When cluster.databases is configured, read the master connection from it

Summary:
Ref T4571. Ref T10759. Ref T10758. This isn't complete, but gets most of the job done:

  - When `cluster.databases` is set up, most things ignore `mysql.host` now.
  - You can `bin/storage upgrade` and stuff works.
  - You can browse around in the web UI and stuff works.

There's still a lot of weird tricky stuff to navigate, and this has real no advantages over configuring a single server yet (no automatic failover, etc).

Test Plan:
  - Configured `cluster.databases` to point at my `t1.micro` hosts in EC2 (master + replica).
  - Ran `bin/storage upgrade`, got a new install setup on them properly.
  - Survived setup warnings, browsed around.
  - Switched back to local config, ran `bin/storage upgrade`, browsed around, went through setup checks.
  - Intentionally broke config (bad hosts, no masters) and things seemed to react reasonably well.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T4571, T10758, T10759

Differential Revision: https://secure.phabricator.com/D15668

scripts/sql/manage_storage.php

@@ -19,13 +19,6 @@ EOHELP
 );
 $args->parseStandardArguments();
 
-$conf = PhabricatorEnv::newObjectFromConfig(
-  'mysql.configuration-provider',
-  array($dao = null, 'w'));
-
-$default_user       = $conf->getUser();
-$default_host       = $conf->getHost();
-$default_port       = $conf->getPort();
 $default_namespace  = PhabricatorLiskDAO::getDefaultStorageNamespace();
 
 try {
@@ -41,10 +34,8 @@ try {
         'name'    => 'user',
         'short'   => 'u',
         'param'   => 'username',
-        'default' => $default_user,
         'help'    => pht(
-          "Connect with __username__ instead of the configured default ('%s').",
-          $default_user),
+          'Connect with __username__ instead of the configured default.'),
       ),
       array(
         'name'    => 'password',
@@ -84,11 +75,21 @@ 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.'));
+}
+
+$default_user = $ref->getUser();
+$default_host = $ref->getHost();
+$default_port = $ref->getPort();
+
 $test_api = id(new PhabricatorStorageManagementAPI())
   ->setUser($default_user)
   ->setHost($default_host)
   ->setPort($default_port)
-  ->setPassword($conf->getPassword())
+  ->setPassword($ref->getPass())
   ->setNamespace($args->getArg('namespace'));
 
 try {
@@ -120,15 +121,20 @@ try {
 
 if ($args->getArg('password') === null) {
   // This is already a PhutilOpaqueEnvelope.
-  $password = $conf->getPassword();
+  $password = $ref->getPass();
 } else {
   // Put this in a PhutilOpaqueEnvelope.
   $password = new PhutilOpaqueEnvelope($args->getArg('password'));
   PhabricatorEnv::overrideConfig('mysql.pass', $args->getArg('password'));
 }
 
+$selected_user = $args->getArg('user');
+if ($selected_user === null) {
+  $selected_user = $default_user;
+}
+
 $api = id(new PhabricatorStorageManagementAPI())
-  ->setUser($args->getArg('user'))
+  ->setUser($selected_user)
   ->setHost($default_host)
   ->setPort($default_port)
   ->setPassword($password)