Use structured change cache keys

This adds a ChangeKey class which is essentially a structured universal
identifier for a change-like object (Ref, Branch, Change, PR, whatever).

We can use this in ZK objects to reference changes, and by doing so, we
can in many cases avoid actually referencing the change objects
themselves.

This also updates the actual keys in ZK to be sha256sums of the structured
key (for brevity and simplicity of encoding).

Change-Id: I6cd62973d48ad3515f6aa8a8172b9e9c19fcda55

1 files changed, 20 insertions, 7 deletions

diff --git a/zuul/driver/gerrit/gerritconnection.py b/zuul/driver/gerrit/gerritconnection.py
index 7b7107b92..bf71aba1f 100644
--- a/zuul/driver/gerrit/gerritconnection.py
+++ b/zuul/driver/gerrit/gerritconnection.py
@@ -42,7 +42,11 @@ from zuul.driver.gerrit.gerritmodel import GerritChange, GerritTriggerEvent
 from zuul.driver.git.gitwatcher import GitWatcher
 from zuul.lib.logutil import get_annotated_logger
 from zuul.model import Ref, Tag, Branch, Project
-from zuul.zk.change_cache import AbstractChangeCache, ConcurrentUpdateError
+from zuul.zk.change_cache import (
+    AbstractChangeCache,
+    ChangeKey,
+    ConcurrentUpdateError,
+)
 from zuul.zk.event_queues import ConnectionEventQueue, EventReceiverElection
 
 # HTTP timeout in seconds
@@ -311,7 +315,9 @@ class GerritEventConnector(threading.Thread):
         # cache as it may be a dependency
         if event.change_number:
             refresh = True
-            key = str((event.change_number, event.patch_number))
+            key = ChangeKey(self.connection.connection_name, None,
+                            'GerritChange', str(event.change_number),
+                            str(event.patch_number))
             if self.connection._change_cache.get(key) is None:
                 refresh = False
                 for tenant in self.connection.sched.abide.tenants.values():
@@ -760,7 +766,8 @@ class GerritConnection(ZKChangeCacheMixin, BaseConnection):
         # Ensure number and patchset are str
         number = str(number)
         patchset = str(patchset)
-        key = str((number, patchset))
+        key = ChangeKey(self.connection_name, None,
+                        'GerritChange', number, patchset)
         change = self._change_cache.get(key)
         if change and not refresh:
             return change
@@ -776,7 +783,8 @@ class GerritConnection(ZKChangeCacheMixin, BaseConnection):
 
     def _getTag(self, event):
         tag = event.ref[len('refs/tags/'):]
-        key = str((event.project_name, tag, event.newrev))
+        key = ChangeKey(self.connection_name, None,
+                        'Tag', tag, event.newrev)
         change = self._change_cache.get(key)
         if change:
             return change
@@ -794,7 +802,8 @@ class GerritConnection(ZKChangeCacheMixin, BaseConnection):
         return change
 
     def _getBranch(self, event, branch, ref):
-        key = str((event.project_name, branch, event.newrev))
+        key = ChangeKey(self.connection_name, None,
+                        'Branch', branch, event.newrev)
         change = self._change_cache.get(key)
         if change:
             return change
@@ -812,7 +821,8 @@ class GerritConnection(ZKChangeCacheMixin, BaseConnection):
         return change
 
     def _getRef(self, event):
-        key = str((event.project_name, event.ref, event.newrev))
+        key = ChangeKey(self.connection_name, None,
+                        'Ref', event.ref, event.newrev)
         change = self._change_cache.get(key)
         if change:
             return change
@@ -856,6 +866,7 @@ class GerritConnection(ZKChangeCacheMixin, BaseConnection):
                     result.message):
                 if match != change_id:
                     continue
+                # Note: This is not a ChangeCache ChangeKey
                 key = (result.number, result.current_patchset)
                 if key in seen:
                     continue
@@ -992,7 +1003,9 @@ class GerritConnection(ZKChangeCacheMixin, BaseConnection):
             return True
 
         data = self.queryChange(change.number)
-        key = str((change.number, change.patchset))
+        key = ChangeKey(self.connection_name, None,
+                        'GerritChange', str(change.number),
+                        str(change.patchset))
 
         def _update_change(c):
             c.update(data, self)