health: add dns_query module alarm (#8434)

health/Makefile.am

@@ -41,6 +41,7 @@ dist_healthconfig_DATA = \
     health.d/couchdb.conf \
     health.d/disks.conf \
     health.d/dnsmasq_dhcp.conf \
+    health.d/dns_query.conf \
     health.d/dockerd.conf \
     health.d/elasticsearch.conf \
     health.d/entropy.conf \

health/health.d/dns_query.conf

@@ -0,0 +1,12 @@
+
+# detect dns query failure
+
+template: dns_query_time_query_time
+      on: dns_query_time.query_time
+  lookup: average -10s unaligned foreach *
+   units: ms
+   every: 10s
+    warn: $this == nan
+   delay: up 20s down 5m multiplier 1.5 max 1h
+    info: query round trip time
+      to: sysadmin