Loop shell script until successful log message - shell

Question

I am trying to get a shell script to recognize when an app instance has come up. That way it can continue issuing commands.
I've been thinking it would be something like this:
#/bin/bash
startApp.sh
while [ `tail -f server.log` -ne 'regex line indicating success' ]
do
sleep 5
done
echo "App up"
But, even if this worked, it wouldn't address some concerns:
What if the app doesn't come up, how long will it wait
What if there is an error when bringing the app up
How can I capture the log line and echo it
Am I close, or is there a better way? I imagine this is something that other admins have had to overcome.
EDIT:
I found this on super user
https://superuser.com/questions/270529/monitoring-a-file-until-a-string-is-found
tail -f logfile.log | while read LOGLINE
do
[[ "${LOGLINE}" == *"Server Started"* ]] && pkill -P $$ tail
done
My only problem with this is that it might never exit. Is there a way to add in a maximum time?

Answer 1

Ok the first answer was close, but didn't account for everything I thought could happen.
I adapted the code from this link:
Ending tail -f started in a shell script
Here's what I came up with:
#!/bin/bash
instanceDir="/usr/username/server.name"
serverLogFile="$instanceDir/server/app/log/server.log"
function stopServer() {
touch ${serverLogFile}
# 3 minute timeout.
sleep 180 &
local timerPid=$!
tail -n0 -F --pid=${timerPid} ${serverLogFile} | while read line
do
if echo ${line} | grep -q "Shutdown complete"; then
echo 'Server Stopped'
# stop the timer..
kill ${timerPid} > /dev/null 2>&1
fi
done &
echo "Stoping Server."
$instanceDir/bin/stopserver.sh > /dev/null 2>&1
# wait for the timer to expire (or be killed)
wait %sleep
}
function startServer() {
touch ${serverLogFile}
# 3 minute timeout.
sleep 180 &
local timerPid=$!
tail -n0 -F --pid=${timerPid} ${serverLogFile} | while read line
do
if echo ${line} | grep -q "server start complete"; then
echo 'Server Started'
# stop the timer..
kill ${timerPid} > /dev/null 2>&1
fi
done &
echo "Starting Server."
$instanceDir/bin/startserver.sh > /dev/null 2>&1 &
# wait for the timer to expire (or be killed)
wait %sleep
}
stopServer
startServer

Answer 2

Well, tail -f won't ever exit, so that's not what you want.
numLines=10
timeToSleep=5
until tail -n $numLines server.log | grep -q "$serverStartedPattern"; do
sleep $timeToSleep
done
Be sure that $numLines is greater than the number of lines that might show up during $timeToSleep when the server has come up.
This will continue forever; if you want to only allow so much time, you could put a cap on the number of loop iterations with something like this:
let maxLoops=60 numLines=10 timeToSleep=5 success=0
for (( try=0; try < maxLoops; ++try )); do
if tail -n $numLines server.log | grep -q "$serverStartedPattern"; then
echo "Server started!"
success=1
break
fi
sleep $timeToSleep
done
if (( success )); then
echo "Server started!"
else
echo "Server never started!"
fi
exit $(( 1-success ))