Fix excessive CPU usage by rabbitmq-numconsumers Nagios checks.

The previous model for these Nagios checks was kinda crazy -- every
minute, we'd run a full `rabbitmctl list_consumers` for each of the
dozen+ consumers that we have, and then do the exact same parsing
logic for each to determine whether the target queue has a running
consumer to write out a state file.

Because `rabbitmctl list_consumers` takes a small amount of resources,
on systems where CPU is very limited (e.g. t2 style AWS instances),
this minor CPU wastage could be problematic.

Now we just do that `rabbitmqctl list_consumers` once per minute, and
output all the state files from a single command.

Further TODO items on this front include removing the hardcoded list
of queues.

puppet/zulip/files/cron.d/rabbitmq-numconsumers

@@ -2,15 +2,4 @@ SHELL=/bin/bash
 PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
 USER=root
 
-* * * * * root /home/zulip/deployments/current/scripts/nagios/write-rabbitmq-consumers-state-file notify_tornado
-* * * * * root /home/zulip/deployments/current/scripts/nagios/write-rabbitmq-consumers-state-file user_activity
-* * * * * root /home/zulip/deployments/current/scripts/nagios/write-rabbitmq-consumers-state-file user_activity_interval
-* * * * * root /home/zulip/deployments/current/scripts/nagios/write-rabbitmq-consumers-state-file user_presence
-* * * * * root /home/zulip/deployments/current/scripts/nagios/write-rabbitmq-consumers-state-file invites
-* * * * * root /home/zulip/deployments/current/scripts/nagios/write-rabbitmq-consumers-state-file signups
-* * * * * root /home/zulip/deployments/current/scripts/nagios/write-rabbitmq-consumers-state-file message_sender
-* * * * * root /home/zulip/deployments/current/scripts/nagios/write-rabbitmq-consumers-state-file feedback_messages
-* * * * * root /home/zulip/deployments/current/scripts/nagios/write-rabbitmq-consumers-state-file error_reports
-* * * * * root /home/zulip/deployments/current/scripts/nagios/write-rabbitmq-consumers-state-file digest_emails
-* * * * * root /home/zulip/deployments/current/scripts/nagios/write-rabbitmq-consumers-state-file email_mirror
-* * * * * root /home/zulip/deployments/current/scripts/nagios/write-rabbitmq-consumers-state-file missedmessage_mobile_notifications
+* * * * * root /home/zulip/deployments/current/scripts/nagios/check-rabbitmq-consumers

scripts/nagios/check-rabbitmq-consumers

@@ -22,10 +22,6 @@ if 'USER' in os.environ and not os.environ['USER'] in ['root', 'rabbitmq']:
 usage = """Usage: check-rabbitmq-consumers --queue=[queue-name] --min-threshold=[min-threshold]"""
 
 parser = optparse.OptionParser(usage=usage)
-parser.add_option('--queue',
-                  dest='queue_name',
-                  default="notify_tornado",
-                  action='store')
 parser.add_option('--min-threshold',
                   dest='min_count',
                   type="int",
@@ -39,19 +35,41 @@ output = subprocess.check_output(['/usr/sbin/rabbitmqctl', 'list_consumers'],
 
 consumers = defaultdict(int) # type: Dict[str, int]
 
+worker_queues = {'error_reports',
+                 'user_presence',
+                 'digest_emails',
+                 'slow_queries',
+                 'missedmessage_mobile_notifications',
+                 'feedback_messages',
+                 'signups',
+                 'notify_tornado',
+                 'message_sender',
+                 'missedmessage_emails',
+                 'email_mirror',
+                 'user_activity_interval',
+                 'invites',
+                 'user_activity'}
+
+for queue_name in worker_queues:
+    consumers[queue_name] = 0
+
 for line in output.split('\n'):
     parts = line.split('\t')
-    if len(parts) and parts[0] == options.queue_name:
+    if len(parts) >= 2:
         consumers[parts[0]] += 1
 
-
 now = int(time.time())
 
-if consumers[options.queue_name] < options.min_count:
+for queue_name in consumers.keys():
+    state_file_path = "/var/lib/nagios_state/check-rabbitmq-consumers-" + queue_name
+    state_file_tmp = state_file_path + "-tmp"
+
+    if consumers[queue_name] < options.min_count:
         status = 2
     else:
         status = 0
-
-print("%s|%s|%s|queue %s has %s consumers, needs %s" % (
-            now, status, states[status], options.queue_name,
-            consumers[options.queue_name], options.min_count))
+    with open(state_file_tmp, "w") as f:
+        f.write("%s|%s|%s|queue %s has %s consumers, needs %s\n" % (
+            now, status, states[status], queue_name,
+            consumers[queue_name], options.min_count))
+    subprocess.check_call(["mv", state_file_tmp, state_file_path])

scripts/nagios/write-rabbitmq-consumers-state-file

@@ -1,16 +0,0 @@
-#!/usr/bin/env bash
-set -e
-
-queue=$1
-
-if [ -z "$queue" ]; then
-    echo "Usage: $0 <queue-name>"
-    exit 2
-fi
-
-ZULIP_DIR=/home/zulip/deployments/current
-STATE_DIR=/var/lib/nagios_state
-STATE_FILE=$STATE_DIR/check-rabbitmq-consumers-$queue
-
-"$ZULIP_DIR/scripts/nagios/check-rabbitmq-consumers" "--queue=$queue" &> "${STATE_FILE}-tmp";
-mv "${STATE_FILE}-tmp" "$STATE_FILE"

tools/travis/production-helper

@@ -81,14 +81,9 @@ if supervisorctl status | grep -vq RUNNING || supervisorctl status | sed 's/^.*u
 fi
 
 echo; echo "Now running RabbitMQ consumer Nagios tests"; echo
+# First run the check that usually runs in cron and populates the state files
+/home/zulip/deployments/current/scripts/nagios/check-rabbitmq-consumers
 for consumer in notify_tornado user_activity user_activity_interval user_presence invites signups message_sender feedback_messages error_reports digest_emails email_mirror missedmessage_mobile_notifications; do
-    if ! /home/zulip/deployments/current/scripts/nagios/write-rabbitmq-consumers-state-file "$consumer"; then
-        # Temporary section while we're debugging why this fails nondeterministically in CI
-        STATE_DIR=/var/lib/nagios_state
-        ls "$STATE_DIR"
-        cat "$STATE_DIR"/*
-        /home/zulip/deployments/current/scripts/nagios/write-rabbitmq-consumers-state-file "$consumer"
-    fi
     if ! /usr/lib/nagios/plugins/zulip_app_frontend/check_rabbitmq_consumers "$consumer"; then
         set +x
         echo