Clients using SYNC to replicate are older implementations, such as
redis-cli --slave, and are not designed to acknowledge the master with
REPLCONF ACK commands, so we don't have any feedback and should not
disconnect them on timeout.
This code is only responsible to take an LRU-evicted fixed length cache
of SHA1 that we are sure all the slaves received.
In this commit only the implementation is provided, but the Redis core
does not use it to actually send EVALSHA to slaves when possible.
The old REDIS_CMD_FORCE_REPLICATION flag was removed from the
implementation of Redis, now there is a new API to force specific
executions of a command to be propagated to AOF / Replication link:
void forceCommandPropagation(int flags);
The new API is also compatible with Lua scripting, so a script that will
execute commands that are forced to be propagated, will also be
propagated itself accordingly even if no change to data is operated.
As a side effect, this new design fixes the issue with scripts not able
to propagate PUBLISH to slaves (issue #873).
Currently it implements three subcommands:
PUBSUB CHANNELS [<pattern>] List channels with non-zero subscribers.
PUBSUB NUMSUB [channel_1 ...] List number of subscribers for channels.
PUBSUB NUMPAT Return number of subscribed patterns.
Sentinel was not able to detect slaves when connected to a very recent
version of Redis master since a previos non-backward compatible change
to INFO broken the parsing of the slaves ip:port INFO output.
This fixes issue #1164
When the semantics changed from logfile = NULL to logfile = "" to log
into standard output, no proper change was made to logStackTrace() to
make it able to work with the new setup.
This commit fixes the issue.
This feature allows the user to specify the minimum number of
connected replicas having a lag less or equal than the specified
amount of seconds for writes to be accepted.
There is a new 'lag' information in the list of slaves, in the
"replication" section of the INFO output.
Also the format was changed in a backward incompatible way in order to
make it more easy to parse if new fields are added in the future, as the
new format is comma separated but has named fields (no longer positional
fields).
Now masters, using the time at which the last REPLCONF ACK was received,
are able to explicitly disconnect slaves that are no longer responding.
Previously the only chance was to see a very long output buffer, that
was highly suboptimal.
ACKs can be also used as a base for synchronous replication. However in
that case they'll be explicitly requested by the master when the client
sends a request that needs to be replicated synchronously.
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.
When master send commands, there is no need for the slave to reply.
Redis used to queue the reply in the output buffer and discard the reply
later, this is a waste of work and it is not clear why it was this way
(I sincerely don't remember).
This commit changes it in order to don't queue the reply at all.
All tests passing.
SUSv3 says that:
The useconds argument shall be less than one million. If the value of
useconds is 0, then the call has no effect.
and actually NetBSD's implementation rejects such a value with EINVAL.
use nanosleep which has no such a limitation instead.
