Check the service serves mounted code changes in CI

.github/workflows/ci.yml

@@ -32,6 +32,7 @@ jobs:
         run: |
           npm install -g @localstack/lstk aws-cdk
           cdk --version
+          lstk setup aws --force --non-interactive
 
       - name: Install Python
         uses: actions/setup-python@v4
@@ -59,6 +60,9 @@ jobs:
           lstk cdk bootstrap aws://000000000000/us-east-1
           lstk cdk deploy --require-approval never
 
+      - name: Run tests
+        run: make test
+
       - name: Send a Slack notification
         if: failure() || github.event_name != 'pull_request'
         uses: ravsamhq/notify-slack-action@v2

Makefile

@@ -26,4 +26,7 @@ deploy:		## Deploy the CDK stack
 	lstk cdk bootstrap
 	lstk cdk deploy --require-approval never
 
-.PHONY: usage install start stop logs deploy
+test:		## Call the service and check that code changes are picked up live
+	./test.sh
+
+.PHONY: usage install start stop logs deploy test

test.sh

@@ -0,0 +1,58 @@
+#!/bin/bash
+# Call the Flask service through the load balancer, then change service/main.py
+# on the host and check the running ECS tasks pick up the change through the
+# mounted volume, without a redeploy.
+set -euo pipefail
+
+STACK=CdkEcsExample
+MAIN=service/main.py
+MAX_ATTEMPTS=${MAX_ATTEMPTS:-40}
+
+LB_DNS=$(lstk aws cloudformation describe-stacks --stack-name "$STACK" \
+  --query "Stacks[0].Outputs[?starts_with(OutputKey, 'DemoServiceLoadBalancerDNS')].OutputValue | [0]" --output text)
+URL="http://$LB_DNS:4566"
+echo "Service URL: $URL"
+
+# Wait until the tasks are up and serving
+response=""
+for attempt in $(seq 1 "$MAX_ATTEMPTS"); do
+  response=$(curl -s -m 5 "$URL/" || true)
+  [ "$response" = "Hello, LocalStack!" ] && break
+  echo "Attempt $attempt/$MAX_ATTEMPTS: service not ready yet"
+  sleep 3
+done
+if [ "$response" != "Hello, LocalStack!" ]; then
+  echo "Test failed: GET / returned '$response'"
+  exit 1
+fi
+echo "PASS: GET / returned '$response'"
+
+response=$(curl -s -m 5 -X POST "$URL/post" -H 'Content-Type: application/json' -d '{"source": "ci"}')
+if [[ "$response" != *"Received data: {'source': 'ci'}"* ]]; then
+  echo "Test failed: POST /post returned '$response'"
+  exit 1
+fi
+echo "PASS: POST /post returned '$response'"
+
+restore() {
+  git checkout -- "$MAIN"
+}
+trap restore EXIT
+
+echo "Changing $MAIN on the host"
+sed -i.bak 's/Hello, LocalStack!/Hello, code mounting!/' "$MAIN" && rm -f "$MAIN.bak"
+
+# Both tasks mount the same directory, so every response should change
+for attempt in $(seq 1 "$MAX_ATTEMPTS"); do
+  response=$(curl -s -m 5 "$URL/" || true)
+  if [ "$response" = "Hello, code mounting!" ]; then
+    echo "PASS: GET / returned '$response' after the change"
+    echo "Test passed: the service reloaded the mounted code"
+    exit 0
+  fi
+  echo "Attempt $attempt/$MAX_ATTEMPTS: still getting '$response'"
+  sleep 3
+done
+
+echo "Test failed: the code change was not picked up"
+exit 1