8 Investigating deadlocks with thread dumps
This chapter covers
- Getting thread dumps using a profiler
- Getting thread dumps using the command line
- Reading thread dumps to investigate issues
- Enhancing thread-dumps investigations with AI
Picture this: You’re at your favorite coffee shop, about to enjoy a well-earned break. You order a cappuccino, and just as you’re about to pay, the cashier’s system freezes. The barista taps the screen, then tries again. Nothing. Meanwhile, the queue behind you is growing.
Behind the counter, two cash registers are blinking with error messages. Turns out, Register A is waiting for Register B to confirm a payment, while Register B is waiting for Register A to process it first. Neither register can proceed, and the entire coffee shop grinds to a halt. Baristas glance at each other helplessly. Customers sigh. Someone dramatically proclaims, “I just wanted coffee!”
Congratulations, you’ve just witnessed a deadlock—only instead of two software threads, it’s two cash registers locked in an eternal standoff. The only way to fix it? A reboot, or some clever debugging to break the cycle.
Now, imagine a similar situation happening inside a Java application. Multiple threads get stuck waiting for each other, and your app stops responding. How do you figure out what went wrong? That’s where thread dumps come in.