fix flaky test and improve error handling

just ignore invalid entries

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

@@ -93,6 +93,7 @@ public class TcpIngestor implements AutoCloseable {
 					}
 
 					if (entry.isPresent()) {
+						LOGGER.trace("adding entry to queue: {}", entry);
 						queue.put(entry.get());
 					}
 
@@ -169,7 +170,7 @@ public class TcpIngestor implements AutoCloseable {
 					db.put(new BlockingQueueIterator<>(queue, Entry.POISON));
 					finished = true;
 				} catch (final Exception e) {
-					e.printStackTrace();
+					LOGGER.warn("Write to database failed. Will retry with the next element.", e);
 				}
 			}
 			return null;

pdb-plotting/src/test/java/org/lucares/performance/db/ingestor/TcpIngestorTest.java

@@ -8,6 +8,7 @@ import java.nio.channels.SocketChannel;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.time.Instant;
 import java.time.OffsetDateTime;
 import java.time.ZoneOffset;
 import java.time.format.DateTimeFormatter;
@@ -15,6 +16,7 @@ import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.concurrent.TimeUnit;
 
 import org.lucares.pdb.api.Entry;
 import org.lucares.performance.db.FileUtils;
@@ -104,6 +106,13 @@ public class TcpIngestorTest {
 		final ByteBuffer src = ByteBuffer.wrap(streamData.toString().getBytes(StandardCharsets.UTF_8));
 		channel.write(src);
 
+		try {
+			// ugly workaround: the channel was close too early and not all data
+			// was received
+			TimeUnit.MILLISECONDS.sleep(10);
+		} catch (final InterruptedException e) {
+			throw new IllegalStateException(e);
+		}
 		channel.close();
 		LOGGER.trace("closed sender connection");
 	}
@@ -126,8 +135,9 @@ public class TcpIngestorTest {
 		return result;
 	}
 
+	@Test
 	public void testIngestionThreadDoesNotDieOnErrors() throws Exception {
-		final OffsetDateTime invalidDate = OffsetDateTime.of(1969, 12, 31, 23, 59, 59, 999, ZoneOffset.UTC);
+		final OffsetDateTime invalidDate = OffsetDateTime.ofInstant(Instant.ofEpochMilli(-1), ZoneOffset.UTC);
 		final OffsetDateTime dateB = OffsetDateTime.now();
 		final String host = "someHost";