buildscripts: Convert GAE CI to Cloud Build

The Google App Engine build now requires Java 17, because the App Engine
libraries are now using Java 17 bytecode. The Kokoro environment doesn't
include Java 17, and while we could make some custom pools to resolve
it, it is easier to swap to Cloud Build than to fight and maintain the
Kokoro images. With Cloud Build we can also restrict permissions easier,
as the same workers aren't used for multiple tasks.

However, the Gradle App Engine plugin doesn't support choosing a service
account for GAE, so I swapped to using gcloud app deploy.

Although we'll be using restricted service accounts, we'll configure
Cloud Build to require a "/gcbrun" GitHub comment except for owners and
collaborators of the repository, similar to the "kokoro:run" label
today.

I swapped the Gradle code to use project properties instead of system
properties, as we really should have been using project properties to
begin with and I didn't want to add new system properties. The sleep has
probably been unnecessary since the turndown of GAE Java 7, when the
architecture of GAE changed considerably. But today it is very possible
a new instance is spun up for that request and GAE does a warmup
request, so the delay seems unlikely to help anything and was excessive
at 20 seconds.

The Cloud Build file _doesn't_ include GAE in its name because it can do
more than GAE testing and it is easy to run things in parallel in Cloud
Build (although they share the worker). In particular, some of the
Android tests may make sense to migrate away from Kokoro.

We're using e2-standard-16 for Kokoro and it takes about 10 minutes.
With the default Cloud Build worker e2-standard-2 it takes 20 minutes,
and with e2-highcpu-8 it takes 10 minutes with 4 minutes spent on app
deploy.

The expectation is to run this with a Java-CI-specific service account,
so we have configure logging ourselves. I chose CLOUD_LOGGING_ONLY
because it was easy, but we'll want to configure GCS in the future to
allow external contributors to see the logs.

Author: ejona86

buildscripts/cloudbuild-testing.yaml

@@ -0,0 +1,64 @@
+substitutions:
+  _GAE_SERVICE_ACCOUNT: appengine-testing-java@grpc-testing.iam.gserviceaccount.com
+options:
+  env:
+  - BUILD_ID=$BUILD_ID
+  - KOKORO_GAE_SERVICE=java-gae-interop-test
+  - DUMMY_DEFAULT_VERSION=dummy-default
+  - GRADLE_OPTS=-Dorg.gradle.jvmargs='-Xmx1g'
+  - GRADLE_FLAGS=-PskipCodegen=true -PskipAndroid=true
+  logging: CLOUD_LOGGING_ONLY
+  machineType: E2_HIGHCPU_8
+
+steps:
+- id: clean-stale-deploys
+  name: gcr.io/cloud-builders/gcloud
+  allowFailure: true
+  script: |
+    #!/usr/bin/env bash
+    set -e
+    echo "Cleaning out stale deploys from previous runs, it is ok if this part fails"
+    # If the test fails, the deployment is leaked.
+    # Delete all versions whose name is not 'dummy-default' and is older than 1 hour.
+    # This expression is an ISO8601 relative date:
+    # https://cloud.google.com/sdk/gcloud/reference/topic/datetimes
+    (gcloud app versions list --format="get(version.id)" \
+        --filter="service=$KOKORO_GAE_SERVICE AND NOT version : '$DUMMY_DEFAULT_VERSION' AND version.createTime<'-p1h'" \
+        | xargs -i gcloud app services delete "$KOKORO_GAE_SERVICE" --version {} --quiet) || true
+
+- name: gcr.io/cloud-builders/docker
+  args: ['build', '-t', 'gae-build', 'buildscripts/gae-build/']
+
+- id: build
+  name: gae-build
+  script: |
+    #!/usr/bin/env bash
+    exec ./gradlew $GRADLE_FLAGS :grpc-gae-interop-testing-jdk8:appengineStage
+
+- id: deploy
+  name: gcr.io/cloud-builders/gcloud
+  args:
+    - app
+    - deploy
+    - gae-interop-testing/gae-jdk8/build/staged-app/app.yaml
+    - --service-account=$_GAE_SERVICE_ACCOUNT
+    - --no-promote
+    - --no-stop-previous-version
+    - --version=cb-$BUILD_ID
+
+- id: runInteropTestRemote
+  name: eclipse-temurin:17-jdk
+  env:
+  - PROJECT_ID=$PROJECT_ID
+  script: |
+    #!/usr/bin/env bash
+    exec ./gradlew $GRADLE_FLAGS --stacktrace -PgaeDeployVersion="cb-$BUILD_ID" \
+        -PgaeProjectId="$PROJECT_ID" :grpc-gae-interop-testing-jdk8:runInteropTestRemote
+
+- id: cleanup
+  name: gcr.io/cloud-builders/gcloud
+  script: |
+    #!/usr/bin/env bash
+    set -e
+    echo "Performing cleanup now."
+    gcloud app services delete "$KOKORO_GAE_SERVICE" --version "cb-$BUILD_ID" --quiet

buildscripts/gae-build/Dockerfile

@@ -0,0 +1,10 @@
+FROM eclipse-temurin:17-jdk
+
+# The AppEngine Gradle plugin downloads and runs its own gcloud to get the .jar
+# to link against, so we need Python even if we use gcloud deploy directly
+# instead of using the plugin.
+RUN export DEBIAN_FRONTEND=noninteractive && \
+    apt-get update && \
+    apt-get upgrade -y && \
+    apt-get install -y --no-install-recommends python3 && \
+    rm -rf /var/lib/apt/lists/*

buildscripts/kokoro/gae-interop.sh

@@ -58,6 +58,7 @@ def createDefaultVersion() {
     return new java.text.SimpleDateFormat("yyyyMMdd't'HHmmss").format(new Date())
 }
 
+def nonShadowedProject = project
 // [START model]
 appengine {
     // App Engine tasks configuration
@@ -67,13 +68,13 @@ appengine {
 
     deploy {
         // deploy configuration
-        projectId = 'GCLOUD_CONFIG'
+        projectId = nonShadowedProject.findProperty('gaeProjectId') ?: 'GCLOUD_CONFIG'
         // default - stop the current version
-        stopPreviousVersion = System.getProperty('gaeStopPreviousVersion') ?: true
+        stopPreviousVersion = nonShadowedProject.findProperty('gaeStopPreviousVersion') ?: true
         // default - do not make this the promoted version
-        promote = System.getProperty('gaePromote') ?: false
-        // Use -DgaeDeployVersion if set, otherwise the version is null and the plugin will generate it
-        version = System.getProperty('gaeDeployVersion', createDefaultVersion())
+        promote = nonShadowedProject.findProperty('gaePromote') ?: false
+        // Use -PgaeDeployVersion if set, otherwise the version is null and the plugin will generate it
+        version = nonShadowedProject.findProperty('gaeDeployVersion') ?: createDefaultVersion()
     }
 }
 // [END model]
@@ -83,6 +84,10 @@ version = '1.0-SNAPSHOT'          // Version in generated output
 
 /** Returns the service name. */
 String getGaeProject() {
+    def configuredProjectId = appengine.deploy.projectId
+    if (!"GCLOUD_CONFIG".equals(configuredProjectId)) {
+        return configuredProjectId
+    }
     def stream = new ByteArrayOutputStream()
     exec {
         executable 'gcloud'
@@ -110,11 +115,8 @@ String getAppUrl(String project, String service, String version) {
 }
 
 tasks.register("runInteropTestRemote") {
-    dependsOn appengineDeploy
+    mustRunAfter appengineDeploy
     doLast {
-        // give remote app some time to settle down
-        sleep(20000)
-
         def appUrl = getAppUrl(
                 getGaeProject(),
                 getService(project.getProjectDir().toPath()),