mirror of https://github.com/hashicorp/consul
135 lines
3.9 KiB
Markdown
135 lines
3.9 KiB
Markdown
---
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layout: "intro"
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page_title: "KV Data"
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sidebar_current: "gettingstarted-kv"
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description: |-
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In addition to providing service discovery and integrated health checking, Consul provides an easy to use KV store. This can be used to hold dynamic configuration, assist in service coordination, build leader election, and enable anything else a developer can think to build.
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---
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# KV 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 KV 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 enable anything else a developer can think to build.
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This step assumes you have at least one Consul agent already running.
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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 in
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the KV store. There are two ways to interact with the Consul KV store: via the
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HTTP API and via the Consul KV CLI. The examples below show using the Consul KV
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CLI because it is the easiest to get started. For more advanced integrations,
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you may want to use the [Consul KV HTTP API][kv-api]
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First let us explore the KV store. We can ask Consul for the value of the key at
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the path named `redis/config/minconns`:
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```sh
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$ consul kv get redis/config/minconns
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Error! No key exists at: redis/config/minconns
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```
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As you can see, we get no result, which makes sense because there is no data in
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the KV store. Next we can insert or "put" values into the KV store.
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```sh
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$ consul kv put redis/config/minconns 1
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Success! Data written to: redis/config/minconns
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$ consul kv put redis/config/maxconns 25
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Success! Data written to: redis/config/maxconns
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$ consul kv put -flags=42 redis/config/users/admin abcd1234
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Success! Data written to: redis/config/users/admin
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```
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Now that we have keys in the store, we can query for the value of individual
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keys:
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```sh
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$ consul kv get redis/config/minconns
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1
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```
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Consul retains additional metadata about the field, which is retrieved using the
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`-detailed` flag:
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```sh
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$ consul kv get -detailed redis/config/minconns
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CreateIndex 207
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Flags 0
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Key redis/config/minconns
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LockIndex 0
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ModifyIndex 207
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Session -
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Value 1
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```
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For the key "redis/config/users/admin", we set a `flag` value of 42. All keys
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support setting a 64-bit integer flag value. This is not used internally by
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Consul, but it can be used by clients to add meaningful metadata to any KV.
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It is possible to list all the keys in the store using the `recurse` options.
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Results will be returned in lexicographical order:
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```sh
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$ consul kv get -recurse
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redis/config/maxconns:25
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redis/config/minconns:1
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redis/config/users/admin:abcd1234
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```
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To delete a key from the Consul KV store, issue a "delete" call:
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```sh
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$ consul kv delete redis/config/minconns
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Success! Deleted key: redis/config/minconns
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```
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It is also possible to delete an entire prefix using the `recurse` option:
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```sh
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$ consul kv delete -recurse redis
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Success! Deleted keys with prefix: redis
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```
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To update the value of an existing key, "put" a value at the same path:
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```sh
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$ consul kv put foo bar
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$ consul kv get foo
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bar
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$ consul kv put foo zip
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$ consul kv get foo
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zip
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```
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Consul can provide atomic key updates using a Check-And-Set operation. To perform a CAS operation, specify the `-cas` flag:
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```sh
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$ consul kv put -cas -modify-index=123 foo bar
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Success! Data written to: foo
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$ consul kv put -cas -modify-index=123 foo bar
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Error! Did not write to foo: CAS failed
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```
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In this case, the first CAS update succeeds because the index is 123. The second
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operation fails because the index is no longer 123.
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## Next Steps
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These are only a few examples of what the API supports. For the complete
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documentation, please see [Consul KV HTTP API][kv-api] or
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[Consul KV CLI][kv-cli] documentation.
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Next, we will look at the [web UI](ui.html) options supported by Consul.
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[kv-api]: /api/kv.html
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[kv-cli]: /docs/commands/kv.html
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