log stdout/stderr of the gnuplot process

pdb-plotting/src/main/java/org/lucares/recommind/logs/Gnuplot.java

@@ -1,10 +1,16 @@
 package org.lucares.recommind.logs;
 
+import java.io.BufferedReader;
 import java.io.File;
 import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.lang.ProcessBuilder.Redirect;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Path;
 import java.util.Collection;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -19,6 +25,10 @@ public class Gnuplot {
 	private static final String ENV_GNUPLOT_HOME = "GNUPLOT_HOME";
 	private static final String PROPERTY_GNUPLOT_HOME = "gnuplot.home";
 	private final Path tmpDirectory;
+	
+	// This would be bad style if this code was executed in a web-container, because it would cause a memory leak.
+	// But this code is only (and will only) be executed as standalone application.
+	private static final ExecutorService POOL = Executors.newCachedThreadPool();
 
 	public Gnuplot(final Path tmpDirectory) {
 		this.tmpDirectory = tmpDirectory;
@@ -33,15 +43,18 @@ public class Gnuplot {
 		LOGGER.debug(gnuplotFileContent);
 
 		final File gnuplotFile = File.createTempFile("gnuplot", ".dem", tmpDirectory.toFile());
-		//Files.write(gnuplotFileContent, gnuplotFile, StandardCharsets.UTF_8);
 		Files.asCharSink(gnuplotFile, StandardCharsets.UTF_8).write(gnuplotFileContent);
 
 		final long start = System.nanoTime();
 
 		try {
-			final ProcessBuilder processBuilder = new ProcessBuilder(gnuplotBinary(), gnuplotFile.getAbsolutePath());
+			final ProcessBuilder processBuilder = new ProcessBuilder(gnuplotBinary(), gnuplotFile.getAbsolutePath())//
-			processBuilder.inheritIO();
+			.redirectOutput(Redirect.PIPE)//
+			.redirectError(Redirect.PIPE);
+			
 			final Process process = processBuilder.start();
+			logOutput("stderr", process.getErrorStream());
+			logOutput("stdout", process.getInputStream());
 			process.waitFor();
 		} catch (final IOException e) {
 			if (e.getMessage().contains("No such file or directory")) {
@@ -56,6 +69,22 @@ public class Gnuplot {
 		METRICS_LOGGER.debug("gnuplot: {}ms", (System.nanoTime() - start) / 1_000_000.0);
 	}
 
+	private void logOutput(final String humanReadableType, final  InputStream stream) throws IOException {
+		
+		POOL.submit(()->{
+			try{
+				final BufferedReader reader = new BufferedReader(new InputStreamReader(stream, StandardCharsets.UTF_8));
+				String line;
+				while(( line = reader.readLine()) != null){
+					LOGGER.info("gnuplot {}: {}", humanReadableType, line);
+				}
+			}
+			catch (Exception e){
+				LOGGER.warn("Exception while reading "+ humanReadableType+ " of gnuplot command", e);
+			}
+		});
+	}
+
 	private String gnuplotBinary() {
 
 		if (System.getProperty(PROPERTY_GNUPLOT_HOME) != null) {