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Merge pull request #2692 from philips/add-migration-guide

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Documentation: add migration notes to backward compatibility
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Xiang Li 2015-04-16 07:05:07 -07:00
commit 38a373ede9
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Documentation/backward_compatibility.md
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@ -20,13 +20,53 @@ The major flag changes are to mostly related to bootstrapping. The `initial-*` f
The documentation of new command line flags can be found at
https://github.com/coreos/etcd/blob/master/Documentation/configuration.md.
#### Data Dir
- Default data dir location has changed from {$hostname}.etcd to {name}.etcd.
#### Data Directory Naming
- The disk format within the data dir has changed. etcd 2.0 should be able to auto upgrade the old data format. Instructions on doing so manually are in the [migration tool doc][migrationtooldoc].
The default data dir location has changed from {$hostname}.etcd to {name}.etcd.
#### Data Directory Migration
The disk format within the data directory changed with etcd 2.0.
If you run etcd 2.0 on an etcd 0.4 data directory it will automatically migrate the data and start.
You will want to coordinate this upgrade by walking through each of your machines in the cluster, stopping etcd 0.4 and then starting etcd 2.0.
If you would rather manually do the migration, to test it out first in another environment, you can use the [migration tool doc][migrationtooldoc].
[migrationtooldoc]: ../tools/etcd-migrate/README.md
#### Snapshot Migration
If you are only interested in the data in etcd you can migrate a snapshot of your data from a v0.4.9+ cluster into a new etcd 2.0 cluster using a snapshot migration.
The advantage of this method is that you are directly dumping only the etcd data so you can run your old and new cluster side-by-side, snapshot the data, import it and then point your applications at this cluster.
The disadvantage is that the etcd indexes of your data will change which may confuse applications that use etcd.
To get started get the newest data snapshot from the 0.4.9+ cluster:
```
curl http://cluster.example.com:4001/v2/migration/snapshot > backup.snap
```
Now, import the snapshot into your new cluster:
```
etcdctl -C new_cluster.example.com import --snap backup.snap
```
If you have a large amount of data, you can specify more concurrent works to copy data in parallel by using `-c` flag.
If you have hidden keys to copy, you can use `--hidden` flag to specify.
And the data will quickly copy into the new cluster:
```
entering dir: /
entering dir: /foo
entering dir: /foo/bar
copying key: /foo/bar/1 1
entering dir: /
entering dir: /foo2
entering dir: /foo2/bar2
copying key: /foo2/bar2/2 2
```
#### Key-Value API
##### Read consistency flag