Iterating over Predis\Connection\Aggregate\RedisCluster returns all
the connections currently mapped in the slots map instead of just the
ones initialized in the pool.
When the slots map is retrieved from Redis (which by default is done
automatically) this allows to iterate over all of the current master
nodes of the cluster. When the underlying use of "CLUSTER SLOTS" is
disabled the iteration returns only connections with a slots range
associated in their parameters or initialized by `-MOVED` responses
to make the behaviour of the iteration consistent between the two
modes of operation.
When various nodes in the configuration are unreachable while trying
to send a command, we should attempt to contact a reachable node to
fetch an updated slots map up to $retryLimit times or until there are
no more servers in the pool before giving up.
It is possible that the slots map fetched from Redis contains stale
data and points to a dead server, this happens when the nodes still
have to agree that a master server is down before promoting a slave
to the role of master. In this case no further attempts to execute
the command are performed and an exception is thrown.
This still needs some more testing and will delay v1.0.4 a few days
past its scheduled release.
This prevents an early failure of the command execution on the client
when one slave gets back online but is still loading the dataset from
disk (when this happens, Redis returns the -LOADING error response).
This commit fixes#280.
When the connection to a node in the cluster fails in the attempt to
execute a command, Predis now removes the failed connection from the
cluster pool and contacts a random node to ask for a fresh slots map
and tries to execute the command once again.
When the cluster is configured to have each master replicated to one
or more slaves, one the slaves is automatically promoted to the role
of master by redis-cluster with this change being reflected in the
output of CLUSTER SLOTS, so the next execution should run just fine.
Our current approach is relatively naive as CLUSTER SLOTS is executed
against a random master node, meaning that the client must open a new
connection and execute one more roundtrip only to fetch the new slots
map. For now it is enough, it is still better than having the client
fail when you actually have somes slaves in your redis-cluster setup,
but one improvement could consist in caching the list of slaves for
each master returned in the response of CLUSTER SLOTS so that when a
connection fails the client can try to guess which connection should
use for the next attempt.
This commit closes#173, closes#215, and closes#314.
When using redis-cluster it is now also possible to pass one slot or
non-contiguous ranges of slots via connection parameters in order to
improve the ability to pre-configure the slots map on the client.
Here is an example:
$parameters = [
'tcp://10.0.0.1:6379?slots=0-5460,5500-5600,11000',
'tcp://10.0.0.2:6379?slots=5461-5499,5600-10921',
'tcp://10.0.0.3:6379?slots=10922-10999,11001-16383',
];
This commit fixes#312 (props to @kenotr0n for the original PR).
Common failures are the use of SELECT with a database index outside
the bound of the configured number of databases in redis.conf or the
use of a wrong password for authentication with AUTH.
This resolves#322.
Now the client can discover the whole replication configuration by
asking to one of the servers (master has the precedence) using the
INFO REPLICATION command. This is obviously a best-effort fallback
and there is no strong guarantee about reliability and efficiency.
By enabling auto-discovery, the client automates this process when
the execution of a command fails because one of the target servers
is unreachable. The replication connection requires an instance of
connection factory associated to it in order to be able to create
new connections on the fly.
It is possible to enable the auto-discovery procedure easily via
client options:
$client = new Predis\Client($servers, [
'replication' => true,
'autodiscovery' => true,
]);
Till Krüss
Ali Yousefi
Daniele Alessandri
Andrii Volin
Remi Collet
Pascal Hofmann