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website: finishing up getting started
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Armon Dadgar
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@ -6,3 +6,109 @@ sidebar_current: "gettingstarted-kv"
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# Key/Value Data
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In addition to providing service discovery and integrated health checking,
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Consul provides an easy to use Key/Value store. This can be used to hold
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dynamic configuration, assist in service coordination, build leader election,
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and any thing else a developer can think to build. The [HTTP API](/docs/agent/http.html) fully
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documents the features of the K/V store.
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## Simple Usage
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To demonstrate how simple it is to get started, we will manipulate a few keys
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in the K/V store. We get started by first starting an agent in server mode:
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```
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$ ./bin/consul agent -server -bootstrap -data-dir /tmp/consul
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...
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```
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Now, we can verify that our K/V store contains no keys:
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```
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$ curl -v http://localhost:8500/v1/kv/?recurse
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* About to connect() to localhost port 8500 (#0)
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* Trying 127.0.0.1... connected
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> GET /v1/kv/?recurse HTTP/1.1
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> User-Agent: curl/7.22.0 (x86_64-pc-linux-gnu) libcurl/7.22.0 OpenSSL/1.0.1 zlib/1.2.3.4 libidn/1.23 librtmp/2.3
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> Host: localhost:8500
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> Accept: */*
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>
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< HTTP/1.1 404 Not Found
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< X-Consul-Index: 1
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< Date: Fri, 11 Apr 2014 02:10:28 GMT
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< Content-Length: 0
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< Content-Type: text/plain; charset=utf-8
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<
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* Connection #0 to host localhost left intact
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* Closing connection #0
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```
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Since there are no keys, we get a 404 response back. Now, we can put a few example keys:
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```
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$ curl -X PUT -d 'test' http://localhost:8500/v1/kv/web/key1
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true
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$ curl -X PUT -d 'test' http://localhost:8500/v1/kv/web/key2?flags=42
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true
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$ curl -X PUT -d 'test' http://localhost:8500/v1/kv/web/sub/key3
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true
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$ curl http://localhost:8500/v1/kv/?recurse
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[{"CreateIndex":97,"ModifyIndex":97,"Key":"web/key1","Flags":0,"Value":"dGVzdA=="},
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{"CreateIndex":98,"ModifyIndex":98,"Key":"web/key2","Flags":42,"Value":"dGVzdA=="},
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{"CreateIndex":99,"ModifyIndex":99,"Key":"web/sub/key3","Flags":0,"Value":"dGVzdA=="}]
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```
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Here we have created 3 keys, each with the value of "test". Note that the `Value` field
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returned is base64 encoded to encode non UTF8 characters. For the "web/key2" key, we set
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a `flag` value of 42. All keys support setting a 64bit integer flag value. This is opaque
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to Consul but can be used by clients.
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Above we retrieved multiple keys using the "?recurse" query parameter, but fetching
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a single key is done by providing the path alone:
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```
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$ curl http://localhost:8500/v1/kv/web/key1
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[{"CreateIndex":97,"ModifyIndex":97,"Key":"web/key1","Flags":0,"Value":"dGVzdA=="}]
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```
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Deleting keys is simple as well. We can delete a single key by specifying the full
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path, or we can recursively delete all keys under a root using "?recurse":
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```
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$ curl -X DELETE http://localhost:8500/v1/kv/web/sub?recurse
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$ curl http://localhost:8500/v1/kv/web?recurse
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[{"CreateIndex":97,"ModifyIndex":97,"Key":"web/key1","Flags":0,"Value":"dGVzdA=="},
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{"CreateIndex":98,"ModifyIndex":98,"Key":"web/key2","Flags":42,"Value":"dGVzdA=="}]
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```
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A key can be updated by setting a new value. Additionally, Consul provides a Check-And-Set
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operation, that enables an atomic key update. This is done by providing the "?cas=" parameter
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with the last `ModifyIndex` value. For example, suppose we wanted to update "web/key1":
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```
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$ curl -X PUT -d 'newval' http://localhost:8500/v1/kv/web/key1?cas=97
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true
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$ curl -X PUT -d 'newval' http://localhost:8500/v1/kv/web/key1?cas=97
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false
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```
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In this case, the first CAS update succeeds because the last modify time is 97.
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However the second operation fails because the `ModifyIndex` is no longer 97.
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We can also make use of the `ModifyIndex` to wait for a key's value to change.
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For example, suppose we wanted to wait for key2 to be modified:
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```
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$ curl "http://localhost:8500/v1/kv/web/key2?index=101&wait=5s"
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[{"CreateIndex":98,"ModifyIndex":101,"Key":"web/key2","Flags":42,"Value":"dGVzdA=="}]
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```
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By providing "?index=" we are asking to wait until the key has a `ModifyIndex` greater
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than 101. However the "?wait=5s" parameter restricts the query to at most 5 seconds,
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returning the current, unchanged value. This can be used to efficiently wait for
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key modifications. Additionally, this same technique can be used to wait for a list
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of keys, waiting only until any of the keys has a newer modification time.
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This is only a few example of what the API supports. For full documentation, please
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reference the [HTTP API](/docs/agent/http.html).
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@ -6,21 +6,22 @@ sidebar_current: "gettingstarted-nextsteps"
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# Next Steps
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That concludes the getting started guide for Serf. Hopefully you're able to
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see that while Serf is an incredibly simple tool, it is also extremely
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powerful. The dead simple membership information and events system that
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Serf provides make up the building blocks of [incredible use cases](/intro/use-cases.html).
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That concludes the getting started guide for Consul. Hopefully you're able to
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see that while Consul is simple to use, it has a powerful set of features.
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And because Serf is completely decentralized, fault tolerant, self-healing,
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etc. it is a dream tool for system administrators and built specifically
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for modern, elastic infrastructures.
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Consul is designed to be friendly to both the DevOps community and
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application developers, making it perfect for modern, elastic infrastructures.
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As a next step, the following resources are available:
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* [Documentation](/docs/index.html) - The documentation is an in-depth reference
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guide to all the features of Serf, including technical details about the
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internals of how Serf operates.
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guide to all the features of Consul, including technical details about the
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internals of how Consul operates.
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* [Guides](/docs/guides/index.html) - This section provides various getting
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started guides with Consul, including how to bootstrap a new datacenter.
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* [Examples](https://github.com/hashicorp/consul/tree/master/demo) - The work-in-progress examples folder within the GitHub
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repository for Consul contains functional examples of various use cases
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of Consul to help you get started with exactly what you need.
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* [Examples](https://github.com/hashicorp/serf/tree/master/demo) - The work-in-progress examples folder within the GitHub
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repository for Serf contains functional examples of various use cases
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of Serf to help you get started with exactly what you need.
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