/*
Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016. All rights reserved.
Contact:
SYSTAP, LLC DBA Blazegraph
2501 Calvert ST NW #106
Washington, DC 20008
licenses@blazegraph.com
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
/*
* Created on Mar 26, 2008
*/
package com.bigdata.counters;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.LineNumberReader;
import java.io.Reader;
public abstract class ProcessReaderHelper extends
AbstractProcessReader {
/**
* The {@link Reader} from which the output of the process will be read.
*/
protected LineNumberReader r = null;
public ProcessReaderHelper() {
}
/**
* Creates a {@link LineNumberReader} from the {@link InputStream}.
*
* @param is
* The input stream from which the output of the process will
* be read.
*/
public void start(InputStream is) {
if (r != null)
throw new IllegalStateException();
super.start( is );
r = new LineNumberReader( new InputStreamReader( is ));
}
/**
* Override to return the {@link ActiveProcess}.
*/
abstract protected ActiveProcess getActiveProcess();
/**
* Returns the next line and blocks if a line is not available.
*
* @return The next line.
*
* @throws InterruptedException
*
* @throws IOException
* if the source is closed.
* @throws InterruptedException
* if the thread has been interrupted (this is
* normal during shutdown).
*/
public String readLine() throws IOException, InterruptedException {
// final Thread t = Thread.currentThread();
while(getActiveProcess().isAlive()) {
if(Thread.interrupted()) {
throw new InterruptedException();
}
if(!r.ready()) {
Thread.sleep(100/*ms*/);
continue;
}
final String s = r.readLine();
if(log.isDebugEnabled()) {
log.debug(s);
}
return s;
}
throw new IOException("Closed");
}
public void run() {
try {
readProcess();
} catch (InterruptedException e) {
if(log.isInfoEnabled())
log.info("Interrupted - will halt.");
} catch (Exception e) {
/*
* Note: An IOException here generally means that the process from
* which we were reading has been killed. This can happen if you
* kill it externally. It can also happen with immediate shutdown.
*
* FIXME If performance counter collection is killed but the client
* is not shutdown then counter collection SHOULD be restarted. This
* is especially true for the data services since the load balancer
* will otherwise not be able to measure their loads, recommend
* moves, etc.
*/
log.error("Counter collection halted: " + e.getMessage(), e);
}
}
/**
* Responsible for reading the data.
*
* @throws Exception
*/
abstract protected void readProcess() throws Exception;
}