Create instance group if it doesn't exist, update it if it does (#513)

* Deploy instance group if it doesn't exist, update it if it does

* Rename push.yml to cd.yml

* Rename some CD steps

.github/workflows/cd.yml

@@ -1,4 +1,4 @@
-name: CI
+name: CD
 
 on:
   push:
@@ -29,7 +29,8 @@ jobs:
         echo "::set-env name=SHA7::$(git rev-parse --short=7 $GITHUB_SHA)"
 
     # Setup gcloud CLI
-    - uses: GoogleCloudPlatform/github-actions/setup-gcloud@master
+    - name: Set up gcloud Cloud SDK environment
+      uses: GoogleCloudPlatform/github-actions/setup-gcloud@master
       with:
         version: '295.0.0'
         project_id: ${{ env.PROJECT_ID }}
@@ -72,19 +73,28 @@ jobs:
     #     --source-ranges 0.0.0.0/0 \
     #     --description="Allow incoming Zcash traffic from anywhere" \
 
-    # Deploy managed instance group using the new instance template
-    # - name: Deploy managed instance group
-    #   run: |
-    #     gcloud compute instance-groups managed create \
-    #       "zebrad-$SHORT_BRANCH_NAME-$SHA7" \
-    #       --template "zebrad-$SHORT_BRANCH_NAME-$SHA7" \
-    #       --health-check zebrad-tracing-filter \
-    #       --initial-delay 30 \
-    #       --region us-central1 \
-    #       --size 2
+    # Check if our destination instance group exists already
+    - name: Check if instance group exists
+      id: does-group-exist
+      continue-on-error: true
+      run: |
+        gcloud compute instance-groups list | grep "zebrad-$SHORT_BRANCH_NAME"
+
+    # Deploy new managed instance group using the new instance template
+    - name: Create managed instance group
+      if: steps.does-group-exist.outcome == 'failure'
+      run: |
+        gcloud compute instance-groups managed create \
+          "zebrad-$SHORT_BRANCH_NAME" \
+          --template "zebrad-$SHORT_BRANCH_NAME-$SHA7" \
+          --health-check zebrad-tracing-filter \
+          --initial-delay 30 \
+          --region us-central1 \
+          --size 2
 
     # Rolls out update to existing group using the new instance template
     - name: Update managed instance group
+      if: steps.does-group-exist.outcome == 'success'
       run: |
         gcloud compute instance-groups managed rolling-action start-update \
           "zebrad-$SHORT_BRANCH_NAME" \