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website: agent getting started modifications

This commit is contained in:
Mitchell Hashimoto 2014-04-14 12:22:03 -07:00
parent 3b0e397851
commit 3e9ef7a122
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website/source/intro/getting-started/agent.html.markdown
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@ -7,8 +7,8 @@ sidebar_current: "gettingstarted-agent"
# Run the Consul Agent
After Consul is installed, the agent must be run. The agent can either run
in a server or client mode. Each datacenter must at least one server, and
a recommended 3 or 5. A single server deployment is _**highly**_ discouraged
in a server or client mode. Each datacenter must have at least one server,
although 3 or 5 is recommended. A single server deployment is _**highly**_ discouraged
as data loss is inevitable in a failure scenario. [This guide](/docs/guides/bootstrapping.html)
covers bootstrapping a new datacenter. All other agents run in client mode, which
is a very lightweight process that registers services, runs health checks,
@ -20,7 +20,7 @@ will be part of the cluster.
For simplicity, we'll run a single Consul agent in server mode right now:
```
$ ./bin/consul agent -server -bootstrap -data-dir /tmp/consul
$ consul agent -server -bootstrap -data-dir /tmp/consul
==> WARNING: Bootstrap mode enabled! Do not enable unless necessary
==> WARNING: It is highly recommended to set GOMAXPROCS higher than 1
==> Starting Consul agent...
@ -63,40 +63,33 @@ $ consul members
Armons-MacBook-Air 10.1.10.38:8301 alive role=consul,dc=dc1,vsn=1,vsn_min=1,vsn_max=1,port=8300,bootstrap=1
```
This command, along with many others, communicates with a running Consul
agent via an internal RPC protocol. When starting the Consul agent, you
may have noticed that it tells you the "RPC addr". This is the address
that commands such as `consul members` use to communicate with the agent.
The output shows our own node, the address it is running on, its
health state, and some metadata associated with the node. Some important
metadata keys to recognize are the `role` and `dc` keys. These tell you
the service name and the datacenter that member is within. These can be
used to lookup nodes and services using the DNS interface, which is covered
shortly.
By default, RPC listens only on loopback, so it is inaccessible outside
of your machine for security reasons.
If you're changed the default RPC address, you'll have to specify
an `-rpc-addr` to both the agent and any commands so that it doesn't
collide with other agents.
It is important to note that the output of the `members` command is
generated by from the [gossip protocol](/docs/internals/gossip.html),
and is eventually consistent. Consul uses this to maintain a strongly
consistent catalog of nodes that can be queried using the [HTTP API](/docs/agent/http.html):
The output from the `members` command is generated based on the
[gossip protocol](/docs/internals/gossip.html) and is eventually consistent.
For a strongly consistent view of the world, use the
[HTTP API](/docs/agent/http.html), which forwards the request to the
Consul servers:
```
$ curl localhost:8500/v1/catalog/nodes
[{"Node":"Armons-MacBook-Air","Address":"10.1.10.38"}]
```
Alternatively, the [DNS interface](/docs/agent/dns.html) could be used:
In addition to the HTTP API, the
[DNS interface](/docs/agent/dns.html) can be used to query the node. Note
that you have to make sure to point your DNS lookups to the Consul agent's
DNS server, which runs on port 8600 by default. The format of the DNS
entries (such as "Armons-MacBook-Air.node.consul") will be covered later.
```
$ dig @127.0.0.1 -p 8600 Armons-MacBook-Air.node.consul
; <<>> DiG 9.8.3-P1 <<>> @127.0.0.1 -p 8600 Armons-MacBook-Air.node.consul
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 63911
;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
;; WARNING: recursion requested but not available
...
;; QUESTION SECTION:
;Armons-MacBook-Air.node.consul. IN A