Alright, so the other day I was digging through some old code, trying to untangle a particularly nasty issue, and yep, it turned out to be another deadlock situation. It got me thinking about all the different kinds of deadlocks I’ve bumped into over the years. Some are just annoying textbook cases, others… well, others have cost me sleep. So, I figured, why not try and categorize them? Put them into a sort of “deadlock tier list” based on how much grief they’ve caused me personally.
Getting Started: Remembering the Pain
First thing I did was just sit back and brainstorm. Didn’t need anything fancy, just started listing out deadlock scenarios I could recall off the top of my head. You know the ones:
- The classic A locks X then Y, while B locks Y then X. Simple, but still trips people up.
- Database deadlocks. Oh boy. Row locks, table locks, gaps locks… transaction isolation levels making things weird. These always seem to pop up at the worst times.
- Resource contention beyond just code locks. Like fighting over a limited pool of connections or file handles.
- Deadlocks involving external services or APIs. Waiting for a response that never comes because the other service is waiting on you. Ugh.
- The really weird ones involving multiple threads, maybe some async stuff thrown in, where figuring out the lock order feels like detective work.
I just kept jotting these down as they came to me, thinking back to specific projects or late-night debugging sessions. It wasn’t super organized at first, just a raw dump of deadlock memories.
Making the Tiers: How Bad Is It Really?
Once I had a decent list, I needed some way to rank them. I decided on a pretty standard tier system, something like S, A, B, C. Here’s roughly what I was thinking for each:
- S-Tier: The absolute nightmares. Hard to reproduce, hard to debug, potentially brings down critical systems. Usually involves distributed systems or very complex interactions. Losing sleep over these.
- A-Tier: Seriously painful. Takes significant effort to track down and fix. Database deadlocks often land here, especially the tricky ones. Causes real headaches and delays.
- B-Tier: Common annoyances. The bread-and-butter deadlocks, like the simple lock inversions. You see them often enough, they’re a pain, but usually solvable without tearing all your hair out.
- C-Tier: Textbook stuff. Almost learning exercises. You fix them, maybe feel a bit silly for letting it happen, and move on.
This felt like a good enough way to start sorting. It’s subjective, yeah, based purely on my own struggles and frustrations.
Sorting Them Out: The Actual Ranking
Then came the actual sorting. I took my messy list and started placing each type into one of the tiers.
The simple AB-BA lock order issue? That felt like a solid B-Tier. It’s common, especially when people aren’t careful, but usually, the fix is straightforward once you spot it.
Database deadlocks were trickier. A simple row lock contention might be B-Tier, but those involving complex transactions, triggers, or different isolation levels? Those definitely lean towards A-Tier for me. They often require deep dives into query plans and transaction logs.
Resource pool exhaustion (like connection pools)? I put that in B-Tier too. Annoying, indicates a potential scaling issue or leak, but usually identifiable through monitoring.
Now, the deadlocks involving multiple services or complex async/await chains where the dependency loop isn’t obvious? S-Tier. Absolutely S-Tier. These are the ones that can be intermittent, hide under load, and require coordinating across different systems or teams to even understand, let alone fix. Debugging these is just brutal sometimes.
Anything involving third-party libraries or systems where you don’t control the locking mechanism internally also tends to creep up towards A or even S, depending on how opaque and critical that external bit is.
Final Look and Thoughts
After shuffling things around a bit, I had my list. It’s not scientific, it’s just based on my gut and my scars from past battles. Looking at it laid out like that was kind of interesting. It reinforces where the real challenges often lie – not always in the simple, localized problems, but in the complex interactions between different parts of a system, or with external dependencies.
Doing this was actually pretty useful. It’s a good reminder of the patterns to watch out for. Maybe calling it a “tier list” is a bit silly, but organizing thoughts based on practical pain points? That felt productive. It’s just a snapshot of my experience, really. Someone else might rank them totally differently based on the kinds of systems they work on.
