How to use MDC with thread pools?
Save MDC (Mapped Diagnostic Context) while in Thread Pool land by wrapping tasks in a MdcAwareRunnable or MdcAwareCallable. This helpful wrapper copies the task's MDC before the task runs and clears it afterwards.
Remember to wrap your tasks in this MdcAwareRunnable for a swim in the ExecutorService - it's MDC safe!
Advanced strategies: Because we can always go deeper
When ThreadPoolExecutor becomes your friend
Customize ThreadPoolExecutor
by overriding beforeExecute
and afterExecute
. This makes sure that your task's MDC values are copied over and restored in absolute secrecy. Well, not really, but it's fun to pretend, isn't it?
Using Spring? Meet the MdcTaskDecorator
If you're using Spring, TaskDecorator
can make your ThreadPoolTaskExecutor
get along with MDC like two peas in a pod:
And the Oscar for the best supporting decorator in a ThreadPoolTaskExecutor
goes to... MdcTaskDecorator
:
Remember, with great MDC comes great responsibility
Your task is to thread carefully! (pun intended) MDC operations should be thread-safe within tasks. Local variables are your friends, while shared state is that friendly-looking stranger offering you unwanted candies.
Getting serious with Monitoring and Reliability
We hate to be the party poopers but evaluate the impact of MDC on your jazzy live systems. MDC operations are like lightweight boxers – punching way above their weight class but with small overhead in high-load scenarios.
But what if it goes wrong? Here are common pitfalls and solutions
Stale MDC values
You don't want old, moldy MDC values, do you? Use MdcAwareRunnable
to clear the MDC once task finishes. Now, subsequent tasks have a sparkling clean context.
Hiccups in MDC context propagation
Got nested tasks? Make sure the MDC context is handed down like a cherished family recipe. You might need extra wrappers or tweaks to manage nested contexts.
Overhead concerns
MDC context copying may have some overhead, you don't want your tasks to run like they're wearing lead boots. Strike the balance between rich, detailed logging and smooth, seamless performance.
Shared state within MDC
If multiple tasks are updating the same MDC keys, it's like a battle royale for data! Use proper synchronization to avoid such data bloodbath and keep the peace.
Handling thread pool shutdown like a pro
Even during a shutdown, you need MDC context for logging. Make sure to clear the decks (and MDC) as a part of your shutdown sequence.
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