remove warning by using the logger

pdb-plotting/src/main/java/org/lucares/pdb/plot/api/PlotSettings.java

@@ -140,4 +140,12 @@ public class PlotSettings {
 			throw new IllegalArgumentException(string + " is an unknown chrono unit");
 		}
 	}
+
+	@Override
+	public String toString() {
+		return "PlotSettings [query=" + query + ", height=" + height + ", width=" + width + ", groupBy=" + groupBy
+				+ ", limitBy=" + limitBy + ", limit=" + limit + ", dateFrom=" + dateFrom + ", dateRange=" + dateRange
+				+ "]";
+	}
+
 }

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

@@ -59,6 +59,8 @@ public class Plotter {
 
 	public PlotResult plot(final PlotSettings plotSettings) throws InternalPlottingException {
 
+		LOGGER.trace("start plot: {}", plotSettings);
+
 		final String tmpSubDir = uniqueDirectoryName();
 		final Path tmpDir = tmpBaseDir.resolve(tmpSubDir);
 		try {
@@ -116,6 +118,7 @@ public class Plotter {
 			throw new InternalPlottingException("Plotting failed: " + e.getMessage(), e);
 		} finally {
 			FileUtils.delete(tmpDir);
+			LOGGER.trace("done plot");
 		}
 	}