15.1 Logging in a Web Application
The importance of logging has
been evident to experienced developers for many years. Arguably,
logging can be as important a part of your framework as exception
handling or even security, both of which may rely on logging
functionality to help carry out their responsibilities. Without
logging, application maintenance can become a nightmare for the
developers. We all know that all
"real" applications periodically go
through maintenance cycles.Still, you may wonder whether logging in web applications is as
necessary and important as logging in other types of applications.
Because web applications can sometimes be smaller and less complex
than their enterprise counterparts, you might think that logging is
less important in these applications. However, with nontrivial web
applications, this is not the caselogging is just as critical
there as it is in an enterprise application.
Log messages can be arbitrarily
broken down into two categories: system messages
and application messages. System messages have
to do with the internal operation of the application, rather than
something specific to a user or datafor example, a system
message might indicate that the application is unable to send an
email because the SMTP host is not responding. On the other hand, an
application message might indicate that the user
"Jane Doe" tried to submit a
purchase order that was above her company's credit
limit.The system message in the first case might be logged with a priority
of "error," whereas the application
message might only get a priority of
"info." We can then set up the
logging environment so that "error"
messages generate an email or a pager message to the system
administrators for immediate attention, while
"info" messages go into a file for
later auditing.The different types and categories of log messages are typically used
for different purposes across organizations. Although many
applications may log messages with the priority of
"error," what's an
error to one organization may just be a warning to another.
There's not a great deal of consistency across
organizations, and there may never beorganizations have
different priorities, and what's critical to one may
not necessarily be critical to another.In this chapter, we generalize the discussion of system versus
application messages. Because views of what's
considered an error differ, there's no general way
to specify what's an error, a warning, or just
general information for your particular application.
That's a decision that you, your development team,
and your product-management group will have to make.
We'll keep our discussion at a higher level and not
focus on these issues. |
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