Docker容器访问大量IP

Question

When running docker containers a swarm cluster do the containers have access to all the IPs of the cluster nodes via ENV variables or otherwise?

I want to run an Elasticsearch instance on each node in my swarm the cluster. And they will discovery each other in unicast mode. Therefore each Elasticsearch instanc needs to be configured with the list of IPs in the cluster.

Answer 1

If you mean that container of one node can access container's IP of other node , then it is not possible . You have to use weave tool to connect container across different node or other tool .

Answer 2

If you are using latest Docker (1.13+) with a swam overlay network, you should be able to get all the cluster's node IPs through DNS round robin.(--endpoint-mode dnsrr)

1) Create an overlay network.

https://docs.docker.com/engine/swarm/networking/

docker network create \
  --driver overlay \
  my-network

2) Verify swam nodes:

docker@node1:~$ docker node ls
ID                            HOSTNAME            STATUS              AVAILABILITY        MANAGER STATUS
5l07yt2itiee60xfq7g6c01e4 *   node1               Ready               Active              Leader
pckn7qo3xpbxvs89ni6whyql3     node2               Ready               Active              

3) Create an alpine container on each nodes using "global" mode:

docker service create --mode global --endpoint-mode dnsrr --name testservice --detach=true --network my-network alpine ash -c "apk update;apk add drill; ping docker.com"

4) verify service is running:

docker@node1:~$ docker service ls
ID                  NAME                MODE                REPLICAS            IMAGE               PORTS
lmy5s3flw763        testservice         global              2/2                 alpine:latest 

5) Verify that containers were deployed on individual nodes:

$ docker-machine ssh node1 "docker ps"
CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS               NAMES
4c7055b01479        alpine:latest       "ash -c 'apk updat..."   2 minutes ago       Up 2 minutes                            testservice.5l07yt2itiee60xfq7g6c01e4.atvascigh3rvxvlzttaotkrua

$ docker-machine ssh node2 "docker ps"
CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS               NAMES
28da546aa0d5        alpine:latest       "ash -c 'apk updat..."   2 minutes ago       Up 2 minutes                            testservice.pckn7qo3xpbxvs89ni6whyql3.ebjz4asni4w1f0srna0p3vj4a

6) Confirm individual virtual IP of each containers on node1 and node2:

| => docker-machine ssh node1 "docker exec 4c7055b01479 ash -c 'ip addr'|grep eth0"
349: eth0@if350: <BROADCAST,MULTICAST,UP,LOWER_UP,M-DOWN> mtu 1450 qdisc noqueue state UP 
    inet 10.0.0.2/24 scope global eth0


| => docker-machine ssh node2 "docker exec 28da546aa0d5 ash -c 'ip addr'|grep eth0"
319: eth0@if320: <BROADCAST,MULTICAST,UP,LOWER_UP,M-DOWN> mtu 1450 qdisc noqueue state UP 
    inet 10.0.0.3/24 scope global eth0

7) Get the container IP addresses for all containers in cluster using Drill dns tool :

| => docker-machine ssh node1 "docker exec 4c7055b01479 ash -c 'drill testservice'"
;; ->>HEADER<<- opcode: QUERY, rcode: NOERROR, id: 60920
;; flags: qr rd ra ; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 0 
;; QUESTION SECTION:
;; testservice. IN  A

;; ANSWER SECTION:
testservice.    600 IN  A   10.0.0.3
testservice.    600 IN  A   10.0.0.2

;; AUTHORITY SECTION:

;; ADDITIONAL SECTION:

;; Query time: 0 msec
;; SERVER: 127.0.0.11
;; WHEN: Thu Jul 20 19:20:49 2017
;; MSG SIZE  rcvd: 83

8) Verify that containers can ping each other:

docker-machine ssh node1 "docker exec 4c7055b01479 ash -c 'ping -c2 10.0.0.3'"
PING 10.0.0.3 (10.0.0.3): 56 data bytes
64 bytes from 10.0.0.3: seq=0 ttl=64 time=0.539 ms
64 bytes from 10.0.0.3: seq=1 ttl=64 time=0.731 ms

--- 10.0.0.3 ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max = 0.539/0.635/0.731 ms



docker-machine ssh node2 "docker exec 28da546aa0d5 ash -c 'ping -c2 10.0.0.2'"
PING 10.0.0.2 (10.0.0.2): 56 data bytes
64 bytes from 10.0.0.2: seq=0 ttl=64 time=0.579 ms
64 bytes from 10.0.0.2: seq=1 ttl=64 time=0.736 ms

--- 10.0.0.2 ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max = 0.579/0.657/0.736 ms