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Changed background_rollback to return true/false depending on if #212

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@sjaakola sjaakola commented Apr 4, 2023

background rollback did happen.
Background rollback should be skipped if the aborting happens due to KILL command issued by user. Some KILL signals, like KILL CONNECTION, wake up the victim too early so that background rollback could happen in parallel with the victim waking up and continuing execution.

@sjaakola sjaakola requested a review from temeo April 4, 2023 10:15
@@ -86,7 +86,7 @@ namespace wsrep
/**
* Perform a background rollback for a transaction.
*/
virtual void background_rollback(wsrep::client_state&) = 0;
virtual bool background_rollback(wsrep::client_state&) = 0;
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Please document the meaning of return value in comment above.

server_service_.background_rollback(client_state_);
/* if background rollback is skipped, reset rollbacker activity */
if (server_service_.background_rollback(client_state_))
client_state_.set_rollbacker_active(false);
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Calling set_rollbacker_active() should be done with lock held to avoid races.

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Also, it is possible that the client session has reached client_state::do_wait_rollback_complete_and_acquire_ownership() while the mutex was unlocked above. In order to wake up the client, the code should also notify the client_state via client_state_.cond_ to wake up the thread which hosts the client session.

background_rollback(wsrep::client_state& client_state) WSREP_OVERRIDE
{
client_state.before_rollback();
client_state.after_rollback();
return false;

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Maybe I do not understand but when this method can return true ?

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This is for unit testing, so it does not necessarily implement all the same behavior as real application.

@sjaakola sjaakola requested a review from temeo April 11, 2023 18:15
background rollback did happen.
Background rollback should be skipped if the aborting happens due to KILL command issued by user.
Some KILL signals, like KILL CONECTION, wake up the victim too early so that background rollback
could happen in parallel with the victim waking up and continuing execution.
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