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From "Rodrigo Ruiz (JIRA)" <>
Subject [jira] Updated: (AXIS-2597) CLONE -SimpleUUIDGen.nextUUID() is very, very, very slow
Date Tue, 24 Apr 2007 11:18:15 GMT


Rodrigo Ruiz updated AXIS-2597:

    Attachment: SimpleUUIDGen.diff

Elwin, it seems you are wrong. From the code snippet you show in the description, the variable
is already declared static, and initialized in a static block. This means it is only created
once per class-loader.

I think the UUID standard comprises several algorithms for building the identifiers. This
would explain why there are more than one generator.

Most of the generation time in SimpleUUIDGen is spent on random value generation. This is
because it uses a SecureRandom instance, which is rather slow.

I believe this class must not be changed too much, as the algorithm must be kept standard

If you do not require secure random generation, you may better use the default one (FastUUIDGen,
in the same package).

I have tried to improve the execution time by moving some of the code to the static block,
and optimizing some of the private methods. The times changed from 16000ms to 12000ms for
100 ids. This means an improvement of around 25%. I attach the patch for these changes.

> CLONE -SimpleUUIDGen.nextUUID() is very, very, very slow
> --------------------------------------------------------
>                 Key: AXIS-2597
>                 URL:
>             Project: Axis
>          Issue Type: Bug
>    Affects Versions: 1.1
>         Environment: Any
>            Reporter: Elwin Ho
>         Attachments: SimpleUUIDGen.diff
> It takes .4917 seconds to generate just one UUID.  (Yes, seconds.)  This renders the
feature very nearly useless.
> In SimpleUUIDGen, there is a simple, but very expensive, bug..  It creates a new instance
of SecureRandom on each call to nextUUID().  Making a new instance of SecureRandom is very
expensive because it has to set up the environment for producing cryptographically strong
random numbers.
> The instance of SecureRandom should be in a static variable and init'ed just once.  Then,
you call getNextLong() when you want another number from it.  It would be much faster that
way without compromising the integrity of the UUIDs generated.
> BTW, If you look at the comment I copied from the code, it appears that this is what
the developer meant to make the SecureRandom instance static, but forgot.
>     /**
>      * Creates a new UUID. The algorithm used is described by The Open Group.
>      * See <a href="">
>      * Universal Unique Identifier</a> for more details.
>      * <p>
>      * Due to a lack of functionality in Java, a part of the UUID is a secure
>      * random. This results in a long processing time when this method is called
>      * for the first time.
>      */
> Here's a proposed fix.  In the member variables, add the following.
>     private static Random secureRandom = null;
>     static {
>         try {
>             secureRandom = SecureRandom.getInstance("SHA1PRNG", "SUN");
>         } catch (Exception e) {
>             secureRandom = new Random();
>         }
>     }
> The, remove the code near line 235 where the SecureRandom is being created.  
> This change should do it just once.

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