| Commit message (Collapse) | Author | Age | Files | Lines |
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Implementing the WAITAOF functionality which would allow the user to
block until a specified number of Redises have fsynced all previous write
commands to the AOF.
Syntax: `WAITAOF <num_local> <num_replicas> <timeout>`
Response: Array containing two elements: num_local, num_replicas
num_local is always either 0 or 1 representing the local AOF on the master.
num_replicas is the number of replicas that acknowledged the a replication
offset of the last write being fsynced to the AOF.
Returns an error when called on replicas, or when called with non-zero
num_local on a master with AOF disabled, in all other cases the response
just contains number of fsync copies.
Main changes:
* Added code to keep track of replication offsets that are confirmed to have
been fsynced to disk.
* Keep advancing master_repl_offset even when replication is disabled (and
there's no replication backlog, only if there's an AOF enabled).
This way we can use this command and it's mechanisms even when replication
is disabled.
* Extend REPLCONF ACK to `REPLCONF ACK <ofs> FACK <ofs>`, the FACK
will be appended only if there's an AOF on the replica, and already ignored on
old masters (thus backwards compatible)
* WAIT now no longer wait for the replication offset after your last command, but
rather the replication offset after your last write (or read command that caused
propagation, e.g. lazy expiry).
Unrelated changes:
* WAIT command respects CLIENT_DENY_BLOCKING (not just CLIENT_MULTI)
Implementation details:
* Add an atomic var named `fsynced_reploff_pending` that's updated
(usually by the bio thread) and later copied to the main `fsynced_reploff`
variable (only if the AOF base file exists).
I.e. during the initial AOF rewrite it will not be used as the fsynced offset
since the AOF base is still missing.
* Replace close+fsync bio job with new BIO_CLOSE_AOF (AOF specific)
job that will also update fsync offset the field.
* Handle all AOF jobs (BIO_CLOSE_AOF, BIO_AOF_FSYNC) in the same bio
worker thread, to impose ordering on their execution. This solves a
race condition where a job could set `fsynced_reploff_pending` to a higher
value than another pending fsync job, resulting in indicating an offset
for which parts of the data have not yet actually been fsynced.
Imposing an ordering on the jobs guarantees that fsync jobs are executed
in increasing order of replication offset.
* Drain bio jobs when switching `appendfsync` to "always"
This should prevent a write race between updates to `fsynced_reploff_pending`
in the main thread (`flushAppendOnlyFile` when set to ALWAYS fsync), and
those done in the bio thread.
* Drain the pending fsync when starting over a new AOF to avoid race conditions
with the previous AOF offsets overriding the new one (e.g. after switching to
replicate from a new master).
* Make sure to update the fsynced offset at the end of the initial AOF rewrite.
a must in case there are no additional writes that trigger a periodic fsync,
specifically for a replica that does a full sync.
Limitations:
It is possible to write a module and a Lua script that propagate to the AOF and doesn't
propagate to the replication stream. see REDISMODULE_ARGV_NO_REPLICAS and luaRedisSetReplCommand.
These features are incompatible with the WAITAOF command, and can result
in two bad cases. The scenario is that the user executes command that only
propagates to AOF, and then immediately
issues a WAITAOF, and there's no further writes on the replication stream after that.
1. if the the last thing that happened on the replication stream is a PING
(which increased the replication offset but won't trigger an fsync on the replica),
then the client would hang forever (will wait for an fack that the replica will never
send sine it doesn't trigger any fsyncs).
2. if the last thing that happened is a write command that got propagated properly,
then WAITAOF will be released immediately, without waiting for an fsync (since
the offset didn't change)
Refactoring:
* Plumbing to allow bio worker to handle multiple job types
This introduces infrastructure necessary to allow BIO workers to
not have a 1-1 mapping of worker to job-type. This allows in the
future to assign multiple job types to a single worker, either as
a performance/resource optimization, or as a way of enforcing
ordering between specific classes of jobs.
Co-authored-by: Oran Agra <oran@redislabs.com>
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# Background
The RDB file is usually generated and used once and seldom used again, but the content would reside in page cache until OS evicts it. A potential problem is that once the free memory exhausts, the OS have to reclaim some memory from page cache or swap anonymous page out, which may result in a jitters to the Redis service.
Supposing an exact scenario, a high-capacity machine hosts many redis instances, and we're upgrading the Redis together. The page cache in host machine increases as RDBs are generated. Once the free memory drop into low watermark(which is more likely to happen in older Linux kernel like 3.10, before [watermark_scale_factor](https://lore.kernel.org/lkml/1455813719-2395-1-git-send-email-hannes@cmpxchg.org/) is introduced, the `low watermark` is linear to `min watermark`, and there'is not too much buffer space for `kswapd` to be wake up to reclaim memory), a `direct reclaim` happens, which means the process would stall to wait for memory allocation.
# What the PR does
The PR introduces a capability to reclaim the cache when the RDB is operated. Generally there're two cases, read and write the RDB. For read it's a little messy to address the incremental reclaim, so the reclaim is done in one go in background after the load is finished to avoid blocking the work thread. For write, incremental reclaim amortizes the work of reclaim so no need to put it into background, and the peak watermark of cache can be reduced in this way.
Two cases are addresses specially, replication and restart, for both of which the cache is leveraged to speed up the processing, so the reclaim is postponed to a right time. To do this, a flag is added to`rdbSave` and `rdbLoad` to control whether the cache need to be kept, with the default value false.
# Something deserve noting
1. Though `posix_fadvise` is the POSIX standard, but only few platform support it, e.g. Linux, FreeBSD 10.0.
2. In Linux `posix_fadvise` only take effect on writeback-ed pages, so a `sync`(or `fsync`, `fdatasync`) is needed to flush the dirty page before `posix_fadvise` if we reclaim write cache.
# About test
A unit test is added to verify the effect of `posix_fadvise`.
In integration test overall cache increase is checked, as well as the cache backed by RDB as a specific TCL test is executed in isolated Github action job.
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* Remove redundant array bio_pending[]. Value at index i identically reflects the
length of list bio_jobs[i]. Better use listLength() instead and discard this array.
(no critical section issues to concern about).
changed returned value of bioPendingJobsOfType() from "long long" to "long".
Remove unused API. Maybe we will use this API later.
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In rewriteAppendOnlyFileBackground, after flushAppendOnlyFile(1),
and before openNewIncrAofForAppend, we should call redis_fsync
to fsync the aof file.
Because we may open a new INCR AOF in openNewIncrAofForAppend,
in the case of using everysec policy, the old AOF file may not
be fsynced in time (or even at all).
When using everysec, we don't want to pay the disk latency from
the main thread, so we will do a background fsync.
Adding a argument for bioCreateCloseJob, a `need_fsync` flag to
indicate that a fsync is required before the file is closed. So we will
fsync the old AOF file before we close it.
A cleanup, we make union become a union, since the free_* args and
the fd / fsync args are never used together.
Co-authored-by: Oran Agra <oran@redislabs.com>
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looks like this field was never actually used and the call to time() is excessive.
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The bio aof fsync fd may be closed by main thread (AOFRW done handler)
and even possibly reused for another socket, pipe, or file.
This can can an EBADF or EINVAL fsync error, which will lead to -MISCONF errors failing all writes.
We just ignore these errno because aof fsync did not really fail.
We handle errno when fsyncing aof in bio, so we could know the real reason
when users get -MISCONF Errors writing to the AOF file error
Issue created with #8419
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In `aof.c`, we call fsync when stop aof, and now print a log to let user know that if fail.
In `cluster.c`, we now return error, the calling function already handles these write errors.
In `redis-cli.c`, users hope to save rdb, we now print a message if fsync failed.
In `rio.c`, we now treat fsync errors like we do for write errors.
In `server.c`, we try to fsync aof file when shutdown redis, we only can print one log if fail.
In `bio.c`, if failing to fsync aof file, we will set `aof_bio_fsync_status` to error , and reject writing just like last writing aof error, moreover also set INFO command field `aof_last_write_status` to error.
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Cleanup key tracking documentation, always cleanup the tracking table, and free the tracking table in an async manner when applicable.
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is swapdb in cluster mode (#8108)
When replica diskless-load type is swapdb in cluster mode, we didn't backup
keys to slots map, so we will lose keys to slots map if fail to sync.
Now we backup keys to slots map at first, and restore it properly when fail.
This commit includes a refactory/cleanup of the backups mechanism (moving it to db.c and re-structuring it a bit).
Co-authored-by: Oran Agra <oran@redislabs.com>
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Refine comment of makeThreadKillable().
This commit can be backported to 5.0, only if we also backport 8b70cb0.
Co-authored-by: Oran Agra <oran@redislabs.com>
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If one thread got SIGSEGV, function sigsegvHandler() would be triggered,
it would call bioKillThreads(). But call pthread_cancel() to cancel itself
would make it block. Also note that if SIGSEGV is caught by bio thread, it
should kill the main thread in order to give a positive report.
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lazyfreeFreeSlotsMapFromBioThread (#7228)
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Currently, there are several types of threads/child processes of a
redis server. Sometimes we need deeply optimise the performance of
redis, so we would like to isolate threads/processes.
There were some discussion about cpu affinity cases in the issue:
https://github.com/antirez/redis/issues/2863
So implement cpu affinity setting by redis.conf in this patch, then
we can config server_cpulist/bio_cpulist/aof_rewrite_cpulist/
bgsave_cpulist by cpu list.
Examples of cpulist in redis.conf:
server_cpulist 0-7:2 means cpu affinity 0,2,4,6
bio_cpulist 1,3 means cpu affinity 1,3
aof_rewrite_cpulist 8-11 means cpu affinity 8,9,10,11
bgsave_cpulist 1,10-11 means cpu affinity 1,10,11
Test on linux/freebsd, both work fine.
Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
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If there's a panic before all threads have been started (say, if file descriptor 0 is closed at exec), the panic response will crash here again.
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Set thread name for each thread of redis-server, this helps us to
monitor the utilization and optimise the performance.
And suggested-by Salvatore, implement this feature for multi
platforms. Currently support linux and bsd, ignore other OS.
An exmaple on Linux:
# top -d 5 -p `pidof redis-server ` -H
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
3682671 root 20 0 227744 8248 3836 R 99.2 0.0 0:19.53 redis-server
3682677 root 20 0 227744 8248 3836 S 26.4 0.0 0:04.15 io_thd_3
3682675 root 20 0 227744 8248 3836 S 23.6 0.0 0:03.98 io_thd_1
3682676 root 20 0 227744 8248 3836 S 23.6 0.0 0:03.97 io_thd_2
3682672 root 20 0 227744 8248 3836 S 0.2 0.0 0:00.02 bio_close_file
3682673 root 20 0 227744 8248 3836 S 0.2 0.0 0:00.02 bio_aof_fsync
3682674 root 20 0 227744 8248 3836 S 0.0 0.0 0:00.00 bio_lazy_free
3682678 root 20 0 227744 8248 3836 S 0.0 0.0 0:00.00 jemalloc_bg_thd
3682682 root 20 0 227744 8248 3836 S 0.0 0.0 0:00.00 jemalloc_bg_thd
3682683 root 20 0 227744 8248 3836 S 0.0 0.0 0:00.00 jemalloc_bg_thd
3682684 root 20 0 227744 8248 3836 S 0.0 0.0 0:00.00 jemalloc_bg_thd
3682685 root 20 0 227744 8248 3836 S 0.0 0.0 0:00.00 jemalloc_bg_thd
3682687 root 20 0 227744 8248 3836 S 0.0 0.0 0:00.00 jemalloc_bg_thd
Another exmaple on FreeBSD-12.1:
PID USERNAME PRI NICE SIZE RES STATE C TIME WCPU COMMAND
5212 root 100 0 48M 7280K CPU2 2 0:26 99.52% redis-server{redis-server}
5212 root 38 0 48M 7280K umtxn 4 0:06 26.94% redis-server{io_thd_3}
5212 root 36 0 48M 7280K umtxn 6 0:06 26.84% redis-server{io_thd_1}
5212 root 39 0 48M 7280K umtxn 1 0:06 25.30% redis-server{io_thd_2}
5212 root 20 0 48M 7280K uwait 3 0:00 0.00% redis-server{redis-server}
5212 root 21 0 48M 7280K uwait 2 0:00 0.00% redis-server{bio_close_file}
5212 root 21 0 48M 7280K uwait 3 0:00 0.00% redis-server{bio_aof_fsync}
5212 root 21 0 48M 7280K uwait 0 0:00 0.00% redis-server{bio_lazy_free}
Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
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Another one just to avoid a warning. Slightly more defensive code
anyway.
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We use this new bio.c feature in order to stop our I/O threads if there
is a memory test to do on crash. In this case we don't want anything
else than the main thread to run, otherwise the other threads may mess
with the heap and the memory test will report a false positive.
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This is required to ensure that the signal will be delivered to the main
thread when the watchdog timer expires.
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useful in the future.
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type. Now the function returns 0 when this happens.
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and not just started.
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number of pending jobs of the specified type.
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the job.
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