[docker] A few improvements as per PR review

See comments on #1908

checks.d/docker_daemon.py

@@ -190,7 +190,7 @@ def init(self):
 
 
             # Other options
-            self.collect_image_stats = _is_affirmative(instance.get('collect_images_stats', True))
+            self.collect_image_stats = _is_affirmative(instance.get('collect_images_stats', False))
             self.collect_container_size = _is_affirmative(instance.get('collect_container_size', False))
             self.collect_events = _is_affirmative(instance.get('collect_events', True))
             self.collect_image_size = _is_affirmative(instance.get('collect_image_size', False))
@@ -638,6 +638,7 @@ def _crawl_container_pids(self, container_dict):
             self.warning("Unable to find any pid directory in {0}. "
                 "If you are running the agent in a container, make sure to "
                 'share the volume properly: "/proc:/host/proc:ro". '
+                "See https://github.com/DataDog/docker-dd-agent/blob/master/README.md for more information. "
                 "Network metrics will be missing".format(proc_path))
             self._disable_net_metrics = True
             return container_dict

conf.d/docker.yaml.example

@@ -67,6 +67,6 @@ instances:
     # collect_all_metrics: false
 
     # Collect images stats
-    # Number of available active images and intermediate images as gauges. Default: false.
+    # Number of available active images and intermediate images as gauges. Default: true.
     #
     collect_images_stats: false

conf.d/docker_daemon.yaml.example

@@ -47,9 +47,9 @@ instances:
 
     # Collect images stats
     # Number of available active images and intermediate images as gauges.
-    # Defaults to true.
+    # Defaults to false.
     #
-    collect_images_stats: false
+    # collect_images_stats: false
 
     # Collect disk usage per image with docker.image.size and docker.image.virtual_size metrics.
     # The check gets this size with the `docker images` command.

tests/checks/integration/test_docker_daemon.py

@@ -89,6 +89,7 @@ def test_basic_config_single(self):
             "instances": [{
                 "url": "unix://var/run/docker.sock",
                 "collect_image_size": True,
+                "collect_images_stats": True,
             },
             ],
         }
@@ -133,6 +134,7 @@ def test_basic_config_twice(self):
             "instances": [{
                 "url": "unix://var/run/docker.sock",
                 "tags": custom_tags,
+                "collect_images_stats": True,
             },
             ],
         }
@@ -184,6 +186,7 @@ def test_exclude_filter(self):
             "instances": [{
                 "url": "unix://var/run/docker.sock",
                 "exclude": ["docker_image:nginx"],
+                "collect_images_stats": True,
                 "collect_image_size": True,
             },
             ],
@@ -250,6 +253,7 @@ def test_include_filter(self):
                 "url": "unix://var/run/docker.sock",
                 "include": ["image_name:redis"],
                 "exclude": [".*"],
+                "collect_images_stats": True,
                 "collect_image_size": True,
             },
             ],
@@ -327,6 +331,7 @@ def test_tags_options(self):
                 "url": "unix://var/run/docker.sock",
                 "performance_tags": ["container_command"],
                 "container_tags": ["container_command"],
+                "collect_images_stats": True,
                 "collect_image_size": True,
             },
             ],
@@ -397,6 +402,7 @@ def test_labels_collection(self):
                 "url": "unix://var/run/docker.sock",
                 "collect_labels_as_tags": ["label1"],
                 "collect_image_size": True,
+                "collect_images_stats": True,
             },
             ],
         }
@@ -410,6 +416,7 @@ def test_events(self):
             "init_config": {},
             "instances": [{
                 "url": "unix://var/run/docker.sock",
+                "collect_images_stats": True,
             },
             ],
         }
@@ -460,6 +467,7 @@ def test_container_size(self):
                 "url": "unix://var/run/docker.sock",
                 "collect_container_size": True,
                 "collect_image_size": True,
+                "collect_images_stats": True,
             },
             ],
         }