Add a "memory.hint" parameter to Aphlict

Summary:
Ref T10696. By default, `node` uses 1.5GB, which is enormous overkill for this service and can crowd out other services if it's running next to things like a database on the same host.

Provide a configuration option to adjust it via `--max-old-space-size` and default to 256MB. It only seems to need about 30M locally, so this should be plenty of headroom.

Test Plan:
Ran `bin/aphlict debug`, things seemed OK.

It takes a long time (days?) to grow to 1.5GB so I can't easily test this locally without a lot of work, but I'll keep an eye on it in production.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10696

Differential Revision: https://secure.phabricator.com/D15720

src/applications/aphlict/management/PhabricatorAphlictManagementWorkflow.php

@@ -78,6 +78,7 @@ abstract class PhabricatorAphlictManagementWorkflow
           'logs' => 'optional list<wild>',
           'cluster' => 'optional list<wild>',
           'pidfile' => 'string',
+          'memory.hint' => 'optional int',
         ));
     } catch (Exception $ex) {
       throw new PhutilArgumentUsageException(
@@ -508,10 +509,22 @@ abstract class PhabricatorAphlictManagementWorkflow
     return $root.'/support/aphlict/server/aphlict_server.js';
   }
 
+  private function getNodeArgv() {
+    $argv = array();
+
+    $hint = idx($this->configData, 'memory.hint');
+    $hint = nonempty($hint, 256);
+
+    $argv[] = sprintf('--max-old-space-size=%d', $hint);
+
+    return $argv;
+  }
+
   private function getStartCommand(array $server_argv) {
     return csprintf(
-      '%s %s %Ls',
+      '%R %Ls -- %s %Ls',
       $this->getNodeBinary(),
+      $this->getNodeArgv(),
       $this->getAphlictScriptPath(),
       $server_argv);
   }

src/docs/user/configuration/notifications.diviner

@@ -80,6 +80,9 @@ The configuration file has these settings:
   - `cluster`: //Optional list.// A list of cluster peers. This is an advanced
     feature.
   - `pidfile`: //Required string.// Path to a PID file.
+  - `memory.hint`: //Optional int.// Suggestion to `node` about how much
+    memory to use, via `--max-old-stack-size`. In most cases, this can be
+    left unspecified.
 
 Each server in the `servers` list should be an object with these keys: