Milo: Move instance configuration to luci-config

milo/common/config/settings.proto

Index: milo/common/config/settings.proto
diff --git a/milo/common/config/settings.proto b/milo/common/config/settings.proto
index a843a49cdf535a08912701f168ef17ce02f3a956..30634a559ea727a81b52fb039c815f7de3b3c346 100644
--- a/milo/common/config/settings.proto
+++ b/milo/common/config/settings.proto
@@ -7,11 +7,40 @@ syntax = "proto3";
 package config;
 
 // Settings represents the format for the global (service) config for Milo.
-message Settings{
-  message Buildbot{
+message Settings {
+  message Buildbot {
     // internal_reader is the infra-auth group that is allowed to read internal
     // buildbot data.
     string internal_reader = 1;
+
+    // public_topic is the name of the pubsub topic where public builds come in
+    // from
+    string public_topic = 2;
+
+    // internal_topic is the name of the pubsub topic where internal builds
+    // come in from
+    string internal_topic = 3;
   }
   Buildbot buildbot = 1;
+
+  message Buildbucket {
+    // name is the user friendly name of the Buildbucket instance we're pointing to.
+    string name = 1;
+
+    // host is the hostname of the buildbucket instance we're pointing to (sans schema).
+    string host = 2;
+  }
+  Buildbucket buildbucket = 2;
+
+  message Swarming {
+    // default_host is the hostname of the swarming host Milo defaults to, if
+    // none is specified.  Default host is implicitly an allowed host.
+    string default_host = 1;
+
+    // allowed_hosts is a list of whitelist hostnames of swarming instances

[nodir, 2017/03/24 08:41:15]

is a whitelist of hostnames 

[hinoka, 2017/03/28 17:47:20]

lol oops

+    // that Milo is allowed to talk to.  This is specified here for security
+    // reasons, because Milo will hand out its oauth2 token to a swarming host.

[nodir, 2017/03/24 08:41:15]

We also do that for buildbucket. Should we have a whitelist of buildbucket
hostnames?

[hinoka, 2017/03/28 17:47:21]

For buildbucket I settled on a 1:1 mapping instead of a whitelist.  wdyt?

[nodir, 2017/03/28 18:25:49]

It sounds good, but in the latest patchset the buildbucket builder handler still
accepts "server" query string parameter. What you say here sounds like we should
not allow users to specify that because there can be only one buildbucket
hostname

[hinoka, 2017/03/28 19:21:02]

You're right, that was a mistake.  It's been fixed.

+    repeated string allowed_hosts = 2;
+  }
+  Swarming swarming = 3;
 }