NoSQL数据库，Redis 2.6.0 发布

redis是一个key-value存储系统。和Memcached类似，它支持存储的value类型相对更多，包括string(字符串)、list(链表)、set(集合)和zset(有序集合)。这些数据类型都支持push/pop、add/remove及取交集并集和差集及更丰富的操作，而且这些操作都是原子性的。在此基础上，redis支持各种不同方式的排序。与memcached一样，为了保证效率，数据都是缓存在内存中。区别的是redis会周期性的把更新的数据写入磁盘或者把修改操作写入追加的记录文件，并且在此基础上实现了master-slave(主从)同步。


2.6.0 版本改进内存使用；Lua 脚本支持；毫秒精度的过期时间；可以支持无限个客户端数；改进 AOF 生成；提升性能；增加新的命令。下载地址：redis-2.6.0.tar.gz

详细记录：

Redis 2.6 release notes  =======================    ** IMPORTANT ** Check the 'Migrating from 2.4 to 2.6' section at the end of                  this file for information about what changed between 2.4 and                  2.6 and how this may affect your application.    --------------------------------------------------------------------------------  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.  --------------------------------------------------------------------------------    ---[ Redis 2.6.0 ]    * [BUGFIX]   Allow AUTH when server is in -BUSY state because of a slow script.  * [BUGFIX]   MULTI/EXEC flow now makes sense when observed in MONITOR  * [BUGFIX]   SCRIPT KILL now uses different error prefixes for different errors.  * [BUGFIX]   Default memory limit for 32bit archs lowered from 3.5 to 3 GB.  * [BUGFIX]   redis-check-dump is now compatible with RDB files generated by 2.6.  * [IMPROVED] New field in INFO: slave_read_only.    ---[ Redis 2.5.14 (2.6 Release Candidate 8) ]    * [BUGFIX]   Fixed compilation on FreeBSD.  * [IMPROVED] SRANDMEMBER <count> that returns multiple random elements.  * [IMPROVED] Sentinel backported to 2.6. It will be taken in sync with 2.8.  * [IMPROVED] Helper function for scripting to return errors and status replies.  * [IMPROVED] SORT by nosort [ASC|DESC] uses sorted set elements ordering.  * [BUGFIX]   Better resistence to system clock skew.  * [IMPROVED] Warn the user when the configured maxmemory seems odd.  * [BUGFIX]   Hashing function is now murmurhash2 for security purposes.  * [IMPROVED] Install script no longer uses a template but redis.conf itself.    ---[ Redis 2.5.13 (2.6 Release Candidate 7) ]    UPGRADE URGENCY: HIGH    * [BUGFIX]   Theoretical bug in ziplist fixed.  * [BUGFIX]   Better out of memory handling (Log produced in log file).  * [BUGFIX]   Incrementally flush RDB file on slave side while performing the               first synchronization with the master. This makes Redis less               blocking in environments where disk I/O is slow.  * [BUGFIX]   Don't crash with Lua's redis.call() without arguments.  * [BUGFIX]   Don't crash after a big number of Lua calls on 32 bit systems               because of a failed assertion.  * [BUGFIX]   Fix SORT behaviour when called from scripting.  * [BUGFIX]   Adjust slave PING period accordingly to REDIS_HZ define.  * [BUGFIX]   BITCOUNT: fix crash on overflowing arguments.  * [BUGFIX]   Return an error when SELECT argument is not an integer.  * [BUGFIX]   Blocking operations on lists were completely reimplemented for               correctness. Now blocking list ops and pushes originated from               Lua scripts will play well together and will be replicated               and transmitted to the AOF correctly.  * [IMPROVED] Send async PING before starting replication to avoid blocking if               master allows us to connect but it is actually not able to reply.  * [IMPROVED] Support slave-priority for Redis Sentinel.  * [IMPROVED] Hiredis library updated.    ---[ Redis 2.5.12 (2.6 Release Candidate 6) ]    UPGRADE URGENCY: MODERATE.    * [BUGFIX]   Fixed a timing attack on AUTH (Issue #560).  * [BUGFIX]   Don't assume that "char" is signed.  * [BUGFIX]   Check that we have connection before enabling pipe mode.  * [BUGFIX]   Use the optimized version of the function to convert a double to               its string representation. Compilation was disabled because of               a typo in the #if statement.  * [IMPROVED} REPLCONF internal command introduced, now INFO shows slaves with               correct port numbers. This makes 2.5.12 Redis Sentinel compatible.  * [IMPROVED] Truncate short write from the AOF for a cleaner restart. On short               writes (for instance out of space) Redis will now try to remove               the half-written data so that the next restart will work without               the need for the "redis-check-aof" utility.  * [IMPROVED] New in INFO: aof_last_bgrewrite_status  * [IMPROVED] Allow Pub/Sub in contexts where other commands are blocked.  * [BUGFIX]   mark fd as writable when EPOLLERR or EPOLLHUP is returned by               epoll_wait.    ---[ Redis 2.5.11 (2.6 Release Candidate 5) ]    UPGRADE URGENCY: HIGH.    * [BUGFIX]   Fixed Hash corruption when loading an RDB file generated by               previous versions of Redis that encoded hashes using               a different ziplist encoding format for small integers.               All the fileds that are integers in the range 0-255 may not               be recognized, or duplicated un updates, causing a crash               when the ziplist is converted to a real hash. (Issue #547).  * [BUGFIX]   Fixed the count of memory used by output buffers in the               setDeferredMultiBulkLength() function.    ---[ Redis 2.5.10 (2.6 Release Candidate 4) ]    UPGRADE URGENCY: HIGH.    * [BUGFIX]   Allow PREFIX to be overwritten on "make install".  * [BUGFIX]   Run the test with just one client if the computer is slow.  * [BUGFIX]   Event port support in our event driven libray.  * [BUGFIX]   Jemalloc updated to 3.0.0. This fixes a possibly AOF rewrite issue.               See https://github.com/antirez/redis/issues/504 for info.  * [BUGFIX]   Fixed issue #516: ZINTERSTORE / ZUNIONSTORE with mixed sets/zsets.  * [BUGFIX]   Set fd to writable when poll(2) detects POLLERR or POLLHUP event.  * [BUGFIX]   Fixed RESTORE hash failure (Issue #532).  * [IMPROVED] Allow an AOF rewrite buffer > 2GB (Related to issue #504).  * [IMPROVED] Server cron function frequency is now configurable (REDIS_HZ).  * [IMPROVED] Better, less blocking expired keys collection algorithm.  * [FEATURE]  New commands: BITOP and BITCOUNT.  * [FEATURE]  redis-cli --pipe for mass import.    What's new in Redis 2.5.9 (aka 2.6 Release Candidate 3)  =======================================================    UPGRADE URGENCY: critical, upgrade ASAP.    * [BUGFIX] Fix for issue #500 (https://github.com/antirez/redis/pull/500).             Redis 2.6-RC1 and RC2 may corrupt ziplist-encoded sorted sets             produced by Redis 2.4.x.  * [BUGFIX] Fixed several bugs in init.d script.  * [BUGFIX] syncio.c functions modified for speed and correctness. On osx             (and possibly other BSD-based systems) the slave would block on             replication to send the SYNC command when the master was not             available. This is fixed now, but was not affecting Linux installs.  * Now when slave-serve-stale-data is set to yes and the master is down, instead    of reporting a generic error Redis replies with -MASTERDOWN.    What's new in Redis 2.5.8 (aka 2.6 Release Candidate 2)  =======================================================    UPGRADE URGENCY: high for all the users of the KEYS command, otherwise low.    * [BUGFIX] Fix for KEYS command: if the DB contains keys with expires the KEYS             command may return the wrong output, having duplicated or missing             keys. See issue #487 and #488 on github for details.    What's new in Redis 2.5.7 (aka 2.6 Release Candidate 1)  =======================================================    UPGRADE URGENCY: upgrade not recommended because this is an RC release.    * This is the first release candidate for Redis 2.6. We are not aware of    bugs, but part of this code is young and was never tested in production    environments, so handle with care.    An overview of new features and changes in Redis 2.6.x  ======================================================    * Server side Lua scripting, see http://redis.io/commands/eval  * Virtual Memory removed (was deprecated in 2.4)  * Hardcoded limits about max number of clients removed.  * AOF low level semantics is generally more sane, and especially when used    in slaves.  * Milliseconds resolution expires, also added new commands with milliseconds    precision (PEXPIRE, PTTL, ...).  * Better memory usage for "small" lists, ziplists and hashes when fields or    values contain small integers.  * Read only slaves.  * New bit opeations: BITCOUNT and BITOP commands.  * Clients max output buffer soft and hard limits. You can specifiy different    limits for different classes of clients (normal,pubsub,slave).  * More incremental (less blocking) expired keys collection algorithm, in    practical terms this means that Redis is more responsive when a very    big number of keys expire about at the same time.  * AOF is now able to rewrite aggregate data types using variadic commands,    often producing an AOF that is faster to save, load, and is smaller in size.  * Every redis.conf directive is now accepted as a command line option for the    redis-server binary, with the same name and number of arguments.  * Hash table seed randomization for protection against collisions attacks.  * Performances improved when writing large objects to Redis.  * Integrated memory test, see redis-server --test-memory.  * INCRBYFLOAT and HINCRBYFLOAT commands.  * New DUMP, RESTORE, MIGRATE commands (back ported from Redis Cluster to 2.6).  * CRC64 checksump in RDB files.  * Better MONITOR output and behavior (now commands are logged before execution).  * "Software Watchdog" feature to debug latency issues.  * Significant parts of the core refactored or rewritten. New internal APIs    and core changes allowed to develop Redis Cluster on top of the new code,    however for 2.6 all the cluster code was removed, and will be released with    Redis 3.0 when it is more complete and stable.  * Redis ASCII art logo added at startup.  * Crash report on memory violation or failed asserts improved significantly    to make debugging of hard to catch bugs simpler.  * redis-benchmark improvements: ability to run selected tests,    CSV output, faster, better help.  * redis-cli improvements: --eval for comfortable development of Lua scripts.  * SHUTDOWN now supports two optional arguments: "SAVE" and "NOSAVE".  * INFO output split into sections, the command is now able to just show     pecific sections.  * New statistics about how many time a command was called, and how much    execution time it used (INFO commandstats).  * More predictable SORT behavior in edge cases.  * Better support for big endian and *BSD systems.  * Build system improved.    Migrating from 2.4 to 2.6  =========================    Redis 2.4 is mostly a strict subset of 2.6. However there are a few things  that you should be aware of:    * You can't use .rdb and AOF files generated with 2.6 into a 2.4 instance.  * 2.6 slaves can be attached to 2.4 masters, but not the contrary, and only    for the time needed to perform the version upgrade.    There are also a few API differences, that are unlikely to cause problems,  but it is better to keep them in mind:    * SORT now will refuse to sort in numerical mode elements that can't be parsed    as numbers.  * EXPIREs now all have millisecond resolution (but this is very unlikely to    break code that was not conceived exploting the previous resolution error    in some way.)  * INFO output is a bit different now, and contains empty lines and comments    starting with '#'. All the major clients should be already fixed to work    with the new INFO format.  * Slaves are only read-only by default (but you can change this easily    setting the "slave-read-only" configuration option to "no" editing your    redis.conf or using CONFIG SET.    The following INFO fields were renamed for consistency:         changes_since_last_save -> rdb_changes_since_last_save       bgsave_in_progress -> rdb_bgsave_in_progress       last_save_time -> rdb_last_save_time       last_bgsave_status -> rdb_last_bgsave_status       bgrewriteaof_in_progress -> aof_rewrite_in_progress       bgrewriteaof_scheduled -> aof_rewrite_scheduled    The following redis.conf and CONFIG GET / SET parameters changed:        * hash-max-zipmap-entries, now replaced by hash-max-ziplist-entries      * hash-max-zipmap-value, now replaced by hash-max-ziplist-value      * glueoutputbuf option was now completely removed (was deprecated)    --------------------------------------------------------------------------------    Credits: Where not specified the implementation and design are done by  Salvatore Sanfilippo and Pieter Noordhuis. Thanks to VMware 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