• Jay Guo's avatar
    [FAB-13367] Fix flaky etcdraft UT · bebfee73
    Jay Guo authored
    In raft, to commit a message, leader firstly broadcasts
    MsgApp to replicate data, and once it receives MsgAppResp
    from quorum, it
    - applies message to state machine
    - broadcasts another MsgApp to instruct followers to commit
    and these are done in parallel.
    To emulate situation where a node is disconnected *after*
    config block is committed and *before* node add/remove in
    that config block is proposed to raft, `WriteConfigBlock`
    stub on leader was overloaded to disconnect node from the
    network, so that ConfChange is proposed but dropped.
    However this becomes racy when we want to assert the config
    block is committed on followers as well, since we might
    disconnect leader too fast, and cause the second round of
    MsgApp to be dropped, so that config block is not committed
    on followers. This is fine in real case because new leader
    will continue the effort to commit this block.
    To circumvent this flakiness, this CR changes UT to overload
    `StepStub` instead of `WriteConfigBlockStub`, so that we can
    be more precise on when to disconnect a node from network.
    Change-Id: Ic1b7d28c043e779c7cc258c2e08bfaa3578bc429
    Signed-off-by: default avatarJay Guo <guojiannan1101@gmail.com>