Add global session uuid (fixes #524)

src/xdist/remote.py

@@ -22,6 +22,7 @@ class WorkerInteractor(object):
     def __init__(self, config, channel):
         self.config = config
         self.workerid = config.workerinput.get("workerid", "?")
+        self.testrunuid = config.workerinput["testrunuid"]
         self.log = py.log.Producer("worker-%s" % self.workerid)
         if not config.option.debug:
             py.log.setconsumer(self.log._keywords, None)
@@ -112,6 +113,7 @@ class WorkerInteractor(object):
         )
         data["item_index"] = self.item_index
         data["worker_id"] = self.workerid
+        data["testrun_uid"] = self.testrunuid
         assert self.session.items[self.item_index].nodeid == report.nodeid
         self.sendevent("testreport", data=data)
 
@@ -238,6 +240,7 @@ if __name__ == "__channelexec__":
             importpath + os.pathsep + os.environ.get("PYTHONPATH", "")
         )
 
+    os.environ["PYTEST_XDIST_TESTRUNUID"] = workerinput["testrunuid"]
     os.environ["PYTEST_XDIST_WORKER"] = workerinput["workerid"]
     os.environ["PYTEST_XDIST_WORKER_COUNT"] = str(workerinput["workercount"])