Don't retry after Gerrit HTTP 409s

Gerrit will return an HTTP status 409 when you try to modify changes
that are already merged or abandoned. For example if you try to vote on
a change in these closed states. In those cases we don't actually want
to retry the request as doing so is a waste of effort.

Update the gerritconnection drive to handle HTTP 409s as a special case
that should not be retried.

Change-Id: I4bd7b8e5aa512bf0ba1d1bf7dd9a39c3843e6ff6

zuul/driver/gerrit/gerritconnection.py

@@ -48,6 +48,10 @@ from zuul.model import Ref, Tag, Branch, Project
 TIMEOUT = 30
 
 
+class HTTPConflictException(Exception):
+    message = "Received response 409"
+
+
 class GerritChangeData(object):
     """Compatability layer for SSH/HTTP
 
@@ -613,7 +617,9 @@ class GerritConnection(BaseConnection):
             auth=self.auth, timeout=TIMEOUT,
             headers={'User-Agent': self.user_agent})
         self.iolog.debug('Received: %s %s' % (r.status_code, r.text,))
-        if r.status_code != 200:
+        if r.status_code == 409:
+            raise HTTPConflictException()
+        elif r.status_code != 200:
             raise Exception("Received response %s" % (r.status_code,))
         ret = None
         if r.text and len(r.text) > 4:
@@ -637,7 +643,9 @@ class GerritConnection(BaseConnection):
             headers={'Content-Type': 'application/json;charset=UTF-8',
                      'User-Agent': self.user_agent})
         self.iolog.debug('Received: %s %s' % (r.status_code, r.text,))
-        if r.status_code != 200:
+        if r.status_code == 409:
+            raise HTTPConflictException()
+        elif r.status_code != 200:
             raise Exception("Received response %s" % (r.status_code,))
         ret = None
         if r.text and len(r.text) > 4:
@@ -1065,6 +1073,9 @@ class GerritConnection(BaseConnection):
                               (changeid, change.commit, uuid),
                               checkinfo)
                     break
+                except HTTPConflictException:
+                    log.exception("Conflict submitting check data to gerrit.")
+                    break
                 except Exception:
                     log.exception("Error submitting check data to gerrit, "
                                   "attempt %s", x)
@@ -1108,6 +1119,9 @@ class GerritConnection(BaseConnection):
                               (changeid, change.commit),
                               data)
                     break
+                except HTTPConflictException:
+                    log.exception("Conflict submitting data to gerrit.")
+                    break
                 except Exception:
                     log.exception(
                         "Error submitting data to gerrit, attempt %s", x)
@@ -1117,6 +1131,9 @@ class GerritConnection(BaseConnection):
                 try:
                     self.post('changes/%s/submit' % (changeid,), {})
                     break
+                except HTTPConflictException:
+                    log.exception("Conflict submitting data to gerrit.")
+                    break
                 except Exception:
                     log.exception(
                         "Error submitting data to gerrit, attempt %s", x)
@@ -1261,7 +1278,9 @@ class GerritConnection(BaseConnection):
                 auth=self.auth, timeout=TIMEOUT,
                 headers={'User-Agent': self.user_agent})
             self.iolog.debug('Received: %s %s' % (r.status_code, r.text,))
-            if r.status_code != 200:
+            if r.status_code == 409:
+                raise HTTPConflictException()
+            elif r.status_code != 200:
                 raise Exception("Received response %s" % (r.status_code,))
             out = r.text[r.text.find('\n') + 5:]
         else: