Github user adeneche commented on a diff in the pull request:
https://github.com/apache/drill/pull/283#discussion_r46585304
--- Diff: common/src/main/java/org/apache/drill/common/HistoricalLog.java
---
@@ -0,0 +1,179 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.drill.common;
+
+import java.util.Arrays;
+import java.util.LinkedList;
+
+import org.slf4j.Logger;
+
+/**
+ * Utility class that can be used to log activity within a class
+ * for later logging and debugging. Supports recording events and
+ * recording the stack at the time they occur.
+ */
+public class HistoricalLog {
+ private static class Event {
+ private final String note; // the event text
+ private final StackTrace stackTrace; // where the event occurred
+
+ public Event(final String note) {
+ this.note = note;
+ stackTrace = new StackTrace();
+ }
+ }
+
+ private final LinkedList<Event> history = new LinkedList<>();
+ private final String idString; // the formatted id string
+ private Event firstEvent; // the first stack trace recorded
+ private final int limit; // the limit on the number of events kept
+
+ /**
+ * Constructor. The format string will be formatted and have its
arguments
+ * substituted at the time this is called.
+ *
+ * @param idStringFormat {@link String#format} format string that can be
used
+ * to identify this object in a log. Including some kind of unique
identifier
+ * that can be associated with the object instance is best.
+ * @param args for the format string, or nothing if none are required
+ */
+ public HistoricalLog(final String idStringFormat, Object... args) {
+ this(Integer.MAX_VALUE, idStringFormat, args);
+ }
+
+ /**
+ * Constructor. The format string will be formatted and have its
arguments
+ * substituted at the time this is called.
+ *
+ * <p>This form supports the specification of a limit that will limit the
+ * number of historical entries kept (which keeps down the amount of
memory
+ * used). With the limit, the first entry made is always kept (under the
+ * assumption that this is the creation site of the object, which is
usually
+ * interesting), and then up to the limit number of entries are kept
after that.
+ * Each time a new entry is made, the oldest that is not the first is
dropped.
+ * </p>
+ *
+ * @param limit the maximum number of historical entries that will be
kept,
+ * not including the first entry made
+ * @param idStringFormat {@link String#format} format string that can be
used
+ * to identify this object in a log. Including some kind of unique
identifier
+ * that can be associated with the object instance is best.
+ * @param args for the format string, or nothing if none are required
+ */
+ public HistoricalLog(final int limit, final String idStringFormat,
Object... args) {
+ this.limit = limit;
+ this.idString = String.format(idStringFormat, args);
+ }
+
+ /**
+ * Record an event. Automatically captures the stack trace at the time
this is
+ * called. The format string will be formatted and have its arguments
substituted
+ * at the time this is called.
+ *
+ * @param noteFormat {@link String#format} format string that describes
the event
+ * @param args for the format string, or nothing if none are required
+ */
+ public synchronized void recordEvent(final String noteFormat, Object...
args) {
--- End diff --
would it make sense to also store a timestamp for each event ? This would
help debugging sliced buffers
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