README.markdown in zk-1.9.6 vs README.markdown in zk-1.10.0
- old
+ new
@@ -1,12 +1,12 @@
# ZK #
-[](http://travis-ci.org/zk-ruby/zk)
+
-ZK is an application programmer's interface to the Apache [ZooKeeper][] server. It is based on the [zookeeper gem][] which is a multi-Ruby low-level driver. Currently MRI 1.8.7, 1.9.2, 1.9.3, REE, and JRuby are supported. Rubinius 2.0.testing is supported-ish (it's expected to work, but upstream is unstable, so YMMV).
+ZK is an application programmer's interface to the Apache [ZooKeeper][] server. It is based on the [zookeeper gem][] which is a multi-Ruby low-level driver. Currently MRI 1.8.7, 1.9.2, 1.9.3, REE, and JRuby are supported. Rubinius 2.0.testing is supported-ish (it's expected to work, but upstream is unstable, so YMMV).
-ZK is licensed under the [MIT][] license.
+ZK is licensed under the [MIT][] license.
The key place to start in the documentation is with ZK::Client::Base ([rubydoc.info][ZK::Client::Base], [local](/docs/ZK/Client/Base)).
See the [RELEASES][] file for information on what changed between versions.
@@ -25,15 +25,15 @@
ZooKeeper is a multi-purpose tool that is designed to allow you to write code that coordinates many nodes in a cluster. It can be used as a directory service, a configuration database, and can provide cross-cluster [locking][], [leader election][], and [group membership][] (to name a few). It presents to the user what looks like a distributed file system, with a few important differences: every node can have children _and_ data, and there is a 1MB limit on data size for any given node. ZooKeeper provides atomic semantics and a simple API for manipulating data in the heirarchy.
One of the most useful aspects of ZooKeeper is the ability to set "[watches][]" on nodes. This allows one to be notified when a node has been deleted, created, changed, or has had its list of child znodes modified. The asynchronous nature of these watches enables you to write code that can _react_ to changes in your environment without polling and busy-waiting.
-Znodes can be _ephemeral_, which means that when the connection that created them goes away, they're automatically cleaned up, and all the clients that were watching them are notified of the deletion. This is an incredibly useful mechanism for providing _presence_ in a cluster ("which of my thingamabobers are up?). If you've ever run across a stale pid file or lock, you can imagine how useful this feature can be.
+Znodes can be _ephemeral_, which means that when the connection that created them goes away, they're automatically cleaned up, and all the clients that were watching them are notified of the deletion. This is an incredibly useful mechanism for providing _presence_ in a cluster ("which of my thingamabobers are up?). If you've ever run across a stale pid file or lock, you can imagine how useful this feature can be.
Znodes can also be created as _sequence_ nodes, which means that beneath a given path, a node can be created with a given prefix and assigned a unique integer. This, along with the _ephemeral_ property, provide the basis for most of the coordination classes such as [groups][] and [locks][].
-ZooKeeper is easy to deploy in a [Highly Available][ha-config] configuration, and the clients natively understand the clustering and how to resume a session transparently when one of the cluster nodes goes away.
+ZooKeeper is easy to deploy in a [Highly Available][ha-config] configuration, and the clients natively understand the clustering and how to resume a session transparently when one of the cluster nodes goes away.
[watches]: http://zookeeper.apache.org/doc/current/zookeeperProgrammers.html#ch_zkWatches
[locking]: http://zookeeper.apache.org/doc/current/recipes.html#sc_recipes_Locks
[leader election]: http://zookeeper.apache.org/doc/current/recipes.html#sc_leaderElection
[group membership]: http://zookeeper.apache.org/doc/current/recipes.html#sc_outOfTheBox
@@ -62,23 +62,23 @@
[recipes]: http://zookeeper.apache.org/doc/current/recipes.html
[Mongoid]: http://mongoid.org/
[EventMachine]: https://github.com/eventmachine/eventmachine
[zk-eventmachine]: https://github.com/zk-ruby/zk-eventmachine
-## Release info / Changelog
+## Release info / Changelog
See the [RELEASES][] page for more info on features and bugfixes in each release.
## Caveats
ZK strives to be a complete, correct, and convenient way of interacting with ZooKeeper. There are a few things to be aware of:
* In versions < 0.9 there is only *one* event dispatch thread. It is *very important* that you don't block the event delivery thread. In 1.0, there is one delivery thread by default, but you can adjust the level of concurrency, allowing more control and convenience for building your event-driven app.
-* ZK uses threads. You will have to use synchronization primitives if you want to avoid getting hurt. There are use cases that do not require you to think about this, but as soon as you want to register for events, you're using multiple threads.
+* ZK uses threads. You will have to use synchronization primitives if you want to avoid getting hurt. There are use cases that do not require you to think about this, but as soon as you want to register for events, you're using multiple threads.
-* If you're not familiar with developing solutions with zookeeper, you should read about [sessions][] and [watches][] in the Programmer's Guide. Even if you *are* familiar, you should probably go read it again.
+* If you're not familiar with developing solutions with zookeeper, you should read about [sessions][] and [watches][] in the Programmer's Guide. Even if you *are* familiar, you should probably go read it again.
* It is very important that you not ignore connection state events if you're using watches.
* _ACLS: HOW DO THEY WORK?!_ ACL support is mainly faith-based now. I have not had a need for ACLs, and the authors of the upstream [twitter/zookeeper][] code also don't seem to have much experience with them/use for them (purely my opinion, no offense intended). If you are using ACLs and you find bugs or have suggestions, I would much appreciate feedback or examples of how they *should* work so that support and tests can be added.
@@ -86,10 +86,10 @@
[twitter/zookeeper]: https://github.com/twitter/zookeeper
[async-branch]: https://github.com/zk-ruby/zk/tree/dev%2Fasync-conveniences
[chroot]: http://zookeeper.apache.org/doc/current/zookeeperProgrammers.html#ch_zkSessions
[YARD]: http://yardoc.org/
-[sessions]: http://zookeeper.apache.org/doc/current/zookeeperProgrammers.html#ch_zkSessions
+[sessions]: http://zookeeper.apache.org/doc/current/zookeeperProgrammers.html#ch_zkSessions
[watches]: http://zookeeper.apache.org/doc/r3.3.5/zookeeperProgrammers.html#ch_zkWatches
## Users
* [papertrail](http://papertrailapp.com/): Hosted log management service