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About logging¶
This document explains additional information about logging for developers. We assume that you have read About logging in the Hoster’s Guide.
Overview¶
Lino’s default logging messages go only to the console and (when an error
occurs) to the ADMIN_EMAILS
.
When you create a log
directory in your project directory, Lino will
additionally log to a file lino.log
in that directory.
On a production site you probably want to also run a log server.
About logging in a development environment¶
On my development machine I have a runserver script that does:
set LINO_LOGLEVEL=DEBUG
python manage.py runserver
Logging SQL statements¶
The default logging level for the django.db.backends
handler is WARNING. You can change this default value by setting the
LINO_SQL_LOGLEVEL
variable.
- LINO_SQL_LOGLEVEL¶
The logging level to set for the django.db.backends handler instead of the default value
WARNING
.
The Lino logger¶
Side note: Code snippets (lines starting with >>>
) in this document get
tested as part of our development workflow. The following
initialization snippet tells you which demo project is being used in
this document.
>>> from lino import startup
>>> startup('lino_book.projects.noi1e.settings.demo')
>>> from lino.api.doctest import *
>>> from lino import logger
>>> logger.handlers
[<StreamHandler (INFO)>, <AdminEmailHandler (ERROR)>]
>>> logger.info("Hello, world!")
Hello, world!
>>> logger.debug("Foolish humans trying to understand me")
History-aware logging¶
When Lino is in history-aware logging mode, it logs a message
Started %s (using %s) --> PID %s
at process startup (and a message
Done PID %s
at termination).
This kind of messages are usually disturbing for development and testing, but they are interesting for the system administrator of a production site.
The history-aware logging mode is automatically set to True when a logger
directory (log
) exists in the project directory.
Testing the log
directory¶
When a socket file exists (a file named lino.log.sock
in the
log
directory), then Lino assumes that you have a log server
running that is responsible for writing to the lino.log
file.
We are going to play in the min1 demo project:
>>> from atelier.sheller import Sheller
>>> shell = Sheller('lino_book/projects/min1')
The demo sites have no log
directory and hence no lino.log
file.
>>> shell("ls log")
ls: cannot access 'log': No such file or directory
>>> shell("python manage.py prep --noinput")
...
`initdb std demo demo2` started on database .../min1/default.db.
...
Installed 200 object(s) from 8 fixture(s)
For the following snippets we temporarily enable file logging in the min1 demo
site by creating a log
directory.
>>> shell("mkdir log")
>>> shell("python manage.py prep --noinput")
...
Started manage.py prep --noinput (using lino_book.projects.min1.settings) --> PID ...
`initdb std demo demo2` started on database .../min1/default.db.
...
Done manage.py prep --noinput (PID ...)
>>> shell("ls log")
lino.log
>>> shell("cat log/lino.log")
...
2... INFO [lino ...] : Started manage.py prep --noinput (using lino_book.projects.min1.settings) --> PID ...
2... INFO [lino ...] : `initdb std demo demo2` started on database .../min1/default.db.
2...
2... INFO [lino ...] : Done manage.py prep --noinput (PID ...)
When there is a log
directory, the Lino logger will log to the
lino.log
file as well.
The following snippet demonstrates an edge case: we simulate a log server by creating a fake socket file.
>>> shell("rm log/lino.log")
>>> shell("touch log/lino.log.sock")
The process then sends log records to that socket, without asking whether the server actually runs:
>>> shell("python manage.py prep --noinput")
...
Started manage.py prep --noinput (using lino_book.projects.min1.settings) --> PID ...
...
But since in our case no log server is actually running, the lino.log
file has not been written (only the socket file is there):
>>> shell("ls log")
lino.log.sock
Tidy up and remove all traces:
>>> shell("rm log/lino.log.sock")
>>> shell("rmdir log")
Relation between logging level and verbosity¶
The relation between logging level and verbosity is not yet clear.
You can set LINO_LOGLEVEL
to “WARNING” in order to get rid of quite
some messages:
>>> import os
>>> env = dict()
>>> env.update(os.environ)
>>> env.update(LINO_LOGLEVEL="WARNING")
>>> shell("python manage.py prep --noinput", env=env)
...
No changes detected
Operations to perform:
Synchronize unmigrated apps: about, bootstrap3, contacts, countries, extjs, jinja, lino, office, printing, staticfiles, system, users, xl
Apply all migrations: sessions
Synchronizing apps without migrations:
Creating tables...
Creating table system_siteconfig
Creating table users_user
Creating table users_authority
Creating table countries_country
Creating table countries_place
Creating table contacts_partner
Creating table contacts_person
Creating table contacts_companytype
Creating table contacts_company
Creating table contacts_roletype
Creating table contacts_role
Running deferred SQL...
Running migrations:
Applying sessions.0001_initial... OK
Installed 200 object(s) from 8 fixture(s)
Setting LINO_LOGLEVEL
to “WARNING” does not remove messages issued by
Django because Django does not use the logging system to print these messages.
To get rid of these messages as well, you can set verbosity to 0:
>>> shell("python manage.py prep --noinput -v0", env=env)
...