Java doesn't have unsigned types, so a (signed) long is the only way to
transfer the value.

IIRC from peeking at that code, the top bit is unused, which would mean
there's no danger of creating an id value that's ambiguous. Storing and
comparing ids in signed or unsigned 64-bit longs should be fine.

-- brion vibber (brion @ status.net)
On Oct 19, 2010 5:52 AM, "jon" <jonhoff...@gmail.com> wrote:
> Hi,
>
> You wrote that the IDs are "unsigned" 64 bit ints, but the IdWorker is
> pumping out java Longs which are signed. I'm assuming that was a
> typo, but please clarify.
>
>
http://github.com/twitter/snowflake/blob/master/src/main/scala/com/twitter/service/snowflake/IdWorker.scala
>
> Thanks,
>
> - Jon
>
> On Oct 18, 8:19 pm, Matt Harris <thematthar...@twitter.com> wrote:
>> Last week you may remember Twitter planned to enable the new Status ID
>> generator - 'Snowflake' but didn't. The purpose of this email is to
explain
>> the reason why this didn't happen, what we are doing about it, and what
the
>> new release plan is.
>>
>> So what is Snowflake?
>> ------------------------------
>> Snowflake is a service we will be using to generate unique Tweet IDs.
These
>> Tweet IDs are unique 64bit unsigned integers, which, instead of being
>> sequential like the current IDs, are based on time. The full ID is
composed
>> of a timestamp, a worker number, and a sequence number.
>>
>> The problem
>> -----------------
>> Before launch it came to our attention that some programming languages
such
>> as Javascript cannot support numbers with >53bits. This can be easily
>> examined by running a command similar to: (90071992547409921).toString()
in
>> your browsers console or by running the following JSON snippet through
your
>> JSON parser.
>>
>>     {"id": 10765432100123456789, "id_str": "10765432100123456789"}
>>
>> In affected JSON parsers the ID will not be converted successfully and
will
>> lose accuracy. In some parsers there may even be an exception.
>>
>> The solution
>> ----------------
>> To allow javascript and JSON parsers to read the IDs we need to include a
>> string version of any ID when responding in the JSON format. What this
means
>> is Status, User, Direct Message and Saved Search IDs in the Twitter API
will
>> now be returned as an integer and a string in JSON responses. This will
>> apply to the main Twitter API, the Streaming API and the Search API.
>>
>> For example, a status object will now contain an id and an id_str. The
>> following JSON representation of a status object shows the two versions
of
>> the ID fields for each data point.
>>
>> [
>>   {
>>     "coordinates": null,
>>     "truncated": false,
>>     "created_at": "Thu Oct 14 22:20:15 +0000 2010",
>>     "favorited": false,
>>     "entities": {
>>       "urls": [
>>       ],
>>       "hashtags": [
>>       ],
>>       "user_mentions": [
>>         {
>>           "name": "Matt Harris",
>>           "id": 777925,
>>           "id_str": "777925",
>>           "indices": [
>>             0,
>>             14
>>           ],
>>           "screen_name": "themattharris"
>>         }
>>       ]
>>     },
>>     "text": "@themattharris hey how are things?",
>>     "annotations": null,
>>     "contributors": [
>>       {
>>         "id": 819797,
>>         "id_str": "819797",
>>         "screen_name": "episod"
>>       }
>>     ],
>>     "id": 12738165059,
>>     "id_str": "12738165059",
>>     "retweet_count": 0,
>>     "geo": null,
>>     "retweeted": false,
>>     "in_reply_to_user_id": 777925,
>>     "in_reply_to_user_id_str": "777925",
>>     "in_reply_to_screen_name": "themattharris",
>>     "user": {
>>       "id": 6253282
>>       "id_str": "6253282"
>>     },
>>     "source": "web",
>>     "place": null,
>>     "in_reply_to_status_id": 12738040524
>>     "in_reply_to_status_id_str": "12738040524"
>>   }
>> ]
>>
>> What should you do - RIGHT NOW
>> ----------------------------------------------
>> The first thing you should do is attempt to decode the JSON snippet above
>> using your production code parser. Observe the output to confirm the ID
has
>> not lost accuracy.
>>
>> What you do next depends on what happens:
>>
>> * If your code converts the ID successfully without losing accuracy you
are
>> OK but should consider converting to the _str versions of IDs as soon as
>> possible.
>> * If your code has lost accuracy, convert your code to using the _str
>> version immediately. If you do not do this your code will be unable to
>> interact with the Twitter API reliably.
>> * In some language parsers, the JSON may throw an exception when reading
the
>> ID value. If this happens in your parser you will need to ‘pre-parse’ the
>> data, removing or replacing ID parameters with their _str versions.
>>
>> Summary
>> -------------
>> 1) If you develop in Javascript, know that you will have to update your
code
>> to read the string version instead of the integer version.
>>
>> 2) If you use a JSON decoder, validate that the example JSON, above,
decodes
>> without throwing exceptions. If exceptions are thrown, you will need to
>> pre-parse the data. Please let us know the name, version, and language of
>> the parser which throws the exception so we can investigate.
>>
>> Timeline
>> -----------
>> by 22nd October 2010 (Friday): String versions of ID numbers will start
>> appearing in the API responses
>> 4th November 2010 (Thursday) : Snowflake will be turned on but at ~41bit
>> length
>> 26th November 2010 (Friday) : Status IDs will break 53bits in length and
>> cease being usable as Integers in Javascript based languages
>>
>> We understand this isn’t as seamless a transition as we had planned and
>> appreciate for some of you this change requires an update to your code.
>> We’ve tried to give as much time as possible for you to make the
migration
>> and update your code to use the new string representations.
>>
>> Our own products and tools are affected by the change and we will be
making
>> available any pre-parsing snippets we have created to ensure code
continues
>> to work with the new IDs.
>>
>> Thanks for your support and understanding.
>>
>> ---
>> @themattharris
>> Developer Advocate, Twitterhttp://twitter.com/themattharris
>
> --
> Twitter developer documentation and resources: http://dev.twitter.com/doc
> API updates via Twitter: http://twitter.com/twitterapi
> Issues/Enhancements Tracker:
http://code.google.com/p/twitter-api/issues/list
> Change your membership to this group:
http://groups.google.com/group/twitter-development-talk

-- 
Twitter developer documentation and resources: http://dev.twitter.com/doc
API updates via Twitter: http://twitter.com/twitterapi
Issues/Enhancements Tracker: http://code.google.com/p/twitter-api/issues/list
Change your membership to this group: 
http://groups.google.com/group/twitter-development-talk

Reply via email to