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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LANG-1355) TimeZone.getTimeZone() in FastDateParser causes resource contention
Date Tue, 10 Oct 2017 09:01:00 GMT

    [ https://issues.apache.org/jira/browse/LANG-1355?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16198380#comment-16198380
] 

ASF GitHub Bot commented on LANG-1355:
--------------------------------------

Github user kinow commented on a diff in the pull request:

    https://github.com/apache/commons-lang/pull/296#discussion_r143660909
  
    --- Diff: src/main/java/org/apache/commons/lang3/time/FastTimeZone.java ---
    @@ -0,0 +1,90 @@
    +/*
    + * 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.commons.lang3.time;
    +
    +import java.util.TimeZone;
    +import java.util.regex.Matcher;
    +import java.util.regex.Pattern;
    +
    +/**
    + * Faster methods to produce custom time zones.
    + *
    + * @since 3.7
    + */
    +public class FastTimeZone {
    +
    +    private static final TimeZone GREENWICH = new GmtTimeZone(false, 0, 0);
    +
    +    /**
    +     * Get the GMT TimeZone.
    +     * @return A TimeZone with a raw offset of zero.
    +     */
    +    public static TimeZone getGmtTimeZone() {
    +        return GREENWICH;
    +    }
    +
    +    /**
    +     * Get a TimeZone, looking first for GMT custom ids, then falling back to Olson ids.
    +     * A GMT custom id has an optional prefix of GMT, followed by sign, hours digit(s),
optional
    +     * colon(':'), and optional minutes digits: <em>[GMT] (+|-) Hours [[:] Minutes]</em>
    +     *
    +     * @param id A GMT custom id or Olsen id
    +     * @return A timezone
    +     */
    +    public static TimeZone getTimeZone(String id) {
    +        TimeZone tz = getGmtTimeZone(id);
    +        if (tz != null) {
    +            return tz;
    +        }
    +        return TimeZone.getTimeZone(id);
    +    }
    +
    +    private static final Pattern GMT_PATTERN = Pattern.compile("^(?:(?i)GMT)?([+-])?(\\d\\d?)?(:?(\\d\\d?))?$");
    +
    +    /**
    +     * Get a TimeZone with GMT offsets.  A GMT offset must be either 'Z' or match
    +     * (GMT)? hh?(:?mm?)?, where h and m are digits representing hours and minutes.
    --- End diff --
    
    Maybe instead of
    
    > A GMT offset must be either 'Z' or match (GMT)? hh?(:?mm?)?
    
    It should be
    
    > A GMT offset must be 'Z', or 'UTC', or match (GMT)? hh?(:?mm?)?
    
    ?
    



> TimeZone.getTimeZone() in FastDateParser causes resource contention
> -------------------------------------------------------------------
>
>                 Key: LANG-1355
>                 URL: https://issues.apache.org/jira/browse/LANG-1355
>             Project: Commons Lang
>          Issue Type: Bug
>          Components: lang.time.*
>    Affects Versions: 3.6
>         Environment: Windows
>            Reporter: Keith Boone
>            Assignee: Charles Honton
>   Original Estimate: 48h
>  Remaining Estimate: 48h
>
> Under heavy load we are seeing contention in FastDateParser.parse() on calls to TimeZone.getTimeZone().
 TimeZone.getTimeZone() is a synchronized static in the Oracle JVM.
> Our proposed solution is to add a class TimeZoneCache containing a single method getTimeZone()
which gets the requested time zone from a ConcurrentMap, and if not present, looks it up via
TimeZone.getTimeZone() and caches it before returning it.
> Then replace calls to TimeZone.getTimeZone() in FastDateParser ( and whereever else)
to calls to TimeZoneCache.getTimeZone().  
> The reason to add a separate class is because it can also be used by other applications
which heavily parse or format or do other things where TimeZone is repeatedly needed.
> Under extreme load we have seen an 50:1 improvement in calls to FastDateParser.parse().
 This saves about a ms/call in our test environment, and reduces contention.



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