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.

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.

occurs when two or more dbs are replicated and at least one of them is >db10

Fix for slaves chains. Force resync of slaves (simply disconnecting them)  when SLAVEOF turns a master into a slave.

Better MONITOR output, now includes client ip:port or the lua string if the command was executed by the scripting engine.

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.

Fixed replication when multiple slaves are attaching at the same time. The output buffer was not copied correctly between slaves. This fixes issue #141.

AOF fixes in the context of replicaiton (when AOF is used by slave) and CONFIG SET appendonly yes/no.

Replication bug fixed: now non blocking connect is also forced to follow the configured replication timeout.

Return from syncWithMaster() ASAP if the event fired but the instance is no longer a slave. This should fix Issue #145.

Two fixes for replication: Slave performs the AOF rewrite at the right point. Non blocking connect also uses readable handler as with old Linux kernels like 2.6.18 on connection refused the writable even is not fired (kernel bug).

Fixed issue #435 and at the same time introduced explicit ping in the master-slave channel that will detect a blocked master or a broken even if apparently connected TCP link.

Original report and fix:
http://code.google.com/p/redis/issues/detail?id=404

first attempt to non blocking implementation of slave replication and SYNC bulk data download. Never compiled so far...

synchronous I/O networking functions originally used just for replication refactored in a file as generally useful, they are used in the cluster branch for MIGRATE.

slave with attached slaves now close the conection to all the slaves when the connection to the master is lost. Now a slave without a connected link to the master will refuse SYNC from other slaves. Enhanced the replication error reporting. All this will fix Issue 156

Fixed MONITOR output for consistency: now integer encoded values are also formatted like this: "3932"

networking related stuff moved into networking.c

moved more code

more work on layout of source code

SDS instantaneuos memory saving. By Pieter and Salvatore at VMware ;)

cleanly compiling again after the first split, now splitting it in more C files

moving more things around... work in progress

split replication code

splitting more

Sets split

Hash split

replication split

even more splitting

more splitting

minor change