When logging in Java, especially frameworks like Spring, making sure the logging statement has access to the full context of the operation in flight is important. Instead of spamming piles of logging statements in your business logic, you can use a “mapped diagnostic context” to cache useful bits of information during an operation, such that any logging statement can access it.

One of the tools for this is the “Mapped Data Context”, MDC. Essentially, it’s very much like a great big hash map that happens to be thread-local and is meant to be used by the logging framework. It’s a global-ish variable, but without the worst side effects of being global.

Nobody wants to have a Bobby Tables moment in their database. So we need to to sanitize our inputs. Ted C noticed a bunch of stored procedures which contained lines like this:

  @scrubbed = fn_ScrubInput(fn_ScrubInput(@input))

The accountants at Gary's company had a problem: sometimes, when they wanted to check the price to ship a carton of product, that price was zero. No one had, as of yet, actually shipped product for free, but they needed to understand why certain cartons were showing up as having zero cost.

The table which tracks this, CartonFee, has three fields: ID, Carton, and Cost. Carton names are unique, and things like 12x3x6, or Box1, or even Large box. So, given a carton name, it should be pretty easy to update the cost, yes? The stored procedure which does this, spQuickBooks_UpdateCartonCost should be pretty simple.

Graham picked up a ticket regarding their password system. It seemed that several users had tried to put in a perfectly valid password, according to the rules, but it was rejected.

Graham's first step was to attempt to replicate on his own, but couldn't do it. So he followed up with one of the end users, and got them to reveal the password they had tried to use. That allowed him to trigger the bug, so he dug into the debugger to find the root cause.

Sometimes, a block of terrible code exists for a good reason. Usually, it exists because someone was lazy or incompetent, which while not a good reason, at least makes sense. Sometimes, it exists for a stupid reason.

Janet’s company recently bought another company, and now the new company had to be integrated into their IT operations. One of the little, tiny, minuscule known-issues in the new company’s system was that their logging was mis-configured. Instead of putting a new-line after each logging message, it put only a single space.