Add tenant name on NodeRequests for Nodepool

This change adds the tenant name of the current events' context to
NodeRequests and exposes it as a new field on ZooKeeper.  It prepares
for a tenant-aware Nodepool Launcher for it to enforce per-tenant
resource quota.  In addition, Zuul exposes a new statsd metric
``zuul.nodepool.tenant.<tenant>.current_requests`` that drills down the
overall current_requests metric per tenant.

Corresponding Spec can be found here
https://review.opendev.org/c/zuul/zuul/+/788481

Change-Id: I6d47431e939aba2c80f30504b7a48c15f9fc8fb7

doc/source/reference/monitoring.rst

@@ -330,6 +330,14 @@ These metrics are emitted by the Zuul :ref:`scheduler`:
       Persistently high values indicate more testing node resources
       would be helpful.
 
+   .. stat:: tenant.<tenant>.current_requests
+      :type: gauge
+
+      The number of outstanding nodepool requests from Zuul drilled down by
+      <tenant>. If a tenant for a node request cannot be determed, it is
+      reported as ``unknown``. This relates to
+      ``zuul.nodepool.current_requests``.
+
    .. stat:: resources
 
       Holds metrics about resource usage by tenant or project if resources

releasenotes/notes/tenant-information-in-node-request-1ce98b86f7388cd0.yaml

@@ -0,0 +1,7 @@
+---
+features:
+  - |
+    Add new statsd gauge metrics of current open node requests exported as
+    ``zuul.nodepool.tenant.<tenant>.current_requests``. This metric tracks the
+    currently open node requests per tenant. It drills down the overall
+    ``zuul.nodepool.current_requests`` metric.

tests/unit/test_scheduler.py

@@ -493,8 +493,12 @@ class TestScheduler(ZuulTestCase):
             'zuul.nodepool.requests.requested.size.1', value='1', kind='c')
         self.assertReportedStat(
             'zuul.nodepool.requests.fulfilled.size.1', value='1', kind='c')
+        # just check for existence, since we can not know if a request is
+        # in-flight during the sched._stats_inverval
         self.assertReportedStat(
-            'zuul.nodepool.current_requests', value='1', kind='g')
+            'zuul.nodepool.current_requests', kind='g')
+        self.assertReportedStat(
+            'zuul.nodepool.tenant.tenant-one.current_requests', kind='g')
         self.assertReportedStat(
             'zuul.executors.online', value='1', kind='g')
         self.assertReportedStat(

zuul/model.py

@@ -879,6 +879,7 @@ class NodeRequest(object):
         d['state_time'] = self.state_time
         d['relative_priority'] = self.relative_priority
         d['event_id'] = self.event_id
+        d['tenant_name'] = self.tenant_name
         return d
 
     def updateFromDict(self, data):
@@ -887,6 +888,11 @@ class NodeRequest(object):
         self.state_time = data['state_time']
         self.relative_priority = data.get('relative_priority', 0)
         self.event_id = data['event_id']
+        # Make sure we don't update tenant_name to 'None'.
+        # This can happen if nodepool does not report one back and leads
+        # to errors at other places where we rely on that info.
+        if 'tenant_name' in data:
+            self.tenant_name = data['tenant_name']
 
     @classmethod
     def fromDict(cls, data):

zuul/nodepool.py

@@ -54,7 +54,6 @@ class Nodepool(object):
         #  timer   zuul.nodepool.requests.(fulfilled|failed)
         #  timer   zuul.nodepool.requests.(fulfilled|failed).<label>
         #  timer   zuul.nodepool.requests.(fulfilled|failed).<size>
-        #  gauge   zuul.nodepool.current_requests
         if not self.statsd:
             return
         pipe = self.statsd.pipeline()
@@ -78,7 +77,6 @@ class Nodepool(object):
         pipe.incr(key + '.size.%s' % len(request.nodeset.nodes))
         if dt:
             pipe.timing(key + '.size.%s' % len(request.nodeset.nodes), dt)
-        pipe.gauge('zuul.nodepool.current_requests', len(self.requests))
         pipe.send()
 
     def emitStatsResources(self):

zuul/scheduler.py

@@ -448,6 +448,29 @@ class Scheduler(threading.Thread):
                 self.statsd.gauge(f"{base}.management_events",
                                   len(management_event_queues[pipeline.name]))
 
+        self.statsd.gauge('zuul.nodepool.current_requests',
+                          len(self.nodepool.requests))
+
+        # export current_requests stats per tenant
+        tenant_requests = defaultdict(int)
+
+        # need to initialize tenants here explicitly to report a zero for
+        # all tenants for which no requests are in-flight
+        for tenant_name in self.abide.tenants.keys():
+            tenant_requests[tenant_name] = 0
+
+        for r in self.nodepool.requests.values():
+            # might be None, we ignore them for this metric
+            if not r.tenant_name:
+                continue
+            tenant_requests[r.tenant_name] += 1
+
+        for tenant, request_count in tenant_requests.items():
+            self.statsd.gauge(
+                "zuul.nodepool.tenant.{tenant}.current_requests",
+                request_count,
+                tenant=tenant)
+
     def startCleanup(self):
         # Run the first cleanup immediately after the first
         # reconfiguration.