DB_DEADLOCK(1)

💀 DB_DEADLOCK — bestie edition 💀

okay so we're in the DB_DEADLOCK(1) page of the BerkeleyDB Utilities manual, and honestly? this one is a whole vibe. it's the little daemon that finds deadlocks and un-alives one of the lock requests. dramatic? yes. necessary? absolutely. let's get into it 🫶

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✨ NAME ✨

db_deadlock — detect deadlocks and abort lock requests. that's it. that's the job. she's a snitch for stale locks and honestly we love her for it 💅

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🌸 SYNOPSIS 🌸

db_deadlock [-Vv] [-a e | m | n | o | W | w | y ] [-h home] [-L file]
[-t sec.usec]

look at her. compact. iconic. one little line carrying the whole personality 💖

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🦋 DESCRIPTION 🦋

okay so here's the tea. db_deadlock walks the database environment lock region — like, literally traverses it — and every single time it clocks a deadlock, or a lock request that has timed out, it aborts a lock request. bye bestie 👋

by default, when it catches a deadlock, it just picks a random lock request to abort. no strategy, no favorites, pure chaos. and honestly? sometimes that's the move.

run this as a background daemon!! or call the underlying Berkeley DB deadlock detection interfaces some other way. whichever. but you need to do it whenever multiple threads or processes are hitting a database and at least one of them is modifying it. no cap, this is not optional behavior, it's just how it is.

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💅 OPTIONS 💅

• -a — when a deadlock is detected, abort the locker:
  • m — with the most locks
  • n — with the fewest locks
  • o — with the oldest lock
  • W — with the most write locks
  • w — with the fewest write locks
  • y — with the youngest lock

and when lock or transaction timeouts have been specified:

• e — abort any lock request that has timed out

• -h home — specify a home directory for the database environment. if you don't, it just uses the current working directory. it's giving "wherever i am is home" 🏠✨
• -L file — log the execution of the db_deadlock utility to the specified file. the format looks like this, where ### is the process ID, and the date is the time the utility was started:

db_deadlock: ### Wed Jun 15 01:23:45 EDT 1995

heads up: this file will be removed if the db_deadlock utility exits gracefully. so if you wanted receipts, keep an eye on that 👀

• -t sec.usec — check the database environment every sec seconds plus usec microseconds to see if a process has been forced to wait for a lock; if one has, review the database environment lock structures. so like, set a lil heartbeat. 🩺
• -V — write the library version number to the standard output, and exit. short and sweet. periodt.
• -v — run in verbose mode, generating messages each time the detector runs. chatty detector era 💬

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okay important stuff incoming, no skipping:

if the -t option is not specified, db_deadlock will run once and exit. one and done. no lingering.

the db_deadlock utility uses a Berkeley DB environment — as described for the -h option, the environment variable DB_HOME, or because the utility was run in a directory containing a Berkeley DB environment. and listen, to avoid environment corruption when using a Berkeley DB environment, db_deadlock should always be given the chance to detach from the environment and exit gracefully. so be nice to her!! to cause db_deadlock to release all environment resources and exit cleanly, send it an interrupt signal (SIGINT). that's the polite way to say bye 🥺

⚠️ also: the db_deadlock utility does not attempt to create the Berkeley DB shared memory regions if they do not already exist. the application which creates the region should be started first, and then, once the region is created, the db_deadlock utility should be started. order matters bestie, don't come in before the party's set up.

and for the deep lore girlies: the DB_ENV->lock_detect method is the underlying method used by the db_deadlock utility. see the db_deadlock utility source code for an example of using DB_ENV->lock_detect in a IEEE/ANSI Std 1003.1 (POSIX) environment. iykyk 🔥

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👑 EXIT STATUS 👑

the db_deadlock utility exits 0 on success, and >0 if an error occurs. zero = slay, anything above = something went wrong, go look 🫠

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🌈 ENVIRONMENT 🌈

• DB_HOME — if the -h option is not specified and the environment variable DB_HOME is set, it is used as the path of the database home, as described in DB_ENV->open. she's the backup plan. the understudy. the one who steps in when -h doesn't show up 🌟

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🎀 SEE ALSO 🎀

db_archive(1) db_checkpoint(1) db_dump(1) db_hotbackup(1) db_log_verify(1) db_load(1) db_printlog(1) db_recover(1) db_replicate(1) db_stat(1) db_tuner(1) db_upgrade(1) db_verify(1)

the whole friend group. go say hi. they're all in section 1 🧚

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and that's the page!! this is BerkeleyDB 5.3.28, dated 06 December 2016, and you just read DB_DEADLOCK(1). tysm for coming to my ted talk, go abort a lock request responsibly, mwah 💖🌸🦋