Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>If you can't rely on <a href="http://wrapper.tanukisoftware.org/" rel="nofollow noreferrer">Java Service Wrapper</a> cited <a href="https://stackoverflow.com/a/534680/362">elsewhere</a> (for instance, if you are running on Ubuntu, which has no packaged version of SW) you probably want to do it the old fashioned way: have your program write its PID in /var/run/$progname.pid, and write a standard SysV init script (use for instance the one for ntpd as an example, it's simple) around it. Preferably, make it LSB-compliant, too.</p> <p>Essentially, the start function tests if the program is already running (by testing if /var/run/$progname.pid exists, and the contents of that file is the PID of a running process), and if not run</p> <pre><code>logfile=/var/log/$progname.log pidfile=/var/run/$progname.pid nohup java -Dpidfile=$pidfile $jopts $mainClass &lt;/dev/null &gt; $logfile 2&gt;&amp;1 </code></pre> <p>The stop function checks on /var/run/$progname.pid, tests if that file is the PID of a running process, verifies that it is a Java VM (so as not to kill a process that simply reused the PID from a dead instance of my Java daemon) and then kills that process. </p> <p>When called, my main() method will start by writing its PID in the file defined in System.getProperty("pidfile").</p> <p>One major hurdle, though: in Java, there is no simple and standard way to get the PID of the process the JVM runs in.</p> <p>Here is what I have come up with:</p> <pre><code>private static String getPid() { File proc_self = new File("/proc/self"); if(proc_self.exists()) try { return proc_self.getCanonicalFile().getName(); } catch(Exception e) { /// Continue on fall-back } File bash = new File("/bin/bash"); if(bash.exists()) { ProcessBuilder pb = new ProcessBuilder("/bin/bash","-c","echo $PPID"); try { Process p = pb.start(); BufferedReader rd = new BufferedReader(new InputStreamReader(p.getInputStream())); return rd.readLine(); } catch(IOException e) { return String.valueOf(Thread.currentThread().getId()); } } // This is a cop-out to return something when we don't have BASH return String.valueOf(Thread.currentThread().getId()); } </code></pre>
    singulars
    1. This table or related slice is empty.
    1. POHow to Daemonize a Java Program?
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USagweber
    1. USVarkhan
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. CONo need for the Java to write the PID, the script can do it as well (echo $! > /var/run/my.pid) Also, since usually only root can write to /var/run you can have the shell script running as root and the daemon run as another user.
      singulars
      1. PO
      1. USDavid Rabinowitz
    2. COExcept you can't change uid or euid in java, so you have to do it from the shell, with sudo... it's a bit of a pain if you ask me. It's easier to have /var/run and var/log writable to the user you run as...
      singulars
      1. PO
      1. USVarkhan
    3. COAlso, the rationale for having Java write the pid file / lock file is to have a mean to know whether the initialization phase of the daemon completed successfully (by writing at the end of that phase).
      singulars
      1. PO
      1. USVarkhan
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload