Incremental flushing in rio.c is only used to avoid huge kernel buffers
synched to slow disks creating big latency spikes, so this fix has no
durability implications, however it is certainly more correct to make
sure that the FILE buffers are flushed to the kernel before calling
fsync on the file descriptor.
Thanks to Li Shao Kai for reporting this issue in the Redis mailing
list.
Incremental flushing in rio.c is only used to avoid huge kernel buffers
synched to slow disks creating big latency spikes, so this fix has no
durability implications, however it is certainly more correct to make
sure that the FILE buffers are flushed to the kernel before calling
fsync on the file descriptor.
Thanks to Li Shao Kai for reporting this issue in the Redis mailing
list.
One of the simple heuristics used by Redis Cluster in order to avoid
losing data in the typical failure modes created by the asynchronous
replication with the slaves (a master is unable, when accepting a
write, to immediately tell if it should be really accepted or refused
because of a configuration change), is to wait some time before to
rejoin the cluster after being partitioned away from the majority of
instances.
A similar condition happens when a master is restarted. It does not know
if it was already failed over, nor if all the clients have already an
updated configuration about the cluster map, so it is possible that
clients will try to write to stale masters that were restarted.
In a similar way this commit changes masters behavior so they wait
2000 milliseconds before accepting writes after a reboot. There is
nothing special about 2 seconds if not to be a value supposedly larger
a few orders of magnitude compared to the cluster bus communication
latencies.
One of the simple heuristics used by Redis Cluster in order to avoid
losing data in the typical failure modes created by the asynchronous
replication with the slaves (a master is unable, when accepting a
write, to immediately tell if it should be really accepted or refused
because of a configuration change), is to wait some time before to
rejoin the cluster after being partitioned away from the majority of
instances.
A similar condition happens when a master is restarted. It does not know
if it was already failed over, nor if all the clients have already an
updated configuration about the cluster map, so it is possible that
clients will try to write to stale masters that were restarted.
In a similar way this commit changes masters behavior so they wait
2000 milliseconds before accepting writes after a reboot. There is
nothing special about 2 seconds if not to be a value supposedly larger
a few orders of magnitude compared to the cluster bus communication
latencies.
The code was doing checks for slaves that should be done only when the
instance is currently a master. Switching a slave from a master to
another one should just work.
The code was doing checks for slaves that should be done only when the
instance is currently a master. Switching a slave from a master to
another one should just work.
When an instance is potentially set to replicate with another master, it
is conceptually disconnected forever, since we have no old copy of the
dataset for this master in memory.
When an instance is potentially set to replicate with another master, it
is conceptually disconnected forever, since we have no old copy of the
dataset for this master in memory.
CLUSTER FORGET is not useful if we can't remove a node from all the
nodes of our cluster because of the Gossip protocol that keeps adding
a given node to nodes where we already tried to remove it.
So now CLUSTER FORGET implements a nodes blacklist that is set and
checked by the Gossip section processing function. This way before a
node is re-added at least 60 seconds must elapse since the FORGET
execution.
This means that redis-trib has some time to remove a node from a whole
cluster. It is possible that in the future it will be uesful to raise
the 60 sec figure to something bigger.
CLUSTER FORGET is not useful if we can't remove a node from all the
nodes of our cluster because of the Gossip protocol that keeps adding
a given node to nodes where we already tried to remove it.
So now CLUSTER FORGET implements a nodes blacklist that is set and
checked by the Gossip section processing function. This way before a
node is re-added at least 60 seconds must elapse since the FORGET
execution.
This means that redis-trib has some time to remove a node from a whole
cluster. It is possible that in the future it will be uesful to raise
the 60 sec figure to something bigger.
