[threeten-dev] [threeten-develop] Move tzdb compiler out of j.t.z

[Xueming Shen]

webrev has been updated to work with the java/time world.

http://cr.openjdk.java.net/~sherman/jdk8_threeten/tzcompiler/

-Sherman

On 01/04/2013 12:39 PM, Xueming Shen wrote:
> Stephen,
>
> Here is the webrev of planB, with a copycat sun.tools.tzdb.ZoneRules (need
> to access to the internal state of zonerules which is not currently exposed by
> public apis. may need a better alternative for the name)
>
> http://cr.openjdk.java.net/~sherman/jdk8_threeten/tzcompiler
>
> -Sherman
>
> On 12/27/2012 07:27 AM, Xueming Shen wrote:
>> Due to the lack of access to ZoneRules' serialization form directly. The "form" is actually
>> inside ZoneRules now. Outsourcing (the plan B) is an alternative. I guess the performance
>> will be indeed a concern, if you actually have all the historical zone date inside one tzdb.jar.
>> But I still don't understand why you want to do that:-) Given the nature of how the
>> tzdb database is organized, all the historical data are all included in the latest version.
>> I can guess, it may be useful, if you want to recover from an invalid zdt (created early with
>> an earlier version of "latest" rules" at certain point, but do you really need such an
>> "infrastructure" to support such kind of "rare" case. And given the current spec and impl
>> of zdt,  most developer should be happy to be able to recover simply from the ldt and
>> offset info (based on what they really mean of "zdt" in their use case).
>>
>> We will go with plan B.
>>
>> -Sherman
>>
>> On 12/27/2012 9:58 AM, Stephen Colebourne wrote:
>>> On 23 December 2012 08:18, Xueming Shen<xueming.shen at oracle.com>  wrote:
>>>> Here is the webrev for moving the tzdb compiler out of j.t.z package.
>>>>
>>>> http://cr.openjdk.java.net/~sherman/jdk8_threeten/tzc/
>>>>
>>>> The approach here appears to cause a slower startup compared to the
>>>> existing one, as it uses ObjectOutput/InputStream directly to write out and
>>>> read in zrules, instead of the DateOutput/InputStream, in which the existing
>>>> impl can take advantage of the direct access to Ser to write out/read in
>>>> "byte[]" of the zrules, so the TzdbZoneRuleProvider can do lazy-init. The
>>>> compiler can't do it now because the Ser is package private.
>>> Is the slow down due to ObjectInputStream, or the lack of access to Ser?
>>>
>>> My preference would be to duplicate the logic from Ser into the
>>> builder (or possibly move it to a sun package helper class). More like
>>> plan B.
>>>
>>> Performance reading large tzdb files has been a problem in the past,
>>> which is why the format is structured as it is, and the loader
>>> carefully caches byte arrays. (Used to take over 30 seconds to start).
>>>
>>> It is important to test and ensure that a tzdb file with a large
>>> number of versions of the database also loads quickly (I'm aware that
>>> Oracle may not like this scenario, but the API supports historic
>>> versions and the tool should provide a mechanism to create a file that
>>> has those historic versions).
>>>
>>> Stephen
>>>
>>>
>>>> The plan-B is to externalize the Ser.write/read to somewhere, so the byte[]
>>>> of the zrules' serialization form can be shared by the tzdb compiler (output
>>>> side) and the tzdb provider (input side). Given we are talking about 600+
>>>> zone (the rules number is bigger) and a total<  40k data here, I took the
>>>> simple, but slow, approach. We can revisit the start-up issue later, if it
>>>> indeed
>>>> is a concern. Let me know if you have concern of this approach, we can go
>>>> Plan-B.
>>>>
>>>> I brought back the test for the ZoneRulesBuilder, as promised. But it
>>>> appears
>>>> there is a test failure at line#805. I have not looked into the detail yet.
>>>> Just
>>>> wonder if you have any idea.
>>>>
>>>> The changes in ZoneRulesBuilder are to workaround the
>>>> beforeOffset==afterOffset issue. The old implementation creates the trans
>>>> even two offsets are the same (use that package private constructor which
>>>> does not do sanity check), but then throw it away. The code now does the
>>>> sanity check before creating the trans.
>>>>
>>>> -Sherman
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>