Class: Clickwrap::StatementIdentityLock

Inherits:
ApplicationRecord show all
Defined in:
lib/clickwrap/models/statement_identity_lock.rb

Overview

A small coordination row for one exact statement identity or actor-wide state scope. Evidence stays in Event; this table exists because a row lock cannot be taken before the first projection/event creates its row.

Persisting one lock per identity avoids adapter-specific advisory locks. On PostgreSQL and MySQL each acquisition is a real row lock; SQLite emits no locking clause (Arel's SQLite visitor is a no-op for FOR UPDATE), so what serializes writers there is the database-wide write lock — a different mechanism whose contention surfaces as SQLITE_BUSY rather than a blocked row. The concurrency test lane runs on PostgreSQL and MySQL for exactly this reason. Callers acquire several identities in digest order so policies with more than one one-time statement cannot deadlock by choosing a different order.

Class Method Summary collapse

Class Method Details

.acquire!(identity_digest) ⇒ Object 



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# File 'lib/clickwrap/models/statement_identity_lock.rb', line 22

def self.acquire!(identity_digest)
  lock_row = create_or_find_by!(identity_digest:) do |row|
    row.created_at = Clickwrap.now
  end
  lock_row.lock!
  lock_row
end

.acquire_for_actor!(actor_reference) ⇒ Object 



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# File 'lib/clickwrap/models/statement_identity_lock.rb', line 34

def self.acquire_for_actor!(actor_reference)
  acquire!(actor_state_scope_for(actor_reference))
end

.actor_state_scope_for(actor_reference) ⇒ Object 



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# File 'lib/clickwrap/models/statement_identity_lock.rb', line 30

def self.actor_state_scope_for(actor_reference)
  Digest.digest_canonical({ "actor_state_reference" => actor_reference.to_s })
end