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| # 探討Pod中有多個container之狀況 | ||
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| 在服務的配置上，有時候會需要把一個以上的container包在同一個Pod上(回憶一下，Pod是部屬的最小單位，可以有一個以上的container，但是不可切分，到時候會被deploy在同一台主機上)，在這樣的情況下，可以觀察一下container的狀況... | ||
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| PS: 下面測試是在一台master與一台worker上，預設pod都會長在worker上... | ||
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| ``` | ||
| # k8s-2pod.yml | ||
| apiVersion: v1 | ||
| kind: Pod | ||
| metadata: | ||
| name: myweb | ||
| labels: | ||
| app: web | ||
| spec: | ||
| containers: | ||
| - name: db | ||
| image: couchdb | ||
| ports: | ||
| - containerPort: 5984 | ||
| - name: ap | ||
| image: peihsinsu/simpleweb | ||
| ports: | ||
| - containerPort: 3000 | ||
| ``` | ||
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| 啟動服務... | ||
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| ``` | ||
| kubctl create -f k8s-2pod.yml | ||
| ``` | ||
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| 分別登入，啟動的container確認一下IP位置 | ||
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| 先登入k8s worker，可以用docker ps看到simpleweb與couchdb都長在這台worker上... | ||
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| ``` | ||
| root@simon-k8s-worker1:~# docker ps | ||
| CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES | ||
| 8982a7b6a806 peihsinsu/simpleweb "/usr/bin/npm start" 9 minutes ago Up 9 minutes k8s_ap.b2d53365_myweb_default_1e96a60e-62a3-11e6-8794-42010af0001d_d81c6081 | ||
| 0c5d3d95760a couchdb "tini -- /docker-entr" 9 minutes ago Up 9 minutes k8s_db.95762e7a_myweb_default_1e96a60e-62a3-11e6-8794-42010af0001d_a21af38c | ||
| 5966e6515709 gcr.io/google_containers/pause-amd64:3.0 "/pause" 9 minutes ago Up 9 minutes k8s_POD.7af92679_myweb_default_1e96a60e-62a3-11e6-8794-42010af0001d_b0814640 | ||
| 555834a906e1 gcr.io/google_containers/hyperkube-amd64:v1.3.5 "/hyperkube proxy --m" 2 days ago Up 25 hours kube_proxy_a913a | ||
| cf0b6bdfb91d gcr.io/google_containers/hyperkube-amd64:v1.3.5 "/hyperkube kubelet -" 2 days ago Up 25 hours kube_kubelet_a4b58 | ||
| ``` | ||
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| 接下來，可以透過docker exec分別登入所啟動的兩個container，並檢查他們的IP... | ||
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| 先登入simpleweb... | ||
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| ``` | ||
| root@simon-k8s-worker1:~# docker exec -it 8982a7b6a806 bash | ||
| rpc error: code = 2 desc = oci runtime error: exec failed: exec: "bash": executable file not found in $PATH | ||
| root@simon-k8s-worker1:~# docker exec -it 8982a7b6a806 sh | ||
| /app # ifconfig -a | ||
| eth0 Link encap:Ethernet HWaddr 02:42:0A:01:54:02 | ||
| inet addr:10.1.84.2 Bcast:0.0.0.0 Mask:255.255.255.0 | ||
| inet6 addr: fe80::42:aff:fe01:5402%32668/64 Scope:Link | ||
| UP BROADCAST RUNNING MULTICAST MTU:1432 Metric:1 | ||
| RX packets:2 errors:0 dropped:0 overruns:0 frame:0 | ||
| TX packets:3 errors:0 dropped:0 overruns:0 carrier:0 | ||
| collisions:0 txqueuelen:0 | ||
| RX bytes:168 (168.0 B) TX bytes:258 (258.0 B) | ||
| lo Link encap:Local Loopback | ||
| inet addr:127.0.0.1 Mask:255.0.0.0 | ||
| inet6 addr: ::1%32668/128 Scope:Host | ||
| UP LOOPBACK RUNNING MTU:65536 Metric:1 | ||
| RX packets:0 errors:0 dropped:0 overruns:0 frame:0 | ||
| TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 | ||
| collisions:0 txqueuelen:0 | ||
| RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) | ||
| /app # | ||
| ``` | ||
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| 再登入couchdb... | ||
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| ``` | ||
| root@simon-k8s-worker1:~# docker exec -it 0c5d3d95760a bash | ||
| root@myweb:/var/lib/couchdb# ip addr | ||
| 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default | ||
| link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 | ||
| inet 127.0.0.1/8 scope host lo | ||
| valid_lft forever preferred_lft forever | ||
| inet6 ::1/128 scope host | ||
| valid_lft forever preferred_lft forever | ||
| 19: eth0@if20: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1432 qdisc noqueue state UP group default | ||
| link/ether 02:42:0a:01:54:02 brd ff:ff:ff:ff:ff:ff | ||
| inet 10.1.84.2/24 scope global eth0 | ||
| valid_lft forever preferred_lft forever | ||
| inet6 fe80::42:aff:fe01:5402/64 scope link tentative dadfailed | ||
| valid_lft forever preferred_lft forever | ||
| root@myweb:/var/lib/couchdb# | ||
| ``` | ||
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| 上面會發現兩個container的服務所取得的internal ip address相同，這是因為pod內部使用了network binding的方式，讓pod內的container都用同一個IP位置，這樣在內部溝通上可以比較簡單... 可以透過docker inspect中搜尋"NetworkMode"來看到這部分的設定... | ||
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| ``` | ||
| # docker inspect 8982a7b6a806 | ||
| [ | ||
| { | ||
| "Id": "8982a7b6a806d472255e38cef164ae08b0080fd0257aa376d02a0cfda66cc960", | ||
| "Created": "2016-08-15T04:45:46.841268011Z", | ||
| "Path": "/usr/bin/npm", | ||
| ....(skip) | ||
| "HostConfig": { | ||
| "Binds": [ | ||
| "/var/lib/kubelet/pods/1e96a60e-62a3-11e6-8794-42010af0001d/volumes/kubernetes.io~secret/default-token-2h2ok:/var/run/secrets/kubernetes.io/serviceaccount:ro", | ||
| "/var/lib/kubelet/pods/1e96a60e-62a3-11e6-8794-42010af0001d/etc-hosts:/etc/hosts", | ||
| "/var/lib/kubelet/pods/1e96a60e-62a3-11e6-8794-42010af0001d/containers/ap/d81c6081:/dev/termination-log" | ||
| ], | ||
| "ContainerIDFile": "", | ||
| "LogConfig": { | ||
| "Type": "json-file", | ||
| "Config": {} | ||
| }, | ||
| "NetworkMode": "container:5966e65157097b45d6acf56d26924421f9a86f031b134b74d07a2ffab9b0d66c", | ||
| ....(skip) | ||
| } | ||
| ] | ||
| ``` | ||
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| 這個動作相當於在docker 1.12中使用"--network container:[id or name]"來綁定ip到另一個container... | ||
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| ``` | ||
| docker run -d --name db couchdb | ||
| docker run -d --network container:db peihsinsu/simpleweb | ||
| ``` | ||
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| ## 參考 | ||
| * 關於network binding的官方文件： https://docs.docker.com/engine/reference/run/#/network-container |