What does the binlog dump thread do?

Question

Options

• AIt monitors and schedules the rotation/deletion of the binary logs.
• BIt reads the relay log and executes the events contained in them.
• CIt acquires a lock on the binary log for reading each event to be sent to the slave.
• DIt connects to the master and asks it to send updates recorded in its binary logs.

• A
  6% (2)
• B
  6% (2)
• C
  3% (1)
• D
  85% (29)

Explanation

D is correct because the binlog dump thread runs on the master server - when a replica connects to the master requesting replication, the master spawns a binlog dump thread that reads from the binary log and streams those events to the replica. It's the master-side component of the replication pipeline.

Why the others are wrong:

• A describes the binary log rotation/purge mechanism (governed by settings like expire_logs_days), not a dedicated thread role.
• B describes the SQL thread on the replica, which replays events from the relay log - a completely different thread on the opposite server.
• C is a distractor mixing up locking mechanics; while the dump thread does read the binary log, acquiring locks on relay logs for execution is associated with replica threads, not the master's dump thread.

Memory tip: Think "dump = deliver from master." The binlog dump thread dumps (sends) binary log data from the master to whoever asks - the slave's I/O thread is the one doing the asking (D), making D the initiating action from the slave's perspective that triggers the dump thread on the master side. Pair it with: Slave I/O thread requests → Master dump thread responds → Slave SQL thread executes.

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