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Add leader module to README.

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Ben Johnson
2013-12-16 08:00:16 -07:00
parent 2ce587ebc7
commit 296eaf7b34
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@@ -926,6 +926,41 @@ curl -X DELETE http://127.0.0.1:4001/mod/v2/lock/customer1?index=customer1
curl -X DELETE http://127.0.0.1:4001/mod/v2/lock/customer1?name=bar
```
### Leader Election
The Leader Election module wraps the Lock module to allow clients to come to consensus on a single value.
This is useful when you want one server to process at a time but allow other servers to fail over.
The API is similar to the Lock module but is limited to simple strings values.
Here's the API:
**Attempt to set a value for the "order_processing" leader key:**
```sh
curl -X POST http://127.0.0.1:4001/mod/v2/leader/order_processing?ttl=60 -d name=myserver1.foo.com
```
**Retrieve the current value for the "order_processing" leader key:**
```sh
curl http://127.0.0.1:4001/mod/v2/leader/order_processing
myserver1.foo.com
```
**Remove a value from the "order_processing" leader key:**
```sh
curl -X POST http://127.0.0.1:4001/mod/v2/leader/order_processing?name=myserver1.foo.com
```
If multiple clients attempt to set the value for a key then only one will succeed.
The other clients will hang until the current value is removed because of TTL or because of a `DELETE` operation.
Multiple clients can submit the same value and will all be notified when that value succeeds.
To update the TTL of a value simply reissue the same `POST` command that you used to set the value.
## Contributing
See [CONTRIBUTING](https://github.com/coreos/etcd/blob/master/CONTRIBUTING.md) for details on submitting patches and contacting developers via IRC and mailing lists.