Lift Diffusion Conduit call proxying to the root level of Conduit

Summary:
Ref T13552. Some Diffusion conduit calls may only be served by a node which hosts a working copy on disk, so they're proxied if received by a different node.

This capability is currently bound tightly to "DiffusionRequest", which is a bundle of context parameters used by some Diffusion calls. However, call proxying is not fundamentally a Diffusion behavior.

I want to perform proxying on a "*.search" call which does not use the "DiffusionRequest" parameter bundle. Lift proxying to the root level of Conduit.

Test Plan: Browsed diffusion in a clusterized repsository.

Maniphest Tasks: T13552

Differential Revision: https://secure.phabricator.com/D21442

src/applications/conduit/method/ConduitAPIMethod.php

@@ -120,9 +120,21 @@ abstract class ConduitAPIMethod
   public function executeMethod(ConduitAPIRequest $request) {
     $this->setViewer($request->getUser());
 
+    $client = $this->newConduitCallProxyClient($request);
+    if ($client) {
+      // We're proxying, so just make an intracluster call.
+      return $client->callMethodSynchronous(
+        $this->getAPIMethodName(),
+        $request->getAllParameters());
+    }
+
     return $this->execute($request);
   }
 
+  protected function newConduitCallProxyClient(ConduitAPIRequest $request) {
+    return null;
+  }
+
   abstract public function getAPIMethodName();
 
   /**

src/applications/conduit/protocol/ConduitAPIRequest.php

@@ -51,6 +51,10 @@ final class ConduitAPIRequest extends Phobject {
     return $this->user;
   }
 
+  public function getViewer() {
+    return $this->getUser();
+  }
+
   public function setOAuthToken(
     PhabricatorOAuthServerAccessToken $oauth_token) {
     $this->oauthToken = $oauth_token;

src/applications/diffusion/conduit/DiffusionQueryConduitAPIMethod.php

@@ -85,6 +85,35 @@ abstract class DiffusionQueryConduitAPIMethod
    * should occur after @{method:getResult}, like formatting a timestamp.
    */
   final protected function execute(ConduitAPIRequest $request) {
+    $drequest = $this->getDiffusionRequest();
+
+    // We pass this flag on to prevent proxying of any other Conduit calls
+    // which we need to make in order to respond to this one. Although we
+    // could safely proxy them, we take a big performance hit in the common
+    // case, and doing more proxying wouldn't exercise any additional code so
+    // we wouldn't gain a testability/predictability benefit.
+    $is_cluster_request = $request->getIsClusterRequest();
+    $drequest->setIsClusterRequest($is_cluster_request);
+
+    $viewer = $request->getViewer();
+    $repository = $drequest->getRepository();
+
+    // TODO: Allow web UI queries opt out of this if they don't care about
+    // fetching the most up-to-date data? Synchronization can be slow, and a
+    // lot of web reads are probably fine if they're a few seconds out of
+    // date.
+    id(new DiffusionRepositoryClusterEngine())
+      ->setViewer($viewer)
+      ->setRepository($repository)
+      ->synchronizeWorkingCopyBeforeRead();
+
+    return $this->getResult($request);
+  }
+
+
+  protected function newConduitCallProxyClient(ConduitAPIRequest $request) {
+    $viewer = $request->getViewer();
+
     $identifier = $request->getValue('repository');
     if ($identifier === null) {
       $identifier = $request->getValue('callsign');
@@ -92,7 +121,7 @@ abstract class DiffusionQueryConduitAPIMethod
 
     $drequest = DiffusionRequest::newFromDictionary(
       array(
-        'user' => $request->getUser(),
+        'user' => $viewer,
         'repository' => $identifier,
         'branch' => $request->getValue('branch'),
         'path' => $request->getValue('path'),
@@ -106,46 +135,16 @@ abstract class DiffusionQueryConduitAPIMethod
           $identifier));
     }
 
-    // Figure out whether we're going to handle this request on this device,
-    // or proxy it to another node in the cluster.
-
-    // If this is a cluster request and we need to proxy, we'll explode here
-    // to prevent infinite recursion.
-
-    $is_cluster_request = $request->getIsClusterRequest();
-    $viewer = $request->getUser();
-
     $repository = $drequest->getRepository();
-    $client = $repository->newConduitClient(
-      $viewer,
-      $is_cluster_request);
+
+    $client = $repository->newConduitClientForRequest($request);
     if ($client) {
-      // We're proxying, so just make an intracluster call.
-      return $client->callMethodSynchronous(
-        $this->getAPIMethodName(),
-        $request->getAllParameters());
-    } else {
-
-      // We pass this flag on to prevent proxying of any other Conduit calls
-      // which we need to make in order to respond to this one. Although we
-      // could safely proxy them, we take a big performance hit in the common
-      // case, and doing more proxying wouldn't exercise any additional code so
-      // we wouldn't gain a testability/predictability benefit.
-      $drequest->setIsClusterRequest($is_cluster_request);
-
-      $this->setDiffusionRequest($drequest);
-
-      // TODO: Allow web UI queries opt out of this if they don't care about
-      // fetching the most up-to-date data? Synchronization can be slow, and a
-      // lot of web reads are probably fine if they're a few seconds out of
-      // date.
-      id(new DiffusionRepositoryClusterEngine())
-        ->setViewer($viewer)
-        ->setRepository($repository)
-        ->synchronizeWorkingCopyBeforeRead();
-
-      return $this->getResult($request);
+      return $client;
     }
+
+    $this->setDiffusionRequest($drequest);
+
+    return null;
   }
 
   protected function getResult(ConduitAPIRequest $request) {

src/applications/repository/storage/PhabricatorRepository.php

@@ -2241,6 +2241,23 @@ final class PhabricatorRepository extends PhabricatorRepositoryDAO
     return $client;
   }
 
+  public function newConduitClientForRequest(ConduitAPIRequest $request) {
+    // Figure out whether we're going to handle this request on this device,
+    // or proxy it to another node in the cluster.
+
+    // If this is a cluster request and we need to proxy, we'll explode here
+    // to prevent infinite recursion.
+
+    $viewer = $request->getViewer();
+    $is_cluster_request = $request->getIsClusterRequest();
+
+    $client = $this->newConduitClient(
+      $viewer,
+      $is_cluster_request);
+
+    return $client;
+  }
+
   public function getPassthroughEnvironmentalVariables() {
     $env = $_ENV;