When database connection exceptions occur, raise them to the setup layer

Summary:
Ref T13141. Currently, during first-time setup we don't surface all the details about connection exceptions that we could: the underlying exception is discarded inside cluster connection management.

This isn't a huge issue since the reason for connection problems is usually fairly obvious, but in at least one case (see T13141) we hit a less-than-obvious exception.

Instead, store the original exception and propagate the message up the stack so users have more information about the problem.

Test Plan:
  - Configured an intentionally bad MySQL username.
  - Restarted Apache and loaded Phabricator.
  - Got a more helpful exception with a specific authentication error message.

{F5622361}

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13141

Differential Revision: https://secure.phabricator.com/D19454

src/infrastructure/cluster/PhabricatorDatabaseRef.php

@@ -29,6 +29,7 @@ final class PhabricatorDatabaseRef
   private $connectionLatency;
   private $connectionStatus;
   private $connectionMessage;
+  private $connectionException;
 
   private $replicaStatus;
   private $replicaMessage;
@@ -453,6 +454,7 @@ final class PhabricatorDatabaseRef
       return false;
     }
 
+    $this->connectionException = null;
     try {
       $connection->openConnection();
       $reachable = true;
@@ -463,6 +465,7 @@ final class PhabricatorDatabaseRef
       // yet.
       throw $ex;
     } catch (Exception $ex) {
+      $this->connectionException = $ex;
       $reachable = false;
     }
 
@@ -506,6 +509,10 @@ final class PhabricatorDatabaseRef
     return $this->healthRecord;
   }
 
+  public function getConnectionException() {
+    return $this->connectionException;
+  }
+
   public static function getActiveDatabaseRefs() {
     $refs = array();
 

src/infrastructure/storage/lisk/PhabricatorLiskDAO.php

@@ -80,6 +80,8 @@ abstract class PhabricatorLiskDAO extends LiskDAO {
     $master = PhabricatorDatabaseRef::getMasterDatabaseRefForApplication(
       $application);
 
+    $master_exception = null;
+
     if ($master && !$master->isSevered()) {
       $connection = $master->newApplicationConnection($database);
       if ($master->isReachable($connection)) {
@@ -91,6 +93,8 @@ abstract class PhabricatorLiskDAO extends LiskDAO {
         PhabricatorEnv::setReadOnly(
           true,
           PhabricatorEnv::READONLY_UNREACHABLE);
+
+        $master_exception = $master->getConnectionException();
       }
     }
 
@@ -108,7 +112,7 @@ abstract class PhabricatorLiskDAO extends LiskDAO {
       $this->raiseUnconfigured($database);
     }
 
-    $this->raiseUnreachable($database);
+    $this->raiseUnreachable($database, $master_exception);
   }
 
   private function raiseImproperWrite($database) {
@@ -136,13 +140,22 @@ abstract class PhabricatorLiskDAO extends LiskDAO {
         $database));
   }
 
-  private function raiseUnreachable($database) {
-    throw new PhabricatorClusterStrandedException(
-      pht(
-        'Unable to establish a connection to any database host '.
-        '(while trying "%s"). All masters and replicas are completely '.
-        'unreachable.',
-        $database));
+  private function raiseUnreachable($database, Exception $proxy = null) {
+    $message = pht(
+      'Unable to establish a connection to any database host '.
+      '(while trying "%s"). All masters and replicas are completely '.
+      'unreachable.',
+      $database);
+
+    if ($proxy) {
+      $proxy_message = pht(
+        '%s: %s',
+        get_class($proxy),
+        $proxy->getMessage());
+      $message = $message."\n\n".$proxy_message;
+    }
+
+    throw new PhabricatorClusterStrandedException($message);
   }