Logging Exceptions To Your SQLAlchemy Database
So you'd like to log to your database, rather than a file. Well, here's a brief rundown of exactly how you'd do that.
First we need to define a Log model for SQLAlchemy (do this in myapp.models):
from sqlalchemy import Column from sqlalchemy.types import DateTime, Integer, String from sqlalchemy.sql import func from sqlalchemy.ext.declarative import declarative_base Base = declarative_base() class Log(Base): __tablename__ = 'logs' id = Column(Integer, primary_key=True) # auto incrementing logger = Column(String) # the name of the logger. (e.g. myapp.views) level = Column(String) # info, debug, or error? trace = Column(String) # the full traceback printout msg = Column(String) # any custom log you may have included created_at = Column(DateTime, default=func.now()) # the current timestamp def __init__(self, logger=None, level=None, trace=None, msg=None): self.logger = logger self.level = level self.trace = trace self.msg = msg def __unicode__(self): return self.__repr__() def __repr__(self): return "<Log: %s - %s>" % (self.created_at.strftime('%m/%d/%Y-%H:%M:%S'), self.msg[:50])
Not too much exciting is occuring here. We've simply created a new table named 'logs'.
Before we get into how we use this table for good, here's a quick review of how logging works in a script:
# http://docs.python.org/howto/logging.html#configuring-logging import logging # create logger logger = logging.getLogger('simple_example') logger.setLevel(logging.DEBUG) # create console handler and set level to debug ch = logging.StreamHandler() ch.setLevel(logging.DEBUG) # create formatter formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s') # add formatter to ch ch.setFormatter(formatter) # add ch to logger logger.addHandler(ch) # 'application' code logger.debug('debug message') logger.info('info message') logger.warn('warn message') logger.error('error message') logger.critical('critical message')
What you should gain from the above intro is that your handler uses a formatter and does the heavy lifting of executing the output of the logging.LogRecord. The output actually comes from logging.Handler.emit, a method we will now override as we create our SQLAlchemyHandler.
Let's subclass Handler now (put this in myapp.handlers):
import logging import traceback import transaction from models import Log, DBSession class SQLAlchemyHandler(logging.Handler): # A very basic logger that commits a LogRecord to the SQL Db def emit(self, record): trace = None exc = record.__dict__['exc_info'] if exc: trace = traceback.format_exc(exc) log = Log( logger=record.__dict__['name'], level=record.__dict__['levelname'], trace=trace, msg=record.__dict__['msg'],) DBSession.add(log) transaction.commit()
For a little more depth, logging.LogRecord, for which record is an instance, contains all it's nifty log information in it's __dict__ attribute.
Now, we need to add this logging handler to our .ini configuration files. Before we add this, our production.ini file should contain something like:
We must add our SQLAlchemyHandler to the mix. So make the following changes to your production.ini file.
The changes we made simply allow Paster to recognize a new handler - sqlalchemy, located at [handler_sqlalchemy]. Most everything else about this configuration should be straightforward. If anything is still baffling, then use this as a good opportunity to read the Python logging documentation.
Below is an example of how you might use the logger in myapp.views:
import logging from pyramid.view import view_config from pyramid.response import Response log = logging.getLogger(__name__) @view_config(route_name='home') def root(request): log.debug('exception impending!') try: 1/0 except: log.exception('1/0 error') log.info('test complete') return Response("test complete!")
When this view code is executed, you'll see up to three (depending on the level of logging you allow in your configuation file) records!
For more power, match this up with pyramid_exclog at http://docs.pylonsproject.org/projects/pyramid_exclog/en/latest/