Greg Harris created KAFKA-15815:
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Summary: JsonRestServer leaks sockets via HttpURLConnection when
keep-alive enabled
Key: KAFKA-15815
URL: https://issues.apache.org/jira/browse/KAFKA-15815
Project: Kafka
Issue Type: Bug
Affects Versions: 3.6.0
Reporter: Greg Harris
By default HttpURLConnection has keep-alive enabled, which allows a single
HttpURLConnection to be left open in order to be re-used for later requests.
This means that despite JsonRestServer calling `close()` on the relevant
InputStream, and calling `disconnect()` on the connection itself, the
HttpURLConnection does not call `close()` on the underlying socket.
This affects the Trogdor AgentTest and CoordinatorTest suites, where most of
the methods make HTTP requests using the JsonRestServer. The effect is that ~32
sockets are leaked per test run, all remaining in the CLOSE_WAIT state (half
closed) after the test. This is because the JettyServer has correctly closed
the connections, but the HttpURLConnection has not.
There does not appear to be a way to locally override the HttpURLConnection's
behavior in this case, and only disabling keep-alive overall (via the system
property `http.keepAlive=false`) seems to resolve the socket leaks.
To prevent the leaks, we can move JsonRestServer to an alternative HTTP
implementation, perhaps the jetty-client that Connect uses, or disable
keepAlive during tests.
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