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UserAgent Debugging Made Easy

Earlier today I saw a recent blog post from Gabor Szabo. In it, he shows a very concise way to handle Basic Authentication using LWP::UserAgent. Now, what if you had a problem running the script? How might you go about debugging it? You could add a bunch of print statements. Maybe dump the request and the response objects. That’s entirely valid, but I want to show you a slightly simpler way of going about it, using LWP::ConsoleLogger::Easy.

Gabor’s original script looks like this:

Let’s run it to see what the output looks like.

Here’s the debugging version. Note the important changes are on lines 4 and 9.

The output we get is:

You can see that the debugging version is just one line longer. I added 2 lines and removed a print statement. It prints out a whole pile of (nicely?) formatted information. Let’s try running it with valid credentials. (Brace yourself, there’s going to be a lot of output.)

You can see that I ran the script with LWPCL_REDACT_HEADERS='Authorization'. That’s a handy flag to use if you want to copy/paste an example when asking for help publicly. It replaced the Authorization header value with [REDACTED]. That’s maybe not a big deal here, but there are cases where it’s more important. See also LWP_REDACT_PARAMS.

Let’s make it prettier. We’ll do this by installing HTML::FormatText::Lynx.

Let’s run it again. I’ll only show you the changed part. Instead of just displaying the text with the HTML stripped away, we get something nicer to look at.

Now, we can also turn down the verbosity of the script by passing a flag to debug_ua(). Any integer from 0-8 will do the trick. Let’s try 6.

Let’s see what we get:

That’s far easier to read now.

This is just a very basic example of what you can do with LWP::ConsoleLogger::Easy. There’s a lot more you can do with it and it’s all laid out for you in the documentation. It really shines when you have a user agent which is going through multiple links or if you’re debugging someone else’s API calls. Have fun with it. It beats inserting arbitrary print statements and it could save you from pulling a lot of your own hair out someday.