          NULL),
+      "ts", GST_TYPE_STRUCTURE, gst_structure_new ("value",
+          "type", G_TYPE_GTYPE, G_TYPE_UINT64,
+          "description", G_TYPE_STRING, "event ts",
+          NULL),
+      "factory-type", GST_TYPE_STRUCTURE, gst_structure_new ("value",
+          "type", G_TYPE_GTYPE, G_TYPE_STRING,
+          "description", G_TYPE_STRING, "type name of the factory",
+          NULL),
+      "factory", GST_TYPE_STRUCTURE, gst_structure_new ("value",
+          "type", G_TYPE_GTYPE, G_TYPE_STRING,
+          "description", G_TYPE_STRING, "name of the object factory",
+          NULL),
+      "plugin", GST_TYPE_STRUCTURE, gst_structure_new ("value",
+          "type", G_TYPE_GTYPE, G_TYPE_STRING,
+          "description", G_TYPE_STRING, "name of the plugin",
+          NULL),
+      "source-module", GST_TYPE_STRUCTURE, gst_structure_new ("value",
+          "type", G_TYPE_GTYPE, G_TYPE_STRING,
+          "description", G_TYPE_STRING, "name of the source module this feature is from",
+          NULL),
+     NULL);
+  /* *INDENT-ON* */
+
+  GST_OBJECT_FLAG_SET (tr_factory_used, GST_OBJECT_FLAG_MAY_BE_LEAKED);
+}
+
+static void
+gst_factories_tracer_init (GstFactoriesTracer * self)
+{
+  GstTracer *tracer = GST_TRACER (self);
+
+  gst_tracing_register_hook (tracer, "element-new",
+      G_CALLBACK (do_element_new));
+  gst_tracing_register_hook (tracer, "plugin-feature-loaded",
+      G_CALLBACK (do_plugin_feature_loaded));
+}
diff --git a/plugins/tracers/gstfactories.h b/plugins/tracers/gstfactories.h
new file mode 100644
index 0000000000..950551538a
--- /dev/null
+++ b/plugins/tracers/gstfactories.h
@@ -0,0 +1,46 @@
+/* GStreamer
+ * Copyright (C) 2021 Collabora Ltd.
+ *  @author: Olivier Crete <olivier.crete@collabora.com>
+ *
+ * gstfactories.h: A trace to log which plugin & factories are being used
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#ifndef __GST_FACTORIES_TRACER_H__
+#define __GST_FACTORIES_TRACER_H__
+
+#include <gst/gst.h>
+#include <gst/gsttracer.h>
+
+G_BEGIN_DECLS
+
+G_DECLARE_FINAL_TYPE(GstFactoriesTracer, gst_factories_tracer, GST,
+    FACTORIES_TRACER, GstTracer)
+/**
+ * GstFactoriesTracer:
+ *
+ * Opaque #GstFactoriesTracer data structure
+ */
+struct _GstFactoriesTracer {
+  GstTracer 	 parent;
+
+  /*< private >*/
+};
+
+G_END_DECLS
+
+#endif /* __GST_FACTORIES_TRACER_H__ */
diff --git a/plugins/tracers/gsttracers.c b/plugins/tracers/gsttracers.c
index b03e25aeec..e5fe5d0581 100644
--- a/plugins/tracers/gsttracers.c
+++ b/plugins/tracers/gsttracers.c
@@ -29,6 +29,7 @@
 #include "gstrusage.h"
 #include "gststats.h"
 #include "gstleaks.h"
+#include "gstfactories.h"
 
 static gboolean
 plugin_init (GstPlugin * plugin)
@@ -47,6 +48,9 @@ plugin_init (GstPlugin * plugin)
     return FALSE;
   if (!gst_tracer_register (plugin, "leaks", gst_leaks_tracer_get_type ()))
     return FALSE;
+  if (!gst_tracer_register (plugin, "factories",
+          gst_factories_tracer_get_type ()))
+    return FALSE;
   return TRUE;
 }
 
diff --git a/plugins/tracers/meson.build b/plugins/tracers/meson.build
index 879cd9394f..8039c9be85 100644
--- a/plugins/tracers/meson.build
+++ b/plugins/tracers/meson.build
@@ -10,6 +10,7 @@ gst_tracers_sources = [
   'gstleaks.c',
   'gststats.c',
   'gsttracers.c',
+  'gstfactories.c'
 ]
 
 if gst_debug
diff --git a/tools/gst-stats.c b/tools/gst-stats.c
index 8b490905c0..597c1ba1b7 100644
--- a/tools/gst-stats.c
+++ b/tools/gst-stats.c
@@ -47,6 +47,8 @@ static GstClockTime last_ts = G_GUINT64_CONSTANT (0);
 static guint total_cpuload = 0;
 static gboolean have_cpuload = FALSE;
 
+static GPtrArray *plugin_stats = NULL;
+
 static gboolean have_latency = FALSE;
 static gboolean have_element_latency = FALSE;
 static gboolean have_element_reported_latency = FALSE;
@@ -122,6 +124,22 @@ typedef struct
   guint cpuload;
 } GstThreadStats;
 
+static const gchar *FACTORY_TYPES[] = {
+  "element",
+  "device-provider",
+  "typefind",
+  "dynamic-type",
+};
+
+#define N_FACTORY_TYPES G_N_ELEMENTS(FACTORY_TYPES)
+
+typedef struct
+{
+  gchar *name;
+
+  GPtrArray *factories[N_FACTORY_TYPES];
+} GstPluginStats;
+
 /* stats helper */
 
 static gint
@@ -283,6 +301,36 @@ free_thread_stats (gpointer data)
   g_slice_free (GstThreadStats, data);
 }
 
+static GstPluginStats *
+new_plugin_stats (const gchar * plugin_name)
+{
+  GstPluginStats *plugin = g_slice_new (GstPluginStats);
+  guint i;
+
+  plugin->name = g_strdup (plugin_name);
+
+  for (i = 0; i < N_FACTORY_TYPES; i++)
+    plugin->factories[i] = g_ptr_array_new_with_free_func (g_free);
+
+  g_ptr_array_add (plugin_stats, plugin);
+
+  return plugin;
+}
+
+static void
+free_plugin_stats (gpointer data)
+{
+  GstPluginStats *plugin = data;
+  guint i;
+
+  g_free (plugin->name);
+
+  for (i = 0; i < N_FACTORY_TYPES; i++)
+    g_ptr_array_unref (plugin->factories[i]);
+
+  g_slice_free (GstPluginStats, data);
+}
+
 static void
 do_pad_stats (GstPadStats * stats, guint elem_ix, guint size, guint64 ts,
     guint64 buffer_ts, guint64 buffer_dur, GstBufferFlags buffer_flags)
@@ -608,6 +656,48 @@ do_element_reported_latency (GstStructure * s)
   have_element_reported_latency = TRUE;
 }
 
+static void
+do_factory_used (GstStructure * s)
+{
+  const gchar *factory = NULL;
+  const gchar *factory_type = NULL;
+  const gchar *plugin_name = NULL;
+  GstPluginStats *plugin = NULL;
+  guint i, f;
+
+  factory = gst_structure_get_string (s, "factory");
+  factory_type = gst_structure_get_string (s, "factory-type");
+  plugin_name = gst_structure_get_string (s, "plugin");
+
+  if (!g_strcmp0 (plugin_name, "staticelements"))
+    return;
+
+  if (plugin_name == NULL || plugin_name[0] == 0)
+    plugin_name = "built-in";
+
+  for (f = 0; f < N_FACTORY_TYPES; f++)
+    if (!g_strcmp0 (factory_type, FACTORY_TYPES[f]))
+      break;
+  if (f == N_FACTORY_TYPES)
+    return;
+
+  for (i = 0; i < plugin_stats->len; i++) {
+    GstPluginStats *tmp_plugin = g_ptr_array_index (plugin_stats, i);
+    if (!strcmp (tmp_plugin->name, plugin_name)) {
+      plugin = tmp_plugin;
+      break;
+    }
+  }
+
+  if (plugin == NULL)
+    plugin = new_plugin_stats (plugin_name);
+
+  if (factory && factory[0] &&
+      !g_ptr_array_find_with_equal_func (plugin->factories[f], factory,
+          g_str_equal, NULL))
+    g_ptr_array_add (plugin->factories[f], g_strdup (factory));
+}
+
 /* reporting */
 
 static gint
@@ -874,6 +964,8 @@ init (void)
       free_latency_stats);
   element_reported_latencies = g_queue_new ();
 
+  plugin_stats = g_ptr_array_new_with_free_func (free_plugin_stats);
+
   return TRUE;
 }
 
@@ -902,12 +994,32 @@ done (void)
     element_reported_latencies = NULL;
   }
 
+  g_clear_pointer (&plugin_stats, g_ptr_array_unref);
+
   if (raw_log)
     g_regex_unref (raw_log);
   if (ansi_log)
     g_regex_unref (ansi_log);
 }
 
+static gint
+compare_plugin_stats (gconstpointer a, gconstpointer b)
+{
+  const GstPluginStats *plugin_a = *(GstPluginStats **) a;
+  const GstPluginStats *plugin_b = *(GstPluginStats **) b;
+
+  return strcmp (plugin_a->name, plugin_b->name);
+}
+
+static gint
+compare_string (gconstpointer a, gconstpointer b)
+{
+  const char *str_a = *(const char **) a;
+  const char *str_b = *(const char **) b;
+
+  return strcmp (str_a, str_b);
+}
+
 static void
 print_stats (void)
 {
@@ -1012,6 +1124,43 @@ print_stats (void)
         (GFunc) reported_latencies_foreach_print_stats, NULL);
     puts ("");
   }
+
+  if (plugin_stats->len > 0) {
+    guint i, j, f;
+
+    g_ptr_array_sort (plugin_stats, compare_plugin_stats);
+
+    printf ("Plugins used: ");
+    for (i = 0; i < plugin_stats->len; i++) {
+      GstPluginStats *ps = g_ptr_array_index (plugin_stats, i);
+      printf ("%s%s", i == 0 ? "" : ";", ps->name);
+    }
+    printf ("\n");
+
+    for (f = 0; f < N_FACTORY_TYPES; f++) {
+      gboolean first = TRUE;
+
+      printf ("%c%ss: ", g_ascii_toupper (FACTORY_TYPES[f][0]),
+          FACTORY_TYPES[f] + 1);
+      for (i = 0; i < plugin_stats->len; i++) {
+        GstPluginStats *ps = g_ptr_array_index (plugin_stats, i);
+
+        if (ps->factories[f]->len > 0) {
+          printf ("%s%s:", first ? "" : ";", ps->name);
+          first = FALSE;
+
+          g_ptr_array_sort (ps->factories[f], compare_string);
+
+          for (j = 0; j < ps->factories[f]->len; j++) {
+            const gchar *factory = g_ptr_array_index (ps->factories[f], j);
+
+            printf ("%s%s", j == 0 ? "" : ",", factory);
+          }
+        }
+      }
+      printf ("\n");
+    }
+  }
 }
 
 static void
@@ -1072,6 +1221,8 @@ collect_stats (const gchar * filename)
                   do_element_latency_stats (s);
                 } else if (!strcmp (name, "element-reported-latency")) {
                   do_element_reported_latency (s);
+                } else if (!strcmp (name, "factory-used")) {
+                  do_factory_used (s);
                 } else {
                   // TODO(ensonic): parse the xxx.class log lines
                   if (!g_str_has_suffix (data, ".class")) {