Redis 6.0 正式版终于发布了！除了多线程还有什么新功能？

Redis 6.0.1 于 2020 年 5 月 2 日正式发布了，如 Redis 做者 antirez 所说，这是迄今为止最“企业”化的版本，也是有史以来改动最大的一个 Redis 版本，同时也是参与开发人数最多的一个版本。

因此在使用此版本以前，建议各位开发者先进行深刻的测试再考虑投产，毕竟生产坏境无小事。好了，回到本文的重点，接下来咱们来重点看下 Redis 6.0.1 给咱们带来了那些新功能。

Redis新功能介绍

Redis 6 的更新日志，主要包含如下五部分的内容：

1. Redis 6.0-RC1 版新功能介绍；
2. Redis 6.0-RC2 版新功能介绍；
3. Redis 6.0-RC3 版新功能介绍；
4. Redis 6.0-RC4 版新功能介绍；
5. Redis 6.0.0 GA 版新功能介绍。

除了以上这些版本的更新日志外，还有 6.0.1 正式版的更新日志，不过这个正式版的发布时间只比 Redis 6.0.0 GA 晚了两天，所以只修复了一些 bug，因此咱们只须要看以上五个日志便可。

1.Redis 6.0-rc1 更新日志

官方更新日志以下：

Redis 6 improves Redis in a number of key areas and is one of the largest Redis releases in the history of the project, so here we'll list only the biggest features in this release:

• The modules system now has a number of new APIs that allow module authors   to make things otherwise not possible in the past. It is possible to   store arbitrary module private data in RDB files, to hook on different   server events, capture and rewrite commands executions, block clients on   keys, and so forth.
• The Redis active expire cycle was rewritten for much faster eviction of keys   that are already expired. Now the effort is tunable.
• Redis now supports SSL on all channels.
• ACL support, you can define users that can run only certain commands and/or   can only access only certain keys patterns.
• Redis now supports a new protocol called RESP3, which returns more   semantical replies: new clients using this protocol can understand just   from the reply what type to return to the calling program.
• There is server-side support for client-side caching of key values. This   feature is still experimental and will get more changes during the next   release candidates, but you can already test it and read about it here:   https://redis.io/topics/client-side-caching
• Redis can now optionally use threads to handle I/O, allowing to serve   2 times as much operations per second in a single instance when   pipelining cannot be used.
• Diskless replication is now supported even on replicas: a replica is now   able, under certain conditions the user can configure, to load the RDB   in the first synchronization directly from the socket to the memory.
• Redis-benchmark now supports a Redis Cluster mode.
• SRANDMEMBER and similar commands have a better distribution.
• Redis-cli improvements.
• Systemd support rewritten.
• A Redis Cluster proxy was released here:   https://github.com/artix75/redis-cluster-proxy
• A Disque module for Redis was released here:   https://github.com/antirez/disque-module

此版本新增的内容最大，以下列表所示：

• 众多新模块（modules）API
• 更好的过时循环（expire cycle）
• SSL
• ACLs 权限控制
• RESP3 协议
• 客户端缓存（Client side caching）
• 多线程 IO（Threaded I/O）
• 无盘复制副本（Diskless replication on replicas）
• Redis-benchmark 的集群支持和 redis-cli 优化
• 重写 Systemd 支持（Systemd support rewrite）
• Redis 集群代理与 Redis 6 一同发布（但在不一样的 repo）
• Disque 模块与 Redis 6 一同发布

2.Redis 6.0-rc2 更新日志

Hi Redis users, Redis 6 is approaching and will be released 30th of April. New release candidates will be released at the end of March, then another one mid April, to finally reach the GA at the end of April.

Redis 6 RC2 brings many fixes and new things, especially in the area of client side caching. This is the list of big changes in this release. As usually you can find the full list of commits at the end:

New features and improvements:

• ACL LOG: log denied commands, keys accesses and authentications.
• Client side caching redesigned. Now we use keys not caching slots.
• Client side caching: Broadcasting mode implemented.
• Client side caching: OPTIN/OPTOUT modes implemented.
• Remove RDB files used for replication in persistence-less instances (option).

Fixes (only selected ones, see commits for all the fixes):

• Different fixes to streams in edge cases.
• Fix duplicated CLIENT SETNAME reply because of RESP3 changes.
• Fix crash due to new active expire division by zero.
• Avoid sentinel changes promoted_slave to be its own replica.
• Fix bug on KEYS command where pattern starts with * followed by \x00.
• Threaded I/O: now the main thread is used as well to do I/O.
• Many fixes to modules APIs, and more to come in the next RCs.
• ld2string should fail if string contains \0 in the middle.
• Make the Redis test more reliable.
• Fix SPOP returning nil (see #4709). WARNING: API change.

Redis 6 RC2 带来了许多修复和新功能，尤为是客户端的缓存功能，此版本的重大更改以下列表。

• ACL LOG：记录拒绝的命令，密钥访问和身份验证。
• 从新设计了客户端缓存。如今，咱们使用密钥而不是缓存插槽。
• 客户端缓存：已实现广播模式。
• 客户端缓存：已实现 OPTIN/OPTOUT 模式。
• 删除用于在非持久性实例中进行复制的 RDB 文件（可选）。
• 修复程序（仅选定的修复程序，请参阅全部修复程序的提交）：
• 在边缘状况下对流的不一样修复。
• 修正因为 RESP3 更改而致使重复的 CLIENT SETNAME 答复。
• 修正因新的有效到期除以零而致使的崩溃。
• 避免将哨兵更改提高为本身的副本。
• 修复了 KEYS 命令中以 * 开头，后跟 \x00 的错误。
• 线程 I/O：如今也使用主线程来执行 I/O。
• 对模块API进行了许多修复，而在下一个RC中还会有更多修复。
• 若是字符串中间包含 \0，则 ld2string 应该失败。
• 使 Redis 测试更可靠。

3.Redis 6.0-rc3 更新日志

Dear users, this is a list of the major changes in this release, please check  the list of commits for detail:

• Fix crash due to refactoring for SSL, for the connection code.
• Precise timeouts for blocking commands. Now the timeouts have HZ   resolution regardless of the number of connected clinets. New timeouts   are stored in a radix tree and sorted by expire time.
• Fix rare crash when resizing the event loop because of CONFIG maxclients.
• Fix systemd readiness after successful partial resync.
• Redis-cli ask password mode to be prompted at startup (for additional safety).
• Keyspace notifications added to MIGRATE / RESTORE.
• Threaded I/O bugs fixed.
• Implement new ACL style AUTH in Sentinel.
• Make 'requirepass' more backward compatible with Redis <= 5.
• ACL: Handle default user as disabled if it's off regardless of "nopass".
• Fix a potential inconsistency when upgrading an instance in Redis Cluster   and restarting it. The instance will act as a replica but will actually be   set as a master immediately. However the choice of what to do with already   expired keys, on loading, was made from the POV of replicas.
• Abort transactions after -READONLY error.
• Many different fixes to module APIs.
• BITFIELD_RO added to call the command on read only replicas.
• PSYNC2: meaningful offset implementation. Allow the disconnected master   that is still sending PINGs to replicas, to be able to successfully   PSYNC incrementally to new slaves, discarding the last part of the   replication backlog consisting only of PINGs.
• Fix pipelined MULTI/EXEC during Lua scripts are in BUSY state.
• Re-fix propagation API in modules, broken again after other changes.

这个版本主要是修复了一些 bug，以下列表所示：

• 修复了因为重构 SSL 而致使的链接代码崩溃。
• 用于阻止命令的精确超时。如今超时已达到 HZ 分辨率，不管链接的 clinet 数量如何。新超时存储在基数树中并按到期时间排序。
• 修复了因为 CONFIG maxclients 而调整事件循环大小时发生的罕见崩溃。
• 修正部分从新同步成功后的 systemd 准备状况。
• Redis-cli 询问密码模式将在启动时提示（以提升安全性）。
• 键空间通知已添加到 MIGRATE/RESTORE。
• 修复了线程 I/O 错误。
• 在 Sentinel 中实现新的 ACL 样式 AUTH。
• 使 'requirepass' 与 Redis<=5 更向后兼容。
• ACL：若是默认用户关闭，则将其视为禁用状态，而无论其是否为“ nopass”。
• 修复了在 Redis 群集中升级实例时可能出现的不一致问题
• -READONLY 错误后停止事务。
• 对模块 API 的许多不一样修复。
• 添加了 BITFIELD_RO 以在只读副本上调用该命令。
• PSYNC2：有意义的偏移量实现。容许断开链接的主机仍在向副本发送 PING，以便可以成功 PSYNC 以增量方式传递给新的从站，从而丢弃了仅由 PING 组成的复制积压。
• 修正 Lua 脚本处于繁忙状态时流水线的 MULTI/EXEC。
• 从新修复模块中的传播 API，在其余更改后再次中断。

4.Redis 6.0-rc4 更新日志

Hi all, this the latest release candidate of Redis 6. This is likely to be very similar to what you'll see in Redis 6 GA. Please test it and report any issue :-)

Main changes in this release:

* Big INFO speedup when using a lot of of clients.     * Big speedup on all the blocking commands: now blocking       on the same key is O(1) instead of being O(N).     * Stale replicas now allow MULTI/EXEC.     * New command: LCS (Longest Common Subsequence).     * Add a new configuration to make DEL like UNLINK.     * RDB loading speedup.     * Many bugs fixed (see the commit messages at the end of this node)

此版本主要新增的内容以下：

• 提升了大量客户端链接时使用 INFO 命令的查询速度。
• 在全部阻止命令上都大大加快了速度：如今能够阻止在同一键上是 O（1）而不是 O（N）。
• 陈旧的副本如今容许 MULTI/EXEC。
• 新命令：LCS（最长公共子序列）。
• 添加新配置以使 DEL 像 UNLINK。
• RDB 加载加速。
• 修复了许多错误。

5.Redis 6.0.0 GA 更新日志

Upgrade urgency CRITICAL: many bugs fixed compared to the last release                           candidate. Better to upgrade if you see things                           affecting your environment in the changelog.

Hi all, finally we have Redis 6.0.0 GA! Enjoy this new Redis release. Most of the documentation was updated today so that you can likely find what you are looking for about the new features at redis.io. This is the list of what changed compared to the previoius release candidate:

• XCLAIM AOF/replicas propagation fixed.
• Client side caching: new NOLOOP option to avoid getting notified about   changes performed by ourselves.
• ACL GENPASS now uses HMAC-SHA256 and have an optional "bits" argument.   It means you can use it as a general purpose "secure random strings"   primitive!
• Cluster "SLOTS" subcommand memory optimization.
• The LCS command is now a subcommand of STRALGO.
• Meaningful offset for replicas as well. More successful partial   resynchronizations.
• Optimize memory usage of deferred replies.
• Faster CRC64 algorithm for faster RDB loading.
• XINFO STREAM FULL, a new subcommand to get the whole stream state.
• CLIENT KILL USER.
• MIGRATE AUTH2 option, for ACL style authentication support.
• Other random bugfixes.

此日志更新的主要内容以下：

• XCLAIM AOF/replicas 传播已修复。
• 客户端缓存：新的 NOLOOP 选项以免收到有关本身执行的更改。
• ACL GENPASS 如今使用 HMAC-SHA256，并具备一个可选的“位”参数。这意味着您能够将其用做通用的“安全随机字符串”原始！
• 群集“SLOTS”子命令的内存优化。
• LCS 命令如今是 STRALGO 的子命令。
• 副本的有意义的偏移量。更成功的部分从新同步。
• 优化延迟回复的内存使用。
• 更快的 CRC64 法可更快地加载 RDB。
• XINFO STREAM FULL，一个新的子命令，用于获取整个流状态。
• CLIENT KILL USER <用户名>。
• MIGRATE AUTH2 选项，用于 ACL 样式身份验证支持。
• 修正了一些其余错误。

Redis 6.0.1 正式版的下载地址为：https://redis.io/

官方的更新日志（英文）：https://raw.githubusercontent.com/antirez/redis/6.0/00-RELEASENOTES

总结

综合以上全部版本的更新日志，咱们发现此次 Redis 6.0 带来的主要功能是：

• 提供了众多的新模块（modules）API
• 提供了客户端缓存功能
• 多线程 I/O 能力
• 提高了 RDB 日志的加载速度
• 修改了若干个 bug 和一些优化

其中多线程 I/O 是咱们最关注的功能了，有人用它和单线程的版本作了一个性能测试，以下图所示：

（注：图片来源于 iTushou.com）

从以上结果能够看到 GET/SET 命令在多线程版本中的性能相比单线程已经翻倍了。

整体来讲，这次 Redis 6.0 带给咱们的功能仍是不少且比较实用的，只是版本改动很大，所以咱们须要必定的时间和大量的测试验证以后才建议上线。