Split up registerScheduler() and onLoad() methods

This is an early preparation step for removing the RPC calls between
zuul-web and the scheduler.

In order to do so we must initialize the ConfigLoader in zuul-web which
requires all connections to be available. Therefore, this change ensures
that we can load all connections in zuul-web without providing a
scheduler instance.

To avoid unnecessary traffic from a zuul-web instance the onLoad()
method initializes the change cache only if a scheduler instance is
available on the connection.

Change-Id: I3c1d2995e81e17763ae3454076ab2f5ce87ab1fc

1 files changed, 6 insertions, 1 deletions

diff --git a/zuul/connection/__init__.py b/zuul/connection/__init__.py
index 5a69dbb55..03eaee300 100644
--- a/zuul/connection/__init__.py
+++ b/zuul/connection/__init__.py
@@ -68,7 +68,7 @@ class BaseConnection(object, metaclass=abc.ABCMeta):
         except Exception:
             self.log.exception("Exception reporting event stats")
 
-    def onLoad(self):
+    def onLoad(self, zk_client):
         pass
 
     def onStop(self):
@@ -136,6 +136,7 @@ class ZKBranchCacheMixin:
     # Expected to be defined by the connection and to be an instance
     # of BranchCache
     _branch_cache = None
+    read_only = False
 
     @abc.abstractmethod
     def isBranchProtected(self, project_name: str, branch_name: str,
@@ -243,6 +244,10 @@ class ZKBranchCacheMixin:
         if branches is not None:
             return sorted(branches)
 
+        if self.read_only:
+            raise RuntimeError(
+                "Won't fetch project branches as read-only is set.")
+
         # We need to perform a query
         branches = self._fetchProjectBranches(project, exclude_unprotected)
         self.log.info("Got branches for %s" % project.name)