Bug 188228

Summary:	[ Sierra Release WK1 ] 7 Layout Tests in imported/w3c/web-platform-tests/service-workers/service-worker/ServiceWorkerGlobalScope/ are Flakey
Product:	WebKit	Reporter:	Truitt Savell <tsavell>
Component:	Tools / Tests	Assignee:	Nobody <webkit-unassigned>
Status:	NEW ---
Severity:	Normal	CC:	ap, lforschler, realdawei, ryanhaddad, youennf
Priority:	P2
Version:	WebKit Nightly Build
Hardware:	Unspecified
OS:	Unspecified

Description Truitt Savell 2018-08-01 10:36:41 PDT

The following layout tests are failing on Sierra Release WK1

These tests fail in succession randomly
imported/w3c/web-platform-tests/service-workers/service-worker/ServiceWorkerGlobalScope/close.https.html
imported/w3c/web-platform-tests/service-workers/service-worker/ServiceWorkerGlobalScope/extendable-message-event-constructor.https.html
imported/w3c/web-platform-tests/service-workers/service-worker/ServiceWorkerGlobalScope/extendable-message-event.https.html
imported/w3c/web-platform-tests/service-workers/service-worker/ServiceWorkerGlobalScope/postmessage.https.html
imported/w3c/web-platform-tests/service-workers/service-worker/ServiceWorkerGlobalScope/registration-attribute.https.html
imported/w3c/web-platform-tests/service-workers/service-worker/ServiceWorkerGlobalScope/service-worker-error-event.https.html
imported/w3c/web-platform-tests/service-workers/service-worker/ServiceWorkerGlobalScope/unregister.https.html

Probable cause:
Test history shows these tests have all failed at the same time twice so far with 15 successful runs in-between. They all have a Harness Timeout issue. 

Example:
--- /Volumes/Data/slave/sierra-release-tests-wk2/build/layout-test-results/imported/w3c/web-platform-tests/service-workers/service-worker/ServiceWorkerGlobalScope/close.https-expected.txt
+++ /Volumes/Data/slave/sierra-release-tests-wk2/build/layout-test-results/imported/w3c/web-platform-tests/service-workers/service-worker/ServiceWorkerGlobalScope/close.https-actual.txt
@@ -1,4 +1,5 @@
 
-PASS ServiceWorkerGlobalScope: close operation 
-PASS ServiceWorkerGlobalScope close operation 
+Harness Error (TIMEOUT), message = null
 
+TIMEOUT ServiceWorkerGlobalScope: close operation Test timed out
+

I do not have a regression point yet or repro steps. First failure was in https://build.webkit.org/builders/Apple%20Sierra%20Release%20WK2%20(Tests)/builds/10842.
I assume that something is setting a state for all 7 tests. 

Flakiness Dashboard:

https://webkit-test-results.webkit.org/dashboards/flakiness_dashboard.html#showAllRuns=true&tests=imported%2Fw3c%2Fweb-platform-tests%2Fservice-workers%2Fservice-worker%2FServiceWorkerGlobalScope%2Fclose.https.html%20imported%2Fw3c%2Fweb-platform-tests%2Fservice-workers%2Fservice-worker%2FServiceWorkerGlobalScope%2Fextendable-message-event-constructor.https.html%20imported%2Fw3c%2Fweb-platform-tests%2Fservice-workers%2Fservice-worker%2FServiceWorkerGlobalScope%2Fextendable-message-event.https.html%20imported%2Fw3c%2Fweb-platform-tests%2Fservice-workers%2Fservice-worker%2FServiceWorkerGlobalScope%2Fpostmessage.https.html%20imported%2Fw3c%2Fweb-platform-tests%2Fservice-workers%2Fservice-worker%2FServiceWorkerGlobalScope%2Fregistration-attribute.https.html%20imported%2Fw3c%2Fweb-platform-tests%2Fservice-workers%2Fservice-worker%2FServiceWorkerGlobalScope%2Fservice-worker-error-event.https.html%20imported%2Fw3c%2Fweb-platform-tests%2Fservice-workers%2Fservice-worker%2FServiceWorkerGlobalScope%2Funregister.https.html