prevent parallel plot requests

Plotting can take a long time and use a lot of resources. 
Multiple plot requests can cause the machine to run OOM.

We are now allowing plots for 500k files again. This is mainly to
prevent unwanted plots of everything.

pdb-ui/src/main/java/org/lucares/pdbui/PdbController.java

@@ -10,6 +10,7 @@ import java.util.List;
 import java.util.Locale;
 import java.util.Map;
 import java.util.SortedSet;
+import java.util.concurrent.locks.ReentrantLock;
 
 import org.lucares.pdb.datastore.Proposal;
 import org.lucares.pdb.plot.api.PlotSettings;
@@ -50,6 +51,8 @@ public class PdbController implements HardcodedValues {
 
 	private final Plotter plotter;
 	private final PerformanceDb db;
+	
+	private final ReentrantLock plotterLock = new ReentrantLock();
 
 	public PdbController(final PerformanceDb db, final Plotter plotter) {
 		this.db = db;
@@ -71,20 +74,32 @@ public class PdbController implements HardcodedValues {
 			produces = MediaType.APPLICATION_JSON_UTF8_VALUE //
 	)
 	@ResponseBody
-	PlotResponse createPlot(@RequestBody final PlotRequest request) throws InternalPlottingException {
+	PlotResponse createPlot(@RequestBody final PlotRequest request)
+			throws InternalPlottingException, InterruptedException {
 
-		final PlotSettings plotSettings = PlotSettingsTransformer.toSettings(request);
+		final PlotSettings plotSettings = PlotSettingsTransformer
+				.toSettings(request);
 
-		try {
-			final PlotResult result = plotter.plot(plotSettings);
+		// TODO the UI should cancel requests that are in flight before sending a plot request
+		if (plotterLock.tryLock()) {
+			try {
+				final PlotResult result = plotter.plot(plotSettings);
 
-			final String imageUrl = WEB_IMAGE_OUTPUT_PATH + "/" + result.getImageName();
-			LOGGER.trace("image url:  {}", imageUrl);
-			System.gc();
+				final String imageUrl = WEB_IMAGE_OUTPUT_PATH + "/"
+						+ result.getImageName();
+				LOGGER.trace("image url:  {}", imageUrl);
+				System.gc();
 
-			return new PlotResponse(DataSeries.toMap(result.getDataSeries()), imageUrl);
-		} catch (final NoDataPointsException e) {
-			throw new NotFoundException(e);
+				return new PlotResponse(
+						DataSeries.toMap(result.getDataSeries()), imageUrl);
+			} catch (final NoDataPointsException e) {
+				throw new NotFoundException(e);
+			} finally {
+				plotterLock.unlock();
+			}
+
+		} else {
+			throw new ServiceUnavailableException("Too many parallel requests!");
 		}
 	}
 

pdb-ui/src/main/java/org/lucares/pdbui/ServiceUnavailableException.java

@@ -0,0 +1,14 @@
+package org.lucares.pdbui;
+
+import org.springframework.http.HttpStatus;
+import org.springframework.web.bind.annotation.ResponseStatus;
+
+@ResponseStatus(value = HttpStatus.SERVICE_UNAVAILABLE, reason = "Service Unavailable")
+public class ServiceUnavailableException extends RuntimeException {
+
+	private static final long serialVersionUID = -4512668277873760500L;
+
+	public ServiceUnavailableException(String message) {
+		super(message);
+	}
+}

performanceDb/src/main/java/org/lucares/performance/db/TagsToFile.java

@@ -80,7 +80,7 @@ public class TagsToFile implements AutoCloseable {
 		final List<PdbFile> result = new ArrayList<>();
 		
 		final List<Doc> searchResult = db.search(query);
-		if (searchResult.size() > 100_000){
+		if (searchResult.size() > 500_000){
 			throw new IllegalStateException("Too many results.");
 		}