1. 21 Aug, 2015 2 commits
    • antirez's avatar
      49f2f691
    • antirez's avatar
      startBgsaveForReplication(): handle waiting slaves state change. · c2ff9de3
      antirez authored
      Before this commit, after triggering a BGSAVE it was up to the caller of
      startBgsavForReplication() to handle slaves in WAIT_BGSAVE_START in
      order to update them accordingly. However when the replication target is
      the socket, this is not possible since the process of updating the
      slaves and sending the FULLRESYNC reply must be coupled with the process
      of starting an RDB save (the reason is, we need to send the FULLSYNC
      command and spawn a child that will start to send RDB data to the slaves
      ASAP).
      
      This commit moves the responsibility of handling slaves in
      WAIT_BGSAVE_START to startBgsavForReplication() so that for both
      diskless and disk-based replication we have the same chain of
      responsiblity. In order accomodate such change, the syncCommand() also
      needs to put the client in the slave list ASAP (just after the initial
      checks) and not at the end, so that startBgsavForReplication() can find
      the new slave alrady in the list.
      
      Another related change is what happens if the BGSAVE fails because of
      fork() or other errors: we now remove the slave from the list of slaves
      and send an error, scheduling the slave connection to be terminated.
      
      As a side effect of this change the following errors found by
      Oran Agra are fixed (thanks!):
      
      1. rdbSaveToSlavesSockets() on failed fork will get the slaves cleaned
      up, otherwise they remain in a wrong state forever since we setup them
      for full resync before actually trying to fork.
      
      2. updateSlavesWaitingBgsave() with replication target set as "socket"
      was broken since the function changed the slaves state from
      WAIT_BGSAVE_START to WAIT_BGSAVE_END via
      replicationSetupSlaveForFullResync(), so later rdbSaveToSlavesSockets()
      will not find any slave in the right state (WAIT_BGSAVE_START) to feed.
      c2ff9de3
  2. 20 Aug, 2015 3 commits
    • antirez's avatar
      Fixed issues introduced during last merge. · c5a8c8e9
      antirez authored
      c5a8c8e9
    • antirez's avatar
      Force slaves to resync after unsuccessful PSYNC. · 4363fa1d
      antirez authored
      Using chained replication where C is slave of B which is in turn slave of
      A, if B reconnects the replication link with A but discovers it is no
      longer possible to PSYNC, slaves of B must be disconnected and PSYNC
      not allowed, since the new B dataset may be completely different after
      the synchronization with the master.
      
      Note that there are varius semantical differences in the way this is
      handled now compared to the past. In the past the semantics was:
      
      1. When a slave lost connection with its master, disconnected the chained
      slaves ASAP. Which is not needed since after a successful PSYNC with the
      master, the slaves can continue and don't need to resync in turn.
      
      2. However after a failed PSYNC the replication backlog was not reset, so a
      slave was able to PSYNC successfully even if the instance did a full
      sync with its master, containing now an entirely different data set.
      
      Now instead chained slaves are not disconnected when the slave lose the
      connection with its master, but only when it is forced to full SYNC with
      its master. This means that if the slave having chained slaves does a
      successful PSYNC all its slaves can continue without troubles.
      
      See issue #2694 for more details.
      4363fa1d
    • antirez's avatar
  3. 07 Aug, 2015 2 commits
  4. 06 Aug, 2015 2 commits
    • antirez's avatar
      809e2f4d
    • antirez's avatar
      Replication: add REPLCONF CAPA EOF support. · ba323760
      antirez authored
      Add the concept of slaves capabilities to Redis, the slave now presents
      to the Redis master with a set of capabilities in the form:
      
          REPLCONF capa SOMECAPA capa OTHERCAPA ...
      
      This has the effect of setting slave->slave_capa with the corresponding
      SLAVE_CAPA macros that the master can test later to understand if it
      the slave will understand certain formats and protocols of the
      replication process. This makes it much simpler to introduce new
      replication capabilities in the future in a way that don't break old
      slaves or masters.
      
      This patch was designed and implemented together with Oran Agra
      (@oranagra).
      ba323760
  5. 05 Aug, 2015 5 commits
    • antirez's avatar
      Fix replication slave pings period. · 64b28d10
      antirez authored
      For PINGs we use the period configured by the user, but for the newlines
      of slaves waiting for an RDB to be created (including slaves waiting for
      the FULLRESYNC reply) we need to ping with frequency of 1 second, since
      the timeout is fixed and needs to be refreshed.
      64b28d10
    • antirez's avatar
      Make sure we re-emit SELECT after each new slave full sync setup. · 27c0ab23
      antirez authored
      In previous commits we moved the FULLRESYNC to the moment we start the
      BGSAVE, so that the offset we provide is the right one. However this
      also means that we need to re-emit the SELECT statement every time a new
      slave starts to accumulate the changes.
      
      To obtian this effect in a more clean way, the function that sends the
      FULLRESYNC reply was overloaded with a more important role of also doing
      this and chanigng the slave state. So it was renamed to
      replicationSetupSlaveForFullResync() to better reflect what it does now.
      27c0ab23
    • antirez's avatar
      99e4cf4d
    • antirez's avatar
      syncCommand() comments improved. · f6c65d3f
      antirez authored
      f6c65d3f
    • antirez's avatar
      PSYNC initial offset fix. · 9d297218
      antirez authored
      This commit attempts to fix a bug involving PSYNC and diskless
      replication (currently experimental) found by Yuval Inbar from Redis Labs
      and that was later found to have even more far reaching effects (the bug also
      exists when diskstore is off).
      
      The gist of the bug is that, a Redis master replies with +FULLRESYNC to
      a PSYNC attempt that fails and requires a full resynchronization.
      However, the baseline offset sent along with FULLRESYNC was always the
      current master replication offset. This is not ok, because there are
      many reasosn that may delay the RDB file creation. And... guess what,
      the master offset we communicate must be the one of the time the RDB
      was created. So for example:
      
      1) When the BGSAVE for replication is delayed since there is one
         already but is not good for replication.
      2) When the BGSAVE is not needed as we attach one currently ongoing.
      3) When because of diskless replication the BGSAVE is delayed.
      
      In all the above cases the PSYNC reply is wrong and the slave may
      reconnect later claiming to need a wrong offset: this may cause
      data curruption later.
      9d297218
  6. 11 Jun, 2015 1 commit
    • antirez's avatar
      Use best effort address binding to connect to the master · 4e8759c6
      antirez authored
      We usually want to reach the master using the address of the interface
      Redis is bound to (via the "bind" config option). That's useful since
      the master will get (and publish) the slave address getting the peer
      name of the incoming socket connection from the slave.
      
      However, when this is not possible, for example because the slave is
      bound to the loopback interface but repliaces from a master accessed via
      an external interface, we want to still connect with the master even
      from a different interface: in this case it is not really important that
      the master will provide any other address, while it is vital to be able
      to replicate correctly.
      
      Related to issues #2609 and #2612.
      4e8759c6
  7. 01 Apr, 2015 2 commits
    • antirez's avatar
      Net: improve prepareClientToWrite() error handling and comments. · 60a28fad
      antirez authored
      When we fail to setup the write handler it does not make sense to take
      the client around, it is missing writes: whatever is a client or a slave
      anyway the connection should terminated ASAP.
      
      Moreover what the function does exactly with its return value, and in
      which case the write handler is installed on the socket, was not clear,
      so the functions comment are improved to make the goals of the function
      more obvious.
      
      Also related to #2485.
      60a28fad
    • Oran Agra's avatar
      fixes to diskless replication. · aa67aec8
      Oran Agra authored
      master was closing the connection if the RDB transfer took long time.
      and also sent PINGs to the slave before it got the initial ACK, in which case the slave wouldn't be able to find the EOF marker.
      aa67aec8
  8. 24 Mar, 2015 1 commit
    • antirez's avatar
      Replication: disconnect blocked clients when switching to slave role. · 7e78ab4b
      antirez authored
      Bug as old as Redis and blocking operations. It's hard to trigger since
      only happens on instance role switch, but the results are quite bad
      since an inconsistency between master and slave is created.
      
      How to trigger the bug is a good description of the bug itself.
      
      1. Client does "BLPOP mylist 0" in master.
      2. Master is turned into slave, that replicates from New-Master.
      3. Client does "LPUSH mylist foo" in New-Master.
      4. New-Master propagates write to slave.
      5. Slave receives the LPUSH, the blocked client get served.
      
      Now Master "mylist" key has "foo", Slave "mylist" key is empty.
      
      Highlights:
      
      * At step "2" above, the client remains attached, basically escaping any
        check performed during command dispatch: read only slave, in that case.
      * At step "5" the slave (that was the master), serves the blocked client
        consuming a list element, which is not consumed on the master side.
      
      This scenario is technically likely to happen during failovers, however
      since Redis Sentinel already disconnects clients using the CLIENT
      command when changing the role of the instance, the bug is avoided in
      Sentinel deployments.
      
      Closes #2473.
      7e78ab4b
  9. 03 Dec, 2014 1 commit
    • antirez's avatar
      Network bandwidth tracking + refactoring. · 8a67e5d4
      antirez authored
      Track bandwidth used by clients and replication (but diskless
      replication is not tracked since the actual transfer happens in the
      child process).
      
      This includes a refactoring that makes tracking new instantaneous
      metrics simpler.
      8a67e5d4
  10. 12 Nov, 2014 2 commits
    • antirez's avatar
      Diskless SYNC: fix RDB EOF detection. · 90911905
      antirez authored
      RDB EOF detection was relying on the final part of the RDB transfer to
      be a magic 40 bytes EOF marker. However as the slave is put online
      immediately, and because of sockets timeouts, the replication stream is
      actually contiguous with the RDB file.
      
      This means that to detect the EOF correctly we should either:
      
      1) Scan all the stream searching for the mark. Sucks CPU-wise.
      2) Start to send the replication stream only after an acknowledge.
      3) Implement a proper chunked encoding.
      
      For now solution "2" was picked, so the master does not start to send
      ASAP the stream of commands in the case of diskless replication. We wait
      for the first REPLCONF ACK command from the slave, that certifies us
      that the slave correctly loaded the RDB file and is ready to get more
      data.
      90911905
    • antirez's avatar
  11. 31 Oct, 2014 1 commit
    • Matt Stancliff's avatar
      Networking: add more outbound IP binding fixes · f1a6f780
      Matt Stancliff authored
      Same as the original bind fixes (we just missed these the
      first time around).
      
      This helps Redis not automatically send
      connections from the first IP on an interface if we are bound
      to a specific IP address (e.g. with multiple IP aliases on one
      interface, you want to send from _your_ IP, not from the first IP
      on the interface).
      f1a6f780
  12. 29 Oct, 2014 18 commits