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Documentation: add note about consistent=true

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Brandon Philips 2014-07-08 18:21:58 -07:00
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Documentation/api.md
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@ -833,6 +833,8 @@ curl -L http://127.0.0.1:4001/v2/keys/afile -XPUT --data-urlencode value@afile.t
### Read Consistency
#### Read from the Master
Followers in a cluster can be behind the leader in their copy of the keyspace.
If your application wants or needs the most up-to-date version of a key then it should ensure it reads from the current leader.
By using the `consistent=true` flag in your GET requests, etcd will make sure you are talking to the current master.
@ -843,6 +845,19 @@ The client is told the write was successful and the keyspace is updated.
Meanwhile F2 has partitioned from the network and will have an out-of-date version of the keyspace until the partition resolves.
Since F2 missed the most recent write, a client reading from F2 will have an out-of-date version of the keyspace.
Implementation notes on `consistent=true`: If the leader you are talking to is
partitioned it will be unable to determine if it is not currently the master.
In a later version we will provide a mechanism to set an upperbound of time
that the current master can be unable to contact the quorom and still serve
reads.
### Read Linearization
If you want a read that is fully linearized you can use a `quorum=true` GET.
The read will take a very similar path to a write and will have a similar
speed. If you are unsure if you need this feature feel free to email etcd-dev
for advice.
## Lock Module (*Deprecated and Removed*)
The lock module is used to serialize access to resources used by clients.