1. 27 May, 2013 3 commits
    • antirez's avatar
      Don't ACK the master after every command. · efd87031
      antirez authored
      Sending an ACK is now moved into the replicationSendAck() function.
      efd87031
    • antirez's avatar
      dd0adbb7
    • antirez's avatar
      REPLCONF ACK command. · 6b4635f4
      antirez authored
      This special command is used by the slave to inform the master the
      amount of replication stream it currently consumed.
      
      it does not return anything so that we not need to consume additional
      bandwidth needed by the master to reply something.
      
      The master can do a number of things knowing the amount of stream
      processed, such as understanding the "lag" in bytes of the slave, verify
      if a given command was already processed by the slave, and so forth.
      6b4635f4
  2. 05 Mar, 2013 1 commit
  3. 04 Mar, 2013 2 commits
  4. 27 Feb, 2013 1 commit
  5. 13 Feb, 2013 2 commits
  6. 12 Feb, 2013 12 commits
  7. 08 Feb, 2013 1 commit
  8. 05 Feb, 2013 2 commits
    • antirez's avatar
      b70b459b
    • charsyam's avatar
      Turn off TCP_NODELAY on the slave socket after SYNC. · c85647f3
      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.
      c85647f3
  9. 19 Jan, 2013 1 commit
  10. 15 Jan, 2013 1 commit
    • antirez's avatar
      Undo slave-master handshake when SLAVEOF sets a new slave. · ef99e146
      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.
      ef99e146
  11. 03 Jan, 2013 1 commit
  12. 14 Dec, 2012 1 commit
    • antirez's avatar
      serverCron() frequency is now a runtime parameter (was REDIS_HZ). · f1481d4a
      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.
      f1481d4a
  13. 08 Nov, 2012 1 commit
  14. 01 Nov, 2012 1 commit
  15. 04 Oct, 2012 1 commit
    • antirez's avatar
      "Timeout receiving bulk data" error message modified. · f0b9f803
      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.
      f0b9f803
  16. 17 Sep, 2012 1 commit
  17. 02 Sep, 2012 1 commit
    • antirez's avatar
      Send an async PING before starting replication with master. · bb66fc31
      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.
      bb66fc31
  18. 28 Aug, 2012 1 commit
    • antirez's avatar
      Incrementally flush RDB on disk while loading it from a master. · 784b9308
      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).
      784b9308
  19. 05 Jul, 2012 1 commit
    • Saj Goonatilleke's avatar
      Bug fix: slaves being pinged every second · 9edfe635
      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.
      9edfe635
  20. 27 Jun, 2012 2 commits
    • antirez's avatar
      Typo in comment. · 36def8fd
      antirez authored
      36def8fd
    • antirez's avatar
      REPLCONF internal command introduced. · 3a328978
      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.
      3a328978
  21. 24 May, 2012 1 commit
    • antirez's avatar
      Dead code removed from replication.c. · ef379976
      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.
      ef379976
  22. 02 May, 2012 1 commit
  23. 25 Apr, 2012 1 commit