REGRESSION: [ Mac wk2 ] imported/w3c/web-platform-tests/service-workers/service-worker/update-no-cache-request-headers.https.html is a flaky failure

[Truitt Savell]

imported/w3c/web-platform-tests/service-workers/service-worker/update-no-cache-request-headers.https.html

This test is a flakey failure on Mac WK2. It began failing around r253457

History:
https://results.webkit.org/?suite=layout-tests&test=imported%2Fw3c%2Fweb-platform-tests%2Fservice-workers%2Fservice-worker%2Fupdate-no-cache-request-headers.https.html

Diff:
--- /Volumes/Data/slave/highsierra-release-tests-wk2/build/layout-test-results/imported/w3c/web-platform-tests/service-workers/service-worker/update-no-cache-request-headers.https-expected.txt
+++ /Volumes/Data/slave/highsierra-release-tests-wk2/build/layout-test-results/imported/w3c/web-platform-tests/service-workers/service-worker/update-no-cache-request-headers.https-actual.txt
@@ -1,3 +1,3 @@
 
-PASS headers in no-cache mode 
+FAIL headers in no-cache mode promise_test: Unhandled rejection with value: object "TypeError: null is not an object (evaluating 'newWorker.postMessage')"
 

I am able to reproduced this failure by simply running the test, but I could not find a regression point due to the test continuing to fail locally on any revision.

[Radar WebKit Bug Importer]

<rdar://problem/57976344>

[Chris Dumez]

This particular test was not updated in r253457.

[Chris Dumez]

The test seems to do:
  await registration.update();
  const newWorker = registration.installing;

And sometimes, newWorker is null. This may indicate the service worker is already done installing and is now activating or activated.

[Chris Dumez]

(In reply to Chris Dumez from comment #2)
> This particular test was not updated in r253457.

test-request-headers-worker.js & test-request-headers-worker.py were however updated in r253457 and are both used by update-no-cache-request-headers.https.html.

[Chris Dumez]

Looks like I can reproduce like so:
run-webkit-tests --repeat-each=100 imported/w3c/web-platform-tests/service-workers/service-worker/update-no-cache-request-headers.https.html -f

[Chris Dumez]

(In reply to Chris Dumez from comment #5)
> Looks like I can reproduce like so:
> run-webkit-tests --repeat-each=100
> imported/w3c/web-platform-tests/service-workers/service-worker/update-no-
> cache-request-headers.https.html -f

When it fails, the registration has no installing or waiting worker. It only an an active worker, which is the same one as before the update.

[Chris Dumez]

We fail because of this check:
    // If newestWorker is not null, newestWorker's script url equals job's script url with the exclude fragments
    // flag set, and script's source text is a byte-for-byte match with newestWorker's script resource's source
    // text, then:
    if (newestWorker && equalIgnoringFragmentIdentifier(newestWorker->scriptURL(), job.scriptURL) && result.script == newestWorker->script()) {

in SWServerJobQueue::scriptFetchFinished(const ServiceWorkerFetchResult&).

test-request-headers-worker.js is supposed to include a timestamp to make it unique. Maybe the initial install and the update happen so quickly after one another that the timestamp does not have time to change.

[Chris Dumez]

Indeed, it seems that if I replace the timestamp in the script with a uuid, the test is no longer flaky:
diff --git a/LayoutTests/imported/w3c/web-platform-tests/service-workers/service-worker/resources/test-request-headers-worker.py b/LayoutTests/imported/w3c/web-platform-tests/service-workers/service-worker/resources/test-request-headers-worker.py
index d3057057763..e7bdea368dd 100644
--- a/LayoutTests/imported/w3c/web-platform-tests/service-workers/service-worker/resources/test-request-headers-worker.py
+++ b/LayoutTests/imported/w3c/web-platform-tests/service-workers/service-worker/resources/test-request-headers-worker.py
@@ -1,6 +1,7 @@
 import json
 import os
 import time
+import uuid
 
 def main(request, response):
   path = os.path.join(os.path.dirname(__file__),
@@ -9,7 +10,7 @@ def main(request, response):
 
   data = {key:request.headers[key] for key,value in request.headers.iteritems()}
   body = body.replace("%HEADERS%", json.dumps(data))
-  body = body.replace("%TIMESTAMP%", str(time.time()))
+  body = body.replace("%TIMESTAMP%", str(uuid.uuid4()))
 
   headers = []
   headers.append(("ETag", "etag"))

[Chris Dumez]

Created attachment 385807 [details]
Patch

[WebKit Commit Bot]

Comment on attachment 385807 [details]
Patch

Clearing flags on attachment: 385807

Committed r253592: <https://trac.webkit.org/changeset/253592>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.