Related to #5145.
Design note: clients may change type when they turn into replicas or are
moved into the Pub/Sub category and so forth. Moreover the recomputation
of the bytes used is problematic for obvious reasons: it changes
continuously, so as a conservative way to avoid accumulating errors,
each client remembers the contribution it gave to the sum, and removes
it when it is freed or before updating it with the new memory usage.
Initially they needed to be at the end so that we could extend to N
strings in the future, but after further consideration I no longer
believe it's worth it.
There is an inherent race between the deferring client and the
"main" client of the test: While the deferring client issues a blocking
command, we can't know for sure that by the time the "main" client
tries to issue another command (Usually one that unblocks the deferring
client) the deferring client is even blocked...
For lack of a better choice this commit uses TCL's 'after' in order
to give some time for the deferring client to issues its blocking
command before the "main" client does its thing.
This problem probably exists in many other tests but this commit
tries to fix blockonkeys.tcl
Example: Client uses a pipe to send the following to a
stale replica:
MULTI
.. do something ...
DISCARD
The replica will reply the MUTLI with -MASTERDOWN and
execute the rest of the commands... A client using a
pipe might not be aware that MULTI failed until it's
too late.
I can't think of a reason why MULTI/EXEC/DISCARD should
not be executed on stale replicas...
Also, enable MULTI/EXEC/DISCARD during loading
By using a "circular BRPOPLPUSH"-like scenario it was
possible the get the same client on db->blocking_keys
twice (See comment in moduleTryServeClientBlockedOnKey)
The fix was actually already implememnted in
moduleTryServeClientBlockedOnKey but it had a bug:
the funxction should return 0 or 1 (not OK or ERR)
Other changes:
1. Added two commands to blockonkeys.c test module (To
reproduce the case described above)
2. Simplify blockonkeys.c in order to make testing easier
3. cast raxSize() to avoid warning with format spec
