Run the Docker check for one instance.

def check(self, instance):
        """Run the Docker check for one instance."""
        if not self.init_success:
            # Initialization can fail if cgroups are not ready or docker daemon is down. So we retry if needed
            # https://github.com/DataDog/dd-agent/issues/1896
            self.init()

            try:
                if self.docker_util.client is None:
                    message = "Unable to connect to Docker daemon"
                    self.service_check(SERVICE_CHECK_NAME, AgentCheck.CRITICAL,
                                       message=message, tags=self.custom_tags)
                    return
            except Exception as ex:
                self.service_check(SERVICE_CHECK_NAME, AgentCheck.CRITICAL,
                                   message=str(ex), tags=self.custom_tags)
                return

            if not self.init_success:
                # Initialization failed, will try later
                return

        try:
            # Report image metrics
            if self.collect_image_stats:
                self._count_and_weigh_images()

            if Platform.is_k8s():
                self.kube_pod_tags = {}
                if self.kubeutil:
                    try:
                        self.kube_pod_tags = self.kubeutil.get_kube_pod_tags()
                    except Exception as e:
                        self.log.warning('Could not retrieve kubernetes labels: %s' % str(e))

            # containers running with custom cgroups?
            custom_cgroups = _is_affirmative(instance.get('custom_cgroups', False))

            # Get the list of containers and the index of their names
            health_service_checks = True if self.whitelist_patterns else False
            containers_by_id = self._get_and_count_containers(custom_cgroups, health_service_checks)
            containers_by_id = self._crawl_container_pids(containers_by_id, custom_cgroups)

            # Send events from Docker API
            if self.collect_events or self._service_discovery or not self._disable_net_metrics or self.collect_exit_codes:
                self._process_events(containers_by_id)

            # Report performance container metrics (cpu, mem, net, io)
            self._report_performance_metrics(containers_by_id)

            if self.collect_container_size:
                self._report_container_size(containers_by_id)

            if self.collect_container_count:
                self._report_container_count(containers_by_id)

            if self.collect_volume_count:
                self._report_volume_count()

            # Collect disk stats from Docker info command
            if self.collect_disk_stats:
                self._report_disk_stats()

            if health_service_checks:
                self._send_container_healthcheck_sc(containers_by_id)
        except:
            self.log.exception("Docker_daemon check failed")
            self.warning("Check failed. Will retry at next iteration")

        if self.capped_metrics:
            self.filter_capped_metrics()