Kamaki uses the standard Python logger.
All kamaki loggers are named or prefixed after the package they log, e.g., a logger at kamaki/cli/argument/__init__.py should be called kamaki.cli.argument whereas a logger at kamaki/clients/conf.py should be named kamaki.clients.conf. In kamaki/clients/__init__.py there are two loggers that use the package name as prefix, and they detailed bellow.
The kamaki.clients logger contains two subloggers that monitor the HTTP API calls:
kamaki.clients.send for kamaki requests to the server
kamaki.clients.recv for server responses to kamaki
These are the only loggers used for purposes other than mere debugging. Both loggers are defined in the CLI code and are used to (a) log HTTP communication to the log file as well as to (b) show users the HTTP requests and responses in “verbose” or “debug” modes.
When a logger is known to be in kamaki code, the script developer may use this logger to log some needed information. This can be happen either by directly using the Python logger package, or the corresponding kamaki wraper kamaki.cli.logger which allows the definition, activation and deactivation of stream (usually console) or file loggers.
We will use this script as an example to work on. The script registers images from a set of pre-uploaded image files.
First, we shall add a logger to track HTTP communication in /tmp/my_kamaki.log To do this, append the following at the top of the file:
from kamaki.cli.logger import add_file_logger
add_file_logger('kamaki.clients.send', filename='/tmp/my_kamaki.log')
add_file_logger('kamaki.clients.recv', filename='/tmp/my_kamaki.log')
After a run of the script, a new file will be created at /tmp/my_kamaki.log that will contain logs of the form:
> POST https://accounts.okeanos.grnet.gr/identity/v2.0/tokens
> Content-Length: 74
> Content-Type: application/json
> data size:74
< 200 OK
< content-length: 2425
< content-language: en-us
< expires: Wed, 31 Jul 2013 14:27:47 GMT
< vary: X-Auth-Token,Accept-Language
< server: gunicorn/0.14.5
< last-modified: Wed, 31 Jul 2013 14:27:47 GMT
< connection: close
< etag: "43af...36"
< cache-control: no-cache, no-store, must-revalidate, max-age=0
< date: Wed, 31 Jul 2013 14:27:47 GMT
< content-type: application/json; charset=UTF-8
< data size: 2425
Note
user token and http body content are not logged by default. This can be switched on and off by modifing the kamaki.client.Client.LOG_TOKEN and kamaki.client.Client.LOG_DATA flags
As a second example, let’s suppose that we need to see only the http requests of the pithos.list_objects() method and print these to stdout. To achieve that goal, we should get a stream logger and deactivate it when we do not need it anymore.
#! /usr/bin/python
[...]
from kamaki.cli.logger import add_stream_logger, deactivate
add_stream_logger('kamaki.clients')
for img in pithos.list_objects():
deactivate('kamaki.clients')
[...]
When implementing kamaki code, either as part of the main kamaki project or as an extension, it is often useful to use loggers. Developers may also directly use the Python logger module with respect to the naming conventions.
In this example, we want to log the arguments of the register method found in kamaki/clients/image/__init__.py. We will use the Python logger module.
First, we should add a logger initializer at the top of the file.
from logging import getLogger
log = getLogger(__name__)
Now, we should use the log biding to actually log what we need.
[...]
def register(self, name, location, params={}, properties={}):
log.debug('name: %s' % name)
log.debug('location: %s' % location)
log.debug('params: %s' % params)
log.debug('properties: %s' % properties)
[...]
Loggers defined in higher levels of the package hierarchy are inherited. This may cause duplication in logs. Use either a high level loger (e.g. ‘kamaki’ or ‘kamaki.clients’) to log everything, or a specific logger (e.g. ‘kamaki.clients.image’).
add_file_logger('kamaki.clients.image', filename='/tmp/kamaki_image.log')