Create link to previous buildset span

Create a link to the previous buildset span on gate reset. To make this
work we'll start the buildset span when the buildset is created instead
of only when we set the configuration.

This change also adds the `is_remote` flag of the span context of
related links. This is required for creating a `SpanContext` in order to
deserialize the links.

Change-Id: If3a3a83739c1472659d71d05dcf67f84ddce4247

zuul/lib/tracing.py

@@ -62,6 +62,7 @@ def _formatAttributes(attrs):
 def getSpanInfo(span, include_attributes=False):
     """Return a dict for use in serializing a Span."""
     links = [{'context': _formatContext(l.context),
+              'is_remote': l.context.is_remote,
               'attributes': _formatAttributes(l.attributes)}
              for l in span.links]
     attrs = _formatAttributes(span.attributes)
@@ -113,7 +114,8 @@ def restoreSpan(span_info, is_remote=True):
     for link_info in span_info.get('links', []):
         link_context = trace.SpanContext(
             link_info['context']['trace_id'],
-            link_info['context']['span_id'])
+            link_info['context']['span_id'],
+            is_remote=link_info['is_remote'])
         link = trace.Link(link_context, link_info['attributes'])
         links.append(link)
     attributes = span_info.get('attributes', {})

zuul/manager/__init__.py

@@ -1359,9 +1359,7 @@ class PipelineManager(metaclass=ABCMeta):
         # isn't already set.
         tpc = tenant.project_configs.get(item.change.project.canonical_name)
         if not build_set.ref:
-            with trace.use_span(tracing.restoreSpan(item.span_info)):
-                span_info = tracing.startSavedSpan('BuildSet')
-            build_set.setConfiguration(self.current_context, span_info)
+            build_set.setConfiguration(self.current_context)
 
         # Next, if a change ahead has a broken config, then so does
         # this one.  Record that and don't do anything else.

zuul/model.py

@@ -4163,7 +4163,7 @@ class BuildSet(zkobject.ZKObject):
             len(self.builds),
             self.getStateName(self.merge_state))
 
-    def setConfiguration(self, context, span_info):
+    def setConfiguration(self, context):
         with self.activeContext(context):
             # The change isn't enqueued until after it's created
             # so we don't know what the other changes ahead will be
@@ -4183,7 +4183,6 @@ class BuildSet(zkobject.ZKObject):
                 self.merger_items = [i.makeMergerItem() for i in items]
             self.configured = True
             self.configured_time = time.time()
-            self.span_info = span_info
 
     def _toChangeDict(self, item):
         # Inject bundle_id to dict if available, this can be used to decide
@@ -4385,8 +4384,12 @@ class QueueItem(zkobject.ZKObject):
         obj._save(context, data, create=True)
         files_state = (BuildSet.COMPLETE if obj.change.files is not None
                        else BuildSet.NEW)
-        obj.updateAttributes(context, current_build_set=BuildSet.new(
-            context, item=obj, files_state=files_state))
+
+        with trace.use_span(tracing.restoreSpan(obj.span_info)):
+            buildset_span_info = tracing.startSavedSpan("BuildSet")
+            obj.updateAttributes(context, current_build_set=BuildSet.new(
+                context, item=obj, files_state=files_state,
+                span_info=buildset_span_info))
         return obj
 
     def getPath(self):
@@ -4496,11 +4499,21 @@ class QueueItem(zkobject.ZKObject):
         old_build_set = self.current_build_set
         files_state = (BuildSet.COMPLETE if self.change.files is not None
                        else BuildSet.NEW)
-        self.updateAttributes(
-            context,
-            current_build_set=BuildSet.new(context, item=self,
-                                           files_state=files_state),
-            layout_uuid=None)
+
+        with trace.use_span(tracing.restoreSpan(self.span_info)):
+            old_buildset_span = tracing.restoreSpan(old_build_set.span_info)
+            link = trace.Link(
+                old_buildset_span.get_span_context(),
+                attributes={"previous_buildset": old_build_set.uuid})
+            buildset_span_info = tracing.startSavedSpan(
+                "BuildSet", links=[link])
+
+            self.updateAttributes(
+                context,
+                current_build_set=BuildSet.new(context, item=self,
+                                               files_state=files_state,
+                                               span_info=buildset_span_info),
+                layout_uuid=None)
         old_build_set.delete(context)
 
     def addBuild(self, build):