Docker 容器部署 Consul 集群

Consul 介紹

Consul 提供了分布式系統(tǒng)的服務(wù)發(fā)現(xiàn)和配置的解決方案。基于go語言實(shí)現(xiàn)。并且在git上開放了源碼consul-git。consul還包括了分布式一致協(xié)議的實(shí)現(xiàn)，健康檢查和管理UI。Consul和zk相比較起來，更加輕量級(jí)，而且一致性上基于RAFT算法，zk使用的Paxos 算法。跟zk比較起來更加輕量級(jí)，Consul提供了通過一個(gè)DNS或者HTTP接口的方式來控制執(zhí)行，而zk卻需要自己定制解決方案。同樣比較被廣泛使用的服務(wù)發(fā)現(xiàn)解決方案中也有etcd 。etcd也是采用RAFT算法實(shí)現(xiàn)，但是etcd不提供管理UI。Consul跟Vagrant都是Hashicorp 公司的產(chǎn)品。作為一整套的分布式系統(tǒng)解決方案，配合同樣基于go語言實(shí)現(xiàn)的Docker開源技術(shù)，都是一個(gè)不錯(cuò)的選擇。Docker 的簡(jiǎn)單介紹，可以參考 Docker 介紹 （本文后面將不再介紹docker 命令以及容器等相關(guān)概念）。配合Docker來做應(yīng)用容器，用Consul 來做集群的服務(wù)發(fā)現(xiàn)和健康檢查,并且還可以輕量級(jí)得做到水平和垂直可擴(kuò)展。

Consul Agent、Server、Client

通過運(yùn)行 consul agent 命令，可以通過后臺(tái)守護(hù)進(jìn)程的方式運(yùn)行在所有consul集群節(jié)點(diǎn)中。并且可以以server或者client 模式運(yùn)行。并且以HTTP或者DNS 接口方式，負(fù)責(zé)運(yùn)行檢查和服務(wù)同步。Server模式的agent負(fù)責(zé)維護(hù)consul集群狀態(tài)，相應(yīng)RPC查詢，并且還要負(fù)責(zé)和其他數(shù)據(jù)中心（DataCenter）進(jìn)行WAN Gossips交換。Client 節(jié)點(diǎn)是相對(duì)無狀態(tài)的，Client的唯一活動(dòng)就是轉(zhuǎn)發(fā)(foward)請(qǐng)求給Server節(jié)點(diǎn)，以保持低延遲和少資源消耗。
??如下圖,是官網(wǎng)的一個(gè)典型系統(tǒng)結(jié)構(gòu)，Consul建議我們每個(gè)DataCenter的Server的節(jié)點(diǎn)最好在3到5個(gè)之間，以方便在失敗以及數(shù)據(jù)復(fù)制的性能。Client的數(shù)量可以任意。圖中，最重要的兩個(gè)概念一個(gè)是Gossip協(xié)議，一個(gè)是Consensus 協(xié)議。DataCenter的所有節(jié)點(diǎn)都會(huì)參與到Gossip協(xié)議。Client 到Server 會(huì)通過LAN Gossip。所有的節(jié)點(diǎn)都在Gossip pool中，通過消息層來實(shí)現(xiàn)節(jié)點(diǎn)之間的通信以達(dá)到故障檢測(cè)的目的，并且不需要給Client配置Server的地址。而Server節(jié)點(diǎn)還會(huì)參與到WAN Gossip池中。這樣，通過Server節(jié)點(diǎn)就可以讓DataCenter之間做簡(jiǎn)單的服務(wù)發(fā)現(xiàn)。比如增加一個(gè)Datacenter就只需要讓Server節(jié)點(diǎn)參與到Gossip Pool中。并且，DataCneter之間的通信和服務(wù)請(qǐng)求就可以通過WAN Gossip 來隨機(jī)請(qǐng)求另外一個(gè)DataCenter的Server節(jié)點(diǎn)，然后被請(qǐng)求的Server 會(huì)再把請(qǐng)求foward到本DataCenter的leader節(jié)點(diǎn)。Server leader的選舉是通過Consul的Raft 算法實(shí)現(xiàn)。Leader 節(jié)點(diǎn)需要負(fù)責(zé)所有請(qǐng)求和處理，并且這些請(qǐng)求也必須復(fù)制給所有的其他非leader的Server節(jié)點(diǎn)。同樣，非Leader節(jié)點(diǎn)接收到RPC請(qǐng)求的時(shí)候也會(huì)foward 到Leader節(jié)點(diǎn)。
??

在Docker 容器中啟動(dòng)Consul Agent

下載 progrium/consul 鏡像

以Server 模式在容器中啟動(dòng)一個(gè)agent
docker run -p 8600:53/udp -h node1 progrium/consul -server -bootstrap

docker@boot2docker:~$ docker run -p 8600:53/udp -h node1 progrium/consul -server -bootstrap ==> WARNING: Bootstrap mode enabled! Do not enable unless necessary ==> WARNING: It is highly recommended to set GOMAXPROCS higher than 1 ==> Starting raft data migration... ==> Starting Consul agent... ==> Starting Consul agent RPC... ==> Consul agent running!Node name: 'node1'Datacenter: 'dc1'Server: true (bootstrap: true)Client Addr: 0.0.0.0 (HTTP: 8500, HTTPS: -1, DNS: 53, RPC: 8400)Cluster Addr: 172.17.0.1 (LAN: 8301, WAN: 8302)Gossip encrypt: false, RPC-TLS: false, TLS-Incoming: falseAtlas: <disabled>==> Log data will now stream in as it occurs:2015/09/29 03:13:43 [INFO] serf: EventMemberJoin: node1 172.17.0.12015/09/29 03:13:43 [INFO] serf: EventMemberJoin: node1.dc1 172.17.0.12015/09/29 03:13:43 [INFO] raft: Node at 172.17.0.1:8300 [Follower] entering Follower state2015/09/29 03:13:43 [INFO] consul: adding server node1 (Addr: 172.17.0.1:8300) (DC: dc1)2015/09/29 03:13:43 [INFO] consul: adding server node1.dc1 (Addr: 172.17.0.1:8300) (DC: dc1)2015/09/29 03:13:43 [ERR] agent: failed to sync remote state: No cluster leader2015/09/29 03:13:45 [WARN] raft: Heartbeat timeout reached, starting election2015/09/29 03:13:45 [INFO] raft: Node at 172.17.0.1:8300 [Candidate] entering Candidate state2015/09/29 03:13:45 [INFO] raft: Election won. Tally: 12015/09/29 03:13:45 [INFO] raft: Node at 172.17.0.1:8300 [Leader] entering Leader state2015/09/29 03:13:45 [INFO] consul: cluster leadership acquired2015/09/29 03:13:45 [INFO] raft: Disabling EnableSingleNode (bootstrap)2015/09/29 03:13:45 [INFO] consul: New leader elected: node12015/09/29 03:13:45 [INFO] consul: member 'node1' joined, marking health alive2015/09/29 03:13:45 [INFO] agent: Synced service 'consul'

這里試驗(yàn)一下8600(DNS) 接口，然后我們就用dig的方式可以交互和訪問了。

用Docker 容器啟動(dòng)Consul集群

分別啟動(dòng)三個(gè)server節(jié)點(diǎn)

剛才啟動(dòng)單獨(dú)的服務(wù)節(jié)點(diǎn)，用bootstrap。現(xiàn)在啟動(dòng)三個(gè)節(jié)點(diǎn)需要用bootstrap-expect 3 ，并且綁定到容器的同一個(gè)ip,這里綁定到server1上。

docker@boot2docker:~$ docker run -d –name server1 -h server1 progrium/consul -server -bootstrap-expect 3

docker@boot2docker:~JOINIP=”(docker inspect -f ‘{{ .NetworkSettings.IPAddress }}’ server1)”

docker@boot2docker:~dockerrun?d??nameserver2?hserver2progrium/consul?server?joinJOIN_IP

docker@boot2docker:~dockerrun?d??nameserver3?hserver3progrium/consul?server?joinJOIN_IP

然后用docker命令查看已經(jīng)啟動(dòng)的容器。關(guān)于docker 相關(guān)內(nèi)容可以參考“Docker介紹 ”

docker@boot2docker:~$ docker ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 87bd80f8132d progrium/consul "/bin/start -server -" 3 seconds ago Up 2 seconds 53/tcp, 53/udp, 8300-8302/tcp, 8400/tcp, 8500/tcp, 8301-8302/udp server3 a18d0597bf2d progrium/consul "/bin/start -server -" 18 seconds ago Up 17 seconds 53/tcp, 53/udp, 8300-8302/tcp, 8400/tcp, 8301-8302/udp, 8500/tcp server2 448a550224fb progrium/consul "/bin/start -server -" About a minute ago Up About a minute 53/tcp, 53/udp, 8300-8302/tcp, 8400/tcp, 8500/tcp, 8301-8302/udp server1

啟動(dòng)client節(jié)點(diǎn)

docker@boot2docker:~dockerrun?d?p8400:8400?p8500:8500?p8600:53/udp?hclient1progrium/consul?joinJOIN_IP

查看容器信息：

docker@boot2docker:~$ docker ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 0410ad7bb68c progrium/consul "/bin/start -join 172" 4 seconds ago Up 3 seconds 53/tcp, 0.0.0.0:8400->8400/tcp, 8300-8302/tcp, 8301-8302/udp, 0.0.0.0:8500->8500/tcp, 0.0.0.0:8600->53/udp focused_leakey 87bd80f8132d progrium/consul "/bin/start -server -" 3 minutes ago Up 3 minutes 53/tcp, 53/udp, 8300-8302/tcp, 8400/tcp, 8500/tcp, 8301-8302/udp server3 a18d0597bf2d progrium/consul "/bin/start -server -" 3 minutes ago Up 3 minutes 53/tcp, 53/udp, 8300-8302/tcp, 8400/tcp, 8500/tcp, 8301-8302/udp server2 448a550224fb progrium/consul "/bin/start -server -" 4 minutes ago Up 4 minutes 53/tcp, 53/udp, 8300-8302/tcp, 8400/tcp, 8301-8302/udp, 8500/tcp server1

進(jìn)入容器查看

我們可以進(jìn)入容器來查看一下consul是如何管理agent節(jié)點(diǎn)，以及選舉server 的leader的。這個(gè)時(shí)候我們關(guān)掉Server節(jié)點(diǎn),容器name是server1的 448a550224fb 容器，再觀察。
?? 關(guān)閉后server1信息：

==> Gracefully shutting down agent...2015/09/29 04:08:17 [INFO] consul: server starting leave2015/09/29 04:08:17 [INFO] raft: Removed peer 172.17.0.28:8300, stopping replication (Index: 18)2015/09/29 04:08:17 [INFO] raft: Removed peer 172.17.0.29:8300, stopping replication (Index: 18)2015/09/29 04:08:17 [INFO] raft: Removed ourself, transitioning to follower2015/09/29 04:08:17 [INFO] raft: Node at 172.17.0.27:8300 [Follower] entering Follower state2015/09/29 04:08:17 [INFO] serf: EventMemberLeave: server1.dc1 172.17.0.272015/09/29 04:08:17 [INFO] consul: cluster leadership lost2015/09/29 04:08:17 [INFO] raft: aborting pipeline replication to peer 172.17.0.28:83002015/09/29 04:08:17 [INFO] raft: aborting pipeline replication to peer 172.17.0.29:83002015/09/29 04:08:17 [INFO] consul: removing server server1.dc1 (Addr: 172.17.0.27:8300) (DC: dc1)2015/09/29 04:08:18 [INFO] serf: EventMemberLeave: server1 172.17.0.272015/09/29 04:08:18 [INFO] consul: removing server server1 (Addr: 172.17.0.27:8300) (DC: dc1)2015/09/29 04:08:18 [INFO] agent: requesting shutdown2015/09/29 04:08:18 [INFO] consul: shutting down server2015/09/29 04:08:18 [INFO] agent: shutdown complete

server2節(jié)點(diǎn)信息如下：

docker@boot2docker:~$ docker attach server22015/09/29 04:08:18 [INFO] serf: EventMemberLeave: server1 172.17.0.272015/09/29 04:08:18 [INFO] consul: removing server server1 (Addr: 172.17.0.27:8300) (DC: dc1)2015/09/29 04:08:20 [WARN] raft: Rejecting vote from 172.17.0.29:8300 since we have a leader: 172.17.0.27:83002015/09/29 04:08:20 [WARN] raft: Heartbeat timeout reached, starting election2015/09/29 04:08:20 [INFO] raft: Node at 172.17.0.28:8300 [Candidate] entering Candidate state2015/09/29 04:08:21 [INFO] raft: Node at 172.17.0.28:8300 [Follower] entering Follower state2015/09/29 04:08:21 [INFO] consul: New leader elected: server3

可以看到server1 節(jié)點(diǎn)下線，并且重新選舉leader server節(jié)點(diǎn)為server3,再看一下server3 信息如下：

docker@boot2docker:~$ docker attach server32015/09/29 04:08:18 [INFO] serf: EventMemberLeave: server1 172.17.0.272015/09/29 04:08:18 [INFO] consul: removing server server1 (Addr: 172.17.0.27:8300) (DC: dc1)2015/09/29 04:08:20 [WARN] raft: Heartbeat timeout reached, starting election2015/09/29 04:08:20 [INFO] raft: Node at 172.17.0.29:8300 [Candidate] entering Candidate state2015/09/29 04:08:20 [INFO] raft: Duplicate RequestVote for same term: 22015/09/29 04:08:21 [WARN] raft: Election timeout reached, restarting election2015/09/29 04:08:21 [INFO] raft: Node at 172.17.0.29:8300 [Candidate] entering Candidate state2015/09/29 04:08:21 [INFO] raft: Election won. Tally: 22015/09/29 04:08:21 [INFO] raft: Node at 172.17.0.29:8300 [Leader] entering Leader state2015/09/29 04:08:21 [INFO] consul: cluster leadership acquired2015/09/29 04:08:21 [INFO] consul: New leader elected: server32015/09/29 04:08:21 [INFO] raft: pipelining replication to peer 172.17.0.28:83002015/09/29 04:08:21 [INFO] consul: member 'server1' left, deregistering

client 節(jié)點(diǎn)信息如下：

docker@boot2docker:~$ docker attach focused_leakey2015/09/29 04:08:18 [INFO] serf: EventMemberLeave: server1 172.17.0.272015/09/29 04:08:18 [INFO] consul: removing server server1 (Addr: 172.17.0.27:8300) (DC: dc1)2015/09/29 04:08:21 [INFO] consul: New leader elected: server3

總結(jié)

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