Tez 0.5.0 is a developer focused release that stabilizes the APIs and improves
the debugging experience for Tez applications. The following items outline the 
important features of this release

1) Stable APIs - The core DAG and Runtime APIs have been marked stable and
will be compatibly supported going forward. So developers can take a
dependency on these APIs. The convention is that classes,  methods
configuration that have been explicitly annotated as @Public and @Stable are 
going to be compatible. Classes, methods and configurations that have been
marked @Evolving and @Unstable may continue to change going forward. Classes,
methods and configurations that have been marked @Private are not to be used.
2) Documentation - This release produced the first javadocs for Tez and a
number of tutorial like examples have been added to learn the APIs
3) Local mode execution - Tez applications can be run without running a
cluster. This mode is to be used for debugging the application locally.
4) Performance debugging tools - New tools like swimlanes analysis have been
added to help in debugging the performance of Tez applications
5) Support for ACLs - Tez now supports ACLs for fine grained access control to
view and modify DAGs.
6) New intermediate data format - Initial support for a new data format for
intermediate Key Value data for better performance.
7) Added UnorderedPartitionedOutput - This new output was added to write key
value data into partitions with the data being unordered in these partitions.

In addition there have been a number of performance and stability improvements
made. For full details please look at CHANGES.txt in the release artifacts.

There are a number of incompatible changes in this release. For a full list
please look at CHANGES.txt in the release artifacts.

Important incompatible changes for configuration are listed below to help
in migrating existing deployments of 0.4.1-incubating to 0.5.0.

Session vs non-session mode are now determined via configuration via the
following new configuration.
"tez.am.mode.session" DEFAULT = false

New configuration to set the log level for tasks.
"tez.task.log.level" DEFAULT = "INFO"

Configuration to set the AM launch command line options changed from
"tez.am.java.opts" to "tez.am.launch.cmd-opts" with DEFAULT = 
"-server -Djava.net.preferIPv4Stack=true -XX:+PrintGCDetails -verbose:gc 
-XX:+PrintGCTimeStamps -XX:+UseNUMA -XX:+UseParallelGC 
-Dhadoop.metrics.log.level=WARN"

Configuration to set the task launch command line options is 
"tez.task.launch.cmd-opts" with DEFAULT = 
"-server -Djava.net.preferIPv4Stack=true -XX:+PrintGCDetails -verbose:gc 
-XX:+PrintGCTimeStamps -XX:+UseNUMA -XX:+UseParallelGC 
-Dhadoop.metrics.log.level=WARN"

There is no need to add Xmx to the launch Java command line options for the AM
or the tasks. Tez automatically adds these as a fraction of the memory allocated 
to them. If Xmx or Xms options are specifically added by the user then this
automatic addition by Tez is disabled.
"tez.container.max.java.heap.fraction" DEFAULT = 0.8

Configuration to set the environment values for the AM changed 
from "tez.am.launch.env" to "tez.am.env" DEFAULT = 
For Windows : "PATH=%PATH%;%HADOOP_COMMON_HOME%\\bin"
For Linux : "LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$HADOOP_COMMON_HOME/lib/native/"

New configuration to set the environment values for tasks
"tez.task.launch.env" DEFAULT = 
For Windows : "PATH=%PATH%;%HADOOP_COMMON_HOME%\\bin"
For Linux : "LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$HADOOP_COMMON_HOME/lib/native/"
 
The default value of the memory allocated for the AM changes 
"tez.am.resource.memory.mb" DEFAULT = 1024 MB (was 1536 MB)

The behavior of idle container held in session mode changes to having a
minimum number of held containers via new configuration
"tez.am.session.min.held-containers" DEFAULT = 0

Idle containers are released randomly between the following min and max idle
times via new configurations
"tez.am.container.idle.release-timeout-min.millis" DEFAULT = 5 seconds
"tez.am.container.idle.release-timeout-max.millis" DEFAULT = 10 seconds

This configuration is not supported any more
"tez.am.container.session.delay-allocation-millis"

Deployment of TEZ library code changed to packaging and including all
necessary Hadoop/YARN dependencies inside the package. New configuration added
to support deploying TEZ library code where the dependencies are picked from
the cluster
"tez.use.cluster.hadoop-libs" DEFAULT = false

All runtime configurations now have a "tez.runtime." prefix, along with other
incompatible name changes. Please look at CHANGES.txt for full details.
Notably, certain configurations are no longer input/ouput specific.
"tez.runtime.key.comparator.class" replaces
"tez.runtime.intermediate-output.key.comparator.class" &
"tez.runtime.intermediate-input.key.comparator.class"
"tez.runtime.key.class" replaces "tez.runtime.intermediate-output.key.class" &
"tez.runtime.intermediate-input.key.class"
"tez.runtime.value.class" replaces
"tez.runtime.intermediate-output.value.class" &
"tez.runtime.intermediate-input.value.class"
"tez.runtime.compress" replaces
"tez.runtime.intermediate-output.should-compress" &
"tez.runtime.intermediate-input.is-compressed"
"tez.runtime.compress.codec" replaces
"tez.runtime.intermediate-output.compress.codec" &
"tez.runtime.intermediate-input.compress.codec"