mirror of https://github.com/hashicorp/consul
71 lines
2.7 KiB
Markdown
71 lines
2.7 KiB
Markdown
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---
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layout: "docs"
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page_title: "Multiple Datacenters"
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sidebar_current: "docs-guides-datacenters"
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---
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# Multi-Datacenter Deploys
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One of the key features of Consul is it's support for multiple datacenters.
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The [architecture](/docs/internals/architecture.html) of Consul is designed to
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promote a low-coupling of datacenters, so that connectivity issues or
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failure of any datacenter does not impact the availability of Consul in other
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regions. This means each datacenter runs independently, with a dedicated
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group of servers and a private LAN [gossip pool](/docs/internals/gossip.html).
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To get started, we initially just [bootstrap](/docs/guides/bootstrapping.html) each
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datacenter individually. We should have at least two datacenters now, which
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we can refer to as `dc1` and `dc2`, although the names are opaque to Consul.
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The next step is to ensure that all the server nodes join the WAN gossip pool.
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To query the known WAN nodes, we use the `members` command:
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```
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$ consul members -wan
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...
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```
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This will provide a list of all known members in the WAN gossip pool. This should
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only contain server nodes. Client nodes do not participate, since they send requests
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to a datacenter-local server, which then forwards the request to a server in the target datacenter.
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The next step is to simply join all the servers in the WAN pool:
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```
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$ consul join -wan <server 1> <server 2> ...
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...
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```
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The `join` command is used with the `-wan` flag to indicate we are attempting
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to join a server in the WAN gossip pool. As with the LAN gossip, you only need
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to join a single existing member, and the gossip protocol will be used to exchange
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information about all known members. For the initial setup however, each server
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will only know about itself and must be added to the cluster.
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Once this is done the `members` command can be used to verify that
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all server nodes are known about. We can also verify that both datacenters
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are known using the HTTP API:
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```
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$ curl http://localhost:8500/v1/catalog/datacenters
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["dc1", "dc2"]
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```
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As a simple test, you can try to query the nodes in each datacenter:
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```
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$ curl http://localhost:8500/v1/catalog/nodes?dc=dc1
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...
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$ curl http://localhost:8500/v1/catalog/nodes?dc=dc2
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...
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```
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There are a few networking requirements that must be satisfied for this to
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work. Clearly, all server nodes must be able to talk to each other. Otherwise,
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the gossip protocol as well as RPC forwarding will not work. If service discovery
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is to be used across datacenters, then the network must be able to route traffic
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between IP addresses across regions as well. Usually, this means that all datacenters
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must be connected using a VPN or other tunneling mechanism. Consul does not handle
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VPN, address rewriting, or NAT traversal for you.
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