VED-1235 Lambda-to-mock-PDS-in-Ref by amarauzoma · Pull Request #1427 · NHSDigital/immunisation-fhir-api

amarauzoma · 2026-04-17T11:58:33Z

Added a new Lambda function to simulate PDS responses for patient lookups.
Implemented rate limiting with configurable average and spike thresholds.
Updated existing MNS publisher to utilize the new PDS base URL environment variable.
Enhanced tests to cover scenarios with the mock PDS service, including rate limit handling.
Created performance testing scripts to validate MNS behavior under load with the mock PDS.
Updated infrastructure to route PDS calls in the ref environment to the mock endpoint.

- Added a new Lambda function to simulate PDS responses for patient lookups. - Implemented rate limiting with configurable average and spike thresholds. - Updated existing MNS publisher to utilize the new PDS base URL environment variable. - Enhanced tests to cover scenarios with the mock PDS service, including rate limit handling. - Created performance testing scripts to validate MNS behavior under load with the mock PDS. - Updated infrastructure to route PDS calls in the ref environment to the mock endpoint.

- Streamlined the initialization of MockPdsService by consolidating parameters. - Replaced multiple response methods with a unified error handling approach. - Enhanced readability by reducing redundant code in the patient lookup logic. - Updated tests to utilize helper functions for event creation and decision mocking.

- Deleted the performance testing plan document for MNS integration with mocked PDS. - This document outlined objectives, delivery approaches, and existing architecture for implementing a mocked PDS service.

…mock-PDS-in-Ref Made-with: Cursor # Conflicts: # tests/perf_tests/Makefile

- Removed the global service retrieval function and directly initialized the MockPdsService with a Redis client and rate limiter. - Updated the lambda_handler to use the initialized service directly, improving performance and readability. - Adjusted unit tests to accommodate the new service initialization approach, ensuring proper mocking and error handling.

… tests - Updated sonar-project.properties to include coverage report for mock_pds. - Added new unit tests for Mock PDS service to improve test coverage and handle edge cases. - Introduced a new test file for rate limiting functionality in the Mock PDS service. - Updated the quality-checks workflow to run tests for the new mock_pds service.

- Introduced a new Mock PDS Lambda function to simulate PDS responses. - Created an ECR repository for the Mock PDS service with appropriate policies. - Updated deployment workflows to include mock_pds in build flags and image overrides. - Enhanced infrastructure configuration to support the new Mock PDS service, including image URI handling and environment variable setup.

… tracking

…ackend.yml

avshetty1980 · 2026-04-23T12:18:47Z

+[tool.poetry.dependencies]
+python = "~3.11"
+redis = "^6.1.0"
+coverage = "^7.13.2"


should this be under dev dependencies - similar to other lambdas?

Just checked and it seems that there no move is needed here as keeping coverage under tool.poetry.dependencies is consistent with how it is defined across the other lambdas in this repo.

avshetty1980 · 2026-04-23T12:22:04Z

+  count = var.mock_pds_enabled ? 1 : 0
+
+  function_name      = aws_lambda_function.mock_pds_lambda[0].function_name
+  authorization_type = "NONE"


why are we doing authorization_type = NONE?
Does this mean this lambda is freely available from the internet?

Yes, authorization_type = "NONE" makes the Function URL public. We used this to keep the mock PDS endpoint simple for lower-env integration/perf testing. It does not expose real PDS data, but you’re right that it is internet-reachable.

avshetty1980 · 2026-04-23T12:25:45Z

            lambda_dir: ack_backend
+          - lambda_name: mock_pds
+            ecr_repository: imms-mock-pds-repo
+            lambda_dir: mock_pds


does this mean the mock_pds lambda will be created in all envs (including ref)? Dont we only need it for ref?

No, it won’t be created in all environments. mock_pds is in the deploy list, but Terraform only creates the Lambda when mock_pds_enabled=true.
That is only true in dev/ref, so it is only created in ref.

avshetty1980 · 2026-04-23T12:28:40Z

+
+    @staticmethod
+    def _get_method(event: dict) -> str:
+        return event.get("requestContext", {}).get("http", {}).get("method") or event.get("httpMethod") or "GET"


do we need the or GET - why are we protecting for it? wont we only use the method for get?

We only allow GET, but this fallback is to support different API Gateway event formats. Some events provide the method at requestContext.http.method, others at httpMethod. We read either shape, then still validate that it is GET before serving a response.

avshetty1980 · 2026-04-23T12:30:40Z

+        return cls._response(status, {"code": int(status), "message": message})
+
+    @staticmethod
+    def _response(status_code: int, body: dict, content_type: str = "application/json") -> dict:


should status_code be HTTPStatus | int ?

I don't believe there's any changes needed as HTTPStatus is an IntEnum and therefore already compatible with int in type checking/runtime.

avshetty1980 · 2026-04-23T12:32:55Z

+        working-directory: lambdas/mock_pds
+        id: mock_pds
+        env:
+          PYTHONPATH: ${{ env.LAMBDA_PATH }}/mock_pds/src:${{ env.LAMBDA_PATH }}/mock_pds/tests


does this need to exclusively include tests? should it either be src or shared/src like other lambdas?

Good point. I’ve aligned it with the other lambdas and aligned it to be src

avshetty1980 · 2026-04-23T12:44:24Z

-            secret_manager_client=get_secrets_manager_client(),
-            environment=PDS_ENV,
+        environment = os.getenv("PDS_ENV", "int")
+        base_url = os.getenv("PDS_BASE_URL", "").strip() or None


nit: _pds_service is initialised on the first warm lambda invocation, from what I can tell. Therefore PDS_BASE_URL is read once at that point and put into PdsService object, subsequent invocations in the same warm container will not re-read it.

For the mock PDS, aws_lambda_function_url generates a new URL if the resource is ever destroyed and recreated (e.g. during a pr teardown), terraform will update the env var on the consuming Lambda, but warm containers will keep calling the old URL until they are recycled — causing silent PDS failures for an unpredictable window.

you could just ignore this keeping this in mind during your tests or move os.getenv("PDS_BASE_URL") inside [get_pds_service()

Good point about warm container caching and stale PDS_BASE_URL risk after URL recreation. I have implemented a config-aware cache refresh in get_pds_service. We still cache for warm invocation performance, but now reinitialize the PDS client automatically if PDS_BASE_URL or PDS_ENV changes, so we avoid stale URL behavior after mock PDS URL recreation.

avshetty1980

Nice, just a few nits.
I like the average + spike rate limiting with Redis atomicity per window

…ecurity

…mand

sonarqubecloud · 2026-04-29T11:09:31Z

Quality Gate failed

Failed conditions
0.0% Coverage on New Code (required ≥ 80%)

See analysis details on SonarQube Cloud

amarauzoma and others added 2 commits April 17, 2026 12:51

amarauzoma changed the title ~~feat: Introduce Mock PDS Lambda for MNS integration testing~~ VED-1235 Lambda-to-mock-PDS-in-Ref Apr 17, 2026

Thomas-Boyle added 2 commits April 17, 2026 13:03

chore: Remove MNS performance testing plan for mocked PDS

d7421df

- Deleted the performance testing plan document for MNS integration with mocked PDS. - This document outlined objectives, delivery approaches, and existing architecture for implementing a mocked PDS service.

Merge remote-tracking branch 'origin/master' into VED-1235-Lambda-to-…

28cac67

…mock-PDS-in-Ref Made-with: Cursor # Conflicts: # tests/perf_tests/Makefile

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amarauzoma and others added 2 commits April 20, 2026 11:00

Add expected_commit_id input to E2E test workflow for improved commit…

87d68b3

… tracking

Merge branch 'master' into VED-1235-Lambda-to-mock-PDS-in-Ref

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avshetty1980 reviewed Apr 20, 2026

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Comment thread .github/workflows/deploy-backend.yml Outdated

amarauzoma and others added 2 commits April 20, 2026 14:55

Remove mock_pds entry from lambda_image_overrides example in deploy-b…

d4a04fa

…ackend.yml

Add mock_pds_enabled variable to dev environment configuration

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avshetty1980 reviewed Apr 21, 2026

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Comment thread .github/workflows/deploy-backend.yml

amarauzoma added 5 commits April 21, 2026 09:30

Set ref mns_environment to int

d5d0318

Merge origin/master and resolve workflow/terraform conflicts

1fd7c4c

Merge branch 'master' into VED-1235-Lambda-to-mock-PDS-in-Ref

5f97f5f

Update expected_commit_id to use github.sha in E2E tests

b74a32c

Disable mock PDS in development environment

bdf2fe4

Thomas-Boyle previously approved these changes Apr 22, 2026

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avshetty1980 reviewed Apr 23, 2026

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amarauzoma added 3 commits April 29, 2026 10:47

Refactor PDS service caching logic and update coverage dependency

aae6283

Merge branch 'master' into VED-1235-Lambda-to-mock-PDS-in-Ref

ba7d55b

Update Dockerfile to set environment variables for Poetry installation

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Comment thread lambdas/mock_pds/Dockerfile Fixed

amarauzoma added 2 commits April 29, 2026 11:50

Refactor Dockerfile to install Poetry using hashed requirements for s…

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Refactor Dockerfile to improve readability of Poetry installation com…

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amarauzoma commented Apr 17, 2026 • edited by Thomas-Boyle Loading Uh oh! There was an error while loading. Please reload this page.

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sonarqubecloud Bot commented Apr 29, 2026

Quality Gate failed

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amarauzoma commented Apr 17, 2026 •

edited by Thomas-Boyle

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