- 12 Feb, 2013 12 commits
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antirez authored
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antirez authored
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antirez authored
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antirez authored
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antirez authored
When we are preparing an handshake with the slave we can't touch the connection buffer as it'll be used to accumulate differences between the sent RDB file and what arrives next from clients. So in short we can't use addReply() family functions. However we just use write(2) because we know that the socket buffer is empty, since a prerequisite for SYNC to work is that the static buffer and the output list are empty, and in general it is not expected that a client SYNCs after doing some heavy I/O with the master. However a short write connection is explicitly handled to avoid fragility (we simply close the connection and the slave will retry).
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antirez authored
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antirez authored
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antirez authored
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antirez authored
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antirez authored
SELECT was still transmitted to slaves using the inline protocol, that is conceived mostly for humans to type into telnet sessions, and is notably not understood by redis-cli --slave. Now the new protocol is used instead.
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antirez authored
A Redis master sends PING commands to slaves from time to time: doing this ensures that even if absence of writes, the master->slave channel remains active and the slave can feel the master presence, instead of closing the connection for timeout. This commit changes the way PINGs are sent to slaves in order to use the standard interface used to replicate all the other commands, that is, the function replicationFeedSlaves(). With this change the stream of commands sent to every slave is exactly the same regardless of their exact state (Transferring RDB for first synchronization or slave already online). With the previous implementation the PING was only sent to online slaves, with the result that the output stream from master to slaves was not identical for all the slaves: this is a problem if we want to implement partial resyncs in the future using a global replication stream offset. TL;DR: this commit should not change the behaviour in practical terms, but is just something in preparation for partial resynchronization support.
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antirez authored
Before this commit every Redis slave had its own selected database ID state. This was not actually useful as the emitted stream of commands is identical for all the slaves. Now the the currently selected database is a global state that is set to -1 when a new slave is attached, in order to force the SELECT command to be re-emitted for all the slaves. This change is useful in order to implement replication partial resynchronization in the future, as makes sure that the stream of commands received by slaves, including SELECT commands, are exactly the same for every slave connected, at any time. In this way we could have a global offset that can identify a specific piece of the master -> slaves stream of commands.
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- 08 Feb, 2013 1 commit
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antirez authored
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- 05 Feb, 2013 2 commits
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antirez authored
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charsyam authored
Further details from @antirez: It was reported by @StopForumSpam on Twitter that the Redis replication link was strangely using multiple TCP packets for multiple commands. This wastes a lot of bandwidth and is due to the TCP_NODELAY option we enable on the socket after accepting a new connection. However the master -> slave channel is a one-way channel since Redis replication is asynchronous, so there is no point in trying to reduce the latency, we should aim to reduce the bandwidth. For this reason this commit introduces the ability to disable the nagle algorithm on the socket after a successful SYNC. This feature is off by default because the delay can be up to 40 milliseconds with normally configured Linux kernels.
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- 19 Jan, 2013 1 commit
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guiquanz authored
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- 15 Jan, 2013 1 commit
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antirez authored
Issue #828 shows how Redis was not correctly undoing a non-blocking connection attempt with the previous master when the master was set to a new address using the SLAVEOF command. This was also a result of lack of refactoring, so now there is a function to cancel the non blocking handshake with the master. The new function is now used when SLAVEOF NO ONE is called or when SLAVEOF is used to set the master to a different address.
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- 03 Jan, 2013 1 commit
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antirez authored
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- 14 Dec, 2012 1 commit
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antirez authored
REDIS_HZ is the frequency our serverCron() function is called with. A more frequent call to this function results into less latency when the server is trying to handle very expansive background operations like mass expires of a lot of keys at the same time. Redis 2.4 used to have an HZ of 10. This was good enough with almost every setup, but the incremental key expiration algorithm was working a bit better under *extreme* pressure when HZ was set to 100 for Redis 2.6. However for most users a latency spike of 30 milliseconds when million of keys are expiring at the same time is acceptable, on the other hand a default HZ of 100 in Redis 2.6 was causing idle instances to use some CPU time compared to Redis 2.4. The CPU usage was in the order of 0.3% for an idle instance, however this is a shame as more energy is consumed by the server, if not important resources. This commit introduces HZ as a runtime parameter, that can be queried by INFO or CONFIG GET, and can be modified with CONFIG SET. At the same time the default frequency is set back to 10. In this way we default to a sane value of 10, but allows users to easily switch to values up to 500 for near real-time applications if needed and if they are willing to pay this small CPU usage penalty.
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- 08 Nov, 2012 1 commit
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antirez authored
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- 01 Nov, 2012 1 commit
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antirez authored
This also fixes issue #745.
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- 04 Oct, 2012 1 commit
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antirez authored
The new message now contains an hint about modifying the repl-timeout configuration directive if the problem persists. This should normally not be needed, because while the master generates the RDB file it makes sure to send newlines to the replication channel to prevent timeouts. However there are times when masters running on very slow systems can completely stop for seconds during the RDB saving process. In such a case enlarging the timeout value can fix the problem. See issue #695 for an example of this problem in an EC2 deployment.
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- 17 Sep, 2012 1 commit
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antirez authored
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- 02 Sep, 2012 1 commit
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antirez authored
During the first synchronization step of the replication process, a Redis slave connects with the master in a non blocking way. However once the connection is established the replication continues sending the REPLCONF command, and sometimes the AUTH command if needed. Those commands are send in a partially blocking way (blocking with timeout in the order of seconds). Because it is common for a blocked master to accept connections even if it is actually not able to reply to the slave requests, it was easy for a slave to block if the master had serious issues, but was still able to accept connections in the listening socket. For this reason we now send an asynchronous PING request just after the non blocking connection ended in a successful way, and wait for the reply before to continue with the replication process. It is very unlikely that a master replying to PING can't reply to the other commands. This solution was proposed by Didier Spezia (Thanks!) so that we don't need to turn all the replication process into a non blocking affair, but still the probability of a slave blocked is minimal even in the event of a failing master. Also we now use getsockopt(SO_ERROR) in order to check errors ASAP in the event handler, instead of waiting for actual I/O to return an error. This commit fixes issue #632.
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- 28 Aug, 2012 1 commit
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antirez authored
This fixes issue #539. Basically if there is enough free memory the OS may buffer the RDB file that the slave transfers on disk from the master. The file may actually be flused on disk at once by the operating system when it gets closed by Redis, causing the close system call to block for a long time. This patch is a modified version of one provided by yoav-steinberg of @garantiadata (the original version was posted in the issue #539 comments), and tries to flush the OS buffers incrementally (every 8 MB of loaded data).
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- 05 Jul, 2012 1 commit
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Saj Goonatilleke authored
REDIS_REPL_PING_SLAVE_PERIOD controls how often the master should transmit a heartbeat (PING) to its slaves. This period, which defaults to 10, is measured in seconds. Redis 2.4 masters used to ping their slaves every ten seconds, just like it says on the tin. The Redis 2.6 masters I have been experimenting with, on the other hand, ping their slaves *every second*. (master_last_io_seconds_ago never approaches 10.) I think the ping period was inadvertently slashed to one-tenth of its nominal value around the time REDIS_HZ was introduced. This commit reintroduces correct ping schedule behaviour.
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- 27 Jun, 2012 2 commits
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antirez authored
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antirez authored
The REPLCONF command is an internal command (not designed to be directly used by normal clients) that allows a slave to set some replication related state in the master before issuing SYNC to start the replication. The initial motivation for this command, and the only reason currently it is used by the implementation, is to let the slave instance communicate its listening port to the slave, so that the master can show all the slaves with their listening ports in the "replication" section of the INFO output. This allows clients to auto discover and query all the slaves attached into a master. Currently only a single option of the REPLCONF command is supported, and it is called "listening-port", so the slave now starts the replication process with something like the following chat: REPLCONF listening-prot 6380 SYNC Note that this works even if the master is an older version of Redis and does not understand REPLCONF, because the slave ignores the REPLCONF error. In the future REPLCONF can be used for partial replication and other replication related features where there is the need to exchange information between master and slave. NOTE: This commit also fixes a bug: the INFO outout already carried information about slaves, but the port was broken, and was obtained with getpeername(2), so it was actually just the ephemeral port used by the slave to connect to the master as a client.
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- 24 May, 2012 1 commit
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antirez authored
The user @jokea noticed that the following line of code into replication.c made little sense: addReplySds(slave,sdsempty()); Investigating a bit I found that this was introduced by commit 6208b3a7 three years ago in the early stages of Redis. The code apparently is not useful at all, so I'm removing it. This change will not be backported into 2.4 so that in the rare case this should introduce a bug, we'll have a chance to detect it into the development branch. However following the code path it seems like the code is not useful at all, so the risk is truly small.
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- 02 May, 2012 1 commit
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antirez authored
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- 25 Apr, 2012 1 commit
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David Tran authored
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- 31 Mar, 2012 1 commit
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antirez authored
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- 30 Mar, 2012 2 commits
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antirez authored
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Joseph Jang authored
occurs when two or more dbs are replicated and at least one of them is >db10
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- 29 Mar, 2012 1 commit
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antirez authored
Fix for slaves chains. Force resync of slaves (simply disconnecting them) when SLAVEOF turns a master into a slave.
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- 27 Mar, 2012 1 commit
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Premysl Hruby authored
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- 07 Mar, 2012 1 commit
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antirez authored
Better MONITOR output, now includes client ip:port or the lua string if the command was executed by the scripting engine.
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- 29 Feb, 2012 1 commit
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antirez authored
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- 16 Jan, 2012 1 commit
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antirez authored
Don't change the replication state if SLAVE OF is called with arguments specifying the same master we are already connected with. This fixes issues #290.
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- 30 Dec, 2011 1 commit
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antirez authored
Fixed replication when multiple slaves are attaching at the same time. The output buffer was not copied correctly between slaves. This fixes issue #141.
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