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Welcome to the repository for Hue

Note

This is the development-oriented readme. If you want to write notes for end users, please put them in dist/README.

Hue is both a web UI for Hadoop and a framework to create interactive web applications. It features a FileBrowser for accessing HDFS, JobSub and JobBrowser applications for submitting and viewing MapReduce jobs, a Beeswax application for interacting with Hive. On top of that, the web frontend is mostly built from declarative widgets that require no JavaScript and are easy to learn.

File Layout

The "core" stuff is in desktop/core/, whereas installable apps live in apps/. Please place third-party dependencies in the app's ext-py/ directory.

The typical directory structure for inside an application includes:

src/
for Python code
conf/
for configuration (.ini) files to be installed
static/
for static HTML and js resources
templates/
for data to be put through a template engine
docs/
for helpful notes

The python code is structured simply as module/package.py, where module may be "filebrowser" or "jobsub". Because it is unlikely that there are going to be huge conflicts, we're going without a deep nested hierarchy.

URL Layout

core/src/desktop/urls.py contains the current layout for top-level URLs. For the URLs within your application, you should make your own urls.py which will be automatically rooted at /yourappname/ in the global namespace. See apps/hello/src/hello/urls.py for an example.

Development Prerequisites

  1. Also, you'll need these library development packages and tools installed on your system:

    Debian:
    • ant
    • asciidoc
    • gcc
    • g++
    • libmysqlclient-dev
    • libsasl2-dev
    • libsqlite3-dev
    • libxml2-dev
    • libxslt-dev
    • maven2
    • python-dev
    • python-simplejson
    CentOS:
    • ant
    • asciidoc
    • cyrus-sasl-devel
    • gcc
    • gcc-c++
    • libxml2-devel
    • libxslt-devel
    • maven2
    • mysql
    • mysql-devel
    • python-devel
    • python-simplejson (for the crepo tool)
    • sqlite-devel
    MacOS (mac port):
    • liblxml
    • libxml2
    • libxslt
    • mysql5-devel
    • simplejson (easy_install)
    • sqlite3
  2. You need to have crepo installed, and preferably on your path. If it is not on your path, set the environment variable CREPO to point to crepo.py from that distribution. You can clone crepo from http://github.com/cloudera/crepo.git somewhere else on your system.

Getting Started

To build and get the core server running:

$ export HADOOP_HOME=<path-to-hadoop-home>
$ git clone http://github.com/cloudera/hue.git
$ cd hue
$ make apps
$ build/env/bin/hue runserver_plus

To start the helper daemons:

$ build/env/bin/hue beeswax_server
$ build/env/bin/hue jobsubd

Now Hue should be running on http://localhost:8000.

Setting up Hadoop

In order to start up a pseudo-distributed cluster with the plugins enabled, run:

$ ./tools/scripts/configure-hadoop.sh all

After doing so, running jps should show all the daemons running (NN, JT, TT, DN) and you should be able to see the web UI on http://localhost:50030/ and http://localhost:50070/.

FAQ

1: What does "Exception: no app!" mean?

Your template has an error in it. Check for messages from the server that look like:

INFO:root:Processing exception: Unclosed tag 'if'. Looking for one of: else, endif
2: What do I do if I get "There was an error launching ..."?
Turn on debugging by issuing dbug.cookie() in a Firebug console.

Django Conventions

If you need to name your urls (http://docs.djangoproject.com/en/dev/topics/http/urls/#naming-url-patterns) because there's ambiguity in the view, be sure to prefix the name with the application name. The url name namespace is global. So jobsub.list is fine, but list is not.

Hue is using Django 1.1, which supports the notion of URL namespaces: http://docs.djangoproject.com/en/dev/topics/http/urls/#url-namespaces. We have yet to move over our URLs to this construct. Brownie points for the developer who takes this on.

Using and Installing Thrift

Right now, we check in the generated thrift code. To generate the code, you'll need the thrift binary. Compile it like so:

$ git clone http://github.com/dreiss/thrift.git
$ cd thrift
$ ./bootstrap.sh
$ ./configure --with-py=no --with-java=no --with-perl=no --prefix=$HOME/pub

We exclude python, java, and perl because they don't like to install in prefix. If you look around at configure's --help, there are environment variables that determine where those runtime bindings are installed.

$ make && make install

When preparing .thrift files, you can use she-bangs to generate the python bindings like so:

#!/usr/bin/env thrift -r --gen py:new_style -o ../../../

Note

This file is in reStructuredText. You may run rst2html README.rst > README.html to produce a HTML.

Profiling Hue Apps

Hue has a profiling system built in, which can be used to analyze server-side performance of applications. To enable profiling:

$ build/env/bin/hue runprofileserver

Then, access the page that you want to profile. This will create files like /tmp/useradmin.users.000072ms.2011-02-21T13:03:39.745851.prof. The format for the file names is /tmp/<app_module>.<page_url>.<time_taken>.<timestamp>.prof.

Hue uses the hotshot profiling library for instrumentation. The documentation for this library is located at: http://docs.python.org/library/hotshot.html.

To make use of the profiling data quickly, you can create a script that does the following:

#!/usr/bin/python
import hotshot.stats
import sys

stats = hotshot.stats.load(sys.argv[1])
stats.sort_stats('cumulative', 'calls')
stats.print_stats(100)

This script takes in a .prof file, and orders function calls by the cumulative time spent in that function, followed by the number of times the function was called, and then prints out the top 100 time-wasters. For information on the other stats available, take a look at this website: http://docs.python.org/library/profile.html#pstats.Stats

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