This happens only on diskless replicas when attempting to reconnect after
failing to load an RDB file. It is more likely to occur with larger datasets.
After reconnection is initiated, replicationEmptyDbCallback() may get called
and try to write to an unconnected socket. This triggered another issue where
the connection is put into an error state and the connect handler never gets
called. The problem is a regression introduced by commit c17e597.
When all replicas waiting for a bgsave get disconnected (possibly due to output buffer limit),
It may be good to kill the bgsave child. in diskless replication it already happens, but in
disk-based, the child may still serve some purpose (for persistence).
By killing the child, we prevent it from eating COW memory in vain, and we also allow a new child fork sooner for the next full synchronization or bgsave.
We do that only if rdb persistence wasn't enabled in the configuration.
Btw, now, rdbRemoveTempFile in killRDBChild won't block server, so we can killRDBChild safely.
This commit adds streamIteratorStop call in rewriteStreamObject function in some of the return statement. Although currently this will not cause memory leak since stream id is only 16 bytes long.
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>
445a4b6 introudced a makefile script that detects if the toolchain
supports c11, and it looked that it was passing on MacOS and fails on
Ubuntu, looks like Ubuntu's Dash was spawning a background process,
deleted foo.c before gcc tried to compile it.
We're already using bg_unlink in several places to delete the rdb file in the background,
and avoid paying the cost of the deletion from our main thread.
This commit uses bg_unlink to remove the temporary rdb file in the background too.
However, in case we delete that rdb file just before exiting, we don't actually wait for the
background thread or the main thread to delete it, and just let the OS clean up after us.
i.e. we open the file, unlink it and exit with the fd still open.
Furthermore, rdbRemoveTempFile can be called from a thread and was using snprintf which is
not async-signal-safe, we now use ll2string instead.
Redis 6.0 introduces I/O threads, it is so cool and efficient, we use C11
_Atomic to establish inter-thread synchronization without mutex. But the
compiler that must supports C11 _Atomic can compile redis code, that brings a
lot of inconvenience since some common platforms can't support by default such
as CentOS7, so we want to implement redis atomic type to make it more portable.
We have implemented our atomic variable for redis that only has 'relaxed'
operations in src/atomicvar.h, so we implement some operations with
'sequentially-consistent', just like the default behavior of C11 _Atomic that
can establish inter-thread synchronization. And we replace all uses of C11
_Atomic with redis atomic variable.
Our implementation of redis atomic variable uses C11 _Atomic, __atomic or
__sync macros if available, it supports most common platforms, and we will
detect automatically which feature we use. In Makefile we use a dummy file to
detect if the compiler supports C11 _Atomic. Now for gcc, we can compile redis
code theoretically if your gcc version is not less than 4.1.2(starts to support
__sync_xxx operations). Otherwise, we remove use mutex fallback to implement
redis atomic variable for performance and test. You will get compiling errors
if your compiler doesn't support all features of above.
For cover redis atomic variable tests, we add other CI jobs that build redis on
CentOS6 and CentOS7 and workflow daily jobs that run the tests on them.
For them, we just install gcc by default in order to cover different compiler
versions, gcc is 4.4.7 by default installation on CentOS6 and 4.8.5 on CentOS7.
We restore the feature that we can test redis with Helgrind to find data race
errors. But you need install Valgrind in the default path configuration firstly
before running your tests, since we use macros in helgrind.h to tell Helgrind
inter-thread happens-before relationship explicitly for avoiding false positives.
Please open an issue on github if you find data race errors relate to this commit.
Unrelated:
- Fix redefinition of typedef 'RedisModuleUserChangedFunc'
For some old version compilers, they will report errors or warnings, if we
re-define function type.
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.
Rather than blindly evicting until maxmemory limit is achieved, this
update adds a time limit to eviction. While over the maxmemory limit,
eviction will process before each command AND as a timeProc when no
commands are running.
This will reduce the latency impact on many cases, especially pathological
cases like massive used memory increase during dict rehashing.
There is a risk that some other edge cases (like massive pipelined use
of MGET) could cause Redis memory usage to keep growing despite the
eviction attempts, so a new maxmemory-eviction-tenacity config is
introduced to let users mitigate that.
This commit makes stream object returning "stream" as encoding type in OBJECT ENCODING subcommand and DEBUG OBJECT command.
Till now, it would return "unknown"
This is a catch-all test to confirm that that rewrite produces a valid
output for all parameters and that this process does not introduce
undesired configuration changes.
Save parameters should either be default or whatever specified in the
config file. This fixes an issue introduced in #7092 which causes
configuration file settings to be applied on top of the defaults.
Improve RM_Call inline documentation about the fmt argument
so that we don't completely depend on the web docs.
Co-authored-by: Oran Agra <oran@redislabs.com>
There was a bug. Although cluster replicas would allow read commands,
they would not allow a MULTI-EXEC that's composed solely of read commands.
Adds tests for coverage.
Co-authored-by: Oran Agra <oran@redislabs.com>
Co-authored-by: Eran Liberty <eranl@amazon.com>
Starting redis 6.0 and the changes we made to the diskless master to be
suitable for TLS, I made the master avoid reaping (wait3) the pid of the
child until we know all replicas are done reading their rdb.
I did that in order to avoid a state where the rdb_child_pid is -1 but
we don't yet want to start another fork (still busy serving that data to
replicas).
It turns out that the solution used so far was problematic in case the
fork child was being killed (e.g. by the kernel OOM killer), in that
case there's a chance that we currently disabled the read event on the
rdb pipe, since we're waiting for a replica to become writable again.
and in that scenario the master would have never realized the child
exited, and the replica will remain hung too.
Note that there's no mechanism to detect a hung replica while it's in
rdb transfer state.
The solution here is to add another pipe which is used by the parent to
tell the child it is safe to exit. this mean that when the child exits,
for whatever reason, it is safe to reap it.
Besides that, i'm re-introducing an adjustment to REPLCONF ACK which was
part of #6271 (Accelerate diskless master connections) but was dropped
when that PR was rebased after the TLS fork/pipe changes (5a47794).
Now that RdbPipeCleanup no longer calls checkChildrenDone, and the ACK
has chance to detect that the child exited, it should be the one to call
it so that we don't have to wait for cron (server.hz) to do that.
Fix issues with writeConn() which resulted with corruption of the stream by leaving an extra byte in the buffer. The trigger for this is partial writes or write errors which were not experienced on Linux but reported on macOS.
During long running scripts or loading RDB/AOF, we may need to do some
defragging. Since processEventsWhileBlocked is called periodically at
unknown intervals, and many cron jobs either depend on run_with_period
(including active defrag), or rely on being called at server.hz rate
(i.e. active defrag knows ho much time to run by looking at server.hz),
the whileBlockedCron may have to run a loop triggering the cron jobs in it
(currently only active defrag) several times.
Other changes:
- Adding a test for defrag during aof loading.
- Changing key-load-delay config to take negative values for fractions
of a microsecond sleep
DEBUG ZIPLIST <key> currently returns the following error string if the
key is not a ziplist: "ERR Not an sds encoded string.". This looks like
an accidental copy/paste error from the error returned in the else if
branch above where this string is returned if the key is not an sds
string. The command was added in
ac61f9062583d67dd43f7d698824464d1e30d84b and looking at the commit,
nothing indicates that it is not an accidental typo.
The error string now returns a correct error: "Not a ziplist encoded
object", which accurately describes the error.
The previous algorithm is of O(n^2) time complexity.
It would have run through the ziplist entries one by one, each time doing a `realloc` and a
`memmove` (moving the entire tail of the ziplist).
The new algorithm is O(n), it runs over all the records once, computing the size of the `realloc`
needed, then does one `realloc`, and run thought the records again doing many smaller `memmove`s,
each time moving just one record.
So this change reduces many reallocs, and moves each record just once.
Co-authored-by: zhumaohua <zhumaohua@megvii.com>
Co-authored-by: Oran Agra <oran@redislabs.com>
Update adds a general source for retrieving a monotonic time.
In addition, AE has been updated to utilize the new monotonic
clock for timer processing.
This performance improvement is **not** enabled in a default build due to various H/W compatibility
concerns, see README.md for details. It does however change the default use of gettimeofday with
clock_gettime and somewhat improves performance.
This update provides the following
1. An interface for retrieving a monotonic clock. getMonotonicUs returns a uint64_t (aka monotime)
with the number of micro-seconds from an arbitrary point. No more messing with tv_sec/tv_usec.
Simple routines are provided for measuring elapsed milli-seconds or elapsed micro-seconds (the
most common use case for a monotonic timer). No worries about time moving backwards.
2. High-speed assembler implementation for x86 and ARM. The standard method for retrieving the
monotonic clock is POSIX.1b (1993): clock_gettime(CLOCK_MONOTONIC, timespec*). However, most
modern processors provide a constant speed instruction clock which can be retrieved in a fraction
of the time that it takes to call clock_gettime. For x86, this is provided by the RDTSC
instruction. For ARM, this is provided by the CNTVCT_EL0 instruction. As a compile-time option,
these high-speed timers can be chosen. (Default is POSIX clock_gettime.)
3. Refactor of event loop timers. The timer processing in ae.c has been refactored to use the new
monotonic clock interface. This results in simpler/cleaner logic and improved performance.
65a3307bc (released in 6.0.6) has a side effect, when processCommand
rejects a command with pre-made shared object error string, it trims the
newlines from the end of the string. if that string is later used with
addReply, the newline will be missing, breaking the protocol, and
leaving the client hung.
It seems that the only scenario which this happens is when replying with
-LOADING to some command, and later using that reply from the CONFIG
SET command (still during loading). this will result in hung client.
Refactoring the code in order to avoid trimming these newlines from
shared string objects, and do the newline trimming only in other cases
where it's needed.
Co-authored-by: Guy Benoish <guy.benoish@redislabs.com>
During a long AOF or RDB loading, the memory stats were not updated, and
INFO would return stale data, specifically about fragmentation and RSS.
In the past some of these were sampled directly inside the INFO command,
but were moved to cron as an optimization.
This commit introduces a concept of loadingCron which should take
some of the responsibilities of serverCron.
It attempts to limit it's rate to approximately the server Hz, but may
not be very accurate.
In order to avoid too many system call, we use the cached ustime, and
also make sure to update it in both AOF loading and RDB loading inside
processEventsWhileBlocked (it seems AOF loading was missing it).
If the server gets MULTI command followed by only read
commands, and right before it gets the EXEC it reaches OOM,
the client will get OOM response.
So, from now on, it will get OOM response only if there was
at least one command that was tagged with `use-memory` flag
A first step to enable a consistent full percentile analysis on query latency so that we can fully understand the performance and stability characteristics of the redis-server system we are measuring. It also improves the instantaneous reported metrics, and the csv output format.
Otherwise, it is treated as a single allocation and freed synchronously. The following logic is used for estimating the effort in constant-ish time complexity:
1. Check the number of nodes.
1. Add an allocation for each consumer group registered inside the stream.
1. Check the number of PELs in the first CG, and then add this count times the number of CGs.
1. Check the number of consumers in the first CG, and then add this count times the number of CGs.
The previous fix using _Atomic was insufficient, since we check and set it in
different places.
The implications of this bug are just that a portion of the bug report will be shown
twice, in the race case of two concurrent crashes.
When calling to LPOS command when RANK is higher than matches,
the return value is non valid response. For example:
```
LPUSH l a
:1
LPOS l b RANK 5 COUNT 10
*-4
```
It may break client-side parser.
Now, we count how many replies were replied in the array.
```
LPUSH l a
:1
LPOS l b RANK 5 COUNT 10
*0
```
