ci(gocd): Skip canary stage in regions without canary (#213)

Follow-up to #209. The gocd pipelines unconditionally apply the canary
stage, even in regions that do not have canary deployments. This
succeeds instantly because no deployment is found, but introduces
unnecessary wait time.

With this change, we conditionally emit the canary stage only if a
region uses canary deployments.

Author: jan-auer

gocd/templates/pipelines/objectstore.libsonnet

@@ -1,43 +1,51 @@
 local utils = import '../libs/utils.libsonnet';
 local gocdtasks = import 'github.com/getsentry/gocd-jsonnet/libs/gocd-tasks.libsonnet';
 
-local deploy_canary(region) = [
-  {
-    'deploy-canary': {
-      fetch_materials: true,
-      jobs: {
-        create_sentry_release: {
-          environment_variables: {
-            SENTRY_ORG: 'sentry',
-            SENTRY_PROJECT: 'objectstore',
-            SENTRY_AUTH_TOKEN: '{{SECRET:[devinfra-sentryio][token]}}',
-            SENTRY_ENVIRONMENT: region + '-canary',
-          },
-          timeout: 60,
-          elastic_profile_id: 'objectstore',
-          tasks: [
-            gocdtasks.script(importstr '../bash/create-sentry-release.sh'),
-          ],
-        },
-        deploy: {
-          timeout: 300,
-          elastic_profile_id: 'objectstore',
-          environment_variables: {
-            K8S_ENVIRONMENT: 'canary',
-            PAUSE_MESSAGE: 'Pausing pipeline due to canary failure.',
+// NOTE: Sync with objectstore-k8s in getsentry/ops.
+local region_has_canary(region) =
+  region == 'de' || region == 'us';
+
+local deploy_canary(region) =
+  if region_has_canary(region) then
+    [
+      {
+        'deploy-canary': {
+          fetch_materials: true,
+          jobs: {
+            create_sentry_release: {
+              environment_variables: {
+                SENTRY_ORG: 'sentry',
+                SENTRY_PROJECT: 'objectstore',
+                SENTRY_AUTH_TOKEN: '{{SECRET:[devinfra-sentryio][token]}}',
+                SENTRY_ENVIRONMENT: region + '-canary',
+              },
+              timeout: 60,
+              elastic_profile_id: 'objectstore',
+              tasks: [
+                gocdtasks.script(importstr '../bash/create-sentry-release.sh'),
+              ],
+            },
+            deploy: {
+              timeout: 300,
+              elastic_profile_id: 'objectstore',
+              environment_variables: {
+                K8S_ENVIRONMENT: 'canary',
+                PAUSE_MESSAGE: 'Pausing pipeline due to canary failure.',
+              },
+              tasks: [
+                gocdtasks.script(importstr '../bash/deploy.sh'),
+                gocdtasks.script(importstr '../bash/wait-canary.sh'),
+                // TODO: Add sentry error checks
+                // TODO: Add datadog monitors
+                utils.pause_on_failure(),
+              ],
+            },
           },
-          tasks: [
-            gocdtasks.script(importstr '../bash/deploy.sh'),
-            gocdtasks.script(importstr '../bash/wait-canary.sh'),
-            // TODO: Add sentry error checks
-            // TODO: Add datadog monitors
-            utils.pause_on_failure(),
-          ],
         },
       },
-    },
-  },
-];
+    ]
+  else
+    [];
 
 local deploy_primary(region) = [
   {