mirror of https://github.com/hashicorp/consul
79 lines
2.9 KiB
Markdown
79 lines
2.9 KiB
Markdown
---
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layout: "docs"
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page_title: "External Services"
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sidebar_current: "docs-guides-external"
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description: |-
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Very few infrastructures are entirely self-contained. Most rely on a multitude of external service providers. Consul supports this by allowing for the definition of external services, services that are not provided by a local node.
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---
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# Registering an External Service
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Very few infrastructures are entirely self-contained. Most rely on a multitude
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of external service providers. Consul supports this by allowing for the definition
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of external services, services that are not provided by a local node. There's also a
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companion project called [Consul ESM](https://github.com/hashicorp/consul-esm) which
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is a daemon that functions as an external service monitor that can help run health
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checks for external services.
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Most services are registered in Consul through the use of a
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[service definition](/docs/agent/services.html). However, this approach registers
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the local node as the service provider. In the case of external services, we must
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instead register the service with the catalog rather than as part of a standard
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node service definition.
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Once registered, the DNS interface will be able to return the appropriate A
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records or CNAME records for the service. The service will also appear in standard
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queries against the API. Consul must be configured with a list of
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[recursors](/docs/agent/options.html#recursors) for it to be able to resolve
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external service addresses.
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Let us suppose we want to register a "search" service that is provided by
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"www.google.com". We might accomplish that like so:
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```text
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$ curl -X PUT -d '{"Datacenter": "dc1", "Node": "google",
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"Address": "www.google.com",
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"Service": {"Service": "search", "Port": 80}}'
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http://127.0.0.1:8500/v1/catalog/register
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```
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Add an upstream DNS server to the list of recursors to Consul's configuration. Example with Google's public DNS server:
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```text
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"recursors":["8.8.8.8"]
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```
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If we do a DNS lookup now, we can see the new search service:
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```text
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; <<>> DiG 9.8.3-P1 <<>> @127.0.0.1 -p 8600 search.service.consul.
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; (1 server found)
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;; global options: +cmd
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;; Got answer:
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;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 13313
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;; flags: qr aa rd ra; QUERY: 1, ANSWER: 4, AUTHORITY: 0, ADDITIONAL: 0
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;; QUESTION SECTION:
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;search.service.consul. IN A
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;; ANSWER SECTION:
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search.service.consul. 0 IN CNAME www.google.com.
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www.google.com. 264 IN A 74.125.239.114
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www.google.com. 264 IN A 74.125.239.115
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www.google.com. 264 IN A 74.125.239.116
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;; Query time: 41 msec
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;; SERVER: 127.0.0.1#8600(127.0.0.1)
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;; WHEN: Tue Feb 25 17:45:12 2014
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;; MSG SIZE rcvd: 178
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```
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If at any time we want to deregister the service, we simply do:
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```text
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$ curl -X PUT -d '{"Datacenter": "dc1", "Node": "google"}' http://127.0.0.1:8500/v1/catalog/deregister
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```
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This will deregister the `google` node along with all services it provides.
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For more information, please see the [HTTP Catalog API](/api/catalog.html).
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