lookup_service: documentation for error handling

Update the README to include steps and details on how GCP alerts are
setup.Also mention the actions that need to be taken for handling and
responding to alerts.


Change-Id: I9d56a90006c1d9c16d195470d3f139b44be190f4
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/infra/build/prebuilts-cloud/+/5308657
Tested-by: GCB User <782851717939@cloudbuild.gserviceaccount.com>
Tested-by: Nikhil Gumidelli <nikhilgm@google.com>
Commit-Queue: Nikhil Gumidelli <nikhilgm@google.com>
Reviewed-by: Cindy Lin <xcl@google.com>
1 file changed
tree: 97ecb2496610ec1f4daf9bf6be6b52bb25772318
  1. cloud_functions/
  2. cloudbuild/
  3. cloudsql/
  4. scripts/
  5. .gitignore
  9. PRESUBMIT.cfg
  10. pylintrc
  11. pyproject.toml
  12. README.md

The CrOS Build Prebuilts Cloud Repo

This repo houses all the GCP code for the chromeos-prebuilts project.

Most of the GCP resources are defined and deployed through a terraform+annealing setup as per go/cciac. The terraform code for the resources is defined in the chromeos_prebuilts folder.

Some resources are deployed through Cloud Build and some are managed and deployed manually. Details for how different resource types are managed is documented below.

Cloud Functions

We're using Cloud Functions as a serverless platform for the lookup service.

The entry points for the Cloud Functions are defined in cloud_functions/main.py. Each entry point has a functions_framework decorator which helps receive the function arguments based on the signature type specified.


All changes, once uploaded to Gerrit, are deployed to staging automatically. All changes, once merged, are deployed to production automatically.

We use Proctor/Cloud Build Integrations (go/gcb-ggob) to automatically deploy changes. A Cloud Build build is triggered whenever a new Gerrit patchset is uploaded in the prebuilts-cloud project for the staging environment. See here for details on the Cloud Build trigger setup through Proctor.

During a build, a few things happen:

  • A Google Cloud Storage object is created containing the source code. The exact location can be determined by inspecting the build logs. Example.
  • A new version of the specified Cloud Function is deployed with 100% traffic.
  • The GCB User will add the Verified+1 label and a comment to your Gerrit change upon a successful build. Example.

A Cloud Build trigger can be run manually by following the steps here. Once a CL successfully merged, a separate trigger deploys the latest source code to production.

The scripts and config files for the the cloud build deployments are in the cloudbuild/ folder.

Runtime environment variables for the lookup service cloud function:

  • ENV : Environment, can be one of staging, prod.
  • SQL_CONNECTION_TIMEOUT : Connection timeout for the sqlalchemy engine.
  • PREBUILTS_SQL_INSTANCE_HOST : IP address for the prebuilts cloud sql instance.
  • PREBUILTS_SQL_INSTANCE_PORT : port for the prebuilts cloud sql instance.

General Testing

The main way to test deployed Cloud Functions via a trigger including HTTP requests and Pub/Sub. staging-lookup-service is setup to accept HTTP triggers via the main function. A function cannot have more than one trigger associated with it, but a trigger can be associated with many functions (as long as the functions are unique).

To test staging-lookup-service, go to the Testing tab and click Test the Function. Output is only available if the Cloud Function is deployed using 1st gen environment.

Local testing and development

To develop and test cloud functions locally, we should be able to connect to the cloud sql instance from our local machine/cloudtop. Hence, Public IP has been enabled on the prebuilts-staging instance to accommodate this and the database can be accessed locally through cloud sql auth proxy. Public IP should not be enabled in production.

Note: We are running the cloud function locally but are using GCP's staging environment, including staging Cloud SQL database and Secret Manager instances.

Steps to run cloud functions locally (All of these steps are done outside the chroot):

  • Setup cloud sql auth proxy:
    • Follow the steps here to download and install Cloud SQL Auth proxy.
    • Add the downloaded cloud-sql-proxy to your $PATH.
    • Start the auth proxy:
      $cloud-sql-proxy --address --port 5432 chromeos-prebuilts:us-central1:prebuilts-staging
    • The database should now be accessible locally through the proxy.
  • Install functions-framework.
  • The default values for env variables are in the scripts/.env.defaults file. Add a scripts/.env.local file to override the values. This can be helpful for local testing without checking it into the repo. Env variables used:
    • FUNCTION_SOURCE_FILE : Source file for the cloud function.
    • FUNCTION_TARGET : Entry point for the cloud function.
    • FUNCTION_PORT : Port to run the function on.
    • FUNCTION_SIGNATURE_TYPE : Signature type of the function, which determines the event format. Can be one of http, event or cloudevent.
    • ENV : environment, can be one of staging, prod.
    • TOPIC_NAME_UPDATE_SNAPSHOT_DATA : Topic name of the update snapshot data Pub/Sub topic. Topic name refers to the complete name that uniquely identifies a Pub/Sub topic.
    • TOPIC_NAME_UPDATE_BINHOST_DATA : Topic name of the update binhost data Pub/Sub topic.
  • Additional env variables in scripts/.env.defaults, useful for local testing and development (use the cloud-sql-proxy database host and port).
    • PREBUILTS_SQL_INSTANCE_HOST : IP address for the sql instance.
    • PREBUILTS_SQL_INSTANCE_PORT : Port for the sql instance.
  • Run the cloud function server locally : ./scripts/run_server_local.sh (This script also sets up a virtual env and installs the required packages).
    • In .env.local, update FUNCTION_TARGET and FUNCTION_SIGNATURE_TYPE based on whether you want to run the lookup or the update service.
    • For running the lookup function, FUNCTION_TARGET=lookup_service and FUNCTION_SIGNATURE_TYPE=http
    • For running the update function, FUNCTION_TARGET=update_service and FUNCTION_SIGNATURE_TYPE=cloud_event
  • Invoke the cloud function locally : ./scripts/test_cloud_function_local.sh -r lookup
    • Suitable command line args need to be passed to call the lookup/update service with the required inputs.
    • More details in the ./scripts/test_cloud_function_local.sh file.

Note: The cloud function auto restarts when any of the source files are changed.

Unit Testing

We use pytest as our unittesting framework and VPython to run unittests in a Python VirtualEnv. See here for a list of available wheels. vpython3 run_tests.py will run all unittests by default.

Cloud SQL

We have two Cloud SQL instances:

  1. prebuilts - the production instance
  2. prebuilts-staging - the staging instance


Each instance currently contains a lookup_service database for the project.


During initial development, we are manually deploying changes to the staging instances of both Cloud SQL and Cloud Functions. DO NOT deploy to production instances as the production deployment process will be automated later.

To manually deploy changes:

  1. Upload the .sql file to Cloud Storage in the cloudsql-manual-deployments bucket.
  2. In the Cloud SQL instance overview page, select IMPORT.
  3. Select the .sql file uploaded to Cloud Storage above and select lookup_service as the database destination.
  4. Select Import and wait a few minutes for the import to complete.


The following steps can be used to connect to the database and verify deployments and/or query data:

  1. Open a Cloud Shell console.
  2. Run ./cloud-sql-proxy --port 5432 chromeos-prebuilts:us-central1:staging-prebuilts.
  3. In a separate tab, run psql "host= sslmode=disable dbname=lookup_service user=postgres".
  4. The postgres user password can be found here.


We're using Pub/Sub to receive messages and update metadata for snapshots, binhosts, etc in the database. The update_service cloud functions receive messages as cloud events through Pub/Sub subscriptions via EventArc triggers. Each use case has its own Pub/Sub topic (e.g. update_snapshot_data, update_binhost_data) and the corresponding cloud function processes the messages, performs database operations. With 2nd gen cloud functions, each function can only have one trigger. So each Pub/Sub topic has its own cloud function for processing messages.


PubSub topics are defined and deployed through terraform, in the chromeos_prebuilts folder.

Protocol Buffers

We're using protocol buffers to have a consistent data format when sending, retrieving Pub/Sub messages.

  • The proto definition file related to Pub/Sub is located here.
  • The scripts/gen_proto.sh script compiles and puts the generated proto files in cloud_functions/protobuf/chromiumos/.

Binhost Lookup Service API

The binhost lookup service is a HTTP GET endpoint running in a cloud function. The protocol buffer definitions for the request and response are defined in prebuilts_cloud.proto.

The query parameter to be sent with the request:

  • “filter”: A LookupBinhostsRequest object encoded as a URL safe base64 byte object.

The response is a LookupBinhostsResponse object encoded as a URL safe base64 byte object, sent in the response body.

Secret Manager

GCP Secret Manager is used to store sensitive information that can be accessed by the cloud functions. The secrets are created and managed manually through the cloud console. Secrets being used:

  • prebuilts-db: Name of the prebuilts PostgreSQL instance.
  • prebuilts-db-user: Name of the database user.
  • prebuilts-db-pw : Password for the database user.
  • prebuilts-db-host: Private IP address of the database instance.
  • prebuilts-db-port: Port of the database instance.

NOTE: Name of each of these secrets is prefixed by the environment name. e.g. staging-prebuilts-db

Handling Alerts and Errors

The cloud functions have alerts setup through GCP and the ChromeOS Build team is notified via email when the alert metric breaches the configured threshold (The alerts are configured via terraform).

The incidents can be viewed and managed in the Alerting page in the cloud console. Gen 2 cloud functions use the Cloud run service, the best way to view the logs is to go to the specific cloud function page -> logs -> “View in logs explorer” icon. The logs can be filtered based on time, severity and other filters by altering the query. The incidents auto close when the metrics for the specific alert go back to within the threshold range.

Errors in the Lookup Service

Errors in the lookup-service-binhosts cloud function usually mean the builders/developers did not get the required binhosts, these alerts need to be looked into and fixed so that the builds are fast and efficient.

Errors in the Update Service

Errors in the update-service-snapshot-data, update-service-binhost-data cloud functions usually mean the data from the builders was not saved properly in the database. These alerts are very critical and we need to ensure that the messages are reprocessed after the issue is fixed.

  • The Pub/Sub subscriptions are set to retry failed messages with an exponential back off delay, this ensures that messages are retried (The retention duration is set in the topic and subscription) by the cloud functions till they are successfully processed and acknowledged.
  • Additionally, acknowledged messages can be replayed from a previous point in time by going to the subscription page and clicking on Replay Messages. This can be useful when we update the cloud function code/logic and want to reprocess already acknowledged messages. Note: Replaying messages won't result in duplicates in the DB even if the message was successfully processed before.