From 0facd50bc72a7ca05f44a167a9794c270cd0ad83 Mon Sep 17 00:00:00 2001
From: Prabhat <20185657+CaptainDredge@users.noreply.github.com>
Date: Thu, 5 Oct 2023 12:56:07 -0700
Subject: [PATCH] Race condition fix for datetime optimization (#10385)

* Race condition fix for datetime optimization

Signed-off-by: Prabhat Sharma <ptsharma@amazon.com>

* Changed JavaDateTimeFormatter caching of parser from MRU(most recently used) to a simple last used formatter

Signed-off-by: Prabhat Sharma <ptsharma@amazon.com>

---------

Signed-off-by: Prabhat Sharma <ptsharma@amazon.com>
Co-authored-by: Prabhat Sharma <ptsharma@amazon.com>
---
 .../common/time/JavaDateFormatter.java        | 25 +++++++++----------
 1 file changed, 12 insertions(+), 13 deletions(-)

diff --git a/server/src/main/java/org/opensearch/common/time/JavaDateFormatter.java b/server/src/main/java/org/opensearch/common/time/JavaDateFormatter.java
index 594ebc3b26a73..14191357fb8aa 100644
--- a/server/src/main/java/org/opensearch/common/time/JavaDateFormatter.java
+++ b/server/src/main/java/org/opensearch/common/time/JavaDateFormatter.java
@@ -74,6 +74,7 @@ class JavaDateFormatter implements DateFormatter {
     private final List<DateTimeFormatter> parsers;
     private final JavaDateFormatter roundupParser;
     private final Boolean canCacheLastParsedFormatter;
+    private volatile DateTimeFormatter lastParsedformatter = null;
 
     /**
      * A round up formatter
@@ -150,7 +151,7 @@ JavaDateFormatter getRoundupParser() {
         if (parsers.length == 0) {
             this.parsers = Collections.singletonList(printer);
         } else {
-            this.parsers = new CopyOnWriteArrayList<>(parsers);
+            this.parsers = Arrays.asList(parsers);
         }
         List<DateTimeFormatter> roundUp = createRoundUpParser(format, roundupParserConsumer);
         this.roundupParser = new RoundUpFormatter(format, roundUp);
@@ -235,7 +236,7 @@ private JavaDateFormatter(
         this.printFormat = printFormat;
         this.printer = printer;
         this.roundupParser = roundUpParsers != null ? new RoundUpFormatter(format, roundUpParsers) : null;
-        this.parsers = new CopyOnWriteArrayList<>(parsers);
+        this.parsers = parsers;
         this.canCacheLastParsedFormatter = canCacheLastParsedFormatter;
     }
 
@@ -286,24 +287,22 @@ public TemporalAccessor parse(String input) {
     private TemporalAccessor doParse(String input) {
         if (parsers.size() > 1) {
             Object object = null;
-            DateTimeFormatter lastParsedformatter = null;
+            if (canCacheLastParsedFormatter && lastParsedformatter != null) {
+                ParsePosition pos = new ParsePosition(0);
+                object = lastParsedformatter.toFormat().parseObject(input, pos);
+                if (parsingSucceeded(object, input, pos)) {
+                    return (TemporalAccessor) object;
+                }
+            }
             for (DateTimeFormatter formatter : parsers) {
                 ParsePosition pos = new ParsePosition(0);
                 object = formatter.toFormat().parseObject(input, pos);
                 if (parsingSucceeded(object, input, pos)) {
                     lastParsedformatter = formatter;
-                    break;
+                    return (TemporalAccessor) object;
                 }
             }
-            if (lastParsedformatter != null) {
-                if (canCacheLastParsedFormatter && lastParsedformatter != parsers.get(0)) {
-                    synchronized (parsers) {
-                        parsers.remove(lastParsedformatter);
-                        parsers.add(0, lastParsedformatter);
-                    }
-                }
-                return (TemporalAccessor) object;
-            }
+
             throw new DateTimeParseException("Failed to parse with all enclosed parsers", input, 0);
         }
         return this.parsers.get(0).parse(input);