The implementation of the diskless replication was currently diskless only on the master side.
The slave side was still storing the received rdb file to the disk before loading it back in and parsing it.
This commit adds two modes to load rdb directly from socket:
1) when-empty
2) using "swapdb"
the third mode of using diskless slave by flushdb is risky and currently not included.
other changes:
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distinguish between aof configuration and state so that we can re-enable aof only when sync eventually
succeeds (and not when exiting from readSyncBulkPayload after a failed attempt)
also a CONFIG GET and INFO during rdb loading would have lied
When loading rdb from the network, don't kill the server on short read (that can be a network error)
Fix rdb check when performed on preamble AOF
tests:
run replication tests for diskless slave too
make replication test a bit more aggressive
Add test for diskless load swapdb
jemalloc 5 doesn't immediately release memory back to the OS, instead there's a decaying
mechanism, which doesn't work when there's no traffic (no allocations).
this is most evident if there's no traffic after flushdb, the RSS will remain high.
1) enable jemalloc background purging
2) explicitly purge in flushdb
Now threads are stopped even when the connections drop immediately to
zero, not allowing the networking code to detect the condition and stop
the threads. serverCron() will handle that.
This is just an experiment for now, there are a couple of race
conditions, mostly harmless for the performance gain experiment that
this commit represents so far.
The general idea here is to take Redis single threaded and instead
fan-out on expansive kernel calls: write(2) in this case, but the same
concept could be easily implemented for read(2) and protcol parsing.
However just threading writes like in this commit, is enough to evaluate
if the approach is sounding.
Fixes#6012.
As long as "INFO is broken", this should be adequate IMO. Once we rework
`INFO`, perhaps into RESP3, this implementation should be revisited.
Adding another new filed categories at the end of
command reply, it's easy to read and distinguish
flags and categories, also compatible with old format.
That's not REALLY needed, but... right now with LASTSAVE being the only
command tagged as "admin" but not "dangerous" what happens is that after
rewrites the rewrite engine will produce from the rules:
user default on +@all ~* -@dangerous nopass
The rewrite:
user default on nopass ~* +@all -@admin -@dangerous +lastsave
Which is correct but will have users wondering about why LASTSAVE has
something special.
Since LASTSAVE after all also leaks information about the underlying
server configuration, that may not be great for SAAS vendors, let's tag
it as dangerous as well and forget about this issue :-)
This way the behavior is very similar to the past one.
This is useful in order to remember the user she probably failed to
configure a password correctly.
