OSX LaunchAgent for app that launches another app

Question

I'm trying to set up a local LaunchAgent for cassandra and am running into an issue since bin/cassandra is just a shell script that launches:

/usr/bin/java -ea -javaagent:blah blah blah blah blah blah blah

My LaunchAgent launches the script but either never launches cassandra or doesn't allow it to spawn sub-processes, or, well I'm not entirely sure what's happening but it seems I've run into this issue before. The only way I know of to get this to work is to change my LaunchAgent from:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN"
    "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>Label</key>
    <string>com.cassandra.agent</string>

    <key>RunAtLoad</key>
    <true/>

    <key>KeepAlive</key>
    <true/>

    <key>UserName</key>
    <string>root</string>

    <key>ProgramArguments</key>
    <array>
        <string>/path/to/cassandra/bin/cassandra</string>
    </array>

    <key>WorkingDirectory</key>
    <string>/path/to/cassandra/bin</string>
</dict>
</plist>

to...

...
<key>ProgramArguments</key>
<array>
    <string>/usr/bin/java</string>
    <string>-ea</string>
    <string>-javaagent:blah</string>
    <string>blah</string>
    <string>blah</string>
    <string>blah</string>
    <string>blah</string>
    <string>blah</string>
    <string>blah</string>
</array>

I'm wondering if anyone knows how I can just reference the shell script from the LaunchAgent instead of pulling all the args from ps aux

Have you tried to prepend the shell script with an actual shell binary that should execute the script, i.e. /bin/sh? — Thomas Keller, Sep 19 '11 at 22:03
@tommyd - nice idea, but no luck :( Same thing -- an immediate check shows the process `/bin/sh /path/to/bin/cassandra` but a few ms later and the process is gone — , Sep 19 '11 at 22:17

score 0 · Accepted Answer · answered Sep 19 '11 at 23:16

I'm not specifically familiar with cassandra, but my guess is that it's daemonizing itself (i.e. dropping into the background). launchd doesn't like its children to daemonize themselves; it expects then to stay in the foreground where it can keep an eye on them. If one daemonizes itself, launchd thinks it's exited (which, technically, it has), cleans up any leftover subprocesses (including the now daemonized process), and relaunches it. Lather, rinse, repeat.

According to this entry in the cassandra wiki, you can pass cassandra the -f flag to make it stay in the foreground, and keep launchd happy:

<key>ProgramArguments</key>
<array>
    <string>/opt/local/bin/cassandra</string>
    <string>-f</string>
</array>

Accept for the answer, +1 for the explanation which is more helpful in the long run :) — , Sep 19 '11 at 23:22

OSX LaunchAgent for app that launches another app

1 Answers1