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From mchucarr...@apache.org
Subject git commit: first draft of a "developing client v2" document.
Date Tue, 03 Jun 2014 15:37:01 GMT
Repository: incubator-aurora
Updated Branches:
  refs/heads/master fffabd320 -> cc2a92d2b


first draft of a "developing client v2" document.

Testing Done:
n/a

Bugs closed: aurora-20

Reviewed at https://reviews.apache.org/r/22032/


Project: http://git-wip-us.apache.org/repos/asf/incubator-aurora/repo
Commit: http://git-wip-us.apache.org/repos/asf/incubator-aurora/commit/cc2a92d2
Tree: http://git-wip-us.apache.org/repos/asf/incubator-aurora/tree/cc2a92d2
Diff: http://git-wip-us.apache.org/repos/asf/incubator-aurora/diff/cc2a92d2

Branch: refs/heads/master
Commit: cc2a92d2b97ad8be5b01b3214b765d3f56163687
Parents: fffabd3
Author: Mark Chu-Carroll <mchucarroll@twopensource.com>
Authored: Tue Jun 3 11:36:26 2014 -0400
Committer: Mark Chu-Carroll <mchucarroll@twitter.com>
Committed: Tue Jun 3 11:36:26 2014 -0400

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 docs/developing-aurora-client.md | 114 ++++++++++++++++++++++++++++++++++
 1 file changed, 114 insertions(+)
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http://git-wip-us.apache.org/repos/asf/incubator-aurora/blob/cc2a92d2/docs/developing-aurora-client.md
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diff --git a/docs/developing-aurora-client.md b/docs/developing-aurora-client.md
new file mode 100644
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+++ b/docs/developing-aurora-client.md
@@ -0,0 +1,114 @@
+
+Getting Started
+=================
+
+Aurora consists of four main pieces: the scheduler (which finds resources in the cluster
that can be used to run a job), the executor (which uses the resources assigned by the scheduler
to run a job), the command-line client, and the web-ui. For information about working on the
scheduler or the webUI, see the file "developing-aurora-scheduler.md" in this directory.
+
+If you want to work on the command-line client, this is the place for you!
+
+The client is written in Python, and unlike the server side of things, we build the client
using the Pants build tool, instead of Gradle. Pants is a tool that was built by twitter for
handling builds of large collaborative systems. You can see a detailed explanation of
+pants [here](http://pantsbuild.github.io/python-readme.html).
+
+To build the client executable, run the following in a command-shell:
+
+    $ ./pants src/main/python/apache/aurora/client/cli:aurora2
+
+This will produce a python executable _pex_ file in `dist/aurora2.pex`. Pex files
+are fully self-contained executables: just copy the pex file into your path, and you'll be
able to run it. For example, for a typical installation:
+
+    $ cp dist/aurora2.pex /usr/local/bin/aurora
+
+To run all of the client tests:
+
+    $ ./pasts src/test/python/apache/aurora/client/:all
+
+
+Client Versions
+==================
+
+There are currently two versions of the aurora client, imaginatively known as v1 and v2.
All new development is done entirely in v2, but we continue to support and fix bugs in v1,
until we get to the point where v2 is feature-complete and tested, and aurora users have had
some time at adapt and switch their processes to use v2.
+
+Both versions are built on the same underlying API code.
+
+Client v1 was implemented using twitter.common.app. The command-line processing code for
v1 can be found in `src/main/python/apache/aurora/client/commands` and
+`src/main/python/apache/aurora/client/bin`.
+
+Client v2 was implemented using its own noun/verb framework. The client v2 code can be found
in `src/main/python/apache/aurora/client/cli`, and the noun/verb framework can be
+found in the `__init__.py` file in that directory.
+
+
+Building and Testing the Client
+=================================
+
+Building and testing the client code are both done using Pants. The relevant targets to know
about are:
+
+   * Build a client v2 executable: `./pants src/main/python/apache/aurora/client/cli:aurora2`
+   * Test client v2 code: `./pants ./pants src/test/python/apache/aurora/client/cli:all`
+   * Build a client v1 executable: `./pants src/main/python/apache/aurora/client/bin:aurora_client`
+   * Test client v1 code: `./pants src/main/python/apache/aurora/client/commands:all`
+   * Test all client code: `./pants src/main/python/apache/aurora/client:all`
+
+
+Overview of the Client Architecture
+=====================================
+
+The client is built on a stacked architecture:
+
+   1. At the lowest level, we have a thrift RPC API interface
+    to the aurora scheduler. The interface is declared in thrift, in the file
+    `src/main/thrift/org/apache/aurora/gen/api.thrift`.
+
+  2. On top of the primitive API, we have a client API. The client API
+    takes the primitive operations provided by the scheduler, and uses them
+    to implement client-side behaviors. For example, when you update a job,
+    on the scheduler, that's done by a sequence of operations.  The sequence is implemented
+    by the client API `update` method, which does the following using the thrift API:
+     * fetching the state of task instances in the mesos cluster, and figuring out which
need
+       to be updated;
+     * For each task to be updated:
+         - killing the old version;
+         - starting the new version;
+         - monitoring the new version to ensure that the update succeeded.
+  3. On top of the API, we have the command-line client itself. The core client, at this
level,
+    consists of the interface to the command-line which the user will use to interact with
aurora.
+    The client v2 code is found in `src/python/apache/aurora/client/cli`. In the `cli` directory,
+    the rough structure is as follows:
+       * `__init__.py` contains the noun/verb command-line processing framework used by client
v2.
+       * `jobs.py` contains the implementation of the core `job` noun, and all of its operations.
+       * `bridge.py` contains the implementation of a component that allows us to ship a
+         combined client that runs both v1 and v2 client commands during the transition period.
+       * `client.py` contains the code that binds the client v2 nouns and verbs into an executable.
+
+Running/Debugging the Client
+=============================
+
+For manually testing client changes against a cluster, we use vagrant. To start a virtual
cluster,
+you need to install a working vagrant environment, and then run "vagrant up" for the root
of
+the aurora workspace. This will create a vagrant host named "devcluster", with a mesos master,
+a set of mesos slaves, and an aurora scheduler.
+
+To use the devcluster, you need to bring it up by running `vagrant up`, and then connect
to the vagrant host using `vagrant ssh`. This will open a bash session on the virtual machine
hosting the devcluster. In the home directory, there are two key paths to know about:
+
+   * `~/aurora`: this is a copy of the git workspace in which you launched the vagrant cluster.
+     To test client changes, you'll use this copy.
+   * `/vagrant`: this is a mounted filesystem that's a direct image of your git workspace.
+     This isn't a copy - it is your git workspace. Editing files on your host machine will
+     be immediately visible here, because they are the same files.
+
+Whenever the scheduler is modified, to update your vagrant environment to use the new scheduler,
+you'll need to re-initialize your vagrant images. To do this, you need to run two commands:
+
+   * `vagrant destroy`: this will delete the old devcluster image.
+   * `vagrant up`: this creates a fresh devcluster image based on the current state of your
workspace.
+
+You should try to minimize rebuilding vagrant images; it's not horribly slow, but it does
take a while.
+
+To test client changes:
+
+   * Make a change in your local workspace, and commit it.
+   * `vagrant ssh` into the devcluster.
+   * `cd aurora`
+   * Pull your changes into the vagrant copy: `git pull /vagrant *branchname*`.
+   * Build the modified client using pants.
+   * Run your command using `aurora2`. (You don't need to do any install; the aurora2 command
+     is a symbolic link to the executable generated by pants.)


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