探測本身是 nslookup 指令的一個無窮 while 迴圈。 在 while 迴圈之前,將會設定一個暫存檔以存放 nslookup 回覆。 probefail 和 retries 變數均初始化為 0。
# Set up a temporary file for the nslookup replies. DNSPROBEFILE=/tmp/.$RESOURCE_NAME.probe probefail=0 retries=0 |
設定探測的休息間隔
使用 hatimerun 啟動 nslookup ,傳送 Probe_timeout 值與識別目標主機
基於 nslookup 回覆碼的成功或失敗,設定 probefail 變數
如果 probefail 設定為 1 (失敗),將會確認對 nslookup 的回覆來自資料服務範例而非其他 DNS 伺服器
以下是 while 迴圈碼。
while : do # The interval at which the probe needs to run is specified in the # property THOROUGH_PROBE_INTERVAL. Therefore, set the probe to sleep # for a duration of THOROUGH_PROBE_INTERVAL. sleep $PROBE_INTERVAL # Run an nslookup command of the IP address on which DNS is serving. hatimerun -t $PROBE_TIMEOUT /usr/sbin/nslookup $DNS_HOST $DNS_HOST \ > $DNSPROBEFILE 2>&1 retcode=$? if [ $retcode -ne 0 ]; then probefail=1 fi # Make sure that the reply to nslookup comes from the HA-DNS # server and not from another nameserver mentioned in the # /etc/resolv.conf file. if [ $probefail -eq 0 ]; then # Get the name of the server that replied to the nslookup query. SERVER=` awk ' $1=="Server:" { print $2 }' \ $DNSPROBEFILE | awk -F. ' { print $1 } ' ` if [ -z "$SERVER" ]; then probefail=1 else if [ $SERVER != $DNS_HOST ]; then probefail=1 fi fi fi |