The node receiving the hash slot needs to have a version that wins over
the other versions in order to force the ownership of the slot.
However the current code is far from perfect since a failover can happen
during the manual resharding. The fix is a work in progress but the
bottom line is that the new version must either be voted as usually,
set by redis-trib manually after it makes sure can't be used by other
nodes, or reserved configEpochs could be used for manual operations (for
example odd versions could be never used by slaves and are always used
by CLUSTER SETSLOT NODE).
During slots migration redis-trib can send a number of SETSLOT commands.
Fsyncing every time is a bit too much in production as verified
empirically.
To make sure configs are fsynced on all nodes after a resharding
redis-trib may send something like CLUSTER CONFSYNC.
In this case fsyncs were not providing too much value since anyway
processes can crash in the middle of the resharding of an hash slot, and
redis-trib should be able to recover from this condition anyway.
During slots migration redis-trib can send a number of SETSLOT commands.
Fsyncing every time is a bit too much in production as verified
empirically.
To make sure configs are fsynced on all nodes after a resharding
redis-trib may send something like CLUSTER CONFSYNC.
In this case fsyncs were not providing too much value since anyway
processes can crash in the middle of the resharding of an hash slot, and
redis-trib should be able to recover from this condition anyway.
If the slot is manually assigned to another node, clear the migrating
status regardless of the fact it was previously assigned to us or not,
as long as we no longer have keys for this slot.
This avoid a race during slots migration that may leave the slot in
migrating status in the source node, since it received an update message
from the destination node that is already claiming the slot.
This way we are sure that redis-trib at the end of the slot migration is
always able to close the slot correctly.
If the slot is manually assigned to another node, clear the migrating
status regardless of the fact it was previously assigned to us or not,
as long as we no longer have keys for this slot.
This avoid a race during slots migration that may leave the slot in
migrating status in the source node, since it received an update message
from the destination node that is already claiming the slot.
This way we are sure that redis-trib at the end of the slot migration is
always able to close the slot correctly.
If someone asks for SYNC or PSYNC from redis-cli,
automatically enter slaveMode (as if they ran
redis-cli --slave) and continue printing the replication
stream until either they Ctrl-C or the master gets disconnected.
If someone asks for SYNC or PSYNC from redis-cli,
automatically enter slaveMode (as if they ran
redis-cli --slave) and continue printing the replication
stream until either they Ctrl-C or the master gets disconnected.
Currently this is marginally useful, only to make sure two keys are in
the same hash slot when the cluster is stable (no rehashing in
progress).
In the future it is possible that support will be added to run
mutli-keys operations with keys in the same hash slot.
Currently this is marginally useful, only to make sure two keys are in
the same hash slot when the cluster is stable (no rehashing in
progress).
In the future it is possible that support will be added to run
mutli-keys operations with keys in the same hash slot.
Sometime an osx master with a Linux server over a slow link caused
a strange error where osx called the writable function for
the socket but actually apparently there was no room in the socket
buffer to accept the write: write(2) call returned an EAGAIN error,
that was not checked, so we considered write(2) == 0 always as a connection
reset, which was unfortunate since the bulk transfer has to start again.
Also more errors are logged with the WARNING level in the same code path
now.
Sometime an osx master with a Linux server over a slow link caused
a strange error where osx called the writable function for
the socket but actually apparently there was no room in the socket
buffer to accept the write: write(2) call returned an EAGAIN error,
that was not checked, so we considered write(2) == 0 always as a connection
reset, which was unfortunate since the bulk transfer has to start again.
Also more errors are logged with the WARNING level in the same code path
now.
