Fix tasks dependency when using remote backends

Previously the LMA collector had an explicit dependency on the last
InfluxDB task but this doesn't work when the InfluxDB/Grafana
plugin isn't deployed in the same environment as the collector plugin.

This change makes sure that the LMA collector plugin's tasks will
only be executed once the InfluxDB cluster is fully functional by
pinning both plugins to a well-known task (update_hosts in that case).

Partial-Bug: #1573087
Closes-Bug: #1578194
Change-Id: I830f024e0d1629ae10a8a504c4acbddf23d5c47e

deployment_tasks.yaml

@@ -18,6 +18,7 @@
     - influxdb-cluster-haproxy
     - influxdb-vip
     - influxdb-haproxy
+    - influxdb-installation
   requires: [deploy_start]
   required_for: [deploy_end]
   parameters:
@@ -35,7 +36,9 @@
     strategy:
       type: parallel
 
-# Tasks definitions for deployment
+# Tasks definitions for the deployment
+######################################
+
 - id: influxdb-hiera
   type: puppet
   version: 2.0.0
@@ -108,7 +111,19 @@
   reexecute_on:
     - deploy_changes
 
-# Tasks definitions for post-deployment
+- id: influxdb-installation
+  type: puppet
+  version: 2.0.0
+  requires: [influxdb-haproxy]
+  required_for: [deploy_end]
+  parameters:
+    puppet_manifest: "puppet/manifests/influxdb.pp"
+    puppet_modules: puppet/modules:/etc/puppet/modules
+    timeout: 600
+
+# Tasks definitions for the post-deployment
+###########################################
+
 - id: influxdb-enable-quorum
   type: puppet
   version: 2.0.0
@@ -123,26 +138,15 @@
   reexecute_on:
     - deploy_changes
 
-- id: influxdb-installation
-  type: puppet
-  version: 2.0.0
-  role: [primary-influxdb_grafana, influxdb_grafana]
-  requires: [post_deployment_start]
-  required_for: [post_deployment_end]
-  parameters:
-    puppet_manifest: "puppet/manifests/influxdb.pp"
-    puppet_modules: puppet/modules:/etc/puppet/modules
-    timeout: 600
-
 - id: influxdb-configuration
   type: puppet
   version: 2.0.0
   role: [primary-influxdb_grafana]
-  requires: [post_deployment_start, influxdb-installation]
-  required_for: [post_deployment_end]
-  cross-depends:
-    - name: influxdb-installation
-      role: [primary-influxdb_grafana, influxdb_grafana]
+  requires: [post_deployment_start]
+  # We use update_hosts as an anchor to order the post-deployment tasks executed
+  # by this plugin and the LMA collector plugin. The dependency chain is:
+  # influxdb-configuration -> update_hosts -> (LMA collector tasks)
+  required_for: [post_deployment_end, update_hosts]
   parameters:
     puppet_manifest: "puppet/manifests/influxdb_configuration.pp"
     puppet_modules: puppet/modules:/etc/puppet/modules
@@ -165,6 +169,11 @@
   role: [primary-influxdb_grafana, influxdb_grafana]
   requires: [post_deployment_start, grafana-mysql-provisioning]
   required_for: [post_deployment_end]
+  # The cross-depends parameter is required because the Grafana installation
+  # should only happen once the MySQL database has been provisioned.
+  cross-depends:
+    - name: grafana-mysql-provisioning
+      role: [primary-influxdb_grafana]
   parameters:
     puppet_manifest: "puppet/manifests/grafana.pp"
     puppet_modules: puppet/modules:/etc/puppet/modules
@@ -175,7 +184,8 @@
   version: 2.0.0
   role: [primary-influxdb_grafana]
   requires: [post_deployment_start, grafana-installation]
-  required_for: [post_deployment_end]
+  # See comment above regarding the update_hosts dependency
+  required_for: [post_deployment_end, update_hosts]
   parameters:
     puppet_manifest: "puppet/manifests/grafana_configuration.pp"
     puppet_modules: puppet/modules:/etc/puppet/modules