org.opennms.smoketest.utils.StreamGobbler Maven / Gradle / Ivy

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/*
 * Licensed to The OpenNMS Group, Inc (TOG) under one or more
 * contributor license agreements.  See the LICENSE.md file
 * distributed with this work for additional information
 * regarding copyright ownership.
 *
 * TOG licenses this file to You under the GNU Affero General
 * Public License Version 3 (the "License") or (at your option)
 * any later version.  You may not use this file except in
 * compliance with the License.  You may obtain a copy of the
 * License at:
 *
 *      https://www.gnu.org/licenses/agpl-3.0.txt
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied.  See the License for the specific
 * language governing permissions and limitations under the
 * License.
 */
package org.opennms.smoketest.utils;

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.InterruptedIOException;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.atomic.AtomicInteger;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Starts a thread that reads lines from an input stream, logs them, and stores them in an array list. The list of
 * stored lines is used to search for expected output.
 * 
 * Used for consuming {@code stdout} and {@code stderr} of processes. Processes get blocked when their output buffers
 * are full. Consuming their output prevents them from getting blocked.
 */
public class StreamGobbler extends Thread {

    private static final Logger LOG = LoggerFactory.getLogger(StreamGobbler.class);
    private static final AtomicInteger counter = new AtomicInteger();

    private final InputStream stream;
    private final String kind;
    private final List lines = new ArrayList<>();


    public StreamGobbler(InputStream stream, String kind) {
        super("StreamGobbler-" + counter.incrementAndGet());
        this.stream = stream;
        this.kind = kind;
        setDaemon(true);
        start();
    }

    @Override
    public void run() {
        try (var inputStreamReader = new InputStreamReader(stream)) {
            try (var bufferedReader = new BufferedReader(inputStreamReader)) {
                String line;
                while ((line = bufferedReader.readLine()) != null) {
                    LOG.debug(kind + ": " + line);
                    synchronized (lines) {
                        lines.add(line);
                    }
                }
            }
        } catch (InterruptedIOException e) {
            // ignore
        } catch (Throwable e) {
            LOG.error("error reading stream", e);
        }
        LOG.debug(kind + "");
    }

    public List getLines() {
        synchronized (lines) {
            return new ArrayList(lines);
        }
    }
}