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Merge pull request #2580 from hashicorp/sethvargo/kv_main 

Switch to KV CLI in getting started
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Seth Vargo 2016-12-07 14:42:13 -08:00 committed by GitHub
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pre{
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@ -17,113 +17,118 @@ This step assumes you have at least one Consul agent already running.
## Simple Usage
To demonstrate how simple it is to get started, we will manipulate a few keys
in the K/V store.
To demonstrate how simple it is to get started, we will manipulate a few keys in
the K/V store. There are two ways to interact with the Consul KV store: via the
HTTP API and via the Consul KV CLI. The examples below show using the Consul KV
CLI because it is the easiest to get started. For more advanced integrations,
you may want to use the [Consul KV HTTP API][kv-api]
Querying the local agent we started in the [Run the Agent step](agent.html),
we can first verify that there are no existing keys in the k/v store:
First let us explore the KV store. We can ask Consul for the value of the key at
the path named `redis/config/minconns`:
Also check https://www.hashicorp.com/blog/consul-kv-cli.html for using the 'consul kv' from
the commandline.
```text
$ curl -v http://localhost:8500/v1/kv/?recurse
* About to connect() to localhost port 8500 (#0)
* Trying 127.0.0.1... connected
> GET /v1/kv/?recurse HTTP/1.1
> 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
> Host: localhost:8500
> Accept: */*
>
< HTTP/1.1 404 Not Found
< X-Consul-Index: 1
< Date: Fri, 11 Apr 2014 02:10:28 GMT
< Content-Length: 0
< Content-Type: text/plain; charset=utf-8
<
* Connection #0 to host localhost left intact
* Closing connection #0
```sh
$ consul kv get redis/config/minconns
Error! No key exists at: redis/config/minconns
```
Since there are no keys, we get a 404 response back. Now, we can `PUT` a
few example keys:
As you can see, we get no result, which makes sense because there is no data in
the KV store. Next we can insert or "put" values into the KV store.
```
$ curl -X PUT -d 'test' http://localhost:8500/v1/kv/web/key1
true
$ curl -X PUT -d 'test' http://localhost:8500/v1/kv/web/key2?flags=42
true
$ curl -X PUT -d 'test' http://localhost:8500/v1/kv/web/sub/key3
true
$ curl http://localhost:8500/v1/kv/?recurse
[{"CreateIndex":97,"ModifyIndex":97,"Key":"web/key1","Flags":0,"Value":"dGVzdA=="},
{"CreateIndex":98,"ModifyIndex":98,"Key":"web/key2","Flags":42,"Value":"dGVzdA=="},
{"CreateIndex":99,"ModifyIndex":99,"Key":"web/sub/key3","Flags":0,"Value":"dGVzdA=="}]
```sh
$ consul kv put redis/config/minconns 1
Success! Data written to: redis/config/minconns
$ consul kv put redis/config/maxconns 25
Success! Data written to: redis/config/maxconns
$ consul kv put -flags=42 redis/config/users/admin abcd1234
Success! Data written to: redis/config/users/admin
```
Here we have created 3 keys, each with the value of "test". Note that the
`Value` field returned is base64 encoded to allow non-UTF8 characters. For the
key "web/key2", we set a `flag` value of 42. All keys support setting a 64-bit
integer flag value. This is not used internally by Consul, but it can be used by
clients to add meaningful metadata to any KV.
Now that we have keys in the store, we can query for the value of individual
keys:
After setting the values, we then issued a `GET` request to retrieve multiple
keys using the `?recurse` parameter.
You can also fetch a single key just as easily:
```text
$ curl http://localhost:8500/v1/kv/web/key1
[{"CreateIndex":97,"ModifyIndex":97,"Key":"web/key1","Flags":0,"Value":"dGVzdA=="}]
```sh
$ consul kv get redis/config/minconns
1
```
Deleting keys is simple as well, accomplished by using the `DELETE` verb. We can
delete a single key by specifying the full path, or we can recursively delete all
keys under a root using "?recurse":
Consul retains additional metadata about the field, which is retrieved using the
`-detailed` flag:
```text
$ curl -X DELETE http://localhost:8500/v1/kv/web/sub?recurse
$ curl http://localhost:8500/v1/kv/web?recurse
[{"CreateIndex":97,"ModifyIndex":97,"Key":"web/key1","Flags":0,"Value":"dGVzdA=="},
{"CreateIndex":98,"ModifyIndex":98,"Key":"web/key2","Flags":42,"Value":"dGVzdA=="}]
```sh
$ consul kv get -detailed redis/config/minconns
CreateIndex 207
Flags 0
Key redis/config/minconns
LockIndex 0
ModifyIndex 207
Session -
Value 1
```
A key can be modified by issuing a `PUT` request to the same URI and
providing a different message body. Additionally, Consul provides a
Check-And-Set operation, enabling atomic key updates. This is done by
providing the `?cas=` parameter with the last `ModifyIndex` value from
the GET request. For example, suppose we wanted to update "web/key1":
For the key "redis/config/users/admin", we set a `flag` value of 42. All keys
support setting a 64-bit integer flag value. This is not used internally by
Consul, but it can be used by clients to add meaningful metadata to any KV.
```text
$ curl -X PUT -d 'newval' http://localhost:8500/v1/kv/web/key1?cas=97
true
$ curl -X PUT -d 'newval' http://localhost:8500/v1/kv/web/key1?cas=97
false
It is possible to list all the keys in the store using the `recurse` options.
Results will be returned in lexicographical order:
```sh
$ consul kv get -recurse
redis/config/maxconns:25
redis/config/minconns:1
redis/config/users/admin:abcd1234
```
In this case, the first CAS update succeeds because the `ModifyIndex` is 97.
However the second operation fails because the `ModifyIndex` is no longer 97.
To delete a key from the Consul KV store, issue a "delete" call:
We can also make use of the `ModifyIndex` to wait for a key's value to change.
For example, suppose we wanted to wait for key2 to be modified:
```text
$ curl "http://localhost:8500/v1/kv/web/key2?index=101&wait=5s"
[{"CreateIndex":98,"ModifyIndex":101,"Key":"web/key2","Flags":42,"Value":"dGVzdA=="}]
```sh
$ consul kv delete redis/config/minconns
Success! Deleted key: redis/config/minconns
```
By providing "?index=", we are asking to wait until the key has a `ModifyIndex` greater
than 101. However the "?wait=5s" parameter restricts the query to at most 5 seconds,
returning the current, unchanged value. This can be used to efficiently wait for
key modifications. Additionally, this same technique can be used to wait for a list
of keys, waiting only until any of the keys has a newer modification time.
It is also possible to delete an entire prefix using the `recurse` option:
```sh
$ consul kv delete -recurse redis
Success! Deleted keys with prefix: redis
```
To update the value of an existing key, "put" a value at the same path:
```sh
$ consul kv put foo bar
$ consul kv get foo
bar
$ consul kv put foo zip
$ consul kv get foo
zip
```
Consul can provide atomic key updates using a Check-And_set operation. To perform a CAS operation, specify the `-cas` flag:
```sh
$ consul kv put -cas -modify-index=123 foo bar
Success! Data written to: foo
$ consul kv put -cas -modify-index=123 foo bar
Error! Did not write to foo: CAS failed
```
In this case, the first CAS update succeeds because the index is 123. The second
operation fails because the index is no longer 123.
## Next Steps
These are only a few examples of what the API supports. For full documentation, please
see [the /kv/ route of the HTTP API](/docs/agent/http/kv.html).
These are only a few examples of what the API supports. For the complete
documentation, please see [Consul KV HTTP API][kv-api] or
[Consul KV CLI][kv-cli] documentation.
Next, we will look at the [web UI](ui.html) options supported by Consul.
Also check https://www.hashicorp.com/blog/consul-kv-cli.html for using the 'consul kv' from
the commandline.
[kv-api]: /docs/agent/http/kv.html
[kv-cli]: /docs/commands/kv.html