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phab/src/applications/drydock/blueprint/DrydockBlueprint.php
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DrydockBlueprint.php
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<?php
/**
* @task lease Lease Acquisition
* @task resource Resource Allocation
* @task log Logging
*/
abstract class DrydockBlueprint {
private $activeResource;
private $activeLease;
abstract public function getType();
abstract public function getInterface(
DrydockResource $resource,
DrydockLease $lease,
$type);
abstract public function isEnabled();
public function getBlueprintClass() {
return get_class($this);
}
/* -( Lease Acquisition )-------------------------------------------------- */
/**
* @task lease
*/
final public function filterResource(
DrydockResource $resource,
DrydockLease $lease) {
return $this->canAllocateLease($resource, $lease);
}
/**
* Enforce basic checks on lease/resource compatibility. Allows resources to
* reject leases if they are incompatible, even if the resource types match.
*
* For example, if a resource represents a 32-bit host, this method might
* reject leases that need a 64-bit host. If a resource represents a working
* copy of repository "X", this method might reject leases which need a
* working copy of repository "Y". Generally, although the main types of
* a lease and resource may match (e.g., both "host"), it may not actually be
* possible to satisfy the lease with a specific resource.
*
* This method generally should not enforce limits or perform capacity
* checks. Perform those in @{method:shouldAllocateLease} instead. It also
* should not perform actual acquisition of the lease; perform that in
* @{method:executeAcquireLease} instead.
*
* @param DrydockResource Candidiate resource to allocate the lease on.
* @param DrydockLease Pending lease that wants to allocate here.
* @return bool True if the resource and lease are compatible.
* @task lease
*/
abstract protected function canAllocateLease(
DrydockResource $resource,
DrydockLease $lease);
/**
* @task lease
*/
final public function allocateLease(
DrydockResource $resource,
DrydockLease $lease) {
$scope = $this->pushActiveScope($resource, $lease);
$this->log('Trying to Allocate Lease');
$lease->setStatus(DrydockLeaseStatus::STATUS_ACQUIRING);
$lease->setResourceID($resource->getID());
$lease->attachResource($resource);
$ephemeral_lease = id(clone $lease)->makeEphemeral();
$allocated = false;
$allocation_exception = null;
$resource->openTransaction();
$resource->beginReadLocking();
$resource->reload();
$other_leases = id(new DrydockLease())->loadAllWhere(
'status IN (%Ld) AND resourceID = %d',
array(
DrydockLeaseStatus::STATUS_ACQUIRING,
DrydockLeaseStatus::STATUS_ACTIVE,
),
$resource->getID());
try {
$allocated = $this->shouldAllocateLease(
$resource,
$ephemeral_lease,
$other_leases);
} catch (Exception $ex) {
$allocation_exception = $ex;
}
if ($allocated) {
$lease->save();
}
$resource->endReadLocking();
if ($allocated) {
$resource->saveTransaction();
$this->log('Allocated Lease');
} else {
$resource->killTransaction();
$this->log('Failed to Allocate Lease');
}
if ($allocation_exception) {
$this->logException($allocation_exception);
}
return $allocated;
}
/**
* Enforce lease limits on resources. Allows resources to reject leases if
* they would become over-allocated by accepting them.
*
* For example, if a resource represents disk space, this method might check
* how much space the lease is asking for (say, 200MB) and how much space is
* left unallocated on the resource. It could grant the lease (return true)
* if it has enough remaining space (more than 200MB), and reject the lease
* (return false) if it does not (less than 200MB).
*
* A resource might also allow only exclusive leases. In this case it could
* accept a new lease (return true) if there are no active leases, or reject
* the new lease (return false) if there any other leases.
*
* A lock is held on the resource while this method executes to prevent
* multiple processes from allocating leases on the resource simultaneously.
* However, this means you should implement the method as cheaply as possible.
* In particular, do not perform any actual acquisition or setup in this
* method.
*
* If allocation is permitted, the lease will be moved to `ACQUIRING` status
* and @{method:executeAcquireLease} will be called to actually perform
* acquisition.
*
* General compatibility checks unrelated to resource limits and capacity are
* better implemented in @{method:canAllocateLease}, which serves as a
* cheap filter before lock acquisition.
*
* @param DrydockResource Candidate resource to allocate the lease on.
* @param DrydockLease Pending lease that wants to allocate here.
* @param list<DrydockLease> Other allocated and acquired leases on the
* resource. The implementation can inspect them
* to verify it can safely add the new lease.
* @return bool True to allocate the lease on the resource;
* false to reject it.
* @task lease
*/
abstract protected function shouldAllocateLease(
DrydockResource $resource,
DrydockLease $lease,
array $other_leases);
/**
* @task lease
*/
final public function acquireLease(
DrydockResource $resource,
DrydockLease $lease) {
$scope = $this->pushActiveScope($resource, $lease);
$this->log('Acquiring Lease');
$lease->setStatus(DrydockLeaseStatus::STATUS_ACTIVE);
$lease->setResourceID($resource->getID());
$lease->attachResource($resource);
$ephemeral_lease = id(clone $lease)->makeEphemeral();
try {
$this->executeAcquireLease($resource, $ephemeral_lease);
} catch (Exception $ex) {
$this->logException($ex);
throw $ex;
}
$lease->setAttributes($ephemeral_lease->getAttributes());
$lease->save();
$this->log('Acquired Lease');
}
/**
* Acquire and activate an allocated lease. Allows resources to peform setup
* as leases are brought online.
*
* Following a successful call to @{method:canAllocateLease}, a lease is moved
* to `ACQUIRING` status and this method is called after resource locks are
* released. Nothing is locked while this method executes; the implementation
* is free to perform expensive operations like writing files and directories,
* executing commands, etc.
*
* After this method executes, the lease status is moved to `ACTIVE` and the
* original leasee may access it.
*
* If acquisition fails, throw an exception.
*
* @param DrydockResource Resource to acquire a lease on.
* @param DrydockLease Lease to acquire.
* @return void
*/
abstract protected function executeAcquireLease(
DrydockResource $resource,
DrydockLease $lease);
final public function releaseLease(
DrydockResource $resource,
DrydockLease $lease) {
$scope = $this->pushActiveScope(null, $lease);
$released = false;
$lease->openTransaction();
$lease->beginReadLocking();
$lease->reload();
if ($lease->getStatus() == DrydockLeaseStatus::STATUS_ACTIVE) {
$lease->setStatus(DrydockLeaseStatus::STATUS_RELEASED);
$lease->save();
$released = true;
}
$lease->endReadLocking();
$lease->saveTransaction();
if (!$released) {
throw new Exception("Unable to release lease: lease not active!");
}
}
/* -( Resource Allocation )------------------------------------------------ */
public function canAllocateMoreResources(array $pool) {
return true;
}
abstract protected function executeAllocateResource(DrydockLease $lease);
final public function allocateResource(DrydockLease $lease) {
$scope = $this->pushActiveScope(null, $lease);
$this->log(
pht(
"Blueprint '%s': Allocating Resource for '%s'",
$this->getBlueprintClass(),
$lease->getLeaseName()));
try {
$resource = $this->executeAllocateResource($lease);
$this->validateAllocatedResource($resource);
} catch (Exception $ex) {
$this->logException($ex);
throw $ex;
}
return $resource;
}
/* -( Logging )------------------------------------------------------------ */
/**
* @task log
*/
protected function logException(Exception $ex) {
$this->log($ex->getMessage());
}
/**
* @task log
*/
protected function log($message) {
self::writeLog(
$this->activeResource,
$this->activeLease,
$message);
}
/**
* @task log
*/
public static function writeLog(
DrydockResource $resource = null,
DrydockLease $lease = null,
$message) {
$log = id(new DrydockLog())
->setEpoch(time())
->setMessage($message);
if ($resource) {
$log->setResourceID($resource->getID());
}
if ($lease) {
$log->setLeaseID($lease->getID());
}
$log->save();
}
public static function getAllBlueprints() {
static $list = null;
if ($list === null) {
$blueprints = id(new PhutilSymbolLoader())
->setType('class')
->setAncestorClass('DrydockBlueprint')
->setConcreteOnly(true)
->selectAndLoadSymbols();
$list = ipull($blueprints, 'name', 'name');
foreach ($list as $class_name => $ignored) {
$list[$class_name] = newv($class_name, array());
}
}
return $list;
}
public static function getAllBlueprintsForResource($type) {
static $groups = null;
if ($groups === null) {
$groups = mgroup(self::getAllBlueprints(), 'getType');
}
return idx($groups, $type, array());
}
protected function newResourceTemplate($name) {
$resource = new DrydockResource();
$resource->setBlueprintClass($this->getBlueprintClass());
$resource->setType($this->getType());
$resource->setStatus(DrydockResourceStatus::STATUS_PENDING);
$resource->setName($name);
$resource->save();
$this->activeResource = $resource;
$this->log(
pht(
"Blueprint '%s': Created New Template",
$this->getBlueprintClass()));
return $resource;
}
/**
* Sanity checks that the blueprint is implemented properly.
*/
private function validateAllocatedResource($resource) {
$blueprint = $this->getBlueprintClass();
if (!($resource instanceof DrydockResource)) {
throw new Exception(
"Blueprint '{$blueprint}' is not properly implemented: ".
"executeAllocateResource() must return an object of type ".
"DrydockResource or throw, but returned something else.");
}
$current_status = $resource->getStatus();
$req_status = DrydockResourceStatus::STATUS_OPEN;
if ($current_status != $req_status) {
$current_name = DrydockResourceStatus::getNameForStatus($current_status);
$req_name = DrydockResourceStatus::getNameForStatus($req_status);
throw new Exception(
"Blueprint '{$blueprint}' is not properly implemented: ".
"executeAllocateResource() must return a DrydockResource with ".
"status '{$req_name}', but returned one with status ".
"'{$current_name}'.");
}
}
private function pushActiveScope(
DrydockResource $resource = null,
DrydockLease $lease = null) {
if (($this->activeResource !== null) ||
($this->activeLease !== null)) {
throw new Exception("There is already an active resource or lease!");
}
$this->activeResource = $resource;
$this->activeLease = $lease;
return new DrydockBlueprintScopeGuard($this);
}
public function popActiveScope() {
$this->activeResource = null;
$this->activeLease = null;
}
}
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