> For the complete documentation index, see [llms.txt](https://mariadb.com/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mariadb.com/docs/server/ha-and-performance/optimization-and-tuning/buffers-caches-and-threads/thread-states/replica-io-thread-states.md). # Replica I/O Thread States This article documents thread states that are related to [replica](/docs/server/ha-and-performance/standard-replication/replication-overview.md) I/O threads. These correspond to the `Slave_IO_State` shown by [SHOW REPLICA STATUS](/docs/server/reference/sql-statements/administrative-sql-statements/show/show-replica-status.md) and the `STATE` values listed by the [SHOW PROCESSLIST](/docs/server/reference/sql-statements/administrative-sql-statements/show/show-processlist.md) statement or in the [Information Schema PROCESSLIST Table](/docs/server/reference/system-tables/information-schema/information-schema-tables/information-schema-processlist-table.md) as well as the `PROCESSLIST_STATE` value listed in the [Performance Schema threads Table](/docs/server/reference/system-tables/performance-schema/performance-schema-tables/performance-schema-threads-table.md). | Value | Description | | ---------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | Checking master version | Checking the primary's version, which only occurs very briefly after establishing a connection with the primary. | | Connecting to master | Attempting to connect to primary. | | Queueing master event to the relay log | Event is being copied to the [relay log](/docs/server/server-management/server-monitoring-logs/binary-log/relay-log.md) after being read, where it can be processed by the SQL thread. | | Reconnecting after a failed binlog dump request | Attempting to reconnect to the primary after a previously failed binary log dump request. | | Reconnecting after a failed master event read | Attempting to reconnect to the primary after a previously failed request. After successfully connecting, the state will change to Waiting for master to send event. | | Registering slave on master | Registering the replica on the primary, which only occurs very briefly after establishing a connection with the primary. | | Requesting binlog dump | Requesting the contents of the binary logs from the given log file name and position. Only occurs very briefly after establishing a connection with the primary. | | Waiting for master to send event | Waiting for [binary log](/docs/server/server-management/server-monitoring-logs/binary-log.md) events to arrive after successfully connecting. If there are no new events on the primary, this state can persist for as many seconds as specified by the [slave\_net\_timeout](/docs/server/ha-and-performance/standard-replication/replication-and-binary-log-system-variables.md) system variable, after which the thread will reconnect. Prior to [MariaDB 10.6.18](/docs/release-notes/community-server/10.6/10.6.18.md), [MariaDB 10.11.8](/docs/release-notes/community-server/10.11/10.11.8.md), [MariaDB 11.0.6](/docs/release-notes/community-server/old-releases/11.0/11.0.6.md), [MariaDB 11.1.5](/docs/release-notes/community-server/old-releases/11.1/11.1.5.md), [MariaDB 11.2.4](/docs/release-notes/community-server/old-releases/11.2/11.2.4.md) and [MariaDB 11.4.2](/docs/release-notes/community-server/11.4/11.4.2.md), the time was from SLAVE START. From these versions, the time is since reading the last event. | | Waiting for slave mutex on exit | Waiting for replica mutex while the thread is stopping. Only occurs very briefly. | | Waiting for the slave SQL thread to free enough relay log space. | [Relay log](/docs/server/server-management/server-monitoring-logs/binary-log/relay-log.md) has reached its maximum size, determined by [relay\_log\_space\_limit](/docs/server/ha-and-performance/standard-replication/replication-and-binary-log-system-variables.md) (no limit by default), so waiting for the SQL thread to free up space by processing enough relay log events. | | Waiting for master update | State before connecting to primary. | | Waiting to reconnect after a failed binlog dump request | Waiting to reconnect after a binary log dump request has failed due to disconnection. The length of time in this state is determined by the MASTER\_CONNECT\_RETRY clause of the [CHANGE MASTER TO](/docs/server/reference/sql-statements/administrative-sql-statements/replication-statements/change-master-to.md) statement. | | Waiting to reconnect after a failed master event read | Sleeping while waiting to reconnect after a disconnection error. The time in seconds is determined by the MASTER\_CONNECT\_RETRY clause of the [CHANGE MASTER TO](/docs/server/reference/sql-statements/administrative-sql-statements/replication-statements/change-master-to.md) statement. | *This page is licensed: CC BY-SA / Gnu FDL* {% @marketo/form formId="4316" %}