DrydockAllocatorWorker.php
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Created: Sat, Mar 29, 05:15

DrydockAllocatorWorker.php
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	<?php

	/**
	* @task allocate Allocator
	* @task resource Managing Resources
	* @task lease Managing Leases
	*/
	final class DrydockAllocatorWorker extends DrydockWorker {

	protected function doWork() {
	$lease_phid = $this->getTaskDataValue('leasePHID');
	$lease = $this->loadLease($lease_phid);

	$this->allocateAndAcquireLease($lease);
	}


	/* -( Allocator )---------------------------------------------------------- */


	/**
	* Find or build a resource which can satisfy a given lease request, then
	* acquire the lease.
	*
	* @param DrydockLease Requested lease.
	* @return void
	* @task allocator
	*/
	private function allocateAndAcquireLease(DrydockLease $lease) {
	$blueprints = $this->loadBlueprintsForAllocatingLease($lease);

	// If we get nothing back, that means no blueprint is defined which can
	// ever build the requested resource. This is a permanent failure, since
	// we don't expect to succeed no matter how many times we try.
	if (!$blueprints) {
	$lease
	->setStatus(DrydockLeaseStatus::STATUS_BROKEN)
	->save();
	throw new PhabricatorWorkerPermanentFailureException(
	pht(
	'No active Drydock blueprint exists which can ever allocate a '.
	'resource for lease "%s".',
	$lease->getPHID()));
	}

	// First, try to find a suitable open resource which we can acquire a new
	// lease on.
	$resources = $this->loadResourcesForAllocatingLease($blueprints, $lease);

	// If no resources exist yet, see if we can build one.
	if (!$resources) {
	$usable_blueprints = $this->removeOverallocatedBlueprints(
	$blueprints,
	$lease);

	// If we get nothing back here, some blueprint claims it can eventually
	// satisfy the lease, just not right now. This is a temporary failure,
	// and we expect allocation to succeed eventually.
	if (!$blueprints) {
	// TODO: More formal temporary failure here. We should retry this
	// "soon" but not "immediately".
	throw new Exception(
	pht('No blueprints have space to allocate a resource right now.'));
	}

	$usable_blueprints = $this->rankBlueprints($blueprints, $lease);

	$exceptions = array();
	foreach ($usable_blueprints as $blueprint) {
	try {
	$resources[] = $this->allocateResource($blueprint, $lease);

	// Bail after allocating one resource, we don't need any more than
	// this.
	break;
	} catch (Exception $ex) {
	$exceptions[] = $ex;
	}
	}

	if (!$resources) {
	// TODO: We should distinguish between temporary and permament failures
	// here. If any blueprint failed temporarily, retry "soon". If none
	// of these failures were temporary, maybe this should be a permanent
	// failure?
	throw new PhutilAggregateException(
	pht(
	'All blueprints failed to allocate a suitable new resource when '.
	'trying to allocate lease "%s".',
	$lease->getPHID()),
	$exceptions);
	}

	// NOTE: We have not acquired the lease yet, so it is possible that the
	// resource we just built will be snatched up by some other lease before
	// we can. This is not problematic: we'll retry a little later and should
	// suceed eventually.
	}

	$resources = $this->rankResources($resources, $lease);

	$exceptions = array();
	$allocated = false;
	foreach ($resources as $resource) {
	try {
	$this->acquireLease($resource, $lease);
	$allocated = true;
	break;
	} catch (Exception $ex) {
	$exceptions[] = $ex;
	}
	}

	if (!$allocated) {
	// TODO: We should distinguish between temporary and permanent failures
	// here. If any failures were temporary (specifically, failed to acquire
	// locks)

	throw new PhutilAggregateException(
	pht(
	'Unable to acquire lease "%s" on any resouce.',
	$lease->getPHID()),
	$exceptions);
	}
	}


	/**
	* Get all the @{class:DrydockBlueprintImplementation}s which can possibly
	* build a resource to satisfy a lease.
	*
	* This method returns blueprints which might, at some time, be able to
	* build a resource which can satisfy the lease. They may not be able to
	* build that resource right now.
	*
	* @param DrydockLease Requested lease.
	* @return list<DrydockBlueprintImplementation> List of qualifying blueprint
	* implementations.
	* @task allocator
	*/
	private function loadBlueprintImplementationsForAllocatingLease(
	DrydockLease $lease) {

	$impls = DrydockBlueprintImplementation::getAllBlueprintImplementations();

	$keep = array();
	foreach ($impls as $key => $impl) {
	// Don't use disabled blueprint types.
	if (!$impl->isEnabled()) {
	continue;
	}

	// Don't use blueprint types which can't allocate the correct kind of
	// resource.
	if ($impl->getType() != $lease->getResourceType()) {
	continue;
	}

	if (!$impl->canAnyBlueprintEverAllocateResourceForLease($lease)) {
	continue;
	}

	$keep[$key] = $impl;
	}

	return $keep;
	}


	/**
	* Get all the concrete @{class:DrydockBlueprint}s which can possibly
	* build a resource to satisfy a lease.
	*
	* @param DrydockLease Requested lease.
	* @return list<DrydockBlueprint> List of qualifying blueprints.
	* @task allocator
	*/
	private function loadBlueprintsForAllocatingLease(
	DrydockLease $lease) {
	$viewer = $this->getViewer();

	$impls = $this->loadBlueprintImplementationsForAllocatingLease($lease);
	if (!$impls) {
	return array();
	}

	// TODO: When blueprints can be disabled, this query should ignore disabled
	// blueprints.

	$blueprints = id(new DrydockBlueprintQuery())
	->setViewer($viewer)
	->withBlueprintClasses(array_keys($impls))
	->execute();

	$keep = array();
	foreach ($blueprints as $key => $blueprint) {
	if (!$blueprint->canEverAllocateResourceForLease($lease)) {
	continue;
	}

	$keep[$key] = $blueprint;
	}

	return $keep;
	}


	/**
	* Load a list of all resources which a given lease can possibly be
	* allocated against.
	*
	* @param list<DrydockBlueprint> Blueprints which may produce suitable
	* resources.
	* @param DrydockLease Requested lease.
	* @return list<DrydockResource> Resources which may be able to allocate
	* the lease.
	* @task allocator
	*/
	private function loadResourcesForAllocatingLease(
	array $blueprints,
	DrydockLease $lease) {
	assert_instances_of($blueprints, 'DrydockBlueprint');
	$viewer = $this->getViewer();

	$resources = id(new DrydockResourceQuery())
	->setViewer($viewer)
	->withBlueprintPHIDs(mpull($blueprints, 'getPHID'))
	->withTypes(array($lease->getResourceType()))
	->withStatuses(
	array(
	DrydockResourceStatus::STATUS_PENDING,
	DrydockResourceStatus::STATUS_OPEN,
	))
	->execute();

	$keep = array();
	foreach ($resources as $key => $resource) {
	$blueprint = $resource->getBlueprint();

	if (!$blueprint->canAcquireLeaseOnResource($resource, $lease)) {
	continue;
	}

	$keep[$key] = $resource;
	}

	return $keep;
	}


	/**
	* Remove blueprints which are too heavily allocated to build a resource for
	* a lease from a list of blueprints.
	*
	* @param list<DrydockBlueprint> List of blueprints.
	* @return list<DrydockBlueprint> List with blueprints that can not allocate
	* a resource for the lease right now removed.
	* @task allocator
	*/
	private function removeOverallocatedBlueprints(
	array $blueprints,
	DrydockLease $lease) {
	assert_instances_of($blueprints, 'DrydockBlueprint');

	$keep = array();
	foreach ($blueprints as $key => $blueprint) {
	if (!$blueprint->canAllocateResourceForLease($lease)) {
	continue;
	}

	$keep[$key] = $blueprint;
	}

	return $keep;
	}


	/**
	* Rank blueprints by suitability for building a new resource for a
	* particular lease.
	*
	* @param list<DrydockBlueprint> List of blueprints.
	* @param DrydockLease Requested lease.
	* @return list<DrydockBlueprint> Ranked list of blueprints.
	* @task allocator
	*/
	private function rankBlueprints(array $blueprints, DrydockLease $lease) {
	assert_instances_of($blueprints, 'DrydockBlueprint');

	// TODO: Implement improvements to this ranking algorithm if they become
	// available.
	shuffle($blueprints);

	return $blueprints;
	}


	/**
	* Rank resources by suitability for allocating a particular lease.
	*
	* @param list<DrydockResource> List of resources.
	* @param DrydockLease Requested lease.
	* @return list<DrydockResource> Ranked list of resources.
	* @task allocator
	*/
	private function rankResources(array $resources, DrydockLease $lease) {
	assert_instances_of($resources, 'DrydockResource');

	// TODO: Implement improvements to this ranking algorithm if they become
	// available.
	shuffle($resources);

	return $resources;
	}


	/* -( Managing Resources )------------------------------------------------- */


	/**
	* Perform an actual resource allocation with a particular blueprint.
	*
	* @param DrydockBlueprint The blueprint to allocate a resource from.
	* @param DrydockLease Requested lease.
	* @return DrydockResource Allocated resource.
	* @task resource
	*/
	private function allocateResource(
	DrydockBlueprint $blueprint,
	DrydockLease $lease) {
	$resource = $blueprint->allocateResource($lease);
	$this->validateAllocatedResource($blueprint, $resource, $lease);

	// If this resource was allocated as a pending resource, queue a task to
	// activate it.
	if ($resource->getStatus() == DrydockResourceStatus::STATUS_PENDING) {
	PhabricatorWorker::scheduleTask(
	'DrydockResourceWorker',
	array(
	'resourcePHID' => $resource->getPHID(),
	),
	array(
	'objectPHID' => $resource->getPHID(),
	));
	}

	return $resource;
	}


	/**
	* Check that the resource a blueprint allocated is roughly the sort of
	* object we expect.
	*
	* @param DrydockBlueprint Blueprint which built the resource.
	* @param wild Thing which the blueprint claims is a valid resource.
	* @param DrydockLease Lease the resource was allocated for.
	* @return void
	* @task resource
	*/
	private function validateAllocatedResource(
	DrydockBlueprint $blueprint,
	$resource,
	DrydockLease $lease) {

	if (!($resource instanceof DrydockResource)) {
	throw new Exception(
	pht(
	'Blueprint "%s" (of type "%s") is not properly implemented: %s must '.
	'return an object of type %s or throw, but returned something else.',
	$blueprint->getBlueprintName(),
	$blueprint->getClassName(),
	'allocateResource()',
	'DrydockResource'));
	}

	if (!$resource->isAllocatedResource()) {
	throw new Exception(
	pht(
	'Blueprint "%s" (of type "%s") is not properly implemented: %s '.
	'must actually allocate the resource it returns.',
	$blueprint->getBlueprintName(),
	$blueprint->getClassName(),
	'allocateResource()'));
	}

	$resource_type = $resource->getType();
	$lease_type = $lease->getResourceType();

	if ($resource_type !== $lease_type) {
	// TODO: Destroy the resource here?

	throw new Exception(
	pht(
	'Blueprint "%s" (of type "%s") is not properly implemented: it '.
	'built a resource of type "%s" to satisfy a lease requesting a '.
	'resource of type "%s".',
	$blueprint->getBlueprintName(),
	$blueprint->getClassName(),
	$resource_type,
	$lease_type));
	}
	}


	/* -( Managing Leases )---------------------------------------------------- */


	/**
	* Perform an actual lease acquisition on a particular resource.
	*
	* @param DrydockResource Resource to acquire a lease on.
	* @param DrydockLease Lease to acquire.
	* @return void
	* @task lease
	*/
	private function acquireLease(
	DrydockResource $resource,
	DrydockLease $lease) {

	$blueprint = $resource->getBlueprint();
	$blueprint->acquireLease($resource, $lease);

	$this->validateAcquiredLease($blueprint, $resource, $lease);

	// If this lease has been acquired but not activated, queue a task to
	// activate it.
	if ($lease->getStatus() == DrydockLeaseStatus::STATUS_ACQUIRED) {
	PhabricatorWorker::scheduleTask(
	'DrydockLeaseWorker',
	array(
	'leasePHID' => $lease->getPHID(),
	),
	array(
	'objectPHID' => $lease->getPHID(),
	));
	}
	}


	/**
	* Make sure that a lease was really acquired properly.
	*
	* @param DrydockBlueprint Blueprint which created the resource.
	* @param DrydockResource Resource which was acquired.
	* @param DrydockLease The lease which was supposedly acquired.
	* @return void
	* @task lease
	*/
	private function validateAcquiredLease(
	DrydockBlueprint $blueprint,
	DrydockResource $resource,
	DrydockLease $lease) {

	if (!$lease->isAcquiredLease()) {
	throw new Exception(
	pht(
	'Blueprint "%s" (of type "%s") is not properly implemented: it '.
	'returned from "%s" without acquiring a lease.',
	$blueprint->getBlueprintName(),
	$blueprint->getClassName(),
	'acquireLease()'));
	}

	$lease_phid = $lease->getResourcePHID();
	$resource_phid = $resource->getPHID();

	if ($lease_phid !== $resource_phid) {
	// TODO: Destroy the lease?
	throw new Exception(
	pht(
	'Blueprint "%s" (of type "%s") is not properly implemented: it '.
	'returned from "%s" with a lease acquired on the wrong resource.',
	$blueprint->getBlueprintName(),
	$blueprint->getClassName(),
	'acquireLease()'));
	}
	}


	}

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