Deploying Sourcegraph executors using Terraform on AWS or GCP

Terraform modules are provided to provision machines running executors on AWS and Google Cloud.

Basic Definition

The following is the minimum required definition to deploy an executor.

TERRAFORM
module "executors" {
  source = "sourcegraph/executors/<aws | google>"

  # Find the latest version matching your Sourcegraph version here:
  # - https://github.com/sourcegraph/terraform-google-executors/tags
  # - https://github.com/sourcegraph/terraform-aws-executors/tags
  version = "<version>"

  # AWS specific
  availability_zone = "<availability zone to provision resource in AWS>"
  # Google specific
  region            = "<region to provision in GCP>"
  zone              = "<zone to provision resource in GCP>"

  executor_sourcegraph_external_url            = "<external url>"
  executor_sourcegraph_executor_proxy_password = "<shared secret>"

  # Either:
  executor_queue_name                          = "<codeintel | batches>"
  # Or:
  executor_queue_names                         = "codeintel,batches"

  executor_instance_tag                        = "<tag to filter in stackdriver monitoring>"
  executor_metrics_environment_label           = "<label to filter custom metrics>"
}

See the Terraform Modules for additional configurations.

• AWS
• Google

Terraform Version

Terraform modules 4.2.x and above allow Terraform from 1.1.x to < 2.x to be used.

If using a Terraform module 4.1.x or below, use tfenv to install Terraform 1.1+.

SHELL
tfenv install 1.1.9
tfenv use 1.1.9

Permissions

In order to provision executor resources, specific permissions must be granted.

AWS

Access to get and create in the following resources.

• Auto Scaling
• CloudWatch Logs
• EBS (EC2)
• EC2 (Elastic Compute Cloud)
• IAM (Identity & Access Management)
• VPC (Virtual Private Cloud)

Google

Ensure the IAM API is enabled.

• appengine.applications.get
• clientauthconfig.brands.*
• clientauthconfig.clients.*
• cloudasset.assets.searchAllResources
• cloudnotifications.activities.list
• cloudtrace.insights.get
• cloudtrace.insights.list
• cloudtrace.stats.get
• cloudtrace.tasks.*
• cloudtrace.traces.list
• compute.addresses.*
• compute.autoscalers.*
• compute.disks.*
• compute.firewalls.*
• compute.globalOperations.get
• compute.instanceGroupManagers.*
• compute.instanceGroups.create
• compute.instances.*
• compute.instanceTemplates.*
• compute.networks.*
• compute.regionOperations.get
• compute.subnetworks.*
• compute.zoneOperations.get
• compute.zones.get
• container.clusters.list
• iam.roles.*
• iam.serviceAccountKeys.*
• logging.logEntries.list
• logging.privateLogEntries.list
• monitoring.timeSeries.list
• oauthconfig.testusers.update
• oauthconfig.verification.update
• orgpolicy.policy.get
• resourcemanager.projects.*
• secretmanager.locations.list
• secretmanager.secrets.*
• secretmanager.versions.*

Supported Regions

AWS

• us-east-1
• us-east-2
• us-west-1
• us-west-2
• eu-west-1
• eu-west-2
• eu-west-3
• eu-north-1
• eu-south-1
• eu-central-1
• ap-northeast-1
• ap-northeast-2
• ap-southeast-1
• ap-southeast-2
• ap-southeast-3
• ap-east-1
• ap-south-1
• sa-east-1
• me-south-1
• af-south-1
• ca-central-1

Google

All regions are supported.

Examples

Single Executor

The following examples provision a single executor to pull from the codeintel queue.

• AWS example
• Google example

Multiple Executors

The following examples provision two executors, one to pull from the codeintel queue and the other for the batches queue.

• AWS example
• Google example

Step-by-step Guide

The following is a step-by-step guide on provisioning a single codeintel executor on GCP.

Provision

1. Install Terraform.
2. Install the gcloud CLI
3. Run gcloud auth application-default login
4. Set up your Sourcegraph instance's Site configuration for executors
   1. Click on your profile picture in the top right corner
   2. Select Site admin
   3. Example the Configuration section
   4. Select Site configuration
   5. Set the following,
      • "externalURL": "<URL>"
        • A URL that is accessible from the GCP VM (e.g. a public URL such as https://sourcegraph.example.com)
      • "executors.accessToken": "<new long secret>"
        • Can be generated by running cat /dev/random | base64 | head -c 20
        • The secret will be as displayed REDACTED once it's saved.
      • "codeIntelAutoIndexing.enabled": true
        • This is only for codeintel executors.
5. Download the example files
6. Change the following in providers.tf
   • project to the GCP project to provision the executor in
   • region to the GCP region to provision the executor in
   • zone to the GCP zone to provision the executor in
7. Change the following in main.tf
   • executor_sourcegraph_external_url to the URL configured in your instance's Site configuration
   • executor_sourcegraph_executor_proxy_password to the access token configured in your instance's Site configuration
8. Run terraform init to download the Sourcegraph executor modules.
9. Run terraform plan to preview the changes that will occur to your GCP infrastructure.
10. Run terraform apply and enter "yes" after reviewing the proposed changes to create the executor VM
    • Ensure terraform apply exited with code 0 and did not print any errors
11. Go back to the site admin page, expand Executors, click Instances, and check to see if your executor shows up in the list with a green dot 🟢

Validation

The following can be done to troubleshoot or double-check that the executor has been properly provisioned.

Ensure the executor is listed in the Compute Engine. Either go to Compute Engine in the GCP Console for your project or run the following command.

SHELL
$ gcloud compute instances list
NAME                                          ZONE           MACHINE_TYPE   PREEMPTIBLE  INTERNAL_IP  EXTERNAL_IP    STATUS
sourcegraph-executor-h0rv                     us-central1-c  n1-standard-4               10.0.1.16                   RUNNING
sourcegraph-executors-docker-registry-mirror  us-central1-c  n1-standard-2               10.0.1.2                    RUNNING

You can ssh into to the instance to ensure the service is running. You can open an ssh connection either via the GCP Console or by running the following command.

SHELL
gcloud compute ssh sourcegraph-executor-h0rv

Then run the following command to check if the service is running.

SHELL
you@sourcegraph-executor-h0rv:~$ systemctl status executor
🟢 executor.service - User code executor
     Loaded: loaded (/etc/systemd/system/executor.service; enabled; vendor preset: enabled)
     Active: active (running) since Thu 2021-11-18 02:28:48 UTC; 19s ago

To check the logs, you can either query the Log Explorer in the GCP Console or by running the following command while connected to the instance.

SHELL
you@sourcegraph-executor-h0rv:~$ journalctl -u executor | less
Nov 18 02:31:01 sourcegraph-executor-h0rv executor[2465]: t=2021-11-18T02:31:01+0000 lvl=dbug msg="TRACE internal" host=... path=/.executors/queue/codeintel/dequeue code=204 duration=92.131237ms
Nov 18 02:31:01 sourcegraph-executor-h0rv executor[2465]: t=2021-11-18T02:31:01+0000 lvl=dbug msg="TRACE internal" host=... path=/.executors/queue/codeintel/canceled code=200 duration=90.630467ms
Nov 18 02:31:02 sourcegraph-executor-h0rv executor[2465]: t=2021-11-18T02:31:02+0000 lvl=dbug msg="TRACE internal" host=... path=/.executors/queue/codeintel/dequeue code=204 duration=91.269106ms
Nov 18 02:31:02 sourcegraph-executor-h0rv executor[2465]: t=2021-11-18T02:31:02+0000 lvl=dbug msg="TRACE internal" host=... path=/.executors/queue/codeintel/canceled code=200 duration=161.469685ms

Ensure the EXECUTOR_FRONTEND_URL and EXECUTOR_FRONTEND_PASSWORD in /etc/systemd/system/executor.env are correct

SHELL
cat /etc/systemd/system/executor.env

Ensure the VM can hit your externalURL:

SHELL
you@sourcegraph-executor-h0rv:~$ curl <your externalURL here>
<a href="/sign-in?returnTo=%2F">Found</a>

Configure Auto-indexing

1. Go to the Site admin page
2. Expand Code graph,
3. Select Configuration
4. Click Create new policy, and fill in:
   • Name: TEST
   • Click add a repository pattern
   • Repository pattern #1: set this to an existing repository on your Sourcegraph instance ( e.g. github.com/gorilla/mux)
   • Type: HEAD
   • Retention: Disabled
   • Auto-indexing: Enabled
5. Expand Code graph
6. Select Auto-indexing, and check to see if an indexing job has appeared. If nothing is there:
   • Try clicking Enqueue
   • Try setting a higher update frequency: PRECISE_CODE_INTEL_AUTO_INDEXING_TASK_INTERVAL=10s
   • Try setting a lower delay: PRECISE_CODE_INTEL_AUTO_INDEXING_REPOSITORY_PROCESS_DELAY=10s
7. Once you have a completed indexing job, click Uploads and check to see that an index has been uploaded.
8. Once the index has been uploaded, you should see the PRECISE badge in the hover popover! 🎉

Auto-scaling

NOTE: Auto scaling is currently not supported when downloading and running executor binaries yourself, and on managed instances when using self-hosted executors, since it requires deployment adjustments.

Auto-scaling of executor instances can help to increase concurrency of jobs, without paying for unused resources. With auto-scaling, you can scale down to 0 instances when no workload exist and scale up as far as you like and your cloud provider can support. Auto-scaling needs to be configured separately.

Auto-scaling makes use of the auto-scaling capabilities of the respective cloud provider (AutoScalingGroups on AWS and Instance Groups on GCP). Sourcegraph's worker service publishes a scaling metric (that is, the number of jobs in queue) to the cloud providers. Then, based on that reported value, the auto-scalers add and remove compute resources to match the required amount of compute. The autoscaler will attempt to hold 1 instance running per each executor_jobs_per_instance_scaling items in queue.

For example, if executor_jobs_per_instance_scaling is set to 20 and the queue size is currently 400, then 20instances would be determined as required to handle the load. You might want to tweak this number based on the machine type, concurrency per machine and desired processing speed.

With the Terraform variables executor_min_replicas and executor_max_replicas in the Terraform modules linked to above, you can configure the minimum and maximum number of compute machines to be run at a given time.

For auto-scaling to work, two things must be true:

1. executor_min_replicas must be >= 0 and executor_max_replicas must be > executor_min_replicas.
2. The Sourcegraph instance (its worker service, specifically) needs to publish scaling metrics to the used cloud provider.

For the latter to work, the Sourcegraph instance needs to be configured with the correct credentials that allow it to access the cloud provider.

The credentials submodule in both the AWS and Google executor modules exists for that purpose. When used, the credentials module sets up the credentials on the cloud provider and returns them in the Terraform outputs.

Here's an example of how one would configure auto-scaling.

TERRAFORM
module "executors" {
  source  = "sourcegraph/executors/<aws | google>"
  version = "<version>"

  # Basic configuration...

  # Auto-scaling
  executor_min_replicas              = 0 # Spin down when not in use
  executor_max_replicas              = 30
  executor_jobs_per_instance_scaling = 20
}

module "my-credentials" {
  source  = "sourcegraph/executors/<aws | google>//modules/credentials"
  version = "<version>"

  # AWS
  availability_zone = "<availability zone to provision resource in AWS>" # Removed in 4.2
  # Google
  zone              = "<zone to provision resource in GCP>" # Removed in 4.1

  resource_prefix = "<optional prefix to added to created resources>"
}

# AWS
output "metric_writer_access_key_id" {
  value = module.my-credentials.metric_writer_access_key_id
}

output "metric_writer_secret_key" {
  value     = module.my-credentials.metric_writer_secret_key
  sensitive = true
}

# Google
output "metric_writer_credentials_file" {
  value     = module.my-credentials.metric_writer_credentials_file
  sensitive = true
}

After running terraform apply, the outputs are retrieved by running the following commands.

SHELL
# AWS
$ terraform output metric_writer_access_key_id
$ terraform output metric_writer_secret_key
 
# Google
$ terraform output metric_writer_credentials_file

These outputs are used to configure the Sourcegraph instance (see below).

AWS

The AWS EC2 auto-scaling groups configured by the Sourcegraph Terraform module respond to changes in metric values written to CloudWatch. The target Sourcegraph instance is expected to continuously write these values.

To write the scaling metric to CloudWatch, the worker service must have defined the following environment variables.

Google

The Google Compute Engine auto-scaling groups configured by the Sourcegraph Terraform module respond to changes in metric values written to Cloud Monitoring. The target Sourcegraph instance is expected to continuously write these values.

To write the scaling metric to Cloud Monitoring, the worker service must have defined the following environment variables.

Then either one of the following environment variables must be set.

Testing auto scaling

Once the environment variables have been set and the worker service has been restarted, you should be able to find the scaling metrics in your cloud providers dashboards.

To test if the metric is correctly reported into the Cloud provider:

• On AWS, this can be found in the CloudWatch metrics section. Under All metrics, select the namespace sourcegraph-executor and then the metric environment, queueName. Make sure there are entries returned.
• On Google Cloud, this can be found in the Metrics explorer. Select Resource type: Global and then Metric: custom/executors/queue/size. You should see values reported here. 0 is also an indicator that it works correct.

Next, you can test whether the number of executors rises and shrinks as load spikes occur. Keep in mind that auto-scaling is not a real-time operation on most cloud providers and usually takes a short moment and can have some delays between the metric going down and the desired machine count adjusting.

Upgrading executors

Upgrading executors is relatively uninvolved. Simply follow the instructions below. Also, check the changelog for any Executors related breaking changes or new features or flags that you might want to configure. See Executors maintenance for version compatability.

Step 1: Update the source version of the terraform modules

NOTE: Keep in mind that only one minor version bumps are guaranteed to be disruption-free.

DIFF
module "executors" {
  source = "sourcegraph/executors/<aws | google>"
 
  # Find the latest version matching your Sourcegraph version here:
  # - https://github.com/sourcegraph/terraform-google-executors/tags
  # - https://github.com/sourcegraph/terraform-aws-executors/tags
-  version = "4.0.0"
+  version = "4.1.0"
 
  # AWS specific
  availability_zone = "<availability zone to provision resource in AWS>"
  # Google specific
  region            = "<region to provision in GCP>"
  zone              = "<zone to provision resource in GCP>"
 
  executor_sourcegraph_external_url            = "<external url>"
  executor_sourcegraph_executor_proxy_password = "<shared secret>"
  executor_queue_name                          = "<codeintel | batches>"
  executor_instance_tag                        = "<tag to filter in stackdriver monitoring>"
  executor_metrics_environment_label           = "<label to filter custom metrics>"
}

Step 2: Reapply the terraform configuration

Simply reapply the terraform configuration and executors will be ready to go again.

BASH
terraform apply