call auth completion in free_completions()
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Key: ZOOKEEPER-320
URL: https://issues.apache.org/jira/browse/ZOOKEEPER-320
Project: Zookeeper
Issue Type: Bug
Components: c client
Affects Versions: 3.1.0, 3.0.1, 3.0.0
Reporter: Chris Darroch
Fix For: 3.1.1, 3.2.0
If a client calls zoo_add_auth() with an invalid scheme (e.g., "foo") the
ZooKeeper server will mark their session expired and close the connection.
However, the C client has returned immediately after queuing the new auth data
to be sent with a ZOK return code.
If the client then waits for their auth completion function to be called, they
can wait forever, as no session event is ever delivered to that completion
function. All other completion functions are notified of session events by
free_completions(), which is called by cleanup_bufs() in handle_error() in
handle_socket_error_msg().
In actual fact, what can happen (about 50% of the time, for me) is that the
next call by the IO thread to flush_send_queue() calls send() from within
send_buffer(), and receives a SIGPIPE signal during this send() call. Because
the ZooKeeper C API is a library, it properly does not catch that signal. If
the user's code is not catching that signal either, they experience an abort
caused by an untrapped signal. If they are ignoring the signal -- which is
common in context I'm working in, the Apache httpd server -- then
flush_send_queue()'s error return code is EPIPE, which is logged by
handle_socket_error_msg(), and all non-auth completion functions are notified
of a session event. However, if the caller is waiting for their auth
completion function, they wait forever while the IO thread tries repeatedly to
reconnect and is rejected by the server as having an expired session.
So, first of all, it would be useful to document in the C API portion of the
programmer's guide that trapping or ignoring SIGPIPE is important, as this
signal may be generated by the C API.
Next, the two attached patches call the auth completion function, if any, in
free_completions(), which fixes this problem for me. The second attached patch
includes auth lock/unlock function, as per ZOOKEEPER-319.
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