Redis 6.0 正式版終於發佈了！除了多線程還有什麼新功能？

Redis 6.0.1 於 2020 年 5 月 2 日正式發佈了，如 Redis 做者 antirez 所說，這是迄今爲止最「企業」化的版本，也是有史以來改動最大的一個 Redis 版本，同時也是參與開發人數最多的一個版本。

因此在使用此版本以前，建議各位開發者先進行深刻的測試再考慮投產，畢竟生產壞境無小事。好了，回到本文的重點，接下來咱們來重點看下 Redis 6.0.1 給咱們帶來了那些新功能。

Redis新功能介紹

Redis 6 的更新日誌，主要包含如下五部分的內容：

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

除了以上這些版本的更新日誌外，還有 6.0.1 正式版的更新日誌，不過這個正式版的發佈時間只比 Redis 6.0.0 GA 晚了兩天，所以只修復了一些 bug，因此咱們只須要看以上五個日誌便可。

1.Redis 6.0-rc1 更新日誌

官方更新日誌以下：

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

此版本新增的內容最大，以下列表所示：

• 衆多新模塊（modules）API
• 更好的過時循環（expire cycle）
• SSL
• ACLs 權限控制
• RESP3 協議
• 客戶端緩存（Client side caching）
• 多線程 IO（Threaded I/O）
• 無盤複製副本（Diskless replication on replicas）
• Redis-benchmark 的集羣支持和 redis-cli 優化
• 重寫 Systemd 支持（Systemd support rewrite）
• Redis 集羣代理與 Redis 6 一同發佈（但在不一樣的 repo）
• Disque 模塊與 Redis 6 一同發佈

2.Redis 6.0-rc2 更新日誌

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 帶來了許多修復和新功能，尤爲是客戶端的緩存功能，此版本的重大更改以下列表。

• ACL LOG：記錄拒絕的命令，密鑰訪問和身份驗證。
• 從新設計了客戶端緩存。如今，咱們使用密鑰而不是緩存插槽。
• 客戶端緩存：已實現廣播模式。
• 客戶端緩存：已實現 OPTIN/OPTOUT 模式。
• 刪除用於在非持久性實例中進行復制的 RDB 文件（可選）。
• 修復程序（僅選定的修復程序，請參閱全部修復程序的提交）：
• 在邊緣狀況下對流的不一樣修復。
• 修正因爲 RESP3 更改而致使重複的 CLIENT SETNAME 答覆。
• 修正因新的有效到期除以零而致使的崩潰。
• 避免將哨兵更改提高爲本身的副本。
• 修復了 KEYS 命令中以 * 開頭，後跟 \x00 的錯誤。
• 線程 I/O：如今也使用主線程來執行 I/O。
• 對模塊API進行了許多修復，而在下一個RC中還會有更多修復。
• 若是字符串中間包含 \0，則 ld2string 應該失敗。
• 使 Redis 測試更可靠。

3.Redis 6.0-rc3 更新日誌

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.

這個版本主要是修復了一些 bug，以下列表所示：

• 修復了因爲重構 SSL 而致使的鏈接代碼崩潰。
• 用於阻止命令的精確超時。如今超時已達到 HZ 分辨率，不管鏈接的 clinet 數量如何。新超時存儲在基數樹中並按到期時間排序。
• 修復了因爲 CONFIG maxclients 而調整事件循環大小時發生的罕見崩潰。
• 修正部分從新同步成功後的 systemd 準備狀況。
• Redis-cli 詢問密碼模式將在啓動時提示（以提升安全性）。
• 鍵空間通知已添加到 MIGRATE/RESTORE。
• 修復了線程 I/O 錯誤。
• 在 Sentinel 中實現新的 ACL 樣式 AUTH。
• 使 'requirepass' 與 Redis<=5 更向後兼容。
• ACL：若是默認用戶關閉，則將其視爲禁用狀態，而無論其是否爲「 nopass」。
• 修復了在 Redis 羣集中升級實例時可能出現的不一致問題
• -READONLY 錯誤後停止事務。
• 對模塊 API 的許多不一樣修復。
• 添加了 BITFIELD_RO 以在只讀副本上調用該命令。
• PSYNC2：有意義的偏移量實現。容許斷開鏈接的主機仍在向副本發送 PING，以便可以成功 PSYNC 以增量方式傳遞給新的從站，從而丟棄了僅由 PING 組成的複製積壓。
• 修正 Lua 腳本處於繁忙狀態時流水線的 MULTI/EXEC。
• 從新修復模塊中的傳播 API，在其餘更改後再次中斷。

4.Redis 6.0-rc4 更新日誌

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)

此版本主要新增的內容以下：

• 提升了大量客戶端鏈接時使用 INFO 命令的查詢速度。
• 在全部阻止命令上都大大加快了速度：如今能夠阻止在同一鍵上是 O（1）而不是 O（N）。
• 陳舊的副本如今容許 MULTI/EXEC。
• 新命令：LCS（最長公共子序列）。
• 添加新配置以使 DEL 像 UNLINK。
• RDB 加載加速。
• 修復了許多錯誤。

5.Redis 6.0.0 GA 更新日誌

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.

此日誌更新的主要內容以下：

• XCLAIM AOF/replicas 傳播已修復。
• 客戶端緩存：新的 NOLOOP 選項以免收到有關本身執行的更改。
• ACL GENPASS 如今使用 HMAC-SHA256，並具備一個可選的「位」參數。這意味着您能夠將其用做通用的「安全隨機字符串」原始！
• 羣集「SLOTS」子命令的內存優化。
• LCS 命令如今是 STRALGO 的子命令。
• 副本的有意義的偏移量。更成功的部分從新同步。
• 優化延遲迴復的內存使用。
• 更快的 CRC64 法可更快地加載 RDB。
• XINFO STREAM FULL，一個新的子命令，用於獲取整個流狀態。
• CLIENT KILL USER <用戶名>。
• MIGRATE AUTH2 選項，用於 ACL 樣式身份驗證支持。
• 修正了一些其餘錯誤。

Redis 6.0.1 正式版的下載地址爲：https://redis.io/

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

總結

綜合以上全部版本的更新日誌，咱們發現此次 Redis 6.0 帶來的主要功能是：

• 提供了衆多的新模塊（modules）API
• 提供了客戶端緩存功能
• 多線程 I/O 能力
• 提高了 RDB 日誌的加載速度
• 修改了若干個 bug 和一些優化

其中多線程 I/O 是咱們最關注的功能了，有人用它和單線程的版本作了一個性能測試，以下圖所示：

（注：圖片來源於 iTushou.com）

從以上結果能夠看到 GET/SET 命令在多線程版本中的性能相比單線程已經翻倍了。

整體來講，這次 Redis 6.0 帶給咱們的功能仍是不少且比較實用的，只是版本改動很大，所以咱們須要必定的時間和大量的測試驗證以後才建議上線。