feat: Allow to disable runner max scaling check

lambdas/functions/control-plane/src/scale-runners/scale-up.test.ts

@@ -241,6 +241,14 @@ describe('scaleUp with GHES', () => {
       expect(mockOctokit.actions.createRegistrationTokenForRepo).not.toBeCalled();
     });
 
+    it('does create a runner if maximum is set to -1', async () => {
+      process.env.RUNNERS_MAXIMUM_COUNT = '-1';
+      process.env.ENABLE_EPHEMERAL_RUNNERS = 'false';
+      await scaleUpModule.scaleUp('aws:sqs', TEST_DATA);
+      expect(listEC2Runners).not.toHaveBeenCalled();
+      expect(createRunner).toHaveBeenCalled();
+    });
+
     it('creates a token when maximum runners has not been reached', async () => {
       process.env.ENABLE_EPHEMERAL_RUNNERS = 'false';
       await scaleUpModule.scaleUp('aws:sqs', TEST_DATA);

lambdas/functions/control-plane/src/scale-runners/scale-up.ts

@@ -1,4 +1,4 @@
 import { Octokit } from '@octokit/rest';
 import { addPersistentContextToChildLogger, createChildLogger } from '@terraform-aws-github-runner/aws-powertools-util';
 import { getParameter, putParameter } from '@terraform-aws-github-runner/aws-ssm-util';
 import yn from 'yn';
@@ -277,14 +277,18 @@
   const ghAuth = await createGithubInstallationAuth(installationId, ghesApiUrl);
   const githubInstallationClient = await createOctoClient(ghAuth.token, ghesApiUrl);
   if (!enableJobQueuedCheck || (await isJobQueued(githubInstallationClient, payload))) {
-    const currentRunners = await listEC2Runners({
-      environment,
-      runnerType,
-      runnerOwner,
-    });
-    logger.info(`Current runners: ${currentRunners.length} of ${maximumRunners}`);
+    let scaleUp = true;
+    if (maximumRunners !== -1) {
+      const currentRunners = await listEC2Runners({
+        environment,
+        runnerType,
+        runnerOwner,
+      });
+      logger.info(`Current runners: ${currentRunners.length} of ${maximumRunners}`);
+      scaleUp = currentRunners.length < maximumRunners;
+    }
 
-    if (currentRunners.length < maximumRunners) {
+    if (scaleUp) {
       logger.info(`Attempting to launch a new runner`);
 
       await createRunners(

modules/multi-runner/variables.tf

@@ -160,7 +160,7 @@ variable "multi_runner_config" {
         runner_group_name: "Name of the runner group."
         runner_name_prefix: "Prefix for the GitHub runner name."
         runner_run_as: "Run the GitHub actions agent as user."
-        runners_maximum_count: "The maximum number of runners that will be created."
+        runners_maximum_count: "The maximum number of runners that will be created. Setting the variable to `-1` desiables the maximum check."
         scale_down_schedule_expression: "Scheduler expression to check every x for scale down."
         scale_up_reserved_concurrent_executions: "Amount of reserved concurrent executions for the scale-up lambda function. A value of 0 disables lambda from being triggered and -1 removes any concurrency limitations."
         userdata_template: "Alternative user-data template, replacing the default template. By providing your own user_data you have to take care of installing all required software, including the action runner. Variables userdata_pre/post_install are ignored."

modules/runners/README.md

@@ -204,7 +204,7 @@ yarn run dist
 | <a name="input_runner_run_as"></a> [runner\_run\_as](#input\_runner\_run\_as) | Run the GitHub actions agent as user. | `string` | `"ec2-user"` | no |
 | <a name="input_runners_lambda_s3_key"></a> [runners\_lambda\_s3\_key](#input\_runners\_lambda\_s3\_key) | S3 key for runners lambda function. Required if using S3 bucket to specify lambdas. | `string` | `null` | no |
 | <a name="input_runners_lambda_s3_object_version"></a> [runners\_lambda\_s3\_object\_version](#input\_runners\_lambda\_s3\_object\_version) | S3 object version for runners lambda function. Useful if S3 versioning is enabled on source bucket. | `string` | `null` | no |
-| <a name="input_runners_maximum_count"></a> [runners\_maximum\_count](#input\_runners\_maximum\_count) | The maximum number of runners that will be created. | `number` | `3` | no |
+| <a name="input_runners_maximum_count"></a> [runners\_maximum\_count](#input\_runners\_maximum\_count) | The maximum number of runners that will be created. Setting the variable to `-1` desiables the maximum check. | `number` | `3` | no |
 | <a name="input_s3_runner_binaries"></a> [s3\_runner\_binaries](#input\_s3\_runner\_binaries) | Bucket details for cached GitHub binary. | <pre>object({<br>    arn = string<br>    id  = string<br>    key = string<br>  })</pre> | n/a | yes |
 | <a name="input_scale_down_schedule_expression"></a> [scale\_down\_schedule\_expression](#input\_scale\_down\_schedule\_expression) | Scheduler expression to check every x for scale down. | `string` | `"cron(*/5 * * * ? *)"` | no |
 | <a name="input_scale_up_reserved_concurrent_executions"></a> [scale\_up\_reserved\_concurrent\_executions](#input\_scale\_up\_reserved\_concurrent\_executions) | Amount of reserved concurrent executions for the scale-up lambda function. A value of 0 disables lambda from being triggered and -1 removes any concurrency limitations. | `number` | `1` | no |

modules/runners/variables.tf

@@ -288,7 +288,7 @@ variable "runner_run_as" {
 }
 
 variable "runners_maximum_count" {
-  description = "The maximum number of runners that will be created."
+  description = "The maximum number of runners that will be created. Setting the variable to `-1` desiables the maximum check."
   type        = number
   default     = 3
 }