Redis 3.0 release notes
=======================

WARNING: Redis 3.0 is currently a BETA not suitable for production environments.

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Upgrade urgency levels:

LOW:      No need to upgrade unless there are new features you want to use.
MODERATE: Program an upgrade of the server, but it's not urgent.
HIGH:     There is a critical bug that may affect a subset of users. Upgrade!
CRITICAL: There is a critical bug affecting MOST USERS. Upgrade ASAP.
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--[ Redis 3.0.0 RC1 (version 2.9.101) ] Release date: 9 oct 2014

This is the first release candidate of Redis Cluster.

>> General changes

* [FIX] An very large number of small fixes, old and new, merged in the
        context of a the issue #1906. Please see the issue page here
        for exact credits: https://github.com/antirez/redis/pull/1906
        of each commit. (Matt Stancliff and many others).
* [FIX] SAVE is no longer propagated to AOF / slaves.
* [FIX] GETRANGE test no longer fails for 32 bit builds (Matt Stancliff).
* [FIX] Limit SCAN latency when the hash table is in an odd state (very few
        populted buckets because rehashing is in progress). (Xiaost and
        Salvatore Sanfilippo)

* [NEW] Redis is now able to load truncated AOF files without requiring a
        redis-check-aof utility run. The default now is to load truncated
        (but apparently not corrupted) AOFs, you can change this in redis.conf.
        (Salvatore Sanfilippo).
* [NEW] DEBUG POPULATE two args form implemented. It is now possible to
        call it with DEBUG POPULATE <count> <prefix>. Default prefix
        is "key:" as usually.
* [NEW] INCR: Modify incremented object in-place when possible. This results
        in speed improvements + possibly better memory locality.

>> Cluster changes

* [FIX] Cluster: claim ping_sent time even if we can't connect.
* [FIX] redis-trib should not abort easily on connection issues.
* [FIX] Cluster test: less console-spammy resharding test.
* [FIX] Fix logic to detect we are among a minority.
* [FIX] Process gossip section only for known nodes.

* [NEW] Redis Cluster is stable and tested enough, there is a clear MVP,
        so it was promoted from beta to stable.
* [NEW] New unit 09, Pub/Sub across the cluster.
* [NEW] New unit 08, update messages.
* [NEW] New cluster option to work with partial slots coverage.
* [NEW] More chatty cluster slaves when failover is stalled. They log reason
        with rate limiting, only when reason changes or a given time
        has elapsed.

>> Sentinel changes

* [FIX] Sentinel critical bug fixed: the absolute majority was computed in a
        wrong way because of a programming error. Now the implementation does
        what the specification says and the majority to authorize a failover
        (that should not be confused with the ODOWN quorum) is the majority of
        *all* the Sentinels ever seen for a given master, regardless of their
        current state.
* [FIX] Resolved a memory leak in the hiredis library causing a memory leak
        in Redis Sentinel when a monitored instance or another Sentinel is
        unavailable. Every reconnection attempt will leak a small amount of
        memory, but in the long run the process can reach a considerable size.

* [NEW] Sentinel: ability to announce itself with an arbitrary IP/port to work
        in the context of natted networks. However this is probably still
        not enough since there is no equivalent mechanism for slaves listed
        in the master INFO output. (Dara Kong and Salvatore Sanfilippo)

--[ Redis 3.0.0 Beta 8 (version 2.9.57) ] Release date: 29 jul 2014

This is the 8th beta of Redis 3.0.0.

>> General changes

* [FIX] Solaris compilation issues. (Matt Stancliff, Salvatore Sanfilippo)
* [FIX] Allow shared integer objects if maxmemory policy is not LRU based.
        (Salvatore Sanfilippo)
* [FIX] PFSELFTEST: less false positives. (Salvatore Sanfilippo)
* [FIX] Fail SYNC if background save child aborted due to a signal. (Yossi
        Gottlieb)

* [NEW] Latency framework backported from unstable branch. (Salvatore
        Sanfilippo)
* [NEW] AOF rewrite improved for latency. (Salvatore Sanfilippo)
* [NEW] Pub/Sub PING. (Salvatore Sanfilippo)
* [NEW] Much faster ZUNIONSTORE. (Kyle Hubert, Salvatore Sanfilippo)
* [NEW] Faster ll2string() implementation. (Salvatore Sanfilippo)

>> Cluster changes

* [FIX] CLUSTER RESET: Flush slave dataset on reset. (Salvatore Sanfilippo)
* [FIX] Replica migration: don't migrate to masters that never had slaves
        in the past, but only to masters that remained orphaned after
        failure events. (Salvatore Sanfilippo)

* [NEW] redis-trib: allow to reshard in non-interactive way. (Salvatore
        Sanfilippo)
* [NEW] Cluster test: unit 04, check consistency during resharding. (Salvatore
        Sanfilippo)
* [NEW] Cluster test: unit 05, slave selection. (Salvatore Sanfilippo)
* [NEW] Cluster test: unit 06, slaves with stale data can't failover. (Salvatore
        Sanfilippo)
* [NEW] Cluster test: unit 07, replicas migration. (Salvatore Sanfilippo)

>> Sentinel changes

* No Sentinel changes in this release.

--[ Redis 3.0.0 Beta 7 (version 2.9.56) ] Release date: 30 jun 2014

This is the 7th beta of Redis 3.0.0.

>> General changes

* [FIX] Scripting fixes backported from unstable, see Redis 2.8.12 changelog
        for more info. (Salvatore Sanfilippo)
* [FIX] Cancel SHUTDOWN if initial AOF is being written. (Matt Stancliff)

* [NEW] New command: COMMAND, for commands introspection (Matt Stancliff &
        Salvatore Sanfilippo)
* [NEW] hiredis: Update to latest version. (Matt Stancliff)
* [NEW] Jemalloc updated to 3.6.0. (Salvatore Sanfilippo)

>> Cluster changes

* [FIX] Cluster: clear NOADDR flag when updating node address.
        (Salvatore Sanfilippo)

* [NEW] New CLUSTER SLOTS command to simplify Cluster clients operations.
        (Matt Stancliff)
* [NEW] More Cluster tests. (Salvatore Sanfilippo)
* [NEW] Log when failover authorization are granted / denied.
        (Salvatore Sanfilippo)

>> Sentinel changes

* [FIX] A few Sentinel bugs fixed and improvements, see Redis 2.8.12
        changelog for more info.  (Salvatore Sanfilippo & Matt Stancliff)
* [NEW] New Sentinel-Client handshake protocol, ROLE command, CLIENT KILL,
        all backported to 3.0 branch. (Salvatore Sanfilippo)

--[ Redis 3.0.0 Beta 6 (version 2.9.55) ] Release date: 9 jun 2014

This is the 6th beta of Redis 3.0.0.

>> General changes

* [FIX] Fix software watchdog signal handler crash due to re-entering.
* [FIX] Better Lua number -> string conversion for Lua scripts.
* [FIX] Serious replication bug when min-slaves-* feature is used in slaves
        configuration fixed.
* [FIX] Blocking pop on lists now works when the list is created by commands
        other than *PUSH* (for example SORT STORE).

>> Cluster changes

* [FIX] CRITICAL: For a bug in the implementation of CLUSTER SET-CONFIG-EPOCH
        introduced with beta-3 (especially beta-4 where the command
        is actually used by redis-trib), a configEpoch for a node could
        jump backward, breaking the eventual consistency property of the
        slots -> nodes mapping in the cluster.

>> Sentinel changes

* No changes for Sentinel in this release.

--[ Redis 3.0.0 Beta 5 (version 2.9.54) ] Release date: 26 may 2014

This is the 5th beta of Redis 3.0.0. It does not include any real
worthwhile change (just three days passed since the previous beta), but
fixes two stupid bugs preventing cluster tests to pass.

--[ Redis 3.0.0 Beta 4 (version 2.9.53) ] Release date: 23 may 2014

This is the fourth beta of Redis 3.0.0.

>> General changes

* [NEW] Scripting engine performances improvements.
* [NEW] Log format slightly changed to report current node role.

* [FIX] Correct the HyperLogLog stale cache flag to prevent unnecessary
        computation.

>> Cluster changes

* [NEW] redis-trib: ability to import data from standalone Redis instances.
* [NEW] redis-trib: "fix" subcommand much better at fixing errors.
* [NEW] CLUSTER FAILOVER FORCE implemented.
* [NEW] CLUSTER RESET implemented, it is now possible to completely reset
        nodes and create a new cluster without restarting anything.
* [NEW] Slave validity factor (max estimated data age to still failover)
        is now under the control of the user, and can be configured via
        redis.conf or CONFIG SET. Option name cluster-slave-validity-factor.
* [NEW] Cluster test: failure detection and failover initial tests.
* [NEW] CLUSTER MEET: better error messages when address is invalid.
* [NEW] Bulk-accept new Cluster nodes in the Cluster bus instead of
        performing just a single accept() per event fired.

* [FIX] Bypass data_age check for manual failovers.
* [FIX] Fixed data_age computation / check integer overflow.
* [FIX] Various fixes to Tcl client.tcl Redis Cluster client used in tests.
* [FIX] Better handling of stolen slots.
* [FIX] Don't accept cluster bus connections during startup.

>> Sentinel changes

* [NEW] Generate +config-update-from event when a new config is received.
* [NEW] Log when a failover will be re-attempted again.

* [FIX] Sentinel: Add "dir /tmp" directive in example sentinel.conf.

--[ Redis 3.0.0 Beta 3 (version 2.9.52) ] Release date: 5 may 2014

This is the third beta of Redis 3.0.0.

>> General changes

* [NEW] New data structure: the HyperLogLog (see 2.8 release notes).
* [NEW] Lexicograhical range queries in sorted sets (see 2.8 release notes).
* [NEW] LRU algorithm precision greatly improved.

* [FIX] Redis is now much more responsive to reply with LOADING / BUSY errors.

>> Cluster changes

* [NEW] Cluster testing framework and initial tests.
* [NEW] Cluster epochs collision resolution (make Redis Cluster more resilient
        to admin and programming errors).
* [NEW] Persist / fsync some global state to ensure correct crash-recovery
        semantics.
* [NEW] New command introduced: CLUSTER SET-CONFIG-EPOCH, still not used
        by redis-trib. Will be used to speedup the assignment of unique
        epochs to different nodes at cluster creation time. For now this is
        handled as a side effect of the cluster epochs collision resolution.

* [FIX] Different fixes to redis-trib cluster creation.
* [FIX] Fix an error in the CLUSTER NODES output for nodes slots.

>> Sentinel changes

* [NEW] Sentinels are now able to send update messages in a peer-to-peer
        fashion even if no Redis instances are available. Now the Sentinel
        liveness property that the most updated configuration in a given
        partition is propagated to all the Sentinels is extended to partitions
        without reachable instances.
* [NEW] Sentinel safety properties are now ensured in a crash-recovery system
        model since some state is persisted on disk before replying to other
        nodes, and reloaded at startup.
* [NEW] Sentinel now uses CLIENT SETNAME so that it is easy to identify
        Sentinels using CLIENT LIST among other clients.
* [NEW] Sentinel failure detection and reconnection code improved.

--[ Redis 3.0.0 Beta 2 (version 2.9.51) ] Release date: 11 mar 2014

This is the second beta of Redis 3.0.0.

>> General changes

* [FIX] Sometimes the absolute config file path was obtained in a wrong way.
        This happened when there was a "dir" directive inside the config file
        and at the same time the configuration file was given as a relative
        path to redis-server or redis-sentinel executables.
* [FIX] redis-cli: Automatically enter --slave mode when SYNC or PSYNC are
        called during an interactive session.
* [FIX] BITCOUNT: fixed unaligned access causing issues in sparc and other
        archs not capable of dealing with unaligned accesses. This also makes
        the code faster in archs where unaligned accesses are allowed.
* [FIX] Force INFO used_memory_peak to match peak memory. This generated some
        confusion among users even if it was not an actual bug.
* [FIX] Fixed an critical EVALSHA script cache bug: scripts executed may not
        propagate to AOF / Slaves correctly under certain conditions.
        See issue #1549 at Github for more information.
* [FIX] Fixed multiple bugs resulting into closing the link with master or slave
        during replication without good reasons. This will result in useless
        resynchronizations, or infinite loops where the replication link can't
        be established.
* [FIX] Don't count the time needed to populate the buffers of clients waiting
        in MONITOR mode when populating the Slow Log entries.

* [NEW] Redis-cli updated to use SCAN instead of random sampling via
        RANDOMKEY in order to implement --bigkeys feature. Moreover the
        implementation now supports pipelining and reports more information
        at the end of the scan. Much faster, much better. A special thank
        you to Michael Grunder for this improvement.
* [NEW] redis-cli now supports a new --intrinsic-latency mode that is able
        to meter the latency of a system due to kernel / hypervisor.
        How to use it is explained at http://redis.io/topics/latency.
* [NEW] New command BITPOS: find first bit set or clear in a bitmap.
* [NEW] CONFIG REWRITE calls are now logged.
* [NEW] AOF write errors (like no space on device) no longer abort Redis if the
        fsync policy is none or every second. The database enters a read-only
        mode where every write is refused with an error. Normal operations are
        restored as soon as Redis is able to append again data to the AOF file.
* [NEW] Sentinel now accepts SHUTDOWN command.


>> Cluster changes

* [FIX] Bind the first interface listed in the "bind" configuration directive
        if any, in order to perform outgoing connections. This fixes Cluster
        usage when an address is bound but there are multiple interfaces that
        may be used to connect with other nodes.
* [FIX] When an "Importing" slot is closed via CLUSTER SETSLOT NODE ...
        increment the configEpoch in the special case it is zero.
* [FIX] Current transaction is invalidated on redirection errors.
* [FIX] Abort if port does not allow for a valid cluster bus port that is
        always at fixed +10000 offset.
* [FIX] Keys extraction algorithm fixed for ZUNIONSTORE/ZINTERSTORE and SORT.
* [FIX] Better failover timeout and retry times: failover should now work
        reliabily when node-timeout is very small (a few milliseconds).
* [FIX] Don't allow SORT GET/BY options in Cluster mode.
* [FIX] Clear importing/migrating state when turning from master to slave role.
* [FIX] Set slot error if we receive an update for a busy slot.
* [FIX] Update node configEpoch on UPDATE messages.

* [NEW] Support multi-key operations as long as keys resolve to the same
        hash slot, and the slot is not migrating, or it is migrating but all
        the mentioned keys are available.
* [NEW] New DEBUG command CMDKEYS available to debug / test keys identification
        in Redis commands.
* [NEW] redis-trib: create subcommand is now able to assign spare slaves.
* [NEW] redis-trib: new subcommand 'call'. Exec command in all nodes.


>> Sentinel changes

* [FIX] Sentinel "IDONTKNOW" error removed as it does not made sense with the
        new Sentinel design. This error was actually a fix for a design error
        in the first implementation of Sentinel.
* [FIX] Sentinel: added a missing exit() call to abort after config file
        checks at startup. This error was introduced with an improvement in
        a previous 2.8 release.
* [FIX] Sentinel: better nodes fail over start time desynchronization to avoid
        split-brain during the voting process needed to get authorization to
        fail over. This means the system is less likely to need to retry
        and will fail over faster. No changes in behavior / correctness.

* [NEW] Sentinel unit tests and framework. More tests needed and units must
        be improved in order to have less false positives, but it is a start
        and features a debugging console that is useful to fix tests or to
        inspect bugs causing tests failures.
* [NEW] New Sentinel events: +/-monitor and +set used to monitor when an
        instance to monitor is added or removed, or when a configuration
        is modified via SENTINEL SET.

--[ Redis 3.0.0 Beta 1 (version 2.9.50) ] Release date: 11 Feb 2014

This is the first beta of Redis 3.0.0.

The following is a list of improvements in Redis 3.0, compared to Redis 2.8.

* [NEW] Redis Cluster: a distributed implementation of a subset of Redis.
* [NEW] New "embedded string" object encoding resulting in less cache
        misses. Big speed gain under certain work loads.
* [NEW] WAIT command to block waiting for a write to be transmitted to
        the specified number of slaves.
* [NEW] MIGRATE connection caching. Much faster keys migraitons.
* [NEW] MIGARTE new options COPY and REPLACE.
* [NEW] CLIENT PAUSE command: stop processing client requests for a
        specified amount of time.

Migrating from 2.8 to 3.0
=========================

Redis 3.0 is mostly a strict subset of 2.8, you should not have any problem
upgrading your application from 2.8 to 3.0. However this is a list of small
non-backward compatible changes introduced in the 3.0 release:

* The log format was modified. The prefix of each line included the pid
  in the following format [1234]. Now instead it is 1234:? Where
  '?' is actually the role of the instance. M for master, S for slave, C
  if this process is a saving child (for RDB/AOF), and X for Sentinel.

--------------------------------------------------------------------------------

Credits: Where not specified the implementation and design is done by
Salvatore Sanfilippo. Thanks to Pivotal for making all this possible.
Also many thanks to all the other contributors and the amazing community
we have.

See commit messages for more credits.

Cheers,
Salvatore
