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Website: GH-730 and cleanup for docs/guides/datacenters.html

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Ryan Breen 2015-02-28 22:20:02 -05:00
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@ -3,24 +3,25 @@ layout: "docs"
page_title: "Multiple Datacenters" page_title: "Multiple Datacenters"
sidebar_current: "docs-guides-datacenters" sidebar_current: "docs-guides-datacenters"
description: |- description: |-
One of the key features of Consul is its support for multiple datacenters. The architecture of Consul is designed to promote a low-coupling of datacenters so that connectivity issues or failure of any datacenter does not impact the availability of Consul in other regions. This means each datacenter runs independently, with a dedicated group of servers and a private LAN gossip pool. One of the key features of Consul is its support for multiple datacenters. The architecture of Consul is designed to promote low coupling of datacenters so that connectivity issues or failure of any datacenter does not impact the availability of Consul in other datacenters. This means each datacenter runs independently, each having a dedicated group of servers and a private LAN gossip pool.
--- ---
# Multi-Datacenter Deploys # Multiple Datacenters
One of the key features of Consul is its support for multiple datacenters. One of the key features of Consul is its support for multiple datacenters.
The [architecture](/docs/internals/architecture.html) of Consul is designed to The [architecture](/docs/internals/architecture.html) of Consul is designed to
promote a low-coupling of datacenters so that connectivity issues or promote a low coupling of datacenters so that connectivity issues or
failure of any datacenter does not impact the availability of Consul in other failure of any datacenter does not impact the availability of Consul in other
regions. This means each datacenter runs independently, with a dedicated datacenters. This means each datacenter runs independently, each having a dedicated
group of servers and a private LAN [gossip pool](/docs/internals/gossip.html). group of servers and a private LAN [gossip pool](/docs/internals/gossip.html).
To get started, we initially just [bootstrap](/docs/guides/bootstrapping.html) each To get started, follow the [bootstraping guide](/docs/guides/bootstrapping.html) to
datacenter individually. We should have at least two datacenters now, which start each datacenter. After bootstrapping, we should have two datacenters now which
we can refer to as `dc1` and `dc2`, although the names are opaque to Consul. we can refer to as `dc1` and `dc2`. Note that datacenter names are opaque to Consul;
they are simply labels that help human operators reason about the Consul clusters.
The next step is to ensure that all the server nodes join the WAN gossip pool. To query the known WAN nodes, we use the [`members`](/docs/commands/members.html)
To query the known WAN nodes, we use the `members` command: command with the `-wan` parameter:
```text ```text
$ consul members -wan $ consul members -wan
@ -28,25 +29,28 @@ $ consul members -wan
``` ```
This will provide a list of all known members in the WAN gossip pool. This should This will provide a list of all known members in the WAN gossip pool. This should
only contain server nodes. Client nodes do not participate, since they send requests only contain server nodes. Client nodes send requests to a datacenter-local server,
to a datacenter-local server, which then forwards the request to a server in the target datacenter. so they do not participate in WAN gossip. Client requests are forwarded by local
servers to a server in the target datacenter as necessary.
The next step is to simply join all the servers in the WAN pool: The next step is to ensure that all the server nodes join the WAN gossip pool:
```text ```text
$ consul join -wan <server 1> <server 2> ... $ consul join -wan <server 1> <server 2> ...
... ...
``` ```
The `join` command is used with the `-wan` flag to indicate we are attempting The [`join`](/docs/commands/join.html) command is used with the `-wan` flag to indicate
to join a server in the WAN gossip pool. As with the LAN gossip, you only need we are attempting to join a server in the WAN gossip pool. As with LAN gossip, you only
to join a single existing member, and the gossip protocol will be used to exchange need to join a single existing member, and the gossip protocol will be used to exchange
information about all known members. For the initial setup however, each server information about all known members. For the initial setup, however, each server
will only know about itself and must be added to the cluster. will only know about itself and must be added to the cluster.
Once this is done the `members` command can be used to verify that Once the join is complete, the [`members`](/docs/commands/members.html) command can be
all server nodes are known about. We can also verify that both datacenters used to verify that all server nodes gossiping over WAN.
are known using the HTTP API:
We can also verify that both datacenters are known using the
[HTTP Catalog API](/docs/agent/http/catalog.html#catalog_datacenters):
```text ```text
$ curl http://localhost:8500/v1/catalog/datacenters $ curl http://localhost:8500/v1/catalog/datacenters
@ -63,9 +67,9 @@ $ curl http://localhost:8500/v1/catalog/nodes?dc=dc2
``` ```
There are a few networking requirements that must be satisfied for this to There are a few networking requirements that must be satisfied for this to
work. Clearly, all server nodes must be able to talk to each other. Otherwise, work. Of course, all server nodes must be able to talk to each other. Otherwise,
the gossip protocol as well as RPC forwarding will not work. If service discovery the gossip protocol as well as RPC forwarding will not work. If service discovery
is to be used across datacenters, then the network must be able to route traffic is to be used across datacenters, the network must be able to route traffic
between IP addresses across regions as well. Usually, this means that all datacenters between IP addresses across regions as well. Usually, this means that all datacenters
must be connected using a VPN or other tunneling mechanism. Consul does not handle must be connected using a VPN or other tunneling mechanism. Consul does not handle
VPN, address rewriting, or NAT traversal for you. VPN, address rewriting, or NAT traversal for you.