Give bin/storage some replica-aware options

Summary:
Fixes T10758.

  - Adds a "--host" flag. If you specify this, we read your cluster config. This lets you dump from a replica.
  - Adds a "--for-replica" flag to `storage dump`. This makes `mysqldump` include a `CHANGE MASTER ...` statement in the output, which is useful when setting up a replica for the first time.

Test Plan:
  - Dumped master and replica cluster databases.
  - Dumped non-cluster databases.
  - Ran various other commands (help, status, etc).

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10758

Differential Revision: https://secure.phabricator.com/D15714

scripts/sql/manage_storage.php

@@ -30,6 +30,12 @@ try {
         'help'    => pht(
           'Do not prompt before performing dangerous operations.'),
       ),
+      array(
+        'name' => 'host',
+        'param' => 'hostname',
+        'help' => pht(
+          'Connect to __host__ instead of the default host.'),
+      ),
       array(
         'name'    => 'user',
         'short'   => 'u',
@@ -75,10 +81,37 @@ try {
 // First, test that the Phabricator configuration is set up correctly. After
 // we know this works we'll test any administrative credentials specifically.
 
-$ref = PhabricatorDatabaseRef::getMasterDatabaseRef();
-if (!$ref) {
-  throw new Exception(
-    pht('No database master is configured.'));
+$host = $args->getArg('host');
+if (strlen($host)) {
+  $ref = null;
+
+  $refs = PhabricatorDatabaseRef::getLiveRefs();
+
+  // Include the master in case the user is just specifying a redundant
+  // "--host" flag for no reason and does not actually have a database
+  // cluster configured.
+  $refs[] = PhabricatorDatabaseRef::getMasterDatabaseRef();
+
+  foreach ($refs as $possible_ref) {
+    if ($possible_ref->getHost() == $host) {
+      $ref = $possible_ref;
+      break;
+    }
+  }
+
+  if (!$ref) {
+    throw new PhutilArgumentUsageException(
+      pht(
+        'There is no configured database on host "%s". This command can '.
+        'only interact with configured databases.',
+        $host));
+  }
+} else {
+  $ref = PhabricatorDatabaseRef::getMasterDatabaseRef();
+  if (!$ref) {
+    throw new Exception(
+      pht('No database master is configured.'));
+  }
 }
 
 $default_user = $ref->getUser();