Record job build attempts in inventory

Record the number of attempts zuul has made to run this job in the job
inventory. This will help expose reliability information in job logs and
in job log indexers. We want to try and expose job reliability as much
as possible and this is one way to do that.

Change-Id: I2f7c31ce510f59bc569c5db89ce6626d9e3ef436

doc/source/user/jobs.rst

@@ -313,6 +313,13 @@ of item.
 
       A boolean indicating whether the job is voting.
 
+   .. var:: attempts
+
+      An integer count of how many attempts have been made to run this
+      job for the current buildset. If there are pre-run failures or network
+      connectivity issues then previous attempts may have been cancelled,
+      and this value will be greater than 1.
+
    .. var:: project
 
       The item's project.  This is a data structure with the following

tests/unit/test_inventory.py

@@ -143,6 +143,8 @@ class TestInventory(TestInventoryBase):
             self.assertEqual(
                 '/usr/bin/python2', node_vars['ansible_python_interpreter'])
         self.assertIn('zuul', inventory['all']['vars'])
+        self.assertIn('attempts', inventory['all']['vars']['zuul'])
+        self.assertEqual(1, inventory['all']['vars']['zuul']['attempts'])
         z_vars = inventory['all']['vars']['zuul']
         self.assertIn('executor', z_vars)
         self.assertIn('src_root', z_vars['executor'])

zuul/executor/client.py

@@ -318,6 +318,11 @@ class ExecutorClient(object):
             self.sched.onBuildCompleted(build, 'SUCCESS', {}, [])
             return build
 
+        # Update zuul attempts after addBuild above to ensure build_set
+        # is up to date.
+        attempts = build.build_set.getTries(job.name)
+        zuul_params['attempts'] = attempts
+
         functions = getGearmanFunctions(self.gearman)
         function_name = 'executor:execute'
         # Because all nodes belong to the same provider, region and