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From Richard Hirsch <hirsch.d...@gmail.com>
Subject Re: Streaming design for the api2 endpoint - request for comment
Date Tue, 15 Dec 2009 13:39:12 GMT
Then I misinterpreted the original mail. If every person had a stream
for every tag, wouldn't that mean explosion of streams?

On Tue, Dec 15, 2009 at 2:34 PM, Ethan Jewett <esjewett@gmail.com> wrote:
> Actually, having separate streams for each tag is what I'm suggesting,
> I'm just trying to determine when best to create them. If a client
> requests all the streams, they will all be created. Should we talk
> about not streaming individual tags at all? Maybe put a limit on the
> number of streams a client can have open? I'm not sure what the
> performance impact will look like.
>
> Also, I need to amend the original email. I think that because we are
> using Lift Sessions, we will be killing off the session and the
> streams attached to it after a period of time. So I think option 2 and
> option 4 are the same or very similar.
>
> Ethan
>
> On Mon, Dec 14, 2009 at 11:39 PM, Richard Hirsch <hirsch.dick@gmail.com> wrote:
>> Yes it sounds reasonable. I don't think it makes much sense to have
>> separate streams for each tag, etc...
>>
>> I agree option 2 is the best choice.
>>
>> D.
>>
>> On Mon, Dec 14, 2009 at 12:29 AM, Ethan Jewett <esjewett@gmail.com> wrote:
>>> All,
>>>
>>> In the cwiki, we've documented 5 parts of the API we would like to
>>> stream. They are briefly: user timeline, tags, tracks, conversations,
>>> and pools (and possibly the public timeline)
>>>
>>> Of these, one has been implemented: user timeline
>>>
>>> Today I've been able to take some time to start digging into what
>>> needs to be done to implement the rest of the streaming interfaces.
>>> The way the user timeline streaming interface is implemented in the
>>> old and new APIs is the same (because I just copied and slightly
>>> modified the code). The basic idea is that when a session is created,
>>> the streaming API starts "listening" for new messages. When the user
>>> makes a request to the streaming interface for new messages, all the
>>> messages that have built up are delivered.
>>>
>>> This approach poses some significant problems for other types of
>>> streams. For example, if we were going to stream tags in this manner,
>>> we would end up creating a listener for every single active tag in the
>>> system at the time the user initiates a session. We would also have
>>> the dilemma of creating listeners for new tags as the tags are created
>>> in the middle of a session.
>>>
>>> As such, I'm thinking of implementing the other streaming interfaces
>>> differently. Instead of creating listeners when the session is
>>> initiated, I'll create them when the first streaming request for a
>>> tag, pool, track, or conversation comes in. These listeners would then
>>> live on for the rest of the session. This is, I think the best of
>>> several options.
>>>
>>> To summarize the options available:
>>>
>>> 1. Create listeners for everything at the beginning of the session -
>>> not efficient, suffers from difficulties with new tags, pools, etc.
>>> created during the session
>>>
>>> 2. Create listeners for streams as the user requests them and have
>>> these listeners live on for the rest of the session
>>>
>>> 3. Create disposable listeners for each streaming/long-polling request
>>> that are destroyed once the request is answered - this is problematic
>>> because messages that occur between requests will be missed
>>>
>>> 4. Variation of option 2 and 3: Create listeners for streams as the
>>> user requests them and have these listeners life on for the rest of
>>> the session or a specific period of time, whichever comes first (so
>>> the user would have to make occasional requests to ensure the
>>> continuity of the message stream) - I think this is over-complicated
>>> and potentially confusing to developers, but could be a good option if
>>> we run into performance problems with option 2
>>>
>>>
>>> What we'll be left with is that the user timeline will use option 1
>>> and the other streams will use option 2. The user timeline might
>>> switch to option 2 at some point in the future.
>>>
>>> And that was all a very long way of saying, does that sound reasonable
>>> to everyone?
>>>
>>> Ethan
>>>
>>
>

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