Comment 3 for bug 1707633

commit 6ea7d1786122ebb7832611aa96996a68332a29c7
Author: Kenn Takara <email address hidden>
Date: Thu Aug 10 13:49:09 2017 -1000

    Fix for PXC-810 PXC-843
    PXC-810: PXC 5.7: segfault in GCommConn::close in galera_var_node_address
    PXC-843: Joiner hangs after failed SST

    Issue:
    If an SST fails due to a DML (such as OPTIMIZE or ALTER TABLE), which is run as the SST
    is running, then the joiner node can hang (PXC-843). This is due to the applier
    thread picking a transaction off of the recv_q and attempting to apply it, even though
    the thread has been killed.

    This exposed PXC-810, which would then happen while testing for PXC-843.

    Solution:
    For PXC-843, if the SST has failed, then we just drop any transactions that hav
    been received. If the SST has failed, the node should be shutting down anyway.

    For PXC-810, we do an additional check within the critical section to avoid the
    null pointer dereference.