Docker Enterprise Edition supports swarm mode. In this section you'll work through examples of a few basic networking concepts, learn about Bridge and Overlay networking, and finally learning about the Swarm Routing Mesh.
Difficulty: Beginner to Intermediate
Time: Approximately 45 minutes
Tasks:
PWD is a minimal environment, so we will need to add a few tools to help with the workshop. On the manager1 node run:
sudo apt-get update && apt-get install -y curl dnsutils iputils-ping
And run the same command on worker1:
sudo apt-get update && apt-get install -y curl dnsutils iputils-ping
Connect to the manager1 node in your PWD session to explore the existing Docker networks.
The docker network command is the main command for configuring and managing container networks. Run the docker network command from manager1.
$ docker network
Usage: docker network COMMAND
Manage networks
Options:
--help Print usage
Commands:
connect Connect a container to a network
create Create a network
disconnect Disconnect a container from a network
inspect Display detailed information on one or more networks
ls List networks
prune Remove all unused networks
rm Remove one or more networks
Run 'docker network COMMAND --help' for more information on a command.
The command output shows how to use the command as well as all of the docker network sub-commands. As you can see from the output, the docker network command allows you to create new networks, list existing networks, inspect networks, and remove networks. It also allows you to connect and disconnect containers from networks.
Run a docker network ls command on manager1 to view existing container networks on the current Docker host.
$ docker network ls
NETWORK ID NAME DRIVER SCOPE
bf49ba724655 bridge bridge local
f88f42dbcd4c docker_gwbridge bridge local
qcagnwr8f6xh dtr-ol overlay swarm
f34066c16e6a host host local
86zgov3fztu8 ingress overlay swarm
69826fd119d8 none null local
The output above shows the container networks that are created as part of a standard installation of Docker EE.
These networks are cluster-wide in Docker EE. You can run the
docker network lscommand on any other node and you will see the same output.
New networks that you create will also show up in the output of the docker network ls command.
You can see that each network gets a unique ID and NAME. Each network is also associated with a single driver. Notice that the "bridge" network and the "host" network have the same name as their respective drivers.
The docker network inspect command is used to view network configuration details. These details include; name, ID, driver, IPAM driver, subnet info, connected containers, and more.
Use docker network inspect <network> on manager1 to view configuration details of the container networks on your Docker host. The command below shows the details of the network called bridge.
$ docker network inspect bridge
[
{
"Name": "bridge",
"Id": "3430ad6f20bf1486df2e5f64ddc93cc4ff95d81f59b6baea8a510ad500df2e57",
"Created": "2017-04-03T16:49:58.6536278Z",
"Scope": "local",
"Driver": "bridge",
"EnableIPv6": false,
"IPAM": {
"Driver": "default",
"Options": null,
"Config": [
{
"Subnet": "172.17.0.0/16",
"Gateway": "172.17.0.1"
}
]
},
"Internal": false,
"Attachable": false,
"Containers": {},
"Options": {
"com.docker.network.bridge.default_bridge": "true",
"com.docker.network.bridge.enable_icc": "true",
"com.docker.network.bridge.enable_ip_masquerade": "true",
"com.docker.network.bridge.host_binding_ipv4": "0.0.0.0",
"com.docker.network.bridge.name": "docker0",
"com.docker.network.driver.mtu": "1500"
},
"Labels": {}
}
]
NOTE: The syntax of the
docker network inspectcommand isdocker network inspect <network>, where<network>can be either network name or network ID. In the example above we are showing the configuration details for the network called "bridge". Do not confuse this with the "bridge" driver.
Docker has a plugin system to enable different network topologies using different network drivers.
You can see all the installed plugins (for volumes, networks and logging) from the docker info command.
Run docker info on manager1 and locate the list of network plugins:
$ docker info
Containers: 31
Running: 27
Paused: 0
Stopped: 4
Images: 24
Server Version: 17.06.2-ee-11
...
Plugins:
Volume: local
Network: bridge host ipvlan macvlan null overlay
Log: awslogs fluentd gcplogs gelf journald json-file logentries splunk syslog
...
The output above shows the bridge, host, ipvlan, macvlan, null, and overlay drivers are installed. In this workshop you'll learn about the bridge and overlay networks.
Bridge networks are used for connecting Docker containers running on a single server. Containers connected to the same bridge network can reach each other, and they can also reach external resources that the server can access.
Every clean installation of Docker comes with a pre-built network called bridge. Verify this with the docker network ls command on manager1. filtering on the network driver:
$ docker network ls --filter driver=bridge
NETWORK ID NAME DRIVER SCOPE
bf49ba724655 bridge bridge local
f88f42dbcd4c docker_gwbridge bridge local
The output above shows two networks associated with the bridge driver:
-
bridge is a default network created when you install Docker, even in a single-node installation
-
docker_gwbridge is a default network created when you deploy UCP in Docker EE
The output above also shows that the bridge networks are scoped locally. This means that the network only exists on this Docker host. This is true of all networks using the bridge driver - the bridge driver provides single-host networking.
In a Docker EE cluster, these networks are replicated on all the nodes. Every node has its own bridge and docker_gwbridge network, but each is local to the node and there is no traffic between them.
All networks created with the bridge driver are based on a Linux bridge (a.k.a. a virtual switch).
The bridge network is the default network for new containers. This means that unless you specify a different network, all new containers will be connected to the bridge network.
Create a new bridge network on manager1 and call it br.
docker network create -d bridge br
This custom network only exists on node manager1. If you list the networks on another node, you will not see the new br network.
Now create a container called c1 and attach it to your new br network on manager1.
docker container run -itd --net br --name c1 alpine sh
This command will create a new container based on the alpine:latest image.
Running docker network inspect br will show the containers on that network.
$ docker network inspect br
[
{
"Name": "br",
"Id": "056b27c1488e56bda4e11ca0937166f0512031cddd4f4b68ff5bb2a1d11b136a",
"Created": "2018-05-23T10:53:43.594987763Z",
"Scope": "local",
"Driver": "bridge",
...
"Containers": {
"f849e0f45933da5f2324f132ed6224511fc6c8ea95532858ee6753a2a1054746": {
"Name": "c1",
"EndpointID": "f43ccc304a907615fd341b195d2bcce5761c0ab4b9f19ae52a24e56b25b29eb0",
"MacAddress": "02:42:ac:14:00:02",
"IPv4Address": "172.20.0.2/16",
"IPv6Address": ""
}
},
...
}
]
The output to the previous docker network inspect command shows the IP address of the new container. In the previous example it is 172.20.0.2 but yours might be different.
You can get the container's IP address for the br network by inspecting the container and formatting the response:
docker container inspect c1 --format "{{ .NetworkSettings.Networks.br.IPAddress }}"
Ping the IP address of the container from the shell prompt of your Docker host by running ping -c 3 <IPv4 Address> on node0. Remember to use the IP of the container in your environment.
You can get the IP address of the c1 container directly from the Docker engine by running docker inspect --format "{{ .NetworkSettings.Networks.br.IPAddress }}" c1.
$ ping -c 3 172.20.0.2
PING 172.20.0.2 (172.20.0.2) 56(84) bytes of data.
64 bytes from 172.20.0.2: icmp_seq=1 ttl=64 time=0.087 ms
64 bytes from 172.20.0.2: icmp_seq=2 ttl=64 time=0.067 ms
64 bytes from 172.20.0.2: icmp_seq=3 ttl=64 time=0.048 ms
...
The replies above show that the Docker host can ping the container over the bridge network. But, we can also verify the container can connect to the outside world too.
Enter in to the c1 container that you created using the command docker container exec. We will pass the sh command to container exec which puts us in to an interactive shell inside the container.
Enter in to the container and inspect the interfaces of the container:
$ docker exec -it c1 sh
# ip addr show | grep inet
inet 127.0.0.1/8 scope host lo
inet 172.20.0.2/16 scope global eth
The IP address of the container is accessible from the host. Now prove that containers can gain outside access by pinging www.docker.com.
# ping -c 3 www.docker.com
PING www.docker.com (52.85.101.235): 56 data bytes
64 bytes from 52.85.101.235: seq=0 ttl=237 time=7.428 ms
64 bytes from 52.85.101.235: seq=1 ttl=237 time=7.451 ms
64 bytes from 52.85.101.235: seq=2 ttl=237 time=7.406 ms
Exit out of the container.
# exit
Now you will create a second container on this bridge so you can test connectivity between them.
docker container run -itd --net br --name c2 alpine sh
Containers c1 and c2 are connected to the same bridge network, so they are visible to each other and to the Docker host.
Use docker container exec to ping the IP address of the c1 container from c2:
$ docker container exec -it c2 ping -c 2 172.20.0.2
PING 172.20.0.2 (172.20.0.2): 56 data bytes
64 bytes from 172.20.0.2: seq=0 ttl=64 time=0.072 ms
64 bytes from 172.20.0.2: seq=1 ttl=64 time=0.070 ms
...
Now ping container c1 using it's name:
$ docker container exec -it c2 ping -c 2 c1
PING c1 (172.20.0.2): 56 data bytes
64 bytes from 172.20.0.2: seq=0 ttl=64 time=0.095 ms
64 bytes from 172.20.0.2: seq=1 ttl=64 time=0.108 ms
...
The Docker engine provides DNS resolution automatically for all container names and service names.
We've been running containers directly on the manager1 node, using a private network on that node. Connect to worker1 and verify that the container isn't accessible on that node:
$ ping -c 2 -W 2 172.20.0.2
PING 172.20.0.2 (172.20.0.2) 56(84) bytes of data.
--- 172.20.0.2 ping statistics ---
2 packets transmitted, 0 received, 100% packet loss, time 1003ms
The container IP address is private to the host when you're using bridge networking.
Now switch back to manager1 and remove the containers:
docker rm -f c1
docker rm -f c2
In this step we'll start a new NGINX container and map port 8000 on the Docker host to port 80 inside of the container. This means that traffic that hits the Docker host on port 8000 will be passed on to port 80 inside the container.
NOTE: If you start a new container from the official NGINX image without specifying a command to run, the container will run a basic web server on port 80.
Start a new container based off the official NGINX image by running a container on manager1.
docker container run --name web1 -d -p 8000:80 nginx:alpine
Review the container status and port mappings by running docker container ls on manager1, filtering fot the web container name:
$ docker container ls --filter name=web1
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
62782dc5f612 nginx:alpine "nginx -g 'daemon ..." 30 seconds ago Up 29 seconds 0.0.0.0:8000->80/tcp web1
The top line shows the new web1 container running NGINX. Take note of the command the container is running as well as the port mapping - 0.0.0.0:8000->80/tcp maps port 8000 on all host interfaces to port 80 inside the web1 container. This port mapping is what effectively makes the containers web service accessible from external sources (via the Docker hosts IP address on port 8000).
Now that the container is running and mapped to a port on a host interface you can test connectivity to the NGINX web server, by browsing to the master node.
IN the PWD session information, you will see the UCP Hostname listed - it will be a long domain, something like ip172-18-0-6-bc2m2d8qitt0008vqor0.direct.beta-hybrid.play-with-docker.com. Browse to port 8000 at that address and you will see Nginx running - Docker receives the request and routes it into the container.
NOTE: The port mapping is actually port address translation (PAT).
Overlay networks span all the nodes in a Docker swarm mode cluster. Docker EE is built on top of swarm mode. You have multiple nodes in your lab environment so you can verify that containers in an overlay network can reach it other, even if they are running on different hosts.
Run docker node ls on manager1 to verify that you have multiple active nodes in the swarm:
$ docker node ls
ID HOSTNAME STATUS AVAILABILITY MANAGER STATUS
lo6fasr4izuz6okhm411vmyu3 * manager1 Ready Active Leader
o0b82a6jwp3jfibixttb06fk8 worker3 Ready Active
u4xc7yyu1j8hrea4dudr51ncx worker2 Ready Active
wuy5h23ly2y4wx5ccrjiscohv worker1 Ready Active
The ID and HOSTNAME values may be different in your lab. The important thing to check is that both nodes have joined the Swarm and are ready and active.
Now that you have a Swarm initialized it's time to create an overlay network.
Create a new overlay network called overnet by running docker network create -d overlay overnet on manager1.
$ docker network create -d overlay overnet
wlqnvajmmzskn84bqbdi1ytuy
Use the docker network ls command to verify the network was created successfully:
$ docker network ls --filter name=overnet
NETWORK ID NAME DRIVER SCOPE
2s4a0n00wdhd overnet overlay swarm
The new "overnet" network is associated with the overlay driver and is scoped to the entire swarm - compare this to the bridge and nat networks which are locally scoped to a single node.
Run the docker network ls command on worker1 to show all the overlay networks:
$ docker network ls --filter driver=overlay
NETWORK ID NAME DRIVER SCOPE
55f10b3fb8ed bridge bridge local
b7b30433a639 docker_gwbridge bridge local
a7449465c379 host host local
8hq1n8nak54x ingress overlay swarm
06c349b9cc77 none null local
The overnet network is not in the list. This is because Docker only extends overlay networks to hosts when they are needed. This is usually when a host runs a task from a service that is created on the network. We will see this shortly.
Use the docker network inspect command to view more detailed information about the "overnet" network. You will need to run this command from manager1.
$ docker network inspect overnet
[
{
"Name": "overnet",
"Id": "wlqnvajmmzskn84bqbdi1ytuy",
"Created": "0001-01-01T00:00:00Z",
"Scope": "swarm",
"Driver": "overlay",
"EnableIPv6": false,
"IPAM": {
"Driver": "default",
"Options": null,
"Config": []
},
"Internal": false,
"Attachable": false,
"Containers": null,
"Options": {
"com.docker.network.driver.overlay.vxlanid_list": "4097"
},
"Labels": null
}
]
Now that we have an overlay network in our Docker EE cluster, it's time to create a service that uses the network.
Execute the following command from manager1 to create a new service called ubuntu on the overnet network with two tasks/replicas.
docker service create --name ubuntu --detach \
--network overnet \
--replicas 6 \
sixeyed/ubuntu-with-utils sleep infinity
Verify that the service is created and both replicas are up by running docker service ls and filtering on the service name:
$ docker service ls --filter name=ubuntu
ID NAME MODE REPLICAS IMAGE PORTS
yxt9w3573qb5 ubuntu replicated 6/6 sixeyed/ubuntu-with-utils:latest ubuntu:latest
The 6/6 in the REPLICAS column shows that all the tasks in the service are up and running.
Verify that the tasks (replicas) are running on different swarm nodes docker service ps:
$ docker service ps ubuntu
ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ERROR PORTS
5z0u26v62qof ubuntu.1 sixeyed/ubuntu-with-utils:latest worker2 Running Running about a minute ago
ph7ps3273w5m ubuntu.2 sixeyed/ubuntu-with-utils:latest manager1 Running Running about a minute ago
tueyl7niinsb ubuntu.3 sixeyed/ubuntu-with-utils:latest worker3 Running Running about a minute ago
...
The ID and NODE values will be different in your output. The important thing to note is that every Linux node is running at least one replica, which means multiple containers across the swarm, all connected to the same overlay network.
Now that all the nodes are running tasks on the "overnet" network, you will be able to see that network from every node. Connect to worker2 and verify that by running docker network ls and filtering for overlay networks:
$ docker network ls --filter driver=overlay
NETWORK ID NAME DRIVER SCOPE
jfy2cbcbw567 ingress overlay swarm
j20kcrvwhqw4 overnet overlay swarm
You'll learn about the ingress network later in this workshop.
We can also run docker network inspect overnet on worker2 to get more detailed information about the "overnet" network and obtain the IP address of the task:
$ docker network inspect overnet
[
{
"Name": "overnet",
"Id": "j20kcrvwhqw45ujxay2m7q1af",
"Created": "2018-05-23T15:19:36.669608649Z",
"Scope": "swarm",
"Driver": "overlay",
"EnableIPv6": false,
"IPAM": {
"Driver": "default",
"Options": null,
"Config": [
{
"Subnet": "10.0.0.0/24",
"Gateway": "10.0.0.1"
}
]
},
...
"Containers": {
"67264d255b873567c30375e8d021146cbae7c0a162c9297d143471fd14e0ce54": {
"Name": "ubuntu.5.4rrqbneiay7uau63m07blofh5",
"EndpointID": "a1530106c077896f4c24ae7054039a9ea728ae72831955802e92ac8c3bf31075",
"MacAddress": "02:42:0a:00:00:0b",
"IPv4Address": "10.0.0.11/24",
"IPv6Address": ""
}
...
The subnet is specific to the overnet network in the swarm. In this case it is 10.0.0.0/24, which means any containers attached to the network will have an IP address in the range 10.0.0.1 to 10.0.0.254.
You should note that docker network inspect only shows containers/tasks running on the local node. This means that 10.0.0.11 is the IPv4 address of the container running on worker2. Make a note of this IP address for the next step (the IP address in your lab might be different than the one shown here in the lab guide).
To complete this step you will need the IP address of the service task running on the worker that you saw in the previous step (in this example it was 10.0.0.11).
Execute the following commands from worker3, to verify that containers on this node can connect to containers running on worker2.
Store the ID of the service task container to a varable:
id=$(docker container ls --last 1 --format "{{ .ID }}")
And now confirm you can ping the container running on worker3 from the container running on worker2:
$ docker container exec $id ping -c 2 10.0.0.11
PING 10.0.0.11 (10.0.0.11) 56(84) bytes of data.
64 bytes from 10.0.0.11: icmp_seq=1 ttl=64 time=0.163 ms
64 bytes from 10.0.0.11: icmp_seq=2 ttl=64 time=0.174 ms
The output above shows that all the tasks from the ubuntu service are on the same overlay network spanning multiple nodes and that they can use this network to communicate.
Now that you have a working service using an overlay network, let's test service discovery.
Still on worker2, use the container ID you have stored to see how DNS resolution is configured in containers. Run cat /etc/resolv.conf:
$ docker container exec $id cat /etc/resolv.conf
search i4it0iff0fxurmesl4lntkyo2a.bx.internal.cloudapp.net
nameserver 127.0.0.11
options ndots:0 ndots:0
The value that we are interested in is the nameserver 127.0.0.11. This value sends all DNS queries from the container to an embedded DNS resolver running inside the container listening on 127.0.0.11:53. All Docker container run an embedded DNS server at this address.
NOTE: Some of the other values in your file may be different to those shown in this guide.
Try and ping the "ubuntu" name from within the container by running ping -c2 ubuntu.
$ docker container exec $id ping -c 2 ubuntu
PING ubuntu (10.0.0.2) 56(84) bytes of data.
64 bytes from 10.0.0.2: icmp_seq=1 ttl=64 time=0.038 ms
64 bytes from 10.0.0.2: icmp_seq=2 ttl=64 time=0.041 ms
...
The output clearly shows that the container can ping the ubuntu service by name. Notice that the IP address returned is 10.0.0.2. In the next few steps we'll verify that this address is the virtual IP (VIP) assigned to the ubuntu service.
Inspect the configuration of the service by running docker service inspect ubuntu on the manager node manager1. Lets verify that the VIP value matches the value returned by the previous ping command.
$ docker service inspect ubuntu
[
{
"ID": "sua78ut856kq2h1q0dq1lbxik",
"Version": {
"Index": 242
},
"CreatedAt": "2018-06-01T10:43:43.491494388Z",
"UpdatedAt": "2018-06-01T10:43:43.493785595Z",
"Spec": {
"Name": "ubuntu",
"Labels": {},
"TaskTemplate": {
"ContainerSpec": {
"Image": "sixeyed/ubuntu-with-utils:latest@sha256:d6d109a6bc6b610992a9923b6089400e5150bbdc10539d1c1a8f67381bd7f738",
"Args": [
"sleep",
"infinity"
],
"StopGracePeriod": 10000000000,
"DNSConfig": {}
},
...
"EndpointSpec": {
"Mode": "vip"
}
},
"Endpoint": {
"Spec": {
"Mode": "vip"
},
"VirtualIPs": [
{
"NetworkID": "ke2flaxd3nby3zm0bs0fc4dng",
"Addr": "10.0.0.2/24"
}
]
}
}
]
Towards the bottom of the output you will see the VIP of the service listed. The VIP in the output above is 10.0.0.2 but the value may be different in your setup. The important point to note is that the VIP listed here matches the value returned by the ping command.
Now that you're connected to manager1 you can repeate the same ping command using the container running on the manager - you will get a response form the same VIP:
$ id=$(docker container ls --last 1 --format "{{ .ID }}")
$ docker container exec $id ping -c 2 ubuntu
PING ubuntu (10.0.0.2) 56(84) bytes of data.
64 bytes from 10.0.0.2: icmp_seq=1 ttl=64 time=0.046 ms
64 bytes from 10.0.0.2: icmp_seq=2 ttl=64 time=0.043 ms
...
Now let's create a service that utilizes Routing Mesh and the ingress network. Here you'll be creating a single task service that exposes port 5000 on the ingress network.
Create the service with a single replica, using the manager1 node:
docker service create -p 5000:5000 -d --name pets --replicas=1 nicolaka/pets_web:1.0
Browse to UCP and using the left navigation click on Swarm...Services. You'll see the pets service in the list - click on the service and in the details panel on the right you can see a link to the published endpoint:
Click the link and the app will open in a new browser tab:
The domain name you're browsing to is the UCP manager node. The ingress network receives the request and routes it to one of the service tasks - any node in the cluster can respond to the request by internally routing it to a container.
Try scaling up the service. In UCP select the pets service and click Configure:
Select the Scheduling section, and run more tasks by setting the Scale level to 10:
Click save and UCP returns to the service list. The service is scaling up and you can see the container list by clicking on Inspect Resource...Containers:
You'll see containers running on nodes across the cluster. Now refresh the tab with the Pets website. Each time you refresh you'll see a different container ID. Docker swarm load-balances requests across all the tasks in the service.
Delete swarm mode services created above:
docker service rm pets
docker service rm ubuntu
docker network rm overnet
Next we'll move onto networking in Kubernetes. You'll learn how to use Kubernetes in Docker EE to enforce network policies, and restrict which containers can access other containers.