[SOLVED] Trigger action once port is up

Question

Hi,
On my computer I have two programs installed that start as systemctl services after the other. The first program is oracle-xe, a non free DBMS which I have installed from AUR. The second program is TOPdesk, a professional service management tool which is not publicly available. TOPdesk depends on oracle-xe; it connects to the oracle-database via port 1521. The problem is that TOPdesk often fails to start because the "systemctl start oracle-xe" commands ends before the functionality of oracle-xe is available. In particular port 1521 is not up yet when the TOPdesk service is started.
I want to solve this problem with a recursive bash script, which basically stops TOPdesk from starting until port 1521 is up. I then call this script from within the systemctl service, either in the oracle-xe.service after the oracle command, or in the TOPdesk service before the TOPdesk command.
/usr/bin/port1521check.sh file
#!/bin/sh
# this is a recursive bash script
if [ CHECK-IF-PORT-1521-IS-UP ]; then
echo oracle-xe is up
else
sleep 1
echo waiting for oracle-xe
/usr/bin/port1521check.sh
fi
The exact issue here is the CHECK-IF-PORT-1521-IS-UP in the script above. How should this be solved?
These are the two systemctl files that are called. Note the commented line that refers to the script /usr/bin/port1521check.sh
oracle-xe.service file
[Unit]
Description=Oracle XE
[Service]
Type=oneshot
ExecStart=/etc/rc.d/oracle-xe start
#ExecStart=/usr/bin/port1521check.sh
ExecStop=/etc/rc.d/oracle-xe stop
RemainAfterExit=yes
[Install]
WantedBy=multi-user.target
topdesk54.service file
[Unit]
Description=TOPdesk 5.4SP1
Requires=oracle-xe.service
After=oracle-xe.service
[Service]
Type=forking
PIDFile=/opt/topdesk54/TOPdesk.pid
ExecStart=
#ExecStart=/usr/bin/port1521check.sh
ExecStart=/opt/topdesk54/topdesk start defaults
ExecStop=/opt/topdesk54/topdesk stop
RemainAfterExit=yes
[Install]
WantedBy=multi-user.target
Firstly, do you think I am I on the right track with this approach? Secondly, what command or script can I use to actually make this script see that port 1521 is up? Is it possible to use nmap output of a scan of localhost? Google has not been very helpful with this issue.
Many thanks in advance!
Last edited by anadyr (2015-05-14 07:14:27)

Answer 1

Only type=oneshot can have multiple ExecStart= lines, so you cannot call port1521check.sh from topdesk54.service in this manner. I would probably write a wrapper script for topdesk54 that waits for the port then exec's it. You can use nc -z to test a port. Also the env has been sanitized so you may not have a PATH. Also, tail recursion is wierd. So, something like:
#!/usr/bin/bash
until /usr/bin/nc -z -w1 localhost 1521 ; do
echo waiting for oracle-xe
/usr/bin/sleep 1
done
echo oracle-xe is up
exec /opt/topdesk54/topdesk "$@"