2W 字詳解 Redis 集群環(huán)境搭建實(shí)踐

本文是Redis集群學(xué)習(xí)的實(shí)踐總結(jié)（基于Redis 6.0+），詳細(xì)介紹逐步搭建Redis集群環(huán)境的過程，并完成集群伸縮的實(shí)踐。

Redis集群簡介

Redis集群(Redis Cluster) 是Redis提供的分布式數(shù)據(jù)庫方案，通過 分片(sharding) 來進(jìn)行數(shù)據(jù)共享，并提供復(fù)制和故障轉(zhuǎn)移功能。相比于主從復(fù)制、哨兵模式，Redis集群實(shí)現(xiàn)了較為完善的高可用方案，解決了存儲(chǔ)能力受到單機(jī)限制，寫操作無法負(fù)載均衡的問題。

本文是Redis集群學(xué)習(xí)的實(shí)踐總結(jié)，詳細(xì)介紹逐步搭建Redis集群環(huán)境的過程，并完成集群伸縮的實(shí)踐。

發(fā)布過很多?redis 的優(yōu)質(zhì)文章，可以關(guān)注微信公眾號 Java后端，回復(fù) 666 下載這一本 Java技術(shù)棧文檔。

1 Redis集群環(huán)境搭建

方便起見，這里集群環(huán)境的所有節(jié)點(diǎn)全部位于同一個(gè)服務(wù)器上，共6個(gè)節(jié)點(diǎn)以端口號區(qū)分，3個(gè)主節(jié)點(diǎn)+3個(gè)從節(jié)點(diǎn)。集群的簡單架構(gòu)如圖：

本文基于最新的Redis 6.0+，直接從github下載最新的源碼編譯獲得常用工具 redis-server , ?redis-cli 。值得注意的是，從Redis 5.0以后的版本，集群管理軟件 redis-trib.rb 被集成到 redis-cli 客戶端工具中（詳細(xì)可參考cluster-tutorial）。

本節(jié)介紹集群環(huán)境搭建時(shí)，并未借助 redis-trib.rb 快速管理，而是按照標(biāo)準(zhǔn)步驟一步步搭建，這也是為了熟悉集群管理的基本步驟。在集群伸縮實(shí)踐一節(jié)將借助 redis-trib.rb 完成集群重新分片工作。

集群的搭建可以分為四步：

1. 啟動(dòng)節(jié)點(diǎn)：將節(jié)點(diǎn)以集群方式啟動(dòng)，此時(shí)節(jié)點(diǎn)是獨(dú)立的。

2. 節(jié)點(diǎn)握手：將獨(dú)立的節(jié)點(diǎn)連成網(wǎng)絡(luò)。

3. 槽指派：將16384個(gè)槽位分配給主節(jié)點(diǎn)，以達(dá)到分片保存數(shù)據(jù)庫鍵值對的效果。

4. 主從復(fù)制：為從節(jié)點(diǎn)指定主節(jié)點(diǎn)。

1.1 啟動(dòng)節(jié)點(diǎn)

每個(gè)節(jié)點(diǎn)初始狀態(tài)仍為 Master服務(wù)器，唯一不同的是：使用 Cluster 模式啟動(dòng)。需要對配置文件進(jìn)行修改，以端口號為6379的節(jié)點(diǎn)為例，主要修改如下幾項(xiàng)：

#?redis_6379_cluster.conf
port?6379
cluster-enabled?yes
cluster-config-file?"node-6379.conf"
logfile?"redis-server-6379.log"
dbfilename?"dump-6379.rdb"
daemonize?yes

其中 cluster-config-file 參數(shù)指定了集群配置文件的位置，每個(gè)節(jié)點(diǎn)在運(yùn)行過程中，會(huì)維護(hù)一份集群配置文件；每當(dāng)集群信息發(fā)生變化時(shí)（如增減節(jié)點(diǎn)），集群內(nèi)所有節(jié)點(diǎn)會(huì)將最新信息更新到該配置文件；當(dāng)節(jié)點(diǎn)重啟后，會(huì)重新讀取該配置文件，獲取集群信息，可以方便的重新加入到集群中。也就是說，當(dāng)Redis節(jié)點(diǎn)以集群模式啟動(dòng)時(shí)，會(huì)首先尋找是否有集群配置文件，如果有則使用文件中的配置啟動(dòng)，如果沒有，則初始化配置并將配置保存到文件中。集群配置文件由Redis節(jié)點(diǎn)維護(hù)，不需要人工修改。

為6個(gè)節(jié)點(diǎn)修改好相應(yīng)的配置文件后，即可利用 redis-server redis_xxxx_cluster.conf 工具啟動(dòng)6個(gè)服務(wù)器（xxxx表示端口號，對應(yīng)相應(yīng)的配置文件）。利用ps命令查看進(jìn)程：

$?ps?-aux?|?grep?redis
...?800??0.1??0.0??49584??2444??????????Ssl??20:42???0:00?redis-server?127.0.0.1:6379?[cluster]
...?805??0.1??0.0??49584??2440??????????Ssl??20:42???0:00?redis-server?127.0.0.1:6380?[cluster]
...?812??0.3??0.0??49584??2436??????????Ssl??20:42???0:00?redis-server?127.0.0.1:6381?[cluster]
...?817??0.1??0.0??49584??2432??????????Ssl??20:43???0:00?redis-server?127.0.0.1:6479?[cluster]
...?822??0.0??0.0??49584??2380??????????Ssl??20:43???0:00?redis-server?127.0.0.1:6480?[cluster]
...?827??0.5??0.0??49584??2380??????????Ssl??20:43???0:00?redis-server?127.0.0.1:6481?[cluster]

1.2 節(jié)點(diǎn)握手

1.1中將每個(gè)節(jié)點(diǎn)啟動(dòng)后，節(jié)點(diǎn)間是相互獨(dú)立的，他們都處于一個(gè)只包含自己的集群當(dāng)中，以端口號6379的服務(wù)器為例，利用 CLUSTER NODES 查看當(dāng)前集群包含的節(jié)點(diǎn)。

127.0.0.1:6379>?CLUSTER?NODES
37784b3605ad216fa93e976979c43def42bf763d?:6379@16379?myself,master?-?0?0?0?connected?449?4576?5798?7568?8455?12706

我們需要將各個(gè)獨(dú)立的節(jié)點(diǎn)連接起來，構(gòu)成一個(gè)包含多個(gè)節(jié)點(diǎn)的集群，使用?CLUSTER MEET?命令。

$?redis-cli?-p?6379?-c??????????#?-c?選項(xiàng)指定以Cluster模式運(yùn)行redis-cli?127.0.0.1:6379>?CLUSTER?MEET?127.0.0.1?6380?OK?127.0.0.1:6379>?CLUSTER?MEET?127.0.0.1?6381?OK?127.0.0.1:6379>?CLUSTER?MEET?127.0.0.1?6480?OK?127.0.0.1:6379>?CLUSTER?MEET?127.0.0.1?6381?OK?127.0.0.1:6379>?CLUSTER?MEET?127.0.0.1?6382?OK

再次查看此時(shí)集群中包含的節(jié)點(diǎn)情況：

127.0.0.1:6379>?CLUSTER?NODES
c47598b25205cc88abe2e5094d5bfd9ea202335f?127.0.0.1:6380@16380?master?-?0?1603632309283?4?connected
87b7dfacde34b3cf57d5f46ab44fd6fffb2e4f52?127.0.0.1:6379@16379?myself,master?-?0?1603632308000?1?connected
51081a64ddb3ccf5432c435a8cf20d45ab795dd8?127.0.0.1:6381@16381?master?-?0?1603632310292?2?connected
9d587b75bdaed26ca582036ed706df8b2282b0aa?127.0.0.1:6481@16481?master?-?0?1603632309000?5?connected
4c23b25bd4bcef7f4b77d8287e330ae72e738883?127.0.0.1:6479@16479?master?-?0?1603632308000?3?connected
32ed645a9c9d13ca68dba5a147937fb1d05922ee?127.0.0.1:6480@16480?master?-?0?1603632311302?0?connected

可以發(fā)現(xiàn)此時(shí)6個(gè)節(jié)點(diǎn)均作為主節(jié)點(diǎn)加入到集群中， CLUSTER NODES 返回的結(jié)果各項(xiàng)含義如下：

??????????...?

• 節(jié)點(diǎn)id: 由40個(gè)16進(jìn)制字符串組成，節(jié)點(diǎn)id只在集群初始化時(shí)創(chuàng)建一次，然后保存到集群配置文件（即前文提到的cluster-config-file）中，以后節(jié)點(diǎn)重新啟動(dòng)時(shí)會(huì)直接在集群配置文件中讀取。

• port@cport: 前者為普通端口，用于為客戶端提供服務(wù)；后者為集群端口，分配方法為：普通端口+10000，只用于節(jié)點(diǎn)間的通訊。

其余各項(xiàng)的詳細(xì)解釋可以參考官方文檔cluster nodes。

1.3 槽指派

Redis集群通過分片(sharding)的方式保存數(shù)據(jù)庫的鍵值對，整個(gè)數(shù)據(jù)庫被分為16384個(gè)槽(slot)，數(shù)據(jù)庫每個(gè)鍵都屬于這16384個(gè)槽的一個(gè)，集群中的每個(gè)節(jié)點(diǎn)都可以處理0個(gè)或者最多16384個(gè)slot。

槽是數(shù)據(jù)管理和遷移的基本單位。當(dāng)數(shù)據(jù)庫中的16384個(gè)槽都分配了節(jié)點(diǎn)時(shí)，集群處于上線狀態(tài)（ok）；如果有任意一個(gè)槽沒有分配節(jié)點(diǎn)，則集群處于下線狀態(tài)（fail）。

注意，只有主節(jié)點(diǎn)有處理槽的能力，如果將槽指派步驟放在主從復(fù)制之后，并且將槽位分配給從節(jié)點(diǎn)，那么集群將無法正常工作（處于下線狀態(tài)）。

利用?CLUSTER ADDSLOTS

redis-cli??-p?6379?cluster?addslots?{0..5000}
redis-cli??-p?6380?cluster?addslots?{5001..10000}
redis-cli??-p?6381?cluster?addslots?{10001..16383}

槽指派后集群中節(jié)點(diǎn)情況如下：

127.0.0.1:6379>?CLUSTER?NODES
c47598b25205cc88abe2e5094d5bfd9ea202335f?127.0.0.1:6380@16380?master?-?0?1603632880310?4?connected?5001-10000?87b7dfacde34b3cf57d5f46ab44fd6fffb2e4f52?127.0.0.1:6379@16379?myself,master?-?0?1603632879000?1?connected?0-5000?51081a64ddb3ccf5432c435a8cf20d45ab795dd8?127.0.0.1:6381@16381?master?-?0?1603632879000?2?connected?10001-16383?9d587b75bdaed26ca582036ed706df8b2282b0aa?127.0.0.1:6481@16481?master?-?0?1603632878000?5?connected
4c23b25bd4bcef7f4b77d8287e330ae72e738883?127.0.0.1:6479@16479?master?-?0?1603632880000?3?connected
32ed645a9c9d13ca68dba5a147937fb1d05922ee?127.0.0.1:6480@16480?master?-?0?1603632881317?0?connected

127.0.0.1:6379>?CLUSTER?INFO
cluster_state:ok????????????????????????#?集群處于上線狀態(tài)
cluster_slots_assigned:16384?cluster_slots_ok:16384?cluster_slots_pfail:0?cluster_slots_fail:0?cluster_known_nodes:6?cluster_size:3?cluster_current_epoch:5?cluster_my_epoch:1?cluster_stats_messages_ping_sent:4763?cluster_stats_messages_pong_sent:4939?cluster_stats_messages_meet_sent:5?cluster_stats_messages_sent:9707?cluster_stats_messages_ping_received:4939?cluster_stats_messages_pong_received:4768?cluster_stats_messages_received:9707

1.4 主從復(fù)制

上述步驟后，集群節(jié)點(diǎn)均作為主節(jié)點(diǎn)存在，仍不能實(shí)現(xiàn)Redis的高可用，配置主從復(fù)制之后，才算真正實(shí)現(xiàn)了集群的高可用功能。

CLUSTER REPLICATE ?用來讓集群中接收命令的節(jié)點(diǎn)成為 node_id 所指定節(jié)點(diǎn)的從節(jié)點(diǎn)，并開始對主節(jié)點(diǎn)進(jìn)行復(fù)制。

redis-cli??-p?6479?cluster?replicate?87b7dfacde34b3cf57d5f46ab44fd6fffb2e4f52
redis-cli??-p?6480?cluster?replicate?c47598b25205cc88abe2e5094d5bfd9ea202335f
redis-cli??-p?6481?cluster?replicate?51081a64ddb3ccf5432c435a8cf20d45ab795dd8

127.0.0.1:6379>?CLUSTER?NODES
c47598b25205cc88abe2e5094d5bfd9ea202335f?127.0.0.1:6380@16380?master?-?0?1603633105211?4?connected?5001-10000?87b7dfacde34b3cf57d5f46ab44fd6fffb2e4f52?127.0.0.1:6379@16379?myself,master?-?0?1603633105000?1?connected?0-5000?51081a64ddb3ccf5432c435a8cf20d45ab795dd8?127.0.0.1:6381@16381?master?-?0?1603633105000?2?connected?10001-16383?9d587b75bdaed26ca582036ed706df8b2282b0aa?127.0.0.1:6481@16481?slave?51081a64ddb3ccf5432c435a8cf20d45ab795dd8?0?1603633107229?5?connected
4c23b25bd4bcef7f4b77d8287e330ae72e738883?127.0.0.1:6479@16479?slave?87b7dfacde34b3cf57d5f46ab44fd6fffb2e4f52?0?1603633106221?3?connected
32ed645a9c9d13ca68dba5a147937fb1d05922ee?127.0.0.1:6480@16480?slave?c47598b25205cc88abe2e5094d5bfd9ea202335f?0?1603633104000?4?connected

順帶補(bǔ)充，上述步驟1.2，1.3，1.4可以利用 redis-trib.rb 工具整體實(shí)現(xiàn)，在Redis 5.0之后直接利用 redis-cli 完成，參考命令如下：

redis-cli?--cluster?create??127.0.0.1:6379?127.0.0.1:6479??127.0.0.1:6380?127.0.0.1:6480??127.0.0.1:6381?127.0.0.1:6481??--cluster-replicas?1

--cluster-replicas 1 指示給定的創(chuàng)建節(jié)點(diǎn)列表是以主節(jié)點(diǎn)+從節(jié)點(diǎn)對組成的。

1.5 在集群中執(zhí)行命令

集群此時(shí)處于上線狀態(tài)，可以通過客戶端向集群中的節(jié)點(diǎn)發(fā)送命令。接收命令的節(jié)點(diǎn)會(huì)計(jì)算出命令要處理的鍵屬于哪個(gè)槽，并檢查這個(gè)槽是否指派給自己。

• 如果鍵所在的slot剛好指派給了當(dāng)前節(jié)點(diǎn)，會(huì)直接執(zhí)行這個(gè)命令。
• 否則，節(jié)點(diǎn)向客戶端返回 MOVED 錯(cuò)誤，指引客戶端轉(zhuǎn)向 redirect 至正確的節(jié)點(diǎn)，并再次發(fā)送此前的命令。

此處，我們利用 CLUSTER KEYSLOT 查看到鍵 name 所在槽號為5798（被分配在6380節(jié)點(diǎn)），當(dāng)對此鍵操作時(shí)，會(huì)被重定向到相應(yīng)的節(jié)點(diǎn)。對鍵 fruits 的操作與此類似。

127.0.0.1:6379>?CLUSTER?KEYSLOT?name
(integer)?5798
127.0.0.1:6379>?set?name?huey?->?Redirected?to?slot?[5798]?located?at?127.0.0.1:6380?OK?127.0.0.1:6380>

127.0.0.1:6379>?get?fruits?->?Redirected?to?slot?[14943]?located?at?127.0.0.1:6381
"apple"
127.0.0.1:6381>

值得注意的是，當(dāng)我們將命令通過客戶端發(fā)送給一個(gè)從節(jié)點(diǎn)時(shí)，命令會(huì)被重定向至對應(yīng)的主節(jié)點(diǎn)。

127.0.0.1:6480>?KEYS?*
1)?"name"
127.0.0.1:6480>?get?name?->?Redirected?to?slot?[5798]?located?at?127.0.0.1:6380
"huey"

1.6 集群故障轉(zhuǎn)移

集群中主節(jié)點(diǎn)下線時(shí)，復(fù)制此主節(jié)點(diǎn)的所有的從節(jié)點(diǎn)將會(huì)選出一個(gè)節(jié)點(diǎn)作為新的主節(jié)點(diǎn)，并完成故障轉(zhuǎn)移。和主從復(fù)制的配置相似，當(dāng)原先的從節(jié)點(diǎn)再次上線，它會(huì)被作為新主節(jié)點(diǎn)的的從節(jié)點(diǎn)存在于集群中。

下面模擬6379節(jié)點(diǎn)宕機(jī)的情況（將其SHUTDOWN），可以觀察到其從節(jié)點(diǎn)6479將作為新的主節(jié)點(diǎn)繼續(xù)工作。

462:S?26?Oct?14:08:12.750?*?FAIL?message?received?from?c47598b25205cc88abe2e5094d5bfd9ea202335f?about?87b7dfacde34b3cf57d5f46ab44fd6fffb2e4f52?462:S?26?Oct?14:08:12.751?#?Cluster?state?changed:?fail?462:S?26?Oct?14:08:12.829?#?Start?of?election?delayed?for?595?milliseconds?(rank?#0,?offset?9160).?462:S?26?Oct?14:08:13.434?#?Starting?a?failover?election?for?epoch?6.?462:S?26?Oct?14:08:13.446?#?Failover?election?won:?I'm?the?new?master.
462:S?26?Oct?14:08:13.447?#?configEpoch?set?to?6?after?successful?failover?462:M?26?Oct?14:08:13.447?#?Setting?secondary?replication?ID?to?d357886e00341b57bf17e46b6d9f8cf53b7fad21,?valid?up?to?offset:?9161.?New?replication?ID?is?adbf41b16075ea22b17f145186c53c4499864d5b?462:M?26?Oct?14:08:13.447?*?Discarding?previously?cached?master?state.?462:M?26?Oct?14:08:13.448?#?Cluster?state?changed:?ok

6379節(jié)點(diǎn)從宕機(jī)狀態(tài)恢復(fù)后，將作為6380節(jié)點(diǎn)的從節(jié)點(diǎn)存在。

127.0.0.1:6379>?CLUSTER?NODES
51081a64ddb3ccf5432c435a8cf20d45ab795dd8?127.0.0.1:6381@16381?master?-?0?1603692968000?2?connected?10001-16383?c47598b25205cc88abe2e5094d5bfd9ea202335f?127.0.0.1:6380@16380?master?-?0?1603692968504?0?connected?5001-10000?4c23b25bd4bcef7f4b77d8287e330ae72e738883?127.0.0.1:6479@16479?master?-?0?1603692967495?6?connected?0-5000?87b7dfacde34b3cf57d5f46ab44fd6fffb2e4f52?127.0.0.1:6379@16379?myself,slave?4c23b25bd4bcef7f4b77d8287e330ae72e738883?0?1603692964000?1?connected
9d587b75bdaed26ca582036ed706df8b2282b0aa?127.0.0.1:6481@16481?slave?51081a64ddb3ccf5432c435a8cf20d45ab795dd8?0?1603692967000?4?connected
32ed645a9c9d13ca68dba5a147937fb1d05922ee?127.0.0.1:6480@16480?slave?c47598b25205cc88abe2e5094d5bfd9ea202335f?0?1603692967000?5?connected

前文提到 cluster-config-file 會(huì)記錄下集群節(jié)點(diǎn)的狀態(tài)，打開節(jié)點(diǎn)6379的配置文件 nodes-6379.conf ，可以看到 CLUSTER NODES 所示信息均被保存在配置文件中：

51081a64ddb3ccf5432c435a8cf20d45ab795dd8?127.0.0.1:6381@16381?master?-?0?1603694920206?2?connected?10001-16383?c47598b25205cc88abe2e5094d5bfd9ea202335f?127.0.0.1:6380@16380?master?-?0?1603694916000?0?connected?5001-10000?4c23b25bd4bcef7f4b77d8287e330ae72e738883?127.0.0.1:6479@16479?master?-?0?1603694920000?6?connected?0-5000?87b7dfacde34b3cf57d5f46ab44fd6fffb2e4f52?127.0.0.1:6379@16379?myself,slave?4c23b25bd4bcef7f4b77d8287e330ae72e738883?0?1603694918000?1?connected
9d587b75bdaed26ca582036ed706df8b2282b0aa?127.0.0.1:6481@16481?slave?51081a64ddb3ccf5432c435a8cf20d45ab795dd8?0?1603694919000?4?connected
32ed645a9c9d13ca68dba5a147937fb1d05922ee?127.0.0.1:6480@16480?slave?c47598b25205cc88abe2e5094d5bfd9ea202335f?0?1603694919200?5?connected
vars?currentEpoch?6?lastVoteEpoch?0

2 集群伸縮實(shí)踐

集群伸縮的關(guān)鍵在于對集群的進(jìn)行重新分片，實(shí)現(xiàn)槽位在節(jié)點(diǎn)間的遷移。本節(jié)將以在集群中添加節(jié)點(diǎn)和刪除節(jié)點(diǎn)為例，對槽遷移進(jìn)行實(shí)踐。

借助于 redis-cli 中集成的 redis-trib.rb 工具進(jìn)行槽位的管理，工具的幫助菜單如下：

$?redis-cli?--cluster?help
Cluster?Manager?Commands:
??create?????????host1:port1?...?hostN:portN?--cluster-replicas??check??????????host:port?--cluster-search-multiple-owners
??info???????????host:port
??fix????????????host:port?--cluster-search-multiple-owners?--cluster-fix-with-unreachable-masters
??reshard????????host:port?--cluster-from?
?????????????????--cluster-to?
?????????????????--cluster-slots?
?????????????????--cluster-yes?--cluster-timeout?
?????????????????--cluster-pipeline?
?????????????????--cluster-replace
??rebalance??????host:port?--cluster-weight?
?????????????????--cluster-use-empty-masters?--cluster-timeout?
?????????????????--cluster-simulate?--cluster-pipeline?
?????????????????--cluster-threshold?
?????????????????--cluster-replace
??add-node???????new_host:new_port?existing_host:existing_port?--cluster-slave?--cluster-master-id??del-node???????host:port?node_id
??call???????????host:port?command?arg?arg?..?arg?set-timeout????host:port?milliseconds
??import?????????host:port?--cluster-from?
?????????????????--cluster-copy?--cluster-replace
??backup?????????host:port?backup_directory
??help
??
For?check,?fix,?reshard,?del-node,?set-timeout?you?can?specify?the?host?and?port?of?any?working?node?in?the?cluster.

2.1 集群伸縮-添加節(jié)點(diǎn)

考慮在集群中添加兩個(gè)節(jié)點(diǎn)，端口號為6382和6482，其中節(jié)點(diǎn)6482對6382進(jìn)行復(fù)制。
(1) 啟動(dòng)節(jié)點(diǎn)：按照1.1中介紹的步驟，啟動(dòng)6382和6482節(jié)點(diǎn)。

(2) 節(jié)點(diǎn)握手：借助 redis-cli --cluster add-node 命令分別添加節(jié)點(diǎn)6382和6482。

redis-cli?--cluster?add-node?127.0.0.1:6382?127.0.0.1:6379?redis-cli?--cluster?add-node?127.0.0.1:6482?127.0.0.1:6379

$?redis-cli?--cluster?add-node?127.0.0.1:6382?127.0.0.1:6379
>>>?Adding?node?127.0.0.1:6382?to?cluster?127.0.0.1:6379
>>>?Performing?Cluster?Check?(using?node?127.0.0.1:6379)
S:?87b7dfacde34b3cf57d5f46ab44fd6fffb2e4f52?127.0.0.1:6379?slots:?(0?slots)?slave
????replicates?4c23b25bd4bcef7f4b77d8287e330ae72e738883
M:?51081a64ddb3ccf5432c435a8cf20d45ab795dd8?127.0.0.1:6381?slots:[10001-16383]?(6383?slots)?master?1?additional?replica(s)
M:?c47598b25205cc88abe2e5094d5bfd9ea202335f?127.0.0.1:6380?slots:[5001-10000]?(5000?slots)?master?1?additional?replica(s)
M:?4c23b25bd4bcef7f4b77d8287e330ae72e738883?127.0.0.1:6479?slots:[0-5000]?(5001?slots)?master?1?additional?replica(s)
S:?9d587b75bdaed26ca582036ed706df8b2282b0aa?127.0.0.1:6481?slots:?(0?slots)?slave
????replicates?51081a64ddb3ccf5432c435a8cf20d45ab795dd8
S:?32ed645a9c9d13ca68dba5a147937fb1d05922ee?127.0.0.1:6480?slots:?(0?slots)?slave
????replicates?c47598b25205cc88abe2e5094d5bfd9ea202335f
[OK]?All?nodes?agree?about?slots?configuration.?>>>?Check?for?open?slots...?>>>?Check?slots?coverage...
[OK]?All?16384?slots?covered.?>>>?Send?CLUSTER?MEET?to?node?127.0.0.1:6382?to?make?it?join?the?cluster.
[OK]?New?node?added?correctly.
```shell

3)?重新分片：借助 redis-cli --cluster reshard 命令對集群重新分片，使得各節(jié)點(diǎn)槽位均衡（分別從節(jié)點(diǎn)6379/6380/6381中遷移一些slot到節(jié)點(diǎn)6382中）。需要指定：

*?移動(dòng)的槽位數(shù)：最終平均每個(gè)主節(jié)點(diǎn)有4096個(gè)slot，因此總共移動(dòng)4096 slots
*?接收槽位的目標(biāo)節(jié)點(diǎn)ID：節(jié)點(diǎn)6382的ID
*?移出槽位的源節(jié)點(diǎn)ID：節(jié)點(diǎn)6379/6380/6381的ID

```shell
$?redis-cli?--cluster?reshard?127.0.0.1?6479
>>>?Performing?Cluster?Check?(using?node?127.0.0.1:6479)
M:?4c23b25bd4bcef7f4b77d8287e330ae72e738883?127.0.0.1:6479?slots:[0-5000]?(5001?slots)?master?1?additional?replica(s)
S:?32ed645a9c9d13ca68dba5a147937fb1d05922ee?127.0.0.1:6480?slots:?(0?slots)?slave
??replicates?c47598b25205cc88abe2e5094d5bfd9ea202335f
M:?706f399b248ed3a080cf1d4e43047a79331b714f?127.0.0.1:6482?slots:?(0?slots)?master
M:?af81109fc29f69f9184ce9512c46df476fe693a3?127.0.0.1:6382?slots:?(0?slots)?master
M:?51081a64ddb3ccf5432c435a8cf20d45ab795dd8?127.0.0.1:6381?slots:[10001-16383]?(6383?slots)?master?1?additional?replica(s)
S:?9d587b75bdaed26ca582036ed706df8b2282b0aa?127.0.0.1:6481?slots:?(0?slots)?slave
??replicates?51081a64ddb3ccf5432c435a8cf20d45ab795dd8
S:?87b7dfacde34b3cf57d5f46ab44fd6fffb2e4f52?127.0.0.1:6379?slots:?(0?slots)?slave
??replicates?4c23b25bd4bcef7f4b77d8287e330ae72e738883
M:?c47598b25205cc88abe2e5094d5bfd9ea202335f?127.0.0.1:6380?slots:[5001-10000]?(5000?slots)?master?1?additional?replica(s)
[OK]?All?nodes?agree?about?slots?configuration.?>>>?Check?for?open?slots...?>>>?Check?slots?coverage...
[OK]?All?16384?slots?covered.
How?many?slots?do?you?want?to?move?(from?1?to?16384)??4096?What?is?the?receiving?node?ID?

(4) 設(shè)置主從關(guān)系：

redis-cli?-p?6482?cluster?replicate?af81109fc29f69f9184ce9512c46df476fe693a3?

127.0.0.1:6482>?CLUSTER?NODES
32ed645a9c9d13ca68dba5a147937fb1d05922ee?127.0.0.1:6480@16480?slave?c47598b25205cc88abe2e5094d5bfd9ea202335f?0?1603694930000?0?connected
51081a64ddb3ccf5432c435a8cf20d45ab795dd8?127.0.0.1:6381@16381?master?-?0?1603694931000?2?connected?11597-16383?9d587b75bdaed26ca582036ed706df8b2282b0aa?127.0.0.1:6481@16481?slave?51081a64ddb3ccf5432c435a8cf20d45ab795dd8?0?1603694932000?2?connected
706f399b248ed3a080cf1d4e43047a79331b714f?127.0.0.1:6482@16482?myself,slave?af81109fc29f69f9184ce9512c46df476fe693a3?0?1603694932000?8?connected
87b7dfacde34b3cf57d5f46ab44fd6fffb2e4f52?127.0.0.1:6379@16379?slave?4c23b25bd4bcef7f4b77d8287e330ae72e738883?0?1603694932000?6?connected
c47598b25205cc88abe2e5094d5bfd9ea202335f?127.0.0.1:6380@16380?master?-?0?1603694933678?0?connected?6251-10000?4c23b25bd4bcef7f4b77d8287e330ae72e738883?127.0.0.1:6479@16479?master?-?0?1603694932669?6?connected?1250-5000?af81109fc29f69f9184ce9512c46df476fe693a3?127.0.0.1:6382@16382?master?-?0?1603694933000?9?connected?0-1249?5001-6250?10001-11596

2.2 集群伸縮-刪除節(jié)點(diǎn)

這里考慮將新添加的兩個(gè)節(jié)點(diǎn)6382和6482刪除，需要將節(jié)點(diǎn)6382上分配的槽位遷移到其他節(jié)點(diǎn)。

(1) 重新分片： 同樣借助 redis-cli --cluster reshard 命令，將6382節(jié)點(diǎn)上的槽位全部轉(zhuǎn)移到節(jié)點(diǎn)6479上。

$?redis-cli?--cluster?reshard?127.0.0.1?6382
>>>?Performing?Cluster?Check?(using?node?127.0.0.1:6382)
M:?af81109fc29f69f9184ce9512c46df476fe693a3?127.0.0.1:6382?slots:[0-1249],[5001-6250],[10001-11596]?(4096?slots)?master?1?additional?replica(s)
M:?51081a64ddb3ccf5432c435a8cf20d45ab795dd8?127.0.0.1:6381?slots:[11597-16383]?(4787?slots)?master?1?additional?replica(s)
S:?87b7dfacde34b3cf57d5f46ab44fd6fffb2e4f52?127.0.0.1:6379?slots:?(0?slots)?slave
????replicates?4c23b25bd4bcef7f4b77d8287e330ae72e738883
S:?32ed645a9c9d13ca68dba5a147937fb1d05922ee?127.0.0.1:6480?slots:?(0?slots)?slave
????replicates?c47598b25205cc88abe2e5094d5bfd9ea202335f
M:?4c23b25bd4bcef7f4b77d8287e330ae72e738883?127.0.0.1:6479?slots:[1250-5000]?(3751?slots)?master?1?additional?replica(s)
M:?c47598b25205cc88abe2e5094d5bfd9ea202335f?127.0.0.1:6380?slots:[6251-10000]?(3750?slots)?master?1?additional?replica(s)
S:?706f399b248ed3a080cf1d4e43047a79331b714f?127.0.0.1:6482?slots:?(0?slots)?slave
????replicates?af81109fc29f69f9184ce9512c46df476fe693a3
S:?9d587b75bdaed26ca582036ed706df8b2282b0aa?127.0.0.1:6481?slots:?(0?slots)?slave
????replicates?51081a64ddb3ccf5432c435a8cf20d45ab795dd8
[OK]?All?nodes?agree?about?slots?configuration.?>>>?Check?for?open?slots...?>>>?Check?slots?coverage...
[OK]?All?16384?slots?covered.
How?many?slots?do?you?want?to?move?(from?1?to?16384)??4096?What?is?the?receiving?node?ID??4c23b25bd4bcef7f4b77d8287e330ae72e738883
Please?enter?all?the?source?node?IDs.
Type?'all'?to?use?all?the?nodes?as?source?nodes?for?the?hash?slots.
Type?'done'?once?you?entered?all?the?source?nodes?IDs.
Source?node?#1:?af81109fc29f69f9184ce9512c46df476fe693a3
Source?node?#2:?done

127.0.0.1:6379>?CLUSTER?NODES
c47598b25205cc88abe2e5094d5bfd9ea202335f?127.0.0.1:6380@16380?master?-?0?1603773540922?0?connected?6251-10000?87b7dfacde34b3cf57d5f46ab44fd6fffb2e4f52?127.0.0.1:6379@16379?myself,slave?4c23b25bd4bcef7f4b77d8287e330ae72e738883?0?1603773539000?1?connected
4c23b25bd4bcef7f4b77d8287e330ae72e738883?127.0.0.1:6479@16479?master?-?0?1603773541000?10?connected?0-6250?10001-11596?706f399b248ed3a080cf1d4e43047a79331b714f?127.0.0.1:6482@16482?slave?4c23b25bd4bcef7f4b77d8287e330ae72e738883?0?1603773541000?10?connected
32ed645a9c9d13ca68dba5a147937fb1d05922ee?127.0.0.1:6480@16480?slave?c47598b25205cc88abe2e5094d5bfd9ea202335f?0?1603773539000?5?connected
9d587b75bdaed26ca582036ed706df8b2282b0aa?127.0.0.1:6481@16481?slave?51081a64ddb3ccf5432c435a8cf20d45ab795dd8?0?1603773541931?4?connected
af81109fc29f69f9184ce9512c46df476fe693a3?127.0.0.1:6382@16382?master?-?0?1603773539000?9?connected
51081a64ddb3ccf5432c435a8cf20d45ab795dd8?127.0.0.1:6381@16381?master?-?0?1603773540000?2?connected?11597-16383

(2) 刪除節(jié)點(diǎn)： 利用 redis-cli --cluster del-node 命令依次刪除從節(jié)點(diǎn)6482和主節(jié)點(diǎn)6382。

$?redis-cli?--cluster?del-node?127.0.0.1:6482?706f399b248ed3a080cf1d4e43047a79331b714f?>>>?Removing?node?706f399b248ed3a080cf1d4e43047a79331b714f?from?cluster?127.0.0.1:6482
>>>?Sending?CLUSTER?FORGET?messages?to?the?cluster...?>>>?Sending?CLUSTER?RESET?SOFT?to?the?deleted?node.
$?redis-cli?--cluster?del-node?127.0.0.1:6382?af81109fc29f69f9184ce9512c46df476fe693a3?>>>?Removing?node?af81109fc29f69f9184ce9512c46df476fe693a3?from?cluster?127.0.0.1:6382
>>>?Sending?CLUSTER?FORGET?messages?to?the?cluster...?>>>?Sending?CLUSTER?RESET?SOFT?to?the?deleted?node.

127.0.0.1:6379>?CLUSTER?NODES
c47598b25205cc88abe2e5094d5bfd9ea202335f?127.0.0.1:6380@16380?master?-?0?1603773679121?0?connected?6251-10000?87b7dfacde34b3cf57d5f46ab44fd6fffb2e4f52?127.0.0.1:6379@16379?myself,slave?4c23b25bd4bcef7f4b77d8287e330ae72e738883?0?1603773677000?1?connected
4c23b25bd4bcef7f4b77d8287e330ae72e738883?127.0.0.1:6479@16479?master?-?0?1603773678000?10?connected?0-6250?10001-11596?32ed645a9c9d13ca68dba5a147937fb1d05922ee?127.0.0.1:6480@16480?slave?c47598b25205cc88abe2e5094d5bfd9ea202335f?0?1603773680130?5?connected
9d587b75bdaed26ca582036ed706df8b2282b0aa?127.0.0.1:6481@16481?slave?51081a64ddb3ccf5432c435a8cf20d45ab795dd8?0?1603773677099?4?connected
51081a64ddb3ccf5432c435a8cf20d45ab795dd8?127.0.0.1:6381@16381?master?-?0?1603773678112?2?connected?11597-16383

3 總結(jié)

Redis集群環(huán)境的搭建主要包括啟動(dòng)節(jié)點(diǎn)、節(jié)點(diǎn)握手、槽指派和主從復(fù)制等四個(gè)步驟，集群伸縮同樣涉及這幾個(gè)方面。借助 redis-cli --cluster 命令來管理集群環(huán)境，不僅能增加簡便性，還能降低操作失誤的風(fēng)險(xiǎn)。