The HttpBodySubscriberWrapper is a class that ensures that a subscriber will be
subscribed to before it is completed. It also provides hooks to its two
subclasses (one for HTTP/1, one for HTTP/2) that allows subclasses to register
the susbscriber with the HttpClient at subscription time, and to unregister it
when it is eventualy completed, or when the subscription is cancelled.
There is however a race condition that can happen when a subscription is
cancelled: it can happen that unregister is called before register. The
CancelRequestTest has been observed failing once or twice on personal jobs.
Though the particular mechanics of this race is hard to understand, the logs of
the tests have brought sufficient evidence that this is what was happening.
The symptom is finding one subscriber still registered after completion of the
exchange:
test
CancelRequestTest.testGetSendAsync("https://localhost:42711/https1/x/same/interrupt";,
true, true): failure
java.lang.AssertionError: WARNING: tracker for HttpClientImpl(13) has
outstanding operations:
Pending HTTP Requests: 0
Pending HTTP/1.1 operations: 0
Pending HTTP/2 streams: 0
Pending WebSocket operations: 0
Pending TCP connections: 0
Pending Subscribers: 1
Total pending operations: 0
Facade referenced: true
Selector alive: true
The proposed fix hoist special hooks for register/unregister in the superclass,
merges all various volatile boolean states into a single int state, and protect
the state changes to subscribed/register/unregister by the same subscription
lock.
If cancelling the subscription happens at around the same time that the
subscriber is subscribed this ensures that the subscriber won't be removed from
the map before it is added.
-------------
Commit messages:
- 8302635
Changes: https://git.openjdk.org/jdk/pull/12587/files
Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12587&range=00
Issue: https://bugs.openjdk.org/browse/JDK-8302635
Stats: 233 lines in 4 files changed: 190 ins; 22 del; 21 mod
Patch: https://git.openjdk.org/jdk/pull/12587.diff
Fetch: git fetch https://git.openjdk.org/jdk pull/12587/head:pull/12587
PR: https://git.openjdk.org/jdk/pull/12587
