Gather performance data after tempest

This makes us gather a bunch of consistent statistics after we run
tempest that can be use to measure the impact of a given change. These
are stable metrics such as "number of DB queries made" and "how much
memory is each service using after a tempest run."

Note that this will always run after devstack to generate the JSON
file, but there are two things that control its completeness:

 - MYSQL_GATHER_PERFORMANCE must be enabled to get per-db stats
 - Unless tls-proxy is enabled, we will only get API stats for keystone

Change-Id: Ie3b1504256dc1c9c6b59634e86fa98494bcb07b1
diff --git a/roles/capture-performance-data/tasks/main.yaml b/roles/capture-performance-data/tasks/main.yaml
new file mode 100644
index 0000000..2d2cfe4
--- /dev/null
+++ b/roles/capture-performance-data/tasks/main.yaml
@@ -0,0 +1,15 @@
+- name: Generate statistics
+  shell:
+    executable: /bin/bash
+    cmd: |
+      source {{ devstack_conf_dir }}/stackrc
+      python3 {{ devstack_conf_dir }}/tools/get-stats.py \
+        --db-user="$DATABASE_USER" \
+        --db-pass="$DATABASE_PASSWORD" \
+        --db-host="$DATABASE_HOST" \
+        {{ apache_logs }} > {{ stage_dir }}/performance.json
+  vars:
+    apache_logs: >-
+      {% for i in debian_suse_apache_deref_logs.results | default([]) + redhat_apache_deref_logs.results | default([]) %}
+      --apache-log="{{ i.stat.path }}"
+      {% endfor %}