batch entries between TcpIngestor and PerformanceDB

One bottleneck was the blocking queue used to transport entries
from the listener thread to the ingestor thread.
Reduced the bottleneck by batching entries.
Interestingly the batch size of 100 was better than batch size
of 1000 and better than 10.

pdb-api/src/main/java/org/lucares/pdb/api/Entries.java

@@ -0,0 +1,42 @@
+package org.lucares.pdb.api;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.List;
+
+public class Entries implements Iterable<Entry> {
+	/**
+	 * A special {@link Entries} instance that can be used as poison object for
+	 * {@link BlockingQueueIterator}.
+	 */
+	public static final Entries POISON = new Entries(0);
+
+	private final List<Entry> entries;
+
+	public Entries(final int initialSize) {
+		entries = new ArrayList<>(initialSize);
+	}
+
+	public Entries(final Entry... entries) {
+		this.entries = new ArrayList<>(Arrays.asList(entries));
+	}
+
+	public Entries(final Collection<Entry> entries) {
+		this.entries = new ArrayList<>(entries);
+	}
+
+	public void add(final Entry entry) {
+		entries.add(entry);
+	}
+
+	@Override
+	public Iterator<Entry> iterator() {
+		return entries.iterator();
+	}
+
+	public int size() {
+		return entries.size();
+	}
+}

pdb-api/src/main/java/org/lucares/pdb/api/Entry.java

@@ -7,12 +7,6 @@ import java.time.format.DateTimeFormatter;
 
 public class Entry {
 
-	/**
-	 * A special {@link Entry} that can be used as poison object for
-	 * {@link BlockingQueueIterator}.
-	 */
-	public static final Entry POISON = new Entry(Long.MIN_VALUE, -1, null);
-
 	private final long value;
 
 	private final Tags tags;
@@ -39,9 +33,6 @@ public class Entry {
 
 	@Override
 	public String toString() {
-		if (this == POISON) {
-			return "POISON ENTRY";
-		}
 
 		final OffsetDateTime date = Instant.ofEpochMilli(epochMilli).atOffset(ZoneOffset.UTC);
 		return date.format(DateTimeFormatter.ISO_ZONED_DATE_TIME) + " = " + value + " (" + tags.asString() + ")";