This is extremely useful in order to simulate an high load of requests
about different keys, and force Redis to track a lot of informations
about several clients, to simulate real world workloads.
Now that the call also invalidates client side caching slots, it is
important that after an internal flush operation we both send the
notifications to the clients and, at the same time, are able to reclaim
the memory of the tracking table. This may even fix a few edge cases
related to MULTI/EXEC + WATCH during resync, not sure, but in general
looks more correct.
Otherwise what happens is that the tracking table will never get garbage
collected if there are no longer clients with tracking enabled.
Now the invalidation function immediately checks if there is any table
allocated, otherwise it returns ASAP, so the overhead when the feature
is not used should be near zero.
This is especially needed in diskless loading, were a short read could have
caused redis to exit. now the module can handle the error and return to the
caller gracefully.
this fixes#5326
Without such change, the diskless replicas, when loading RDB files from
the socket will not abort when a broken RDB file gets loaded. This is
potentially unsafe, because right now Redis is not able to guarantee
that encoding errors are safe from the POV of memory corruptions (for
instance the LZF library may not be safe against untrusted data?) so
better to abort when the RDB file we are going to load is corrupted.
Instead I/O errors are still returned to the caller without aborting,
so that in case of short read the diskless replica can try again.
now that replica can read rdb directly from the socket, it should avoid exiting
on short read and instead try to re-sync.
this commit tries to have minimal effects on non-diskless rdb reading.
and includes a test that tries to trigger this scenario on various read cases.
* create module API for forking child processes.
* refactor duplicate code around creating and tracking forks by AOF and RDB.
* child processes listen to SIGUSR1 and dies exitFromChild in order to
eliminate a valgrind warning of unhandled signal.
* note that BGSAVE error reply has changed.
valgrind error is:
Process terminating with default action of signal 10 (SIGUSR1)
