Commit 70cbf0c9 authored by julian.gethmann's avatar julian.gethmann

Add docu for environment variables

parent c3d7023c
......@@ -4,6 +4,16 @@ Background information and general remark
Cassandra_ is the current (2018) archiving solution used at KARA. There is a `JavaScript-Object-Notation`_-API available, that can be accessed from within the IBPT-LAN (CN, VPN or las-bernhard.anka.kit.edu).
Usage with different hosts or ports
-----------------------------------
In case you want to run this scripts or library from a place where the host or port does not fit the presets, you need to provide them as environment variables.
For example if you want to run your script ``cassandra_download.py`` and you forwarded ``ankacomm`` via SSH to the port 9999,
you can then call your script in bash like::
CASSANDRA_HOST=localhost; CASSANDRA_PORT=9999 python3 cassandra_download.py
Terminology
-----------
......
......@@ -136,3 +136,16 @@ current directory.
.. _pandas: https://pandas.pydata.org
.. _`offset-aliases`: http://pandas.pydata.org/pandas-docs/stable/timeseries.html#offset-aliases
Environment variables
~~~~~~~~~~~~~~~~~~~~~
Let us assume you tunnelled to a host in the machine network and now you do not have to use the archive gateway, but localhost as the host.
This can easily be accomplished by setting the environment variable ``CASSANDRA_HOST`` and then running your script.
code::
$ CASSANDRA_HOST=localhost python script.py
.. note::
Unfortunately it is not sufficient to set the environment variable from inside your script or e. g. Jupyter notebook.
......@@ -16,6 +16,7 @@ If I write Cassandra I am speaking of this Python class, if I write cassanda I a
Examples <examples>
(Command line) Scripts <scripts>
Module Reference <api/cassandra>
Error messages and trouble shooting <troubleshooting>
Changelog <changelog>
License <license>
Authors <authors>
......
.. _troubleshooting:
Error messages
==============
URLError
~~~~~~~~
Typical causes for the URLError with the message `Maybe you're not inside the ANKA-LAN` are
* You are not inside the IBPT office network nor in it via VPN. You should check this by getting the following URL.
http://ankasr-archiver.anka.kit.edu:9812/archive-access/api/1.0/archive/1/samples/A:SR:BeamInfo:01:Energy?start=1479813320000000000&end=1479813420000000000 Try to do it with wget or curl, because maybe you are working on a different computer than you think ;)
* One of your provided ``PV`` names is wrong
* Your start time is later that your end time
* The cassandra archive is not responding correctly. Did you really double checked the other causes? Then get in contact with Sebastian Marsching or write a JIRA ticket.
......@@ -16,6 +16,11 @@
And finally the :class:`Pvs` class simply provides a :obj:`dict` of some
EPICS Process Variables I often used or could not remember.
Possible environment variables are
* CASSANDRA_HOST
* CASSANDRA_PORT
"""
from __future__ import with_statement
......
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