From: Paul Cuzner <pcuzner@redhat.com>
Date: Thu, 8 Oct 2020 03:30:56 +0000 (+1300)
Subject: mgr/prometheus: Add healthcheck metric for SLOW_OPS
X-Git-Tag: v17.0.0~745^2~1
X-Git-Url: http://git.apps.os.sepia.ceph.com/?a=commitdiff_plain;h=2010432b5045c8f1dd0c052def497e590a1bf2fe;p=ceph.git

mgr/prometheus: Add healthcheck metric for SLOW_OPS

SLOW_OPS is triggered by op tracker, and generates a health
alert but healthchecks do not create metrics for prometheus to
use as alert triggers. This change adds SLOW_OPS metric, and
provides a simple means to extend to other relevant health
checks in the future

If the extract of the value from the health check message fails
we log an error and remove the metric from the metric set. In
addition the metric description has changed to better reflect
the scenarios where SLOW_OPS can be triggered.

Signed-off-by: Paul Cuzner <pcuzner@redhat.com>
---

diff --git a/monitoring/prometheus/alerts/ceph_default_alerts.yml b/monitoring/prometheus/alerts/ceph_default_alerts.yml
index 51d19bfca963e..b14eb15460ccc 100644
--- a/monitoring/prometheus/alerts/ceph_default_alerts.yml
+++ b/monitoring/prometheus/alerts/ceph_default_alerts.yml
@@ -241,3 +241,15 @@ groups:
           description: >
             Pool {{ $labels.name }} will be full in less than 5 days
             assuming the average fill-up rate of the past 48 hours.
+
+  - name: healthchecks
+    rules:
+      - alert: Slow OSD Ops
+        expr: ceph_healthcheck_slow_ops > 0
+        for: 30s
+        labels:
+          severity: warning
+          type: ceph_default
+        annotations:
+          description: >
+            {{ $value }} OSD requests are taking too long to process (osd_op_complaint_time exceeded)
diff --git a/src/pybind/mgr/prometheus/module.py b/src/pybind/mgr/prometheus/module.py
index f50751a677424..f2abf00e4abbb 100644
--- a/src/pybind/mgr/prometheus/module.py
+++ b/src/pybind/mgr/prometheus/module.py
@@ -11,6 +11,7 @@ import time
 from mgr_module import MgrModule, MgrStandbyModule, CommandResult, PG_STATES
 from mgr_util import get_default_addr, profile_method
 from rbd import RBD
+from collections import namedtuple
 try:
     from typing import Optional, Dict, Any, Set
 except:
@@ -108,6 +109,11 @@ DISK_OCCUPATION = ('ceph_daemon', 'device', 'db_device',
 
 NUM_OBJECTS = ['degraded', 'misplaced', 'unfound']
 
+alert_metric = namedtuple('alert_metric', 'name description')
+HEALTH_CHECKS = [
+    alert_metric('SLOW_OPS', 'OSD or Monitor requests taking a long time to process' ),
+]
+
 
 class Metric(object):
     def __init__(self, mtype, name, desc, labels=None):
@@ -432,15 +438,62 @@ class Module(MgrModule):
                 'Number of {} objects'.format(state),
             )
 
+        for check in HEALTH_CHECKS:
+            path = 'healthcheck_{}'.format(check.name.lower())
+            metrics[path] = Metric(
+                'gauge',
+                path,
+                check.description,
+            )
+
         return metrics
 
     @profile_method()
     def get_health(self):
+
+        def _get_value(message, delim=' ', word_pos=0):
+            """Extract value from message (default is 1st field)"""
+            v_str = message.split(delim)[word_pos]
+            if v_str.isdigit():
+                return int(v_str), 0
+            return 0, 1
+
         health = json.loads(self.get('health')['json'])
+        # set overall health
         self.metrics['health_status'].set(
             health_status_to_number(health['status'])
         )
 
+        # Examine the health to see if any health checks triggered need to
+        # become a metric.
+        active_healthchecks = health.get('checks', {})
+        active_names = active_healthchecks.keys()
+
+        for check in HEALTH_CHECKS:
+            path = 'healthcheck_{}'.format(check.name.lower())
+
+            if path in self.metrics:
+
+                if check.name in active_names:
+                    check_data = active_healthchecks[check.name]
+                    message = check_data['summary'].get('message', '')
+                    v, err = 0, 0
+
+                    if check.name == "SLOW_OPS":
+                        # 42 slow ops, oldest one blocked for 12 sec, daemons [osd.0, osd.3] have slow ops.
+                        v, err = _get_value(message)
+
+                    if err:
+                        self.log.error("healthcheck {} message format is incompatible and has been dropped".format(check.name))
+                        # drop the metric, so it's no longer emitted
+                        del self.metrics[path]
+                        continue
+                    else:
+                        self.metrics[path].set(v)
+                else:
+                    # health check is not active, so give it a default of 0
+                    self.metrics[path].set(0)
+
     @profile_method()
     def get_pool_stats(self):
         # retrieve pool stats to provide per pool recovery metrics