DRAFT: add first draft of load simulator by jeastham1993 · Pull Request #172 · DataDog/stickerlandia

jeastham1993 · 2026-01-22T16:39:08Z

Added a first draft of a simple load simulator to get some consistent load running through the service. You can test it out by running mise run load:smoke. It should startup all services, and then run a simple load test that sends data do Datadog.

claude · 2026-01-22T16:43:42Z

Code review

No issues found. Checked for bugs and CLAUDE.md compliance.

Copilot

Pull request overview

This PR adds a comprehensive k6-based load testing simulator for the Stickerlandia application. The simulator tests public endpoints, OAuth 2.1 authentication flows with PKCE, and user registration under concurrent load, with full Docker Compose orchestration and Datadog APM integration.

Changes:

Added k6-based load test script with support for multiple scenarios (public browsing, authenticated flows, registration)
Created Docker Compose overlay configuration for load testing that disables rate limiting and includes all service dependencies
Added 7 mise tasks for running different load test scenarios (smoke tests and sustained load tests)

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 11 comments.

Show a summary per file

File	Description
mise.toml	Added 7 load testing tasks for running smoke and sustained load tests with different scenario combinations
load-tests/load-test.js	Core k6 test script implementing OAuth 2.1 flows, registration, and public browsing scenarios with custom URL rewriting for Docker networking
load-tests/README.md	User documentation for load testing features, usage, configuration, and troubleshooting
docs/feat-load-simulator.md	Technical design document detailing implementation, architecture, and technical challenges solved
docker-compose.yml	Added load-test profile to datadog-agent service
docker-compose.load-test.yml	Docker Compose overlay defining load-simulator service configuration with disabled rate limiting

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Copilot · 2026-01-22T16:47:44Z

+const WORKLOADS = {
+  smoke: { vus: 2, duration: '30s' },
+  load: {
+    stages: [
+      { duration: '1m', target: 10 },
+      { duration: '3m', target: 30 },
+      { duration: '5m', target: 30 },
+      { duration: '1m', target: 0 },
+    ],
+  },
+};


The constant WORKLOADS contains a stage configuration that ramps up load over 10 minutes, but the configuration uses inconsistent duration notation. The load workload uses '1m', '3m', '5m' format while the comment on line 295 and documentation describe it as "10 minutes". Consider verifying this totals 10 minutes as expected: 1m + 3m + 5m + 1m = 10m. This appears correct but could benefit from a comment explaining the total duration.

Copilot · 2026-01-22T16:47:45Z

+  while (res.status >= 300 && res.status < 400 && res.headers['Location']) {
+    let nextUrl = resolveUrl(res.url, res.headers['Location']);
+    nextUrl = rewriteUrl(nextUrl);
+    res = http.get(nextUrl, { redirects: 0, jar });
+  }


The redirect following loops on lines 135-139, 188-192, 287-291, 333-337, and 379-383 don't have a maximum iteration limit. If there's a redirect loop in the application, this could cause the test to hang indefinitely. Consider adding a counter to limit the maximum number of redirects to follow (e.g., 10-20 redirects).

Copilot · 2026-01-22T16:47:45Z

+  while (submitRes.status >= 300 && submitRes.status < 400 && submitRes.headers['Location']) {
+    let nextUrl = resolveUrl(submitRes.url, submitRes.headers['Location']);
+    nextUrl = rewriteUrl(nextUrl);
+    submitRes = http.get(nextUrl, { redirects: 0, jar });
+  }


This redirect following loop lacks a maximum iteration limit (same issue as in performOAuthLogin). If there's a redirect loop, this could hang indefinitely. Consider adding a counter to limit redirects.

Copilot · 2026-01-22T16:47:45Z

+  while (submitRes.status >= 300 && submitRes.status < 400 && submitRes.headers['Location']) {
+    let nextUrl = resolveUrl(submitRes.url, submitRes.headers['Location']);
+    nextUrl = rewriteUrl(nextUrl);
+    submitRes = http.get(nextUrl, { redirects: 0, jar });


This redirect following loop in performRegistration lacks a maximum iteration limit. If there's a redirect loop, this could hang indefinitely. Consider adding a counter to limit redirects.

Suggested change

while (submitRes.status >= 300 && submitRes.status < 400 && submitRes.headers['Location']) {

let nextUrl = resolveUrl(submitRes.url, submitRes.headers['Location']);

nextUrl = rewriteUrl(nextUrl);

submitRes = http.get(nextUrl, { redirects: 0, jar });

const MAX_REDIRECTS = 10;

let redirectCount = 0;

while (

submitRes.status >= 300 &&

submitRes.status < 400 &&

submitRes.headers['Location'] &&

redirectCount < MAX_REDIRECTS

) {

let nextUrl = resolveUrl(submitRes.url, submitRes.headers['Location']);

nextUrl = rewriteUrl(nextUrl);

submitRes = http.get(nextUrl, { redirects: 0, jar });

redirectCount++;

Copilot · 2026-01-22T16:47:45Z

+          http.get(`${BASE_URL}/api/stickers/v1/${stickerId}/image`);
+        }
+      } catch (e) {
+        // JSON parse error - skip sticker detail


The JSON parsing error on line 456 is caught with an empty catch block. This silently swallows parsing errors which could hide issues with the API response format. Consider logging the error with console.warn or console.error to aid in debugging.

Suggested change

// JSON parse error - skip sticker detail

// JSON parse error - skip sticker detail

console.warn('publicBrowsingFlow: failed to parse catalogueRes JSON; skipping sticker detail.', e);

Copilot · 2026-01-22T16:47:46Z

+    const queryPart = url.includes('?') ? url.split('?')[1] : '';
+    const fragmentPart = url.includes('#') ? url.split('#')[1] : '';


The URL parsing in extractTokenFromUrl splits on '?' and '#' to extract query and fragment parts, but doesn't handle the case where both might be present (e.g., 'url?query=1#fragment=2'). When splitting by '?', the fragment part will include the query portion. Consider using a more robust approach that properly separates query and fragment.

Suggested change

const queryPart = url.includes('?') ? url.split('?')[1] : '';

const fragmentPart = url.includes('#') ? url.split('#')[1] : '';

let queryPart = '';

let fragmentPart = '';

// First, split off the fragment so query parsing is not polluted by it

const hashSplit = url.split('#', 2);

const beforeHash = hashSplit[0];

const afterHash = hashSplit.length > 1 ? hashSplit[1] : '';

if (beforeHash && beforeHash.includes('?')) {

queryPart = beforeHash.split('?', 2)[1];

}

if (afterHash) {

fragmentPart = afterHash;

}

Copilot · 2026-01-22T16:47:46Z

+      }
+    }
+  } catch (e) {
+    // Fall through to error


The extractTokenFromUrl function catches all exceptions on line 239 with an empty catch block and falls through to return an error. Consider logging the exception to help with debugging, as this could hide important errors during development and troubleshooting.

Suggested change

// Fall through to error

console.error('Failed to extract token from URL', url, e);

Copilot · 2026-01-22T16:47:46Z

+  while (res.status >= 300 && res.status < 400 && res.headers['Location']) {
+    let nextUrl = resolveUrl(res.url, res.headers['Location']);
+    nextUrl = rewriteUrl(nextUrl);
+    res = http.get(nextUrl, { redirects: 0, jar });
+  }


This redirect following loop in performRegistration lacks a maximum iteration limit. If there's a redirect loop, this could hang indefinitely. Consider adding a counter to limit redirects.

Copilot · 2026-01-22T16:47:47Z

+    depends_on:
+      traefik:
+        condition: service_healthy
+      user-management:
+        condition: service_healthy
+      sticker-catalogue:
+        condition: service_healthy
+      sticker-award:
+        condition: service_healthy
+      web-backend:
+        condition: service_started
+      datadog-agent:
+        condition: service_started


The Docker Compose override for web-backend in this file is missing the user-management-worker service from the depends_on list in the load-simulator service, but the documentation and inline comments indicate it's a required service. The main docker-compose.yml likely has this service, and it should be included here to ensure proper startup ordering.

Copilot · 2026-01-22T16:47:47Z

+          userId = userInfo.user.sub || userInfo.user.id;
+        }
+      } catch (e) {
+        // JSON parse error


The JSON parsing error on line 510 is caught with an empty catch block. This silently swallows parsing errors which could hide issues with the user authentication response. Consider adding console.warn or console.error to log these errors for debugging.

Suggested change

// JSON parse error

// Log JSON parse errors for debugging while keeping behavior unchanged

console.warn('Failed to parse auth user JSON response', {

status: userRes.status,

bodyPreview: String(userRes.body || '').slice(0, 200),

error: String(e),

});

Add support for GameDay demo scenarios with: - Multi-user pool via k6 SharedArray (50 users, round-robin assignment) - Three hardcoded GameDay workload profiles: - gameday:auth (50 RPS on login/logout) - gameday:catalogue (100 RPS on sticker API) - gameday:sustained (30+50 RPS across services) - One new mise task: `WORKLOAD=gameday:auth mise run load:gameday` User pool is only used for gameday:* workloads; smoke/load tests continue to use the default test user. Load test traffic appears in APM as normal requests (by design for demos). Co-Authored-By: Claude <noreply@anthropic.com>

- Add provision-users.js script to register test users via IdP - Export registrationFlow for k6 scenarios - Add registration scenario to gameday:sustained (3 users/min) - Reduce auth RPS from 50 to 10 (IdP capacity limit) - Add mise tasks: load:start, load:stop, load:provision-users, load:gameday:run - Update README with GameDay documentation Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

- Update README with comprehensive GameDay documentation - Add performLogout helper with proper URL rewriting for Docker - Fix logout failing due to localhost:8080 redirects inside Docker Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

scottgerring · 2026-01-23T08:10:11Z

+/**
+ * Extract access_token from URL query string or fragment
+ */
+function extractTokenFromUrl(url) {


This is gross; can't we just use new URL ?

@scottgerring No, we actually can't. The load testing thing (k6) uses a custom JS runtime.

k6 doesn't have the native URL constructor. k6 runs in its own JavaScript runtime (goja), not Node.js or a browser, so standard Web APIs like new URL() and URLSearchParams aren't available. This is a known k6 limitation - you can verify this in the https://grafana.com/docs/k6/latest/javascript-api/

It seems like the k6 recommended way to do it is to use this URL module grafana publishes for k6:
grafana/k6#991
https://github.com/grafana/k6-jslib-url

- Remove separate docker-compose.load-test.yml and merge into main compose with service profiles; disable rate limiting by default in development - Fix rate limiting retry-after logic to only set header when metadata is available (WindowSeconds is for bucketing, not retry timing) - Extract shared URL helpers to load-tests/helpers.js to reduce duplication - Rename gameday terminology to sustained (gameday:auth -> sustained:auth) - Align URL variable naming with web-backend (EXTERNAL_URL -> DEPLOYMENT_HOST_URL) - Add MAX_REDIRECTS constant to prevent infinite redirect loops - Simplify README from 165 to 60 lines - Simplify mise.toml commands to use single compose file with profiles Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

scottgerring · 2026-01-29T15:29:14Z

    container_name: datadog-agent
    profiles:
      - monitoring
+      - load-test


Does it make sense to turn agent on if load-testing is on but monitoring isnt?

@scottgerring Hmm, good question. I guess for what we are using load testing for is to generate data for the agent. Not load testing in the traditional sense. So yeah, I think we should turn load testing on even if monitoring isn't. Which is what this will do right? Or have I misunderstood docker profiles?

This is an agent - so this'll turn on the datadog-agent, if we ask for load-testing

scottgerring · 2026-01-29T15:32:10Z

+# load: Load testing tasks
+# =============================================================================
+
+[tasks."load:smoke"]


1/ Are these docker-only? If yes, they should probably be prefixed appropriately (e.g. compose:load-test:smoke)

2/ Do we really need all these different variants?

@scottgerring yep, agreed. I've updated the name to be compose:load-test:smoke and updated the different variants

scottgerring

approved pending build passing from my conflict resolution

chore: add first draft of load simulator

a888ee4

jeastham1993 requested review from TaraScho, Copilot and scottgerring January 22, 2026 16:39

chore: add env:setup requirement to loadtests

12fb40a

Copilot started reviewing on behalf of jeastham1993 January 22, 2026 16:39 View session

Copilot AI reviewed Jan 22, 2026

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jeastham1993 and others added 4 commits January 22, 2026 19:18

chore: update ratelimit config for loadtest

e960f09

TaraScho reviewed Jan 22, 2026

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Comment thread load-tests/README.md

add user exists exception

eac7bc5

TaraScho reviewed Jan 23, 2026

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Comment thread load-tests/README.md Outdated

TaraScho reviewed Jan 23, 2026

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Comment thread load-tests/README.md Outdated

TaraScho reviewed Jan 23, 2026

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Comment thread load-tests/README.md Outdated

TaraScho reviewed Jan 23, 2026

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Comment thread load-tests/README.md Outdated

scottgerring requested changes Jan 23, 2026

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jeastham1993 and others added 8 commits January 23, 2026 08:48

chore: add Datadog product features

0113ca5

chore: remove duplicate docs

9b1e57c

chore: add links to readme

6950812

chore: cleanup README

183a234

docs: simplify load test README with clearer instructions

339b044

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docs: add Datadog telemetry validation instructions to README

03b1aec

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

chore: address PR feedback

dc6dee9

scottgerring reviewed Jan 29, 2026

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chore: add load simulator to mise

055bc08

chore: add load simulator to mise

acb5356

scottgerring approved these changes Jan 30, 2026

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Merge branch 'main' into feat/load-sim

6c37f0b

scottgerring approved these changes Jan 30, 2026

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scottgerring merged commit 23e0c06 into main Jan 30, 2026
15 checks passed

scottgerring deleted the feat/load-sim branch January 30, 2026 07:40

scottgerring mentioned this pull request Jan 30, 2026

feat: Add load simulator service #160

Closed

	// JSON parse error - skip sticker detail
	// JSON parse error - skip sticker detail
	console.warn('publicBrowsingFlow: failed to parse catalogueRes JSON; skipping sticker detail.', e);

		const queryPart = url.includes('?') ? url.split('?')[1] : '';
		const fragmentPart = url.includes('#') ? url.split('#')[1] : '';

-    const queryPart = url.includes('?') ? url.split('?')[1] : '';
-    const fragmentPart = url.includes('#') ? url.split('#')[1] : '';
+    let queryPart = '';
+    let fragmentPart = '';
+    // First, split off the fragment so query parsing is not polluted by it
+    const hashSplit = url.split('#', 2);
+    const beforeHash = hashSplit[0];
+    const afterHash = hashSplit.length > 1 ? hashSplit[1] : '';
+    if (beforeHash && beforeHash.includes('?')) {
+      queryPart = beforeHash.split('?', 2)[1];
+    }
+    if (afterHash) {
+      fragmentPart = afterHash;
+    }

	// Fall through to error
	console.error('Failed to extract token from URL', url, e);

-        // JSON parse error
+        // Log JSON parse errors for debugging while keeping behavior unchanged
+        console.warn('Failed to parse auth user JSON response', {
+          status: userRes.status,
+          bodyPreview: String(userRes.body || '').slice(0, 200),
+          error: String(e),
+        });

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jeastham1993 commented Jan 22, 2026

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claude Bot commented Jan 22, 2026

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