The reason for this change is to support the upcoming redis-cluster since
it has different behaviors compared to the client-side cluster implementation
provided by Predis. For example redis-cluster will not support key tags or
certain operations currently available with our client-side implementation.
The actual pipeline is wrapped between MULTI and EXEC to ensure that all the
commands are correctly sent and executed on the server. The whole pipeline is
discarded should it fail at a certain point during execution.
We do not use our Predis\Transaction\MultiExecContext abstraction internally
but rely on raw commands since this new executor does not really need full
support for Redis transactions.
We start using SplQueue to enqueue the commands executed inside a MULTI /
EXEC context so that we can dequeue them for parsing their replies later.
This change does not affect performances but makes the code more clean.
Using SplQueue instead of a plain PHP array to queue command instance in
the pipeline is faster and makes the underlying implementation definitely
more clean.
This change is not going to be backported to Predis v0.7 due to changes
in Predis\Pipeline\PipelineContextInterface.
Now Predis\Command\ScriptedCommand uses EVALSHA instead of EVAL internally
so that performances should be better since the client do not resend the
Lua script body on each call.
Plain EVALSHA commands are not affected and will return or throw the error.
The "throw_errors" connection parameter has been removed and replaced by the
new "exceptions" client option since exceptions on -ERR replies returned by
Redis are not generated by connection classes anymore but are thrown by the
client class and other abstractions such as pipeline contexts.
This change does not affect much people using the Predis\Client class (aside
from the different configuration) but gives much more flexibility to those
building their own pieces of code around the internal classes of Predis.
The actual code to switch to master has been implemented only in the
standard and the fire-and-forget executor classes since it does not
make sense to have it in special executors used exclusively when in
client-side clustering mode.
With a negative number Predis will count from the end of the arguments list
to calculate the actual number of keys that will be interpreted as elements
for `KEYS` by the underlying `EVAL` command.
Now developers can pass a client object or an executable context (see
Predis\Transaction\MultiExecContext or Predis\Pipeline\PipelineContext)
interchangeably as parameters to their methods using the new interface
Predis\BasicCliantInterface.
These new interfaces will also allow us to easily create new client
classes aside from the standard Predis\Client one.
Starting with 2.6, Redis uses a slightly different format for the payload
returned by MONITOR for each command. Predis can now adapt to this difference
and returns a new `client` field in the payload object. This new field is
always defined but is set to NULL when connected to Redis < 2.6.
Please note that Redis 2.6 now does not echo the `MONITOR` command as the
first payload when opening a new MONITOR context.
The reason for this change is that not every cluster implementation can support
this behaviour, think of Redis cluster for example. We moved the implementation
of this method in Predis\Connection\PredisCluster since it can still be useful.
Daniele Alessandri