Support working copies and separate allocate + activate steps for resources/leases in Drydock

Summary:
Ref T9253. For resources and leases that need to do something which takes a lot of time or requires waiting, allow them to allocate/acquire first and then activate later.

When we allocate a resource or acquire a lease, the blueprint can either activate it immediately (if all the work can happen quickly/inline) or activate it later. If the blueprint activates it later, we queue a worker to handle activating it.

Rebuild the "working copy" blueprint to work with this model: it allocates/acquires and activates in a separate step, once it is able to acquire a host.

Test Plan: With some power of imagination, brought up a bunch of working copies with `bin/drydock lease --type working-copy ...`

Reviewers: hach-que, chad

Reviewed By: hach-que, chad

Maniphest Tasks: T9253

Differential Revision: https://secure.phabricator.com/D14127

src/__phutil_library_map__.php

@@ -838,6 +838,7 @@ phutil_register_library_map(array(
     'DrydockLeaseSearchEngine' => 'applications/drydock/query/DrydockLeaseSearchEngine.php',
     'DrydockLeaseStatus' => 'applications/drydock/constants/DrydockLeaseStatus.php',
     'DrydockLeaseViewController' => 'applications/drydock/controller/DrydockLeaseViewController.php',
+    'DrydockLeaseWorker' => 'applications/drydock/worker/DrydockLeaseWorker.php',
     'DrydockLog' => 'applications/drydock/storage/DrydockLog.php',
     'DrydockLogController' => 'applications/drydock/controller/DrydockLogController.php',
     'DrydockLogListController' => 'applications/drydock/controller/DrydockLogListController.php',
@@ -861,10 +862,13 @@ phutil_register_library_map(array(
     'DrydockResourceSearchEngine' => 'applications/drydock/query/DrydockResourceSearchEngine.php',
     'DrydockResourceStatus' => 'applications/drydock/constants/DrydockResourceStatus.php',
     'DrydockResourceViewController' => 'applications/drydock/controller/DrydockResourceViewController.php',
+    'DrydockResourceWorker' => 'applications/drydock/worker/DrydockResourceWorker.php',
     'DrydockSFTPFilesystemInterface' => 'applications/drydock/interface/filesystem/DrydockSFTPFilesystemInterface.php',
     'DrydockSSHCommandInterface' => 'applications/drydock/interface/command/DrydockSSHCommandInterface.php',
     'DrydockSlotLock' => 'applications/drydock/storage/DrydockSlotLock.php',
+    'DrydockSlotLockException' => 'applications/drydock/exception/DrydockSlotLockException.php',
     'DrydockWebrootInterface' => 'applications/drydock/interface/webroot/DrydockWebrootInterface.php',
+    'DrydockWorker' => 'applications/drydock/worker/DrydockWorker.php',
     'DrydockWorkingCopyBlueprintImplementation' => 'applications/drydock/blueprint/DrydockWorkingCopyBlueprintImplementation.php',
     'FeedConduitAPIMethod' => 'applications/feed/conduit/FeedConduitAPIMethod.php',
     'FeedPublishConduitAPIMethod' => 'applications/feed/conduit/FeedPublishConduitAPIMethod.php',
@@ -4502,7 +4506,7 @@ phutil_register_library_map(array(
     'DoorkeeperSchemaSpec' => 'PhabricatorConfigSchemaSpec',
     'DoorkeeperTagView' => 'AphrontView',
     'DoorkeeperTagsController' => 'PhabricatorController',
-    'DrydockAllocatorWorker' => 'PhabricatorWorker',
+    'DrydockAllocatorWorker' => 'DrydockWorker',
     'DrydockAlmanacServiceHostBlueprintImplementation' => 'DrydockBlueprintImplementation',
     'DrydockApacheWebrootInterface' => 'DrydockWebrootInterface',
     'DrydockBlueprint' => array(
@@ -4555,6 +4559,7 @@ phutil_register_library_map(array(
     'DrydockLeaseSearchEngine' => 'PhabricatorApplicationSearchEngine',
     'DrydockLeaseStatus' => 'DrydockConstants',
     'DrydockLeaseViewController' => 'DrydockLeaseController',
+    'DrydockLeaseWorker' => 'DrydockWorker',
     'DrydockLog' => array(
       'DrydockDAO',
       'PhabricatorPolicyInterface',
@@ -4584,10 +4589,13 @@ phutil_register_library_map(array(
     'DrydockResourceSearchEngine' => 'PhabricatorApplicationSearchEngine',
     'DrydockResourceStatus' => 'DrydockConstants',
     'DrydockResourceViewController' => 'DrydockResourceController',
+    'DrydockResourceWorker' => 'DrydockWorker',
     'DrydockSFTPFilesystemInterface' => 'DrydockFilesystemInterface',
     'DrydockSSHCommandInterface' => 'DrydockCommandInterface',
     'DrydockSlotLock' => 'DrydockDAO',
+    'DrydockSlotLockException' => 'Exception',
     'DrydockWebrootInterface' => 'DrydockInterface',
+    'DrydockWorker' => 'PhabricatorWorker',
     'DrydockWorkingCopyBlueprintImplementation' => 'DrydockBlueprintImplementation',
     'FeedConduitAPIMethod' => 'ConduitAPIMethod',
     'FeedPublishConduitAPIMethod' => 'FeedConduitAPIMethod',

src/applications/drydock/blueprint/DrydockAlmanacServiceHostBlueprintImplementation.php

@@ -76,7 +76,7 @@ final class DrydockAlmanacServiceHostBlueprintImplementation
         ->needSlotLock("almanac.host.binding({$binding_phid})");
 
       try {
-        return $resource->allocateResource(DrydockResourceStatus::STATUS_OPEN);
+        return $resource->allocateResource();
       } catch (Exception $ex) {
         $exceptions[] = $ex;
       }
@@ -92,11 +92,9 @@ final class DrydockAlmanacServiceHostBlueprintImplementation
     DrydockResource $resource,
     DrydockLease $lease) {
 
-    // TODO: The current rule is one lease per resource, and there's no way to
-    // make that cheaper here than by just trying to acquire the lease below,
-    // so don't do any special checks for now. When we eventually permit
-    // multiple leases per host, we'll need to load leases anyway, so we can
-    // reject fully leased hosts cheaply here.
+    if (!DrydockSlotLock::isLockFree($this->getLeaseSlotLock($resource))) {
+      return false;
+    }
 
     return true;
   }
@@ -106,14 +104,17 @@ final class DrydockAlmanacServiceHostBlueprintImplementation
     DrydockResource $resource,
     DrydockLease $lease) {
 
-    $resource_phid = $resource->getPHID();
-
     $lease
       ->setActivateWhenAcquired(true)
-      ->needSlotLock("almanac.host.lease({$resource_phid})")
+      ->needSlotLock($this->getLeaseSlotLock($resource))
       ->acquireOnResource($resource);
   }
 
+  private function getLeaseSlotLock(DrydockResource $resource) {
+    $resource_phid = $resource->getPHID();
+    return "almanac.host.lease({$resource_phid})";
+  }
+
   public function getType() {
     return 'host';
   }

src/applications/drydock/blueprint/DrydockBlueprintImplementation.php

@@ -67,6 +67,12 @@ abstract class DrydockBlueprintImplementation extends Phobject {
     DrydockResource $resource,
     DrydockLease $lease);
 
+  public function activateLease(
+    DrydockBlueprint $blueprint,
+    DrydockResource $resource,
+    DrydockLease $lease) {
+    throw new PhutilMethodNotImplementedException();
+  }
 
   final public function releaseLease(
     DrydockBlueprint $blueprint,
@@ -198,6 +204,11 @@ abstract class DrydockBlueprintImplementation extends Phobject {
     DrydockBlueprint $blueprint,
     DrydockLease $lease);
 
+  public function activateResource(
+    DrydockBlueprint $blueprint,
+    DrydockResource $resource) {
+    throw new PhutilMethodNotImplementedException();
+  }
 
 /* -(  Resource Interfaces  )------------------------------------------------ */
 
@@ -276,6 +287,9 @@ abstract class DrydockBlueprintImplementation extends Phobject {
       ->setStatus(DrydockResourceStatus::STATUS_PENDING)
       ->setName($name);
 
+    // Pre-allocate the resource PHID.
+    $resource->setPHID($resource->generatePHID());
+
     $this->activeResource = $resource;
 
     $this->log(
@@ -286,6 +300,25 @@ abstract class DrydockBlueprintImplementation extends Phobject {
     return $resource;
   }
 
+  protected function newLease(DrydockBlueprint $blueprint) {
+    return id(new DrydockLease());
+  }
+
+  protected function requireActiveLease(DrydockLease $lease) {
+    $lease_status = $lease->getStatus();
+
+    switch ($lease_status) {
+      case DrydockLeaseStatus::STATUS_ACQUIRED:
+        // TODO: Temporary failure.
+        throw new Exception(pht('Lease still activating.'));
+      case DrydockLeaseStatus::STATUS_ACTIVE:
+        return;
+      default:
+        // TODO: Permanent failure.
+        throw new Exception(pht('Lease in bad state.'));
+    }
+  }
+
   private function pushActiveScope(
     DrydockResource $resource = null,
     DrydockLease $lease = null) {

src/applications/drydock/blueprint/DrydockWorkingCopyBlueprintImplementation.php

@@ -17,21 +17,18 @@ final class DrydockWorkingCopyBlueprintImplementation
 
   public function canAnyBlueprintEverAllocateResourceForLease(
     DrydockLease $lease) {
-    // TODO: These checks are out of date.
     return true;
   }
 
   public function canEverAllocateResourceForLease(
     DrydockBlueprint $blueprint,
     DrydockLease $lease) {
-    // TODO: These checks are out of date.
     return true;
   }
 
   public function canAllocateResourceForLease(
     DrydockBlueprint $blueprint,
     DrydockLease $lease) {
-    // TODO: These checks are out of date.
     return true;
   }
 
@@ -39,82 +36,130 @@ final class DrydockWorkingCopyBlueprintImplementation
     DrydockBlueprint $blueprint,
     DrydockResource $resource,
     DrydockLease $lease) {
-    // TODO: These checks are out of date.
 
-    $resource_repo = $resource->getAttribute('repositoryID');
-    $lease_repo = $lease->getAttribute('repositoryID');
+    $have_phid = $resource->getAttribute('repositoryPHID');
+    $need_phid = $lease->getAttribute('repositoryPHID');
 
-    return ($resource_repo && $lease_repo && ($resource_repo == $lease_repo));
-  }
-
-  public function allocateResource(
-    DrydockBlueprint $blueprint,
-    DrydockLease $lease) {
-
-    $repository_id = $lease->getAttribute('repositoryID');
-    if (!$repository_id) {
-      throw new Exception(
-        pht(
-          "Lease is missing required '%s' attribute.",
-          'repositoryID'));
+    if ($need_phid !== $have_phid) {
+      return false;
     }
 
-    $repository = id(new PhabricatorRepositoryQuery())
-      ->setViewer(PhabricatorUser::getOmnipotentUser())
-      ->withIDs(array($repository_id))
-      ->executeOne();
-
-    if (!$repository) {
-      throw new Exception(
-        pht(
-          "Repository '%s' does not exist!",
-          $repository_id));
+    if (!DrydockSlotLock::isLockFree($this->getLeaseSlotLock($resource))) {
+      return false;
     }
 
-    switch ($repository->getVersionControlSystem()) {
-      case PhabricatorRepositoryType::REPOSITORY_TYPE_GIT:
-        break;
-      default:
-        throw new Exception(pht('Unsupported VCS!'));
-    }
-
-    // TODO: Policy stuff here too.
-    $host_lease = id(new DrydockLease())
-      ->setResourceType('host')
-      ->waitUntilActive();
-
-    $path = $host_lease->getAttribute('path').$repository->getCallsign();
-
-    $this->log(
-      pht('Cloning %s into %s....', $repository->getCallsign(), $path));
-
-    $cmd = $host_lease->getInterface('command');
-    $cmd->execx(
-      'git clone --origin origin %P %s',
-      $repository->getRemoteURIEnvelope(),
-      $path);
-
-    $this->log(pht('Complete.'));
-
-    $resource = $this->newResourceTemplate(
-      $blueprint,
-      pht(
-        'Working Copy (%s)',
-        $repository->getCallsign()));
-    $resource->setStatus(DrydockResourceStatus::STATUS_OPEN);
-    $resource->setAttribute('lease.host', $host_lease->getID());
-    $resource->setAttribute('path', $path);
-    $resource->setAttribute('repositoryID', $repository->getID());
-    $resource->save();
-
-    return $resource;
+    return true;
   }
 
   public function acquireLease(
     DrydockBlueprint $blueprint,
     DrydockResource $resource,
     DrydockLease $lease) {
-    return;
+
+    $lease
+      ->needSlotLock($this->getLeaseSlotLock($resource))
+      ->acquireOnResource($resource);
+  }
+
+  private function getLeaseSlotLock(DrydockResource $resource) {
+    $resource_phid = $resource->getPHID();
+    return "workingcopy.lease({$resource_phid})";
+  }
+
+  public function allocateResource(
+    DrydockBlueprint $blueprint,
+    DrydockLease $lease) {
+
+    $repository_phid = $lease->getAttribute('repositoryPHID');
+    $repository = $this->loadRepository($repository_phid);
+
+    $resource = $this->newResourceTemplate(
+      $blueprint,
+      pht(
+        'Working Copy (%s)',
+        $repository->getCallsign()));
+
+    $resource_phid = $resource->getPHID();
+
+    $host_lease = $this->newLease($blueprint)
+      ->setResourceType('host')
+      ->setOwnerPHID($resource_phid)
+      ->setAttribute('workingcopy.resourcePHID', $resource_phid)
+      ->queueForActivation();
+
+    // TODO: Add some limits to the number of working copies we can have at
+    // once?
+
+    return $resource
+      ->setAttribute('repositoryPHID', $repository->getPHID())
+      ->setAttribute('host.leasePHID', $host_lease->getPHID())
+      ->allocateResource();
+  }
+
+  public function activateResource(
+    DrydockBlueprint $blueprint,
+    DrydockResource $resource) {
+
+    $lease = $this->loadHostLease($resource);
+    $this->requireActiveLease($lease);
+
+    $repository_phid = $resource->getAttribute('repositoryPHID');
+    $repository = $this->loadRepository($repository_phid);
+    $repository_id = $repository->getID();
+
+    $command_type = DrydockCommandInterface::INTERFACE_TYPE;
+    $interface = $lease->getInterface($command_type);
+
+    // TODO: Make this configurable.
+    $resource_id = $resource->getID();
+    $root = "/var/drydock/workingcopy-{$resource_id}";
+    $path = "{$root}/repo/{$repository_id}/";
+
+    $interface->execx(
+      'git clone -- %s %s',
+      (string)$repository->getCloneURIObject(),
+      $path);
+
+    $resource
+      ->setAttribute('workingcopy.root', $root)
+      ->setAttribute('workingcopy.path', $path)
+      ->activateResource();
+  }
+
+  public function activateLease(
+    DrydockBlueprint $blueprint,
+    DrydockResource $resource,
+    DrydockLease $lease) {
+
+    $command_type = DrydockCommandInterface::INTERFACE_TYPE;
+    $interface = $lease->getInterface($command_type);
+
+    $cmd = array();
+    $arg = array();
+
+    $cmd[] = 'git clean -d --force';
+    $cmd[] = 'git reset --hard HEAD';
+    $cmd[] = 'git fetch';
+
+    $commit = $lease->getAttribute('commit');
+    $branch = $lease->getAttribute('branch');
+
+    if ($commit !== null) {
+      $cmd[] = 'git reset --hard %s';
+      $arg[] = $commit;
+    } else if ($branch !== null) {
+      $cmd[] = 'git reset --hard %s';
+      $arg[] = $branch;
+    }
+
+    $cmd = implode(' && ', $cmd);
+    $argv = array_merge(array($cmd), $arg);
+
+    $result = call_user_func_array(
+      array($interface, 'execx'),
+      $argv);
+
+    $lease->activateOnResource($resource);
   }
 
   public function getType() {
@@ -126,7 +171,59 @@ final class DrydockWorkingCopyBlueprintImplementation
     DrydockResource $resource,
     DrydockLease $lease,
     $type) {
-    // TODO: This blueprint doesn't work at all.
+
+    switch ($type) {
+      case DrydockCommandInterface::INTERFACE_TYPE:
+        $host_lease = $this->loadHostLease($resource);
+        $command_interface = $host_lease->getInterface($type);
+
+        $path = $resource->getAttribute('workingcopy.path');
+        $command_interface->setWorkingDirectory($path);
+
+        return $command_interface;
+    }
   }
 
+  private function loadRepository($repository_phid) {
+    $repository = id(new PhabricatorRepositoryQuery())
+      ->setViewer(PhabricatorUser::getOmnipotentUser())
+      ->withPHIDs(array($repository_phid))
+      ->executeOne();
+    if (!$repository) {
+      // TODO: Permanent failure.
+      throw new Exception(
+        pht(
+          'Repository PHID "%s" does not exist.',
+          $repository_phid));
+    }
+
+    switch ($repository->getVersionControlSystem()) {
+      case PhabricatorRepositoryType::REPOSITORY_TYPE_GIT:
+        break;
+      default:
+        // TODO: Permanent failure.
+        throw new Exception(pht('Unsupported VCS!'));
+    }
+
+    return $repository;
+  }
+
+  private function loadHostLease(DrydockResource $resource) {
+    $viewer = PhabricatorUser::getOmnipotentUser();
+
+    $lease_phid = $resource->getAttribute('host.leasePHID');
+
+    $lease = id(new DrydockLeaseQuery())
+      ->setViewer($viewer)
+      ->withPHIDs(array($lease_phid))
+      ->executeOne();
+    if (!$lease) {
+      // TODO: Permanent failure.
+      throw new Exception(pht('Unable to load lease "%s".', $lease_phid));
+    }
+
+    return $lease;
+  }
+
+
 }

src/applications/drydock/exception/DrydockSlotLockException.php

@@ -0,0 +1,25 @@
+<?php
+
+final class DrydockSlotLockException extends Exception {
+
+  private $lockMap;
+
+  public function __construct(array $locks) {
+    $this->lockMap = $locks;
+
+    if ($locks) {
+      $lock_list = array();
+      foreach ($locks as $lock => $owner_phid) {
+        $lock_list[] = pht('"%s" (owned by "%s")', $lock, $owner_phid);
+      }
+      $message = pht(
+        'Unable to acquire slot locks: %s.',
+        implode(', ', $lock_list));
+    } else {
+      $message = pht('Unable to acquire slot locks.');
+    }
+
+    parent::__construct($message);
+  }
+
+}

src/applications/drydock/management/DrydockManagementLeaseWorkflow.php

@@ -40,8 +40,6 @@ final class DrydockManagementLeaseWorkflow
       $attributes = $options->parse($attributes);
     }
 
-    PhabricatorWorker::setRunAllTasksInProcess(true);
-
     $lease = id(new DrydockLease())
       ->setResourceType($resource_type);
     if ($attributes) {

src/applications/drydock/storage/DrydockBlueprint.php

@@ -134,6 +134,15 @@ final class DrydockBlueprint extends DrydockDAO
   }
 
 
+  /**
+   * @task resource
+   */
+  public function activateResource(DrydockResource $resource) {
+    return $this->getImplementation()->activateResource(
+      $this,
+      $resource);
+  }
+
 /* -(  Acquiring Leases  )--------------------------------------------------- */
 
 
@@ -163,6 +172,19 @@ final class DrydockBlueprint extends DrydockDAO
   }
 
 
+  /**
+   * @task lease
+   */
+  public function activateLease(
+    DrydockResource $resource,
+    DrydockLease $lease) {
+    return $this->getImplementation()->activateLease(
+      $this,
+      $resource,
+      $lease);
+  }
+
+
   /**
    * @task lease
    */

src/applications/drydock/storage/DrydockLease.php

@@ -14,6 +14,7 @@ final class DrydockLease extends DrydockDAO
   private $resource = self::ATTACHABLE;
   private $releaseOnDestruction;
   private $isAcquired = false;
+  private $isActivated = false;
   private $activateWhenAcquired = false;
   private $slotLocks = array();
 
@@ -111,7 +112,12 @@ final class DrydockLease extends DrydockDAO
 
     $task = PhabricatorWorker::scheduleTask(
       'DrydockAllocatorWorker',
-      $this->getID());
+      array(
+        'leasePHID' => $this->getPHID(),
+      ),
+      array(
+        'objectPHID' => $this->getPHID(),
+      ));
 
     // NOTE: Scheduling the task might execute it in-process, if we're running
     // from a CLI script. Reload the lease to make sure we have the most
@@ -229,11 +235,11 @@ final class DrydockLease extends DrydockDAO
     if ($this->activateWhenAcquired) {
       $new_status = DrydockLeaseStatus::STATUS_ACTIVE;
     } else {
-      $new_status = DrydockLeaseStatus::STATUS_PENDING;
+      $new_status = DrydockLeaseStatus::STATUS_ACQUIRED;
     }
 
-    if ($new_status === DrydockLeaseStatus::STATUS_ACTIVE) {
-      if ($resource->getStatus() === DrydockResourceStatus::STATUS_PENDING) {
+    if ($new_status == DrydockLeaseStatus::STATUS_ACTIVE) {
+      if ($resource->getStatus() == DrydockResourceStatus::STATUS_PENDING) {
         throw new Exception(
           pht(
             'Trying to acquire an active lease on a pending resource. '.
@@ -263,6 +269,45 @@ final class DrydockLease extends DrydockDAO
     return $this->isAcquired;
   }
 
+  public function activateOnResource(DrydockResource $resource) {
+    $expect_status = DrydockLeaseStatus::STATUS_ACQUIRED;
+    $actual_status = $this->getStatus();
+    if ($actual_status != $expect_status) {
+      throw new Exception(
+        pht(
+          'Trying to activate a lease which has the wrong status: status '.
+          'must be "%s", actually "%s".',
+          $expect_status,
+          $actual_status));
+    }
+
+    if ($resource->getStatus() == DrydockResourceStatus::STATUS_PENDING) {
+      // TODO: Be stricter about this?
+      throw new Exception(
+        pht(
+          'Trying to activate a lease on a pending resource.'));
+    }
+
+    $this->openTransaction();
+
+      $this
+        ->setStatus(DrydockLeaseStatus::STATUS_ACTIVE)
+        ->save();
+
+      DrydockSlotLock::acquireLocks($this->getPHID(), $this->slotLocks);
+      $this->slotLocks = array();
+
+    $this->saveTransaction();
+
+    $this->isActivated = true;
+
+    return $this;
+  }
+
+  public function isActivatedLease() {
+    return $this->isActivated;
+  }
+
 
 /* -(  PhabricatorPolicyInterface  )----------------------------------------- */
 

src/applications/drydock/storage/DrydockResource.php

@@ -16,6 +16,7 @@ final class DrydockResource extends DrydockDAO
 
   private $blueprint = self::ATTACHABLE;
   private $isAllocated = false;
+  private $isActivated = false;
   private $activateWhenAllocated = false;
   private $slotLocks = array();
 
@@ -86,7 +87,7 @@ final class DrydockResource extends DrydockDAO
     return $this;
   }
 
-  public function allocateResource($status) {
+  public function allocateResource() {
     if ($this->getID()) {
       throw new Exception(
         pht(
@@ -131,6 +132,44 @@ final class DrydockResource extends DrydockDAO
     return $this->isAllocated;
   }
 
+  public function activateResource() {
+    if (!$this->getID()) {
+      throw new Exception(
+        pht(
+          'Trying to activate a resource which has not yet been persisted.'));
+    }
+
+    $expect_status = DrydockResourceStatus::STATUS_PENDING;
+    $actual_status = $this->getStatus();
+    if ($actual_status != $expect_status) {
+      throw new Exception(
+        pht(
+          'Trying to activate a resource from the wrong status. Status must '.
+          'be "%s", actually "%s".',
+          $expect_status,
+          $actual_status));
+    }
+
+    $this->openTransaction();
+
+      $this
+        ->setStatus(DrydockResourceStatus::STATUS_OPEN)
+        ->save();
+
+      DrydockSlotLock::acquireLocks($this->getPHID(), $this->slotLocks);
+      $this->slotLocks = array();
+
+    $this->saveTransaction();
+
+    $this->isActivated = true;
+
+    return $this;
+  }
+
+  public function isActivatedResource() {
+    return $this->isActivated;
+  }
+
   public function closeResource() {
 
     // TODO: This is super broken and will race other lease writers!

src/applications/drydock/storage/DrydockSlotLock.php

@@ -8,6 +8,7 @@
  * machine. These optimistic "slot locks" provide a flexible way to do this
  * sort of simple locking.
  *
+ * @task info Getting Lock Information
  * @task lock Acquiring and Releasing Locks
  */
 final class DrydockSlotLock extends DrydockDAO {
@@ -35,6 +36,17 @@ final class DrydockSlotLock extends DrydockDAO {
     ) + parent::getConfiguration();
   }
 
+
+/* -(  Getting Lock Information  )------------------------------------------- */
+
+
+  /**
+   * Load all locks held by a particular owner.
+   *
+   * @param phid Owner PHID.
+   * @return list<DrydockSlotLock> All held locks.
+   * @task info
+   */
   public static function loadLocks($owner_phid) {
     return id(new DrydockSlotLock())->loadAllWhere(
       'ownerPHID = %s',
@@ -42,6 +54,57 @@ final class DrydockSlotLock extends DrydockDAO {
   }
 
 
+  /**
+   * Test if a lock is currently free.
+   *
+   * @param string Lock key to test.
+   * @return bool True if the lock is currently free.
+   * @task info
+   */
+  public static function isLockFree($lock) {
+    return self::areLocksFree(array($lock));
+  }
+
+
+  /**
+   * Test if a list of locks are all currently free.
+   *
+   * @param list<string> List of lock keys to test.
+   * @return bool True if all locks are currently free.
+   * @task info
+   */
+  public static function areLocksFree(array $locks) {
+    $lock_map = self::loadHeldLocks($locks);
+    return !$lock_map;
+  }
+
+
+  /**
+   * Load named locks.
+   *
+   * @param list<string> List of lock keys to load.
+   * @return list<DrydockSlotLock> List of held locks.
+   * @task info
+   */
+  public static function loadHeldLocks(array $locks) {
+    if (!$locks) {
+      return array();
+    }
+
+    $table = new DrydockSlotLock();
+    $conn_r = $table->establishConnection('r');
+
+    $indexes = array();
+    foreach ($locks as $lock) {
+      $indexes[] = PhabricatorHash::digestForIndex($lock);
+    }
+
+    return id(new DrydockSlotLock())->loadAllWhere(
+      'lockIndex IN (%Ls)',
+      $indexes);
+  }
+
+
 /* -(  Acquiring and Releasing Locks  )-------------------------------------- */
 
 
@@ -74,15 +137,20 @@ final class DrydockSlotLock extends DrydockDAO {
         $lock);
     }
 
-    // TODO: These exceptions are pretty tricky to read. It would be good to
-    // figure out which locks could not be acquired and try to improve the
-    // exception to make debugging easier.
-
-    queryfx(
-      $conn_w,
-      'INSERT INTO %T (ownerPHID, lockIndex, lockKey) VALUES %Q',
-      $table->getTableName(),
-      implode(', ', $sql));
+    try {
+      queryfx(
+        $conn_w,
+        'INSERT INTO %T (ownerPHID, lockIndex, lockKey) VALUES %Q',
+        $table->getTableName(),
+        implode(', ', $sql));
+    } catch (AphrontDuplicateKeyQueryException $ex) {
+      // Try to improve the readability of the exception. We might miss on
+      // this query if the lock has already been released, but most of the
+      // time we should be able to figure out which locks are already held.
+      $held = self::loadHeldLocks($locks);
+      $held = mpull($held, 'getOwnerPHID', 'getLockKey');
+      throw new DrydockSlotLockException($held);
+    }
   }
 
 

src/applications/drydock/worker/DrydockAllocatorWorker.php

@@ -5,33 +5,12 @@
  * @task resource Managing Resources
  * @task lease Managing Leases
  */
-final class DrydockAllocatorWorker extends PhabricatorWorker {
-
-  private function getViewer() {
-    return PhabricatorUser::getOmnipotentUser();
-  }
-
-  private function loadLease() {
-    $viewer = $this->getViewer();
-
-    // TODO: Make the task data a dictionary like every other worker, and
-    // probably make this a PHID.
-    $lease_id = $this->getTaskData();
-
-    $lease = id(new DrydockLeaseQuery())
-      ->setViewer($viewer)
-      ->withIDs(array($lease_id))
-      ->executeOne();
-    if (!$lease) {
-      throw new PhabricatorWorkerPermanentFailureException(
-        pht('No such lease "%s"!', $lease_id));
-    }
-
-    return $lease;
-  }
+final class DrydockAllocatorWorker extends DrydockWorker {
 
   protected function doWork() {
-    $lease = $this->loadLease();
+    $lease_phid = $this->getTaskDataValue('leasePHID');
+    $lease = $this->loadLease($lease_phid);
+
     $this->allocateAndAcquireLease($lease);
   }
 
@@ -351,6 +330,20 @@ final class DrydockAllocatorWorker extends PhabricatorWorker {
     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;
   }
 
@@ -429,6 +422,19 @@ final class DrydockAllocatorWorker extends PhabricatorWorker {
     $blueprint->acquireLease($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(),
+        ));
+    }
   }
 
 

src/applications/drydock/worker/DrydockLeaseWorker.php

@@ -0,0 +1,81 @@
+<?php
+
+final class DrydockLeaseWorker extends DrydockWorker {
+
+  protected function doWork() {
+    $lease_phid = $this->getTaskDataValue('leasePHID');
+    $lease = $this->loadLease($lease_phid);
+
+    $this->activateLease($lease);
+  }
+
+
+  private function activateLease(DrydockLease $lease) {
+    $actual_status = $lease->getStatus();
+
+    if ($actual_status != DrydockLeaseStatus::STATUS_ACQUIRED) {
+      throw new PhabricatorWorkerPermanentFailureException(
+        pht(
+          'Trying to activate lease from wrong status ("%s").',
+          $actual_status));
+    }
+
+    $resource_id = $lease->getResourceID();
+
+    $resource = id(new DrydockResourceQuery())
+      ->setViewer($this->getViewer())
+      ->withIDs(array($resource_id))
+      ->executeOne();
+    if (!$resource) {
+      throw new PhabricatorWorkerPermanentFailureException(
+        pht(
+          'Trying to activate lease on invalid resource ("%s").',
+          $resource_id));
+    }
+
+    $resource_status = $resource->getStatus();
+
+    if ($resource_status == DrydockResourceStatus::STATUS_PENDING) {
+      // TODO: This is explicitly a temporary failure -- we are waiting for
+      // the resource to come up.
+      throw new Exception(pht('Resource still activating.'));
+    }
+
+    if ($resource_status != DrydockResourceStatus::STATUS_OPEN) {
+      throw new PhabricatorWorkerPermanentFailureException(
+        pht(
+          'Trying to activate lease on a dead resource (in status "%s").',
+          $resource_status));
+    }
+
+    // NOTE: We can race resource destruction here. Between the time we
+    // performed the read above and now, the resource might have closed, so
+    // we may activate leases on dead resources. At least for now, this seems
+    // fine: a resource dying right before we activate a lease on it should not
+    // be distinguisahble from a resource dying right after we activate a lease
+    // on it. We end up with an active lease on a dead resource either way, and
+    // can not prevent resources dying from lightning strikes.
+
+    $blueprint = $resource->getBlueprint();
+    $blueprint->activateLease($resource, $lease);
+    $this->validateActivatedLease($blueprint, $resource, $lease);
+  }
+
+  private function validateActivatedLease(
+    DrydockBlueprint $blueprint,
+    DrydockResource $resource,
+    DrydockLease $lease) {
+
+    if (!$lease->isActivatedLease()) {
+      throw new Exception(
+        pht(
+          'Blueprint "%s" (of type "%s") is not properly implemented: it '.
+          'returned from "%s" without activating a lease.',
+          $blueprint->getBlueprintName(),
+          $blueprint->getClassName(),
+          'acquireLease()'));
+    }
+
+  }
+
+}

src/applications/drydock/worker/DrydockResourceWorker.php

@@ -0,0 +1,45 @@
+<?php
+
+final class DrydockResourceWorker extends DrydockWorker {
+
+  protected function doWork() {
+    $resource_phid = $this->getTaskDataValue('resourcePHID');
+    $resource = $this->loadResource($resource_phid);
+
+    $this->activateResource($resource);
+  }
+
+
+  private function activateResource(DrydockResource $resource) {
+    $resource_status = $resource->getStatus();
+
+    if ($resource_status != DrydockResourceStatus::STATUS_PENDING) {
+      throw new PhabricatorWorkerPermanentFailureException(
+        pht(
+          'Trying to activate resource from wrong status ("%s").',
+          $resource_status));
+    }
+
+    $blueprint = $resource->getBlueprint();
+    $blueprint->activateResource($resource);
+    $this->validateActivatedResource($blueprint, $resource);
+  }
+
+
+  private function validateActivatedResource(
+    DrydockBlueprint $blueprint,
+    DrydockResource $resource) {
+
+    if (!$resource->isActivatedResource()) {
+      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()'));
+    }
+
+  }
+
+}

src/applications/drydock/worker/DrydockWorker.php

@@ -0,0 +1,39 @@
+<?php
+
+abstract class DrydockWorker extends PhabricatorWorker {
+
+  protected function getViewer() {
+    return PhabricatorUser::getOmnipotentUser();
+  }
+
+  protected function loadLease($lease_phid) {
+    $viewer = $this->getViewer();
+
+    $lease = id(new DrydockLeaseQuery())
+      ->setViewer($viewer)
+      ->withPHIDs(array($lease_phid))
+      ->executeOne();
+    if (!$lease) {
+      throw new PhabricatorWorkerPermanentFailureException(
+        pht('No such lease "%s"!', $lease_phid));
+    }
+
+    return $lease;
+  }
+
+  protected function loadResource($resource_phid) {
+    $viewer = $this->getViewer();
+
+    $resource = id(new DrydockResourceQuery())
+      ->setViewer($viewer)
+      ->withPHIDs(array($resource_phid))
+      ->executeOne();
+    if (!$resource) {
+      throw new PhabricatorWorkerPermanentFailureException(
+        pht('No such resource "%s"!', $resource_phid));
+    }
+
+    return $resource;
+  }
+
+}

src/infrastructure/daemon/workers/PhabricatorWorker.php

@@ -87,6 +87,15 @@ abstract class PhabricatorWorker extends Phobject {
     return $this->data;
   }
 
+  final protected function getTaskDataValue($key, $default = null) {
+    $data = $this->getTaskData();
+    if (!is_array($data)) {
+      throw new PhabricatorWorkerPermanentFailureException(
+        pht('Expected task data to be a dictionary.'));
+    }
+    return idx($data, $key, $default);
+  }
+
   final public function executeTask() {
     $this->doWork();
   }
@@ -149,8 +158,7 @@ abstract class PhabricatorWorker extends Phobject {
 
 
   /**
-   * Wait for tasks to complete. If tasks are not leased by other workers, they
-   * will be executed in this process while waiting.
+   * Wait for tasks to complete.
    *
    * @param list<int>   List of queued task IDs to wait for.
    * @return void
@@ -178,24 +186,9 @@ abstract class PhabricatorWorker extends Phobject {
         break;
       }
 
-      $tasks = id(new PhabricatorWorkerLeaseQuery())
-        ->withIDs($waiting)
-        ->setLimit(1)
-        ->execute();
-
-      if (!$tasks) {
-        // We were not successful in leasing anything. Sleep for a bit and
-        // see if we have better luck later.
-        sleep(1);
-        continue;
-      }
-
-      $task = head($tasks)->executeTask();
-
-      $ex = $task->getExecutionException();
-      if ($ex) {
-        throw $ex;
-      }
+      // We were not successful in leasing anything. Sleep for a bit and
+      // see if we have better luck later.
+      sleep(1);
     }
 
     $tasks = id(new PhabricatorWorkerArchiveTaskQuery())