.. _services-debug:
How To Debug ZOO Services
=========================
:Authors: Luca Delucchi
:Last Updated: $Date: 2015-02-09 15:26:31 +0000 (Mon, 09 Feb 2015) $
There are different ways to debug your services, the most used solutions are via web
or via command line.
Web
----
Using the web request you can see any problem in the log file of Apache.
On Unix system the log file is usually in ``/var/log/apache2`` and the relevant file
is ``error_log``. A simple way to read the file is to use the ``tail`` command,
it permits to see the update of the file for each request ::
tail -f /var/log/apache2/error_log
If the log is not clear enough you can add some more debug information to your code. You have to write
to standard error.
Python
********
Using Python, you can for example do this
.. code-block:: python
import sys
#add this line when you want see an own message
sys.stderr.write("My message")
.. _web_javascript:
Javascript
************
You can user ``alert`` to print a string to standard error:
.. code-block:: javascript
// add this line when you want see an own message
alert('My message')
// you can debug value of inputs, outputs or conf
alert(inputs["S"]["value"])
.. note:: If you try to pass an object it will only return ``[object Object]``
Command line
--------------
It is possible to use the ZOO kernel ``zoo_loader.cgi`` also from command line.
This is really useful to debug in a deeper way your service:
.. code-block:: bash
# in order to use it you have to copy test_service.py and HelloPy.zcfg from
# the example services
./zoo_loader.cgi "service=wps&version=1.0.0&request=execute&identifier=HelloPy&datainputs=a=your name&responsedocument=Result"
Working this way you can use the standard debug system of the actual programming language used
to develop your service.
GDB
*****
From command line you can use also the command line tool `GDB `_
to debug ``zoo_loader.cgi``, you have to run:
.. code-block:: bash
# launch zoo_loader.cgi from gdb
gdb zoo_loader.cgi
# now run your request
run "service=wps&version=1.0.0&request=execute&identifier=HelloPy&datainputs=a=your name&responsedocument=Result"
At this point you can ask help at the `ZOO mailing list `_
copying the result of the command.
Python
**********
For Python, you can use ``pdb``, more info at http://docs.python.org/2/library/pdb.html
.. code-block:: python
import pdb
# add this line when you want investigate your code in more detail
pdb.set_trace()
Javascript
************
You can use ``alert`` also to print in the console, more info in the :ref:`web_javascript` web section