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Merge pull request #437 from bcwaldon/README-indexes

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chore(README): Expand README with more info about indexes
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Brian Waldon
2014-01-02 12:33:49 -08:00
parent fd0d0813ce c17ad07bdb
commit 78e2fc1bc8
1 changed files with 16 additions and 10 deletions
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@@ -94,21 +94,27 @@ curl -L http://127.0.0.1:4001/v2/keys/message -X PUT -d value="Hello world"
}
```
This response contains four fields.
We will introduce three more fields as we try more commands.
The response object contains several attributes:
1. The action of the request; we set the value via a `PUT` request, thus the action is `set`.
1. `action`: the action of the request that was just made.
The request attempted to modify `node.value` via a `PUT` HTTP request, thus the value of action is `set`.
2. The key of the request; we set `/message` to `Hello world`, so the key field is `/message`.
We use a file system like structure to represent the key-value pairs so each key starts with `/`.
2. `node.key`: the HTTP path the to which the request was made.
We set `/message` to `Hello world`, so the key field is `/message`.
Etcd uses a file-system-like structure to represent the key-value pairs, therefore all keys start with `/`.
3. The current value of the key; we set the value to`Hello world`.
3. `node.value`: the value of the key after resolving the request.
In this case, a successful request was made that attempted to change the node's value to `Hello world`.
4. Modified Index is a unique, monotonically incrementing index created for each change to etcd.
Requests that change the index include `set`, `delete`, `update`, `create` and `compareAndSwap`.
Since the `get` and `watch` commands do not change state in the store, they do not change the index.
4. `node.createdIndex`: an index is a unique, monotonically-incrementing integer created for each change to etcd.
This specific index reflects at which point in the etcd state machine a given key was created.
You may notice that in this example the index is `2` even though it is the first request you sent to the server.
This is because there are internal commands that also change the state like adding and syncing servers.
This is because there are internal commands that also change the state behind the scenes like adding and syncing servers.
5. `node.modifiedIndex`: like `node.createdIndex`, this attribute is also an etcd index.
Actions that cause the value to change include `set`, `delete`, `update`, `create` and `compareAndSwap`.
Since the `get` and `watch` commands do not change state in the store, they do not change the value of `node.modifiedIndex`.
### Response Headers