rdbms: avoid DB_PRIMARY queries in getLagFromPtHeartbeat()
The default mode (using server_ids) will now use SHOW REPLICA STATUS data instead of connected to the master. If the source server is not the root source server (e.g. the primary), then lagDetectionOptions should be configured to either specify the primary server ID or use custom channel columns (like WMF sites). Remove getMasterServerInfo() and getPrimaryServerInfo() method. Clean up some related comments and field names. Bug: T299691 Change-Id: I41a57247503a69367cd73d365f8aa8af04398e46
This commit is contained in:
Aaron Schulz
Krinkle
parent
e2b73a455d
commit
8c9398f7f9
2 changed files with 41 additions and 60 deletions
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@ -87,10 +87,11 @@ abstract class DatabaseMysqlBase extends Database {
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* pt-heartbeat assumes the table is at heartbeat.heartbeat
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* and uses UTC timestamps in the heartbeat.ts column.
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* (https://www.percona.com/doc/percona-toolkit/2.2/pt-heartbeat.html)
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* - lagDetectionOptions : if using pt-heartbeat, this can be set to an array map to change
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* the default behavior. Normally, the heartbeat row with the server
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* ID of this server's primary DB will be used. Set the "conds" field to
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* override the query conditions, e.g. ['shard' => 's1'].
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* - lagDetectionOptions : if using pt-heartbeat, this can be set to an array map.
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* The "conds" key overrides the WHERE clause used to find the relevant row in the
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* `heartbeat` table, e.g. ['shard' => 's1']. By default, the row used is the newest
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* row having a server_id matching that of the immediate replication source server
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* for the given replica.
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* - useGTIDs : use GTID methods like MASTER_GTID_WAIT() when possible.
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* - insertSelectIsSafe : force that native INSERT SELECT is or is not safe [default: null]
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* - sslKeyPath : path to key file [default: null]
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@ -507,12 +508,17 @@ abstract class DatabaseMysqlBase extends Database {
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}
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if ( isset( $options['conds'] ) ) {
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// Best method for multi-DC setups: use logical channel names
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$ago = $this->fetchSecondsSinceHeartbeat( $options['conds'] );
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// Custom/explicit method: specify the server_id or use logical channel names.
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// This works well for multi-datacenter setups with read-only "standby masters"
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// in secondary datacenters that are used as replication sources. The `heartbeat`
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// row for the primary server can be found without resorting to slow queries to
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// fetch the server_id of the primary.
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$conds = $options['conds'];
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} else {
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// Standard method: use primary server ID (works with stock pt-heartbeat)
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$masterInfo = $this->getPrimaryServerInfo();
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if ( !$masterInfo ) {
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// Standard method: determine source server ID (works with stock pt-heartbeat).
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// This assumes that the immediate source server is the primary server.
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$sourceInfo = $this->getSourceServerInfo();
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if ( !$sourceInfo ) {
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$this->queryLogger->error(
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"Unable to query primary of {db_server} for server ID",
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$this->getLogContext( [
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@ -523,10 +529,10 @@ abstract class DatabaseMysqlBase extends Database {
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return false; // could not get primary server ID
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}
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$conds = [ 'server_id' => intval( $masterInfo['serverId'] ) ];
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$ago = $this->fetchSecondsSinceHeartbeat( $conds );
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$conds = [ 'server_id' => $sourceInfo['serverId'] ];
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}
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$ago = $this->fetchSecondsSinceHeartbeat( $conds );
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if ( $ago !== null ) {
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return max( $ago, 0.0 );
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}
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@ -541,52 +547,26 @@ abstract class DatabaseMysqlBase extends Database {
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return false;
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}
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protected function getPrimaryServerInfo() {
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if ( !$this->topologicalPrimaryConnRef ) {
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return false; // something is misconfigured
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/**
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* Get information about the direct replication source server for this replica server
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*
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* This only queries the replica itself, avoiding outages due to primary failure
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*
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* @return array<string,mixed>|false Map or false on failure
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*/
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protected function getSourceServerInfo() {
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$row = $this->getServerRoleStatus( 'SLAVE', __METHOD__ );
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if ( $row ) {
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// MariaDB uses Master_Server_Id; MySQL uses Source_Server_Id
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// https://mariadb.com/kb/en/show-replica-status/
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// https://dev.mysql.com/doc/refman/8.0/en/show-replica-status.html
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$id = (int)( $row['Master_Server_Id'] ?? $row['Source_Server_Id'] ?? 0 );
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} else {
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$id = 0;
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}
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$cache = $this->srvCache;
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$key = $cache->makeGlobalKey(
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'mysql',
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'master-info',
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// Using one key for all cluster replica DBs is preferable
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$this->topologicalPrimaryConnRef->getServerName()
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);
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$fname = __METHOD__;
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return $cache->getWithSetCallback(
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$key,
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$cache::TTL_INDEFINITE,
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function () use ( $cache, $key, $fname ) {
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// Get and leave a lock key in place for a short period
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if ( !$cache->lock( $key, 0, 10 ) ) {
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return false; // avoid primary DB connection spike slams
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}
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$flags = self::QUERY_SILENCE_ERRORS | self::QUERY_IGNORE_DBO_TRX | self::QUERY_CHANGE_NONE;
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// Connect to and query the primary DB; catch errors to avoid outages
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try {
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$res = $this->topologicalPrimaryConnRef->query(
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'SELECT @@server_id AS id',
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$fname,
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$flags
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);
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$row = $res ? $res->fetchObject() : false;
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$id = $row ? (int)$row->id : 0;
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} catch ( DBError $e ) {
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$id = 0;
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}
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// Cache the ID if it was retrieved
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return $id ? [ 'serverId' => $id, 'asOf' => time() ] : false;
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}
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);
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}
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protected function getMasterServerInfo() {
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wfDeprecated( __METHOD__, '1.37' );
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return $this->getPrimaryServerInfo();
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// Cache the ID if it was retrieved
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return $id ? [ 'serverId' => $id, 'asOf' => time() ] : false;
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}
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/**
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@ -880,13 +860,14 @@ abstract class DatabaseMysqlBase extends Database {
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/**
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* @param string $role One of "MASTER"/"SLAVE"
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* @param string $fname
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* @return string[] Latest available server status row
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* @return array<string,mixed>|null Latest available server status row; false on failure
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*/
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protected function getServerRoleStatus( $role, $fname = __METHOD__ ) {
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$flags = self::QUERY_IGNORE_DBO_TRX | self::QUERY_CHANGE_NONE;
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$flags = self::QUERY_SILENCE_ERRORS | self::QUERY_IGNORE_DBO_TRX | self::QUERY_CHANGE_NONE;
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$res = $this->query( "SHOW $role STATUS", $fname, $flags );
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$row = $res ? $res->fetchRow() : false;
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return $res->fetchRow() ?: [];
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return ( $row ?: null );
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}
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public function serverIsReadOnly() {
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@ -300,13 +300,13 @@ class DatabaseMysqlBaseTest extends PHPUnit\Framework\TestCase {
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$db = $this->getMockBuilder( DatabaseMysqli::class )
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->disableOriginalConstructor()
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->onlyMethods( [
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'getLagDetectionMethod', 'fetchSecondsSinceHeartbeat', 'getPrimaryServerInfo' ] )
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'getLagDetectionMethod', 'fetchSecondsSinceHeartbeat', 'getSourceServerInfo' ] )
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->getMock();
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$db->method( 'getLagDetectionMethod' )
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->willReturn( 'pt-heartbeat' );
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$db->method( 'getPrimaryServerInfo' )
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$db->method( 'getSourceServerInfo' )
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->willReturn( [ 'serverId' => 172, 'asOf' => time() ] );
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$db->setLBInfo( 'replica', true );
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