[poller-lambdas] limit concurrency of lambda to two (rather than one)

only one lambda should be happening at once, however the lambda queues up its next execution whilst it's still running, so concurrency of 2 should prevent throttling, but also guard against it going haywire
guardian · Dec 13, 2024 · 7260e5c · 7260e5c
1 parent 7cf1ec3
commit 7260e5c
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Showing 2 changed files with 7 additions and 3 deletions.
diff --git a/cdk/lib/__snapshots__/newswires.test.ts.snap b/cdk/lib/__snapshots__/newswires.test.ts.snap
@@ -444,7 +444,7 @@ exports[`The Newswires stack matches the snapshot 1`] = `
         },
         "MemorySize": 128,
         "RecursiveLoop": "Allow",
-        "ReservedConcurrentExecutions": 1,
+        "ReservedConcurrentExecutions": 2,
         "Role": {
           "Fn::GetAtt": [
             "EXAMPLEfixedfrequencyLambdaServiceRoleBA2F232F",
@@ -1267,7 +1267,7 @@ exports[`The Newswires stack matches the snapshot 1`] = `
         },
         "MemorySize": 128,
         "RecursiveLoop": "Allow",
-        "ReservedConcurrentExecutions": 1,
+        "ReservedConcurrentExecutions": 2,
         "Role": {
           "Fn::GetAtt": [
             "EXAMPLElongpollingLambdaServiceRoleF2C4DC08",

diff --git a/cdk/lib/constructs/pollerLambda.ts b/cdk/lib/constructs/pollerLambda.ts
@@ -65,14 +65,18 @@ export class PollerLambda {
 			);
 		}
 
+		// only one lambda should be happening at once, however the lambda queues up its next execution whilst it's still running
+		// so concurrency of 2 should prevent throttling, but also guard against it going haywire
+		const reservedConcurrentExecutions = 2;
+
 		const functionName = `${scope.stack}-${scope.stage}-${lambdaAppName}`;
 		const lambda = new GuLambdaFunction(scope, `${pollerId}Lambda`, {
 			app: lambdaAppName, // varying app tag for each lambda allows riff-raff to find by tag
 			functionName,
 			runtime: LAMBDA_RUNTIME,
 			architecture: LAMBDA_ARCHITECTURE,
 			recursiveLoop: RecursiveLoop.ALLOW, // this allows the lambda to indirectly call itself via the SQS queue
-			reservedConcurrentExecutions: 1,
+			reservedConcurrentExecutions,
 			environment: {
 				[POLLER_LAMBDA_ENV_VAR_KEYS.INGESTION_LAMBDA_QUEUE_URL]:
 					ingestionLambdaQueue.queueUrl,