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Website: substantial rewrite of intro/getting-started/join.html.

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Ryan Breen 10 years ago
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4
website/source/intro/getting-started/agent.html.markdown
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@ -108,7 +108,7 @@ $ dig @127.0.0.1 -p 8600 Armons-MacBook-Air.node.consul
Armons-MacBook-Air.node.consul. 0 IN A 10.1.10.38 Armons-MacBook-Air.node.consul. 0 IN A 10.1.10.38
``` ```
## Stopping the Agent ## <a name="stopping"></a>Stopping the Agent
You can use `Ctrl-C` (the interrupt signal) to gracefully halt the agent. You can use `Ctrl-C` (the interrupt signal) to gracefully halt the agent.
After interrupting the agent, you should see it leave the cluster After interrupting the agent, you should see it leave the cluster
@ -130,5 +130,5 @@ and remove servers.
## Next Steps ## Next Steps
Your simple Consul cluster is up and running. Let's give it some Your simple Consul cluster is up and running. Let's give it some
[services](services.html)! [services](services.html)!

150
website/source/intro/getting-started/join.html.markdown
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@ -3,19 +3,18 @@ layout: "intro"
page_title: "Consul Cluster" page_title: "Consul Cluster"
sidebar_current: "gettingstarted-join" sidebar_current: "gettingstarted-join"
description: |- description: |-
By this point, we've started our first agent and registered and queried one or more services on that agent. This showed how easy it is to use Consul, but didn't show how this could be extended to a scalable production service discovery infrastructure. On this page, we'll create our first real cluster with multiple members. We've started our first agent and registered and queried a service on that agent. This showed how easy it is to use Consul but didn't show how this could be extended to a scalable, production-grade service discovery infrastructure. In this step, we'll create our first real cluster with multiple members.
--- ---
# Consul Cluster # Consul Cluster
By this point, we've started our first agent and registered and queried We've started our first agent and registered and queried a service on that
one or more services on that agent. This showed how easy it is to use agent. This showed how easy it is to use Consul but didn't show how this could
Consul, but didn't show how this could be extended to a scalable production be extended to a scalable, production-grade service discovery infrastructure.
service discovery infrastructure. On this page, we'll create our first In this step, we'll create our first real cluster with multiple members.
real cluster with multiple members.
When a Consul agent is started, it begins without knowledge of any other node, When a Consul agent is started, it begins without knowledge of any other node:
and is an isolated cluster of one. To learn about other cluster members, the it is an isolated cluster of one. To learn about other cluster members, the
agent must _join_ an existing cluster. To join an existing cluster, it only agent must _join_ an existing cluster. To join an existing cluster, it only
needs to know about a _single_ existing member. After it joins, the agent will needs to know about a _single_ existing member. After it joins, the agent will
gossip with this member and quickly discover the other members in the cluster. gossip with this member and quickly discover the other members in the cluster.
@ -23,59 +22,97 @@ A Consul agent can join any other agent, not just agents in server mode.
## Starting the Agents ## Starting the Agents
To simulate a more realistic cluster, we are using a two node cluster in To simulate a more realistic cluster, we will start a two node cluster via
Vagrant. The Vagrantfile can be found in the demo section of the repo [Vagrant](https://www.vagrantup.com/). The Vagrantfile we will be using can
[here](https://github.com/hashicorp/consul/tree/master/demo/vagrant-cluster). be found in the [demo section of the Consul repo]
(https://github.com/hashicorp/consul/tree/master/demo/vagrant-cluster).
We start the first agent on our first node and also specify a node name. We first boot our two nodes:
The node name must be unique and is how a machine is uniquely identified.
By default it is the hostname of the machine, but we'll manually override it.
We are also providing a bind address. This is the address that Consul listens on,
and it *must* be accessible by all other nodes in the cluster. The first node
will act as our server in this cluster. We're still not making a cluster
of servers.
```text ```text
$ consul agent -server -bootstrap-expect 1 -data-dir /tmp/consul \ $ vagrant up
-node=agent-one -bind=172.20.20.10 ```
Once the systems are available, we can ssh into them to begin configuration
of our cluster. We start by logging in to the first node:
```text
$ vagrant ssh n1
```
Each node in a cluster must have a unique name. By default, Consul uses the
hostname of the machine, but we'll manually override it using the [`-node`
command-line option](/docs/agent/options.html#_node).
We will also specify a [`bind` address](/docs/agent/options.html#_bind):
this is the address that Consul listens on, and it *must* be accessible by
all other nodes in the cluster. While a `bind` address is not strictly
necessary (Consul will by default listen on the first private IP on a
system), it's always best to provide one. Production servers often have
multiple interfaces, so specifying a `bind` address insures that you will
never bind Consul to the wrong interface.
The first node will act as our sole server in this cluster, and we indicate
this with the [`server` switch](/docs/agent/options.html#_server).
All together, these settings yield a
[`consul agent`](/docs/commands/agent.html) command like this:
```text
vagrant@n1:~$ consul agent -server -bootstrap-expect 1 \
-data-dir /tmp/consul -node=agent-one -bind=172.20.20.10
... ...
``` ```
Then, in another terminal, start the second agent on the new node. Now, in another terminal, we will connect to the second node:
This time, we set the bind address to match the IP of the second node
as specified in the Vagrantfile. In production, you will generally want ```text
to provide a bind address or interface as well. $ vagrant ssh n2
```
This time, we set the [`bind` address](/docs/agent/options.html#_bind)
address to match the IP of the second node as specified in the Vagrantfile
and the [`node` name](/docs/agent/options.html#_node) to be `agent-two`.
Since this node will not be a Consul server, we don't provide a
[`server` switch](/docs/agent/options.html#_server).
All together, these settings yield a
[`consul agent`](/docs/commands/agent.html) command like this:
```text ```text
$ consul agent -data-dir /tmp/consul -node=agent-two -bind=172.20.20.11 vagrant@n2:~$ consul agent -data-dir /tmp/consul -node=agent-two \
-bind=172.20.20.11
... ...
``` ```
At this point, you have two Consul agents running, one server and one client. At this point, you have two Consul agents running: one server and one client.
The two Consul agents still don't know anything about each other, and are each part of their own The two Consul agents still don't know anything about each other and are each
clusters (of one member). You can verify this by running `consul members` part of their own single-node clusters. You can verify this by running
against each agent and noting that only one member is a part of each. [`consul members`](/docs/commands/members.html) against each agent and noting
that only one member is visible to each agent.
## Joining a Cluster ## Joining a Cluster
Now, let's tell the first agent to join the second agent by running Now, we'll tell the first agent to join the second agent by running
the following command in a new terminal: the following commands in a new terminal:
```text ```text
$ consul join 172.20.20.11 $ vagrant ssh n1
...
vagrant@n1:~$ consul join 172.20.20.11
Successfully joined cluster by contacting 1 nodes. Successfully joined cluster by contacting 1 nodes.
``` ```
You should see some log output in each of the agent logs. If you read You should see some log output in each of the agent logs. If you read
carefully, you'll see that they received join information. If you carefully, you'll see that they received join information. If you
run `consul members` against each agent, you'll see that both agents now run `consul members` against each agent, you'll see that both agents
know about each other: now know about each other:
```text ```text
$ consul members -detailed vagrant@n2:~$ consul members
Node Address Status Tags Node Address Status Type Build Protocol
agent-one 172.20.20.10:8301 alive role=consul,dc=dc1,vsn=2,vsn_min=1,vsn_max=2,port=8300,bootstrap=1 agent-two 172.20.20.11:8301 alive client 0.5.0 2
agent-two 172.20.20.11:8301 alive role=node,dc=dc1,vsn=2,vsn_min=1,vsn_max=2 agent-one 172.20.20.10:8301 alive server 0.5.0 2
``` ```
-> **Remember:** To join a cluster, a Consul agent only needs to -> **Remember:** To join a cluster, a Consul agent only needs to
@ -83,16 +120,27 @@ learn about <em>one existing member</em>. After joining the cluster, the
agents gossip with each other to propagate full membership information. agents gossip with each other to propagate full membership information.
## Auto-joining a Cluster on Start ## Auto-joining a Cluster on Start
Ideally whenever a new node is brought up in your datacenter, it should automatically join the Consul cluster without human intervention. To accomplish this, you can use [Atlas by HashiCorp](https://atlas.hashicorp.com?utm_source=oss&utm_medium=getting-started-join&utm_campaign=consul) and the [`-atlas-join` flag](/docs/agent/options.html#_atlas_join). An example configuration is shown below: Ideally, whenever a new node is brought up in your datacenter, it should
automatically join the Consul cluster without human intervention. To
accomplish this, you can use
[Atlas by HashiCorp](https://atlas.hashicorp.com?utm_source=oss&utm_medium=getting-started-join&utm_campaign=consul)
and the [`-atlas-join` flag](/docs/agent/options.html#_atlas_join).
An example configuration is shown below:
```text ```text
$ consul agent -atlas-join \ $ consul agent -atlas-join \
-atlas=ATLAS_USERNAME/infrastructure \ -atlas=ATLAS_USERNAME/infrastructure \
-atlas-token="YOUR_ATLAS_TOKEN" -atlas-token="YOUR_ATLAS_TOKEN"
``` ```
To get an Atlas username and token, [create an account here](https://atlas.hashicorp.com/account/new?utm_source=oss&utm_medium=getting-started-join&utm_campaign=consul) and replace the respective values in your Consul configuration with your credentials. Now whenever a new node comes up with a Consul agent, it automatically joins your Consul cluster without any hardcoded configurations. To get an Atlas username and token,
[create an account](https://atlas.hashicorp.com/account/new?utm_source=oss&utm_medium=getting-started-join&utm_campaign=consul)
Alternatively, you can use the [`-join` flag](http://www.consul.io/docs/agent/options.html#_join) and replace the respective values in your Consul configuration with your
credentials. Now, whenever a new node comes up with a Consul agent, it
will automatically join your Consul cluster without any hardcoded
configuration.
Alternatively, you can use the
[`-join` flag](http://www.consul.io/docs/agent/options.html#_join)
with a hardcoded address of a known Consul agent to join a cluster. with a hardcoded address of a known Consul agent to join a cluster.
## Querying Nodes ## Querying Nodes
@ -104,10 +152,11 @@ For the DNS API, the structure of the names is `NAME.node.consul` or
`NAME.node.DATACENTER.consul`. If the datacenter is omitted, Consul `NAME.node.DATACENTER.consul`. If the datacenter is omitted, Consul
will only search the local datacenter. will only search the local datacenter.
From "agent-one", query "agent-two": For example, from "agent-one", we can query for the address of the
node "agent-two":
``` ```
$ dig @127.0.0.1 -p 8600 agent-two.node.consul vagrant@n1:~$ dig @127.0.0.1 -p 8600 agent-two.node.consul
... ...
;; QUESTION SECTION: ;; QUESTION SECTION:
@ -119,13 +168,18 @@ agent-two.node.consul. 0 IN A 172.20.20.11
The ability to look up nodes in addition to services is incredibly The ability to look up nodes in addition to services is incredibly
useful for system administration tasks. For example, knowing the address useful for system administration tasks. For example, knowing the address
of the node to SSH into is as easy as making it part of the Consul cluster of the node to SSH into is as easy as making the node a part of the
and querying it. Consul cluster and querying it.
## Leaving a Cluster ## Leaving a Cluster
To leave the cluster, you can either gracefully quit an agent (using To leave the cluster, you can either gracefully quit an agent (using
`Ctrl-C`) or force kill one of the agents. Gracefully leaving allows `Ctrl-C`) or force kill one of the agents. Gracefully leaving allows
the node to transition into the _left_ state, otherwise other nodes the node to transition into the _left_ state; otherwise, other nodes
will detect it as having _failed_. The difference is covered will detect it as having _failed_. The difference is covered
in more detail [here](/intro/getting-started/agent.html#toc_3). in more detail [here](/intro/getting-started/agent.html#stopping).
## Next Steps
We now have a multi-node Consul cluster up and running. Let's make
our services more robust by giving them [health checks](checks.html)!

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