Docker Mastery: Section 8 - (Swarm) Routing Mesh

• section8-66

Udemy

• Docker Mastery: with Kubernetes +Swarm from a Docker Captain

• GitHub: udemy-docker-mastery

• 講師的YouTube

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官方文件 ROUTING MESH

Routing Mesh

• Routing ingress (incoming) packets for a Service to proper Task.
• Spans all nodes in Swarm
• Uses IPVS from Linux Kernel
• Load balances Swarm Servcies across their Tasks
• Two ways this works:
  • Container-to-container in a Overlay network (uses VIP (Virtual IP) )
    • 
  • External traffic incoming to published ports (all nodes listen)
    • 

實作

• docker service create --name search --replicas 3 -p 9200:9200 elasticsearch:2

root@node1:~# docker service create --name search --replicas 3 -p 9200:9200 elasticsearch:2
a2cesy4afyiwyiygvu84b1ogd
overall progress: 3 out of 3 tasks
1/3: running
2/3: running
3/3: running
verify: Service converged
root@node1:~#

• 查看建置情況
  • docker service ps <service-name>
  • 很聰明的自動分配到各個 NODE

root@node1:~# docker service ls
ID                  NAME                MODE                REPLICAS            IMAGE               PORTS
a2cesy4afyiw        search              replicated          3/3                 elasticsearch:2     *:9200->9200/tcp
root@node1:~# docker service ps search
ID                  NAME                IMAGE               NODE                DESIRED STATE       CURRENT STATE                ERROR               PORTS
ka0g6gooqgfk        search.1            elasticsearch:2     node2               Running             Running about a minute ago
vdg221htli9t        search.2            elasticsearch:2     node3               Running             Running about a minute ago
oxnh31i0w4gg        search.3            elasticsearch:2     node1               Running             Running about a minute ago

• curl localhost:9200

  • 多抓幾次 會透過 VIP 抓到不一樣的

root@node1:~# curl localhost:9200
{
  "name" : "Donald Ritter",
  "cluster_name" : "elasticsearch",
  "cluster_uuid" : "v0IGCLB1TZGViXb0TA-W1A",
  "version" : {
    "number" : "2.4.6",
    "build_hash" : "5376dca9f70f3abef96a77f4bb22720ace8240fd",
    "build_timestamp" : "2017-07-18T12:17:44Z",
    "build_snapshot" : false,
    "lucene_version" : "5.5.4"
  },
  "tagline" : "You Know, for Search"
}
root@node1:~# curl localhost:9200
{
  "name" : "Watoomb",
  "cluster_name" : "elasticsearch",
  "cluster_uuid" : "nJLvCm_mQ7egXmOggv9p8g",
  "version" : {
    "number" : "2.4.6",
    "build_hash" : "5376dca9f70f3abef96a77f4bb22720ace8240fd",
    "build_timestamp" : "2017-07-18T12:17:44Z",
    "build_snapshot" : false,
    "lucene_version" : "5.5.4"
  },
  "tagline" : "You Know, for Search"
}
root@node1:~# curl localhost:9200
{
  "name" : "Elf With A Gun",
  "cluster_name" : "elasticsearch",
  "cluster_uuid" : "XruBZZMtQ726jDse2a5law",
  "version" : {
    "number" : "2.4.6",
    "build_hash" : "5376dca9f70f3abef96a77f4bb22720ace8240fd",
    "build_timestamp" : "2017-07-18T12:17:44Z",
    "build_snapshot" : false,
    "lucene_version" : "5.5.4"
  },
  "tagline" : "You Know, for Search"
}

Routing Mesh Continue

• This is staeless load balancing
• This LB is at OSI Layer 3 (TCP), not Layer 4 (DNS)
• Both limitation can be overcome with:
  • Nginx or HAProxy LB proxy, or:
  • Docker Enterprise Edition, which comes with built-in L4 web proxy