137 lines
4.0 KiB
Plaintext
137 lines
4.0 KiB
Plaintext
---
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layout: intro
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page_title: KV Data
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description: >-
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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 dynamic
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configuration, assist in service coordination, build leader election, and
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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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```shell-session
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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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```shell-session
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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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```shell-session
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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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```shell-session
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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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```shell-session
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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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```shell-session
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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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```shell-session
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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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```shell-session
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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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```shell-session
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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](/intro/getting-started/ui) options supported by Consul.
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[kv-api]: /api/kv
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[kv-cli]: /commands/kv
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