LoadMonitor's reliance on LoadBalance::getAnyOpenConnection was removed as part of T265386 and T314020: LoadMonitor connection weighting reimagined:

In T265386#8507591, @gerritbot wrote:

Change 868514 merged by jenkins-bot:

[mediawiki/core@master] rdbms: add CONN_UNTRACKED_GAUGE LoadBalancer flag for LoadMonitor gauging

https://gerrit.wikimedia.org/r/868514

Change 876362 had a related patch set uploaded (by Krinkle; author: Krinkle):

[mediawiki/core@master] Storage: Change LoadBalancer::getAnyOpenConnection to getConnectionRef

https://gerrit.wikimedia.org/r/876362

Change 876362 merged by jenkins-bot:

[mediawiki/core@master] Storage: Change LoadBalancer::getAnyOpenConnection to getConnectionRef

https://gerrit.wikimedia.org/r/876362

Change 974671 had a related patch set uploaded (by Ladsgroup; author: Amir Sarabadani):

[mediawiki/extensions/EventBus@master] Remove JobSerialCommitThreshold

https://gerrit.wikimedia.org/r/974671

Change 974677 had a related patch set uploaded (by Ladsgroup; author: Amir Sarabadani):

[mediawiki/core@master] Remove wgJobSerialCommitThreshold

https://gerrit.wikimedia.org/r/974677

Change 974671 merged by jenkins-bot:

[mediawiki/extensions/EventBus@master] Remove support for $wgJobSerialCommitThreshold

https://gerrit.wikimedia.org/r/974671

Change 974677 merged by jenkins-bot:

[mediawiki/core@master] jobqueue: Remove $wgJobSerialCommitThreshold

https://gerrit.wikimedia.org/r/974677

Only call left is in CP. There is no easy replacement there. CP is part of rdbms and the function is explicitly marked as @internal, We are also phasing direct dependencies to LB anyway, not sure it's worth doing

In T325389#9339135, @Ladsgroup wrote:

Only call left is in CP. There is no easy replacement there. CP is part of rdbms and the function is explicitly marked as @internal, We are also phasing direct dependencies to LB anyway, not sure it's worth doing

We could invert it slightly to remove this. Would that work?

class ChronologyProtector
	public function stageSessionPrimaryPos( LoadBalancer $lb )
		$primaryConn = $lb->getAnyOpenConnection( … );
		$pos = $primaryConn->getPrimaryPos();
		$this->shutdownPositions[] = $pos;
		…

class LBFactory
  public function shutdown(…)
    foreach ( $this->getLBsForOwner() as $lb )
      $this->chronologyProtector->stageSessionPrimaryPos( $lb );

And let LB return the position first:

class ChronologyProtector
	public function stageSessionPrimaryPos( DBPrimaryPos $pos ) {
		$this->shutdownPositions[] = $pos;
		…

class LBFactory
  public function shutdown(…)
    foreach ( $this->getLBsForOwner() as $lb )
      $this->chronologyProtector->stageSessionPrimaryPos( $lb->getPrimaryPos() );

Or if accessible from there:

class ChronologyProtector
	public function stageSessionPrimaryPos( LoadBalancer $lb )
		$pos = $lb->getPrimaryPos()
		$this->shutdownPositions[] = $pos;
		…

class LBFactory
  public function shutdown(…)
    foreach ( $this->getLBsForOwner() as $lb )
      $this->chronologyProtector->stageSessionPrimaryPos( $lb );

Both ways moves the responsibility to LB to deal with known positions. The downside is getPrimaryPos() actually already exists, and it's a bit of a strange method that actually uses getAnyOpenConnection but then *also* proactively opens a new connection, because it's used by waitForReplication to create proactive wait cycles prior to any db writes at the start of some loops/jobs/scripts. So we'd need some kind of getPrimaryPos( POS_OPEN_ONLY | POS_ALLOW_CONNECT ) flag to differentiate the two use cases. Which.. yeah, might as well use getAnyOpenConnection.

Perhaps an alternative is to make getAnyOpenConnection() @internal and maybe move to ILoadBalancerForOwner at some point.

Indeed my biggest problem was that I don't want CP open a primary connection on shutdown on every LB in config (s1-s8, x1, x2, es1-5, etc.) but your fix gave me an idea. Patch coming.

Change 975266 had a related patch set uploaded (by Ladsgroup; author: Amir Sarabadani):

[mediawiki/core@master] rdbms: Drop ILoadBalancer::getAnyOpenConnection()

https://gerrit.wikimedia.org/r/975266

I basically check for connection to primary already existing in LBF itself where there is a function to do exactly that

Change 975266 merged by jenkins-bot:

[mediawiki/core@master] rdbms: Drop ILoadBalancer::getAnyOpenConnection()

https://gerrit.wikimedia.org/r/975266