update check_dns_responsetime; add doc page

check_dns_responsetime

@@ -11,24 +11,22 @@
 #                                             test tcp 53 first
 #                                             check result depends on 1st nameserver only
 # 2022-10-24  v1.2  <axel.hahn@unibe.ch>      shell fixes; remove pipe char in output
+# 2023-07-27  v1.3  <axel.hahn@iml.unibe.ch>  shell fixes; add help page
 # ======================================================================
 
 
-. $(dirname $0)/inc_pluginfunctions
+. $( dirname $0 )/inc_pluginfunctions
+
+self_APPNAME=$( basename $0 | tr [:lower:] [:upper:] )
+self_APPVERSION=1.3
+
 tmpfile=/tmp/check_netstat_out_$$
 infofile=/tmp/check_netstat_out_2_$$
 myHost=$( hostname -f )
 
-echo $myHost | cut -f 3- -d "." | grep "\." >/dev/null
-if [ $? -ne 0 ]; then
-    ph.setStatus unknown
-    ph.status "DNS check for [$myHost] - SKIP: hostname -f returned a FQDN with less than 2 dots"
-    ph.exit
-fi
-
 # set default / override from command line params
-typeset -i iWarnLimit=$(     ph.getValueWithParam  300 w "$@")
-typeset -i iCriticalLimit=$( ph.getValueWithParam 1000 c "$@")
+typeset -i iWarnLimit;     iWarnLimit=$(     ph.getValueWithParam  300 w "$@")
+typeset -i iCriticalLimit; iCriticalLimit=$( ph.getValueWithParam 1000 c "$@")
 
 rm -f $tmpfile $infofile 2>/dev/null
 
@@ -38,23 +36,67 @@ typeset -i iTime=0
 typeset -i iCounter=0
 typeset -i iNotReachable=0
 
+# show help
+function showHelp(){
+    _self=$(basename $0)
+cat <<EOF
+______________________________________________________________________
+
+$self_APPNAME 
+v$self_APPVERSION
+
+(c) Institute for Medical Education - University of Bern
+Licence: GNU GPL 3
+______________________________________________________________________
+
+Loop over all defined dns servers (in /etc/resolv.conf) and check
+each:
+  - detect of port 53 is available (DNS service)
+  - 5x check time of a nslookup for current host (${myHost})
+
+The a warning / critical response will be reached if the maximum time
+of nslookup on the first dns server reaches a limit.
+
+The critical response will be returned if the first of the 
+nameservers is not available.
+
+An unknown response will be returned if the current hostname 
+(hostname -f) is no FQDN.
+
+SYNTAX:
+$_self [ -w VALUE -c VALUE -h ]
+
+OPTIONS:
+
+    -w VALUE       warning level  (default: 300)
+    -c VALUE       critical level (default: 1000)
+    -h or --help   Show this help.
+
+EOF
+}
+
 # ----------------------------------------------------------------------
 # MAIN
 # ----------------------------------------------------------------------
 
 
 # --- check param -h
-if [ "$1" = "-h" ]; then
-    echo "
-    usage: $0 [ -w value -c value -h ]
-
-        -w  Warning level
-        -c  Critical level
-        -h  this help
-    "
-    exit 0
+case "$1" in
+    "--help"|"-h")
+        showHelp
+        exit 0
+        ;;
+    *)
+esac
+
+if ! echo $myHost | cut -f 3- -d "." | grep "\." >/dev/null; then
+    ph.setStatus unknown
+    ph.status "DNS check for [$myHost] - SKIP: hostname -f returned a FQDN with less than 2 dots"
+    ph.exit
 fi
 
+ph.require nslookup
+
 for mydns in $(grep ^nameserver /etc/resolv.conf | awk '{ print $2 } ' )
 do
     iCounter=$iCounter+1
@@ -63,13 +105,12 @@ do
 
     echo "---------- $iCounter - $mydns " >>$infofile
     # todo loop
-    >/dev/tcp/${mydns}/53 >>$infofile 2>&1 
-    if [ $? -ne 0 ]; then
+    if ! >/dev/tcp/${mydns}/53 >>$infofile 2>&1; then
       iNotReachable=$iNotReachable+1
       test $iCounter -eq 1 && ph.setStatus critical
       echo "ERROR: ${mydns} is not reachable on tcp 53" >>$infofile
     else
-        for i in `seq 5`
+        for i in $(seq 5)
         do
             (time nslookup ${myHost} $mydns) >$tmpfile 2>&1
 
@@ -84,7 +125,7 @@ do
         # --- set status
         test $iCounter -eq 1 && ph.setStatusByLimit $iSrvMax $iWarnLimit $iCriticalLimit
 
-        label=$(echo $mydns | sed "s#\.#-#g" )
+        label=${mydns//\./-}
         ph.perfadd "response-$label" "${iSrvMax}"
         test $iSrvMax -gt $iMax && iMax=$iSrvMax
     fi
@@ -93,7 +134,8 @@ do
 done
 
 
-ph.status "DNS check for $myHost - found maximum was $iMax ms - $iNotReachable of $iCounter nameservers not reachable"
+test $iNotReachable -eq 0 && ph.status "DNS check for $myHost - found maximum was $iMax ms - OK: all nameservers are reachable"
+test $iNotReachable -ne 0 && ph.status "DNS check for $myHost - found maximum was $iMax ms - INFO: $iNotReachable of $iCounter nameservers not reachable"
 cat $infofile
 
 rm -f $tmpfile $infofile

docs/20_Checks/_index.md

@@ -18,7 +18,7 @@ There is one include script used by all checks:
 * [check_cpu](check_cpu.md)
 * [check_cronstatus](check_cronstatus.md)
 * [check_disk-io](check_disk-io.md)
-* check_dns_responsetime
+* [check_dns_responsetime](check_dns_responsetime.md)
 * [check_eol](check_eol.md)
 * check_haproxy_health
 * check_haproxy_status

docs/20_Checks/check_dns_responsetime.md

+# CHECK_DNS_RESPONSETIME
+
+## Introduction
+
+**check_dns_responsetime** check dns response time of all dns servers found in local /etc/resolv.conf
+
+## Requirements
+
+* `nslookup` query Internet name servers
+
+## Syntax
+
+```txt
+______________________________________________________________________
+
+CHECK_DNS_RESPONSETIME 
+v1.3
+
+(c) Institute for Medical Education - University of Bern
+Licence: GNU GPL 3
+______________________________________________________________________
+
+Loop over all defined dns servers (in /etc/resolv.conf) and check
+each:
+  - detect of port 53 is available (DNS service)
+  - 5x check time of a nslookup for current host (www.example.com)
+
+The a warning / critical response will be reached if the maximum time
+of nslookup on the first dns server reaches a limit.
+
+The critical response will be returned if the first of the 
+nameservers is not available.
+
+An unknown response will be returned if the current hostname 
+(hostname -f) is no FQDN.
+
+SYNTAX:
+check_dns_responsetime [ -w VALUE -c VALUE -h ]
+
+OPTIONS:
+
+    -w VALUE       warning level  (default: 300)
+    -c VALUE       critical level (default: 1000)
+    -h or --help   Show this help.
+
+```
+
+### Parameters
+
+(none)
+
+## Examples
+
+`$ check_disk-io -m io` returns
+
+```txt
+./check_dns_responsetime
+OK: DNS check for www.example.com - found maximum was 46 ms - OK: all nameservers are reachable
+
+---------- 1 - 8.8.4.4 
+8.8.4.4 #1 >>> 36 ms
+8.8.4.4 #2 >>> 28 ms
+8.8.4.4 #3 >>> 24 ms
+8.8.4.4 #4 >>> 30 ms
+8.8.4.4 #5 >>> 31 ms
+max: 36 ms
+ ^
+ :
+ +--- 1st nameserver is relevant for total status of the check. Limits are warning=300 and critical=1000
+
+
+---------- 2 - 8.8.8.8 
+8.8.8.8 #1 >>> 39 ms
+8.8.8.8 #2 >>> 35 ms
+8.8.8.8 #3 >>> 33 ms
+8.8.8.8 #4 >>> 46 ms
+8.8.8.8 #5 >>> 43 ms
+max: 46 ms
+
+ |response-8-8-4-4=36;; response-8-8-8-8=46;;```