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chore: add PGLocks query to analyze what locks are held in pg #15308

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Merged
merged 6 commits into from
Nov 1, 2024
Merged

chore: add PGLocks query to analyze what locks are held in pg #15308

merged 6 commits into from
Nov 1, 2024

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@Emyrk Emyrk commented Oct 31, 2024 •
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Adds PGLocks query similar to how we have Ping(). I cannot do this via SQLc, as SQLc does not know about pg_locks table.

The string format is able to be changed to extract more value. I recognize this is not perfect, but I wrote it trying to learn more about these locks. It felt valuable enough to keep. Not all values are handled correctly here, I'll add functionality as required.

Some example output

  1. Open a TX in mode serializable and run GetQuotaConsumedForUser()
794-<nil> [granted] <nil>/virtualxid/ExclusiveLock: waiting to acquire virtual tx id lock
793-<nil> [granted] <nil>/virtualxid/ExclusiveLock: waiting to acquire virtual tx id lock
794-<nil> [granted] pg_locks/relation/AccessShareLock: 
793-<nil> [granted] workspace_builds/relation/AccessShareLock: 
793-<nil> [granted] workspace_builds/tuple/SIReadLock: page=0 tuple=1
793-<nil> [granted] workspace_builds_job_id_key/relation/AccessShareLock: 
793-<nil> [granted] workspace_builds_pkey/relation/AccessShareLock: 
793-<nil> [granted] workspace_builds_workspace_id_build_number_key/page/SIReadLock: page=1
793-<nil> [granted] workspace_builds_workspace_id_build_number_key/relation/AccessShareLock: 
793-<nil> [granted] workspaces/relation/AccessShareLock: 
793-<nil> [granted] workspaces/relation/SIReadLock: 
793-<nil> [granted] workspaces_owner_id_lower_idx/relation/AccessShareLock: 
793-<nil> [granted] workspaces_owner_id_lower_idx/page/SIReadLock: page=1
793-<nil> [granted] workspaces_pkey/relation/AccessShareLock:
  1. Run UpdateWorkspaceBuildCostByID in the TX
868-<nil> [granted] <nil>/virtualxid/ExclusiveLock: waiting to acquire virtual tx id lock
867- 3689 [granted] <nil>/transactionid/ExclusiveLock: ???
867-<nil> [granted] <nil>/virtualxid/ExclusiveLock: waiting to acquire virtual tx id lock
868-<nil> [granted] pg_locks/relation/AccessShareLock: 
867-<nil> [granted] workspace_builds/relation/AccessShareLock: 
867-<nil> [granted] workspace_builds/relation/RowExclusiveLock: 
867-<nil> [granted] workspace_builds_job_id_key/relation/AccessShareLock: 
867-<nil> [granted] workspace_builds_job_id_key/relation/RowExclusiveLock: 
867-<nil> [granted] workspace_builds_pkey/relation/RowExclusiveLock: 
867-<nil> [granted] workspace_builds_pkey/relation/AccessShareLock: 
867-<nil> [granted] workspace_builds_pkey/page/SIReadLock: page=1
867-<nil> [granted] workspace_builds_workspace_id_build_number_key/relation/RowExclusiveLock: 
867-<nil> [granted] workspace_builds_workspace_id_build_number_key/relation/AccessShareLock: 
867-<nil> [granted] workspace_builds_workspace_id_build_number_key/page/SIReadLock: page=1
867-<nil> [granted] workspaces/relation/AccessShareLock: 
867-<nil> [granted] workspaces/relation/SIReadLock: 
867-<nil> [granted] workspaces_owner_id_lower_idx/relation/AccessShareLock: 
867-<nil> [granted] workspaces_owner_id_lower_idx/page/SIReadLock: page=1
867-<nil> [granted] workspaces_pkey/relation/AccessShareLock:

Specifically these are the new locks aquired:

868-<nil> [granted] <nil>/virtualxid/ExclusiveLock: waiting to acquire virtual tx id lock
867- 3689 [granted] <nil>/transactionid/ExclusiveLock: ???
868-<nil> [granted] pg_locks/relation/AccessShareLock: 
867-<nil> [granted] workspace_builds/relation/RowExclusiveLock: 
867-<nil> [granted] workspace_builds_job_id_key/relation/RowExclusiveLock: 
867-<nil> [granted] workspace_builds_pkey/relation/RowExclusiveLock: 
867-<nil> [granted] workspace_builds_pkey/page/SIReadLock: page=1
867-<nil> [granted] workspace_builds_workspace_id_build_number_key/relation/RowExclusiveLock:

Used to respond here: #15261 (comment)

@Emyrk Emyrk marked this pull request as ready for review October 31, 2024 15:04
Emyrk
Emyrk commented Oct 31, 2024
View reviewed changes
coderd/database/pglocks.go
Comment on lines +50 to +57
case "relation":
details = ""
case "page":
details = fmt.Sprintf("page=%d", *l.Page)
case "tuple":
details = fmt.Sprintf("page=%d tuple=%d", *l.Page, *l.Tuple)
case "virtualxid":
details = "waiting to acquire virtual tx id lock"
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Will implement this as needed. Not going to be exhaustive here right now

@Emyrk Emyrk requested a review from spikecurtis October 31, 2024 16:32
@Emyrk Emyrk merged commit 3a9270d into stevenmasley/postgres_tx_serial Nov 1, 2024
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@Emyrk Emyrk deleted the stevenmasley/postgres_tx_serial_pg_locks branch November 1, 2024 13:25
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