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[whatwg] WebSocket bufferedAmount includes overhead or not

From: Niklas Beischer <no@opera.com>
Date: Thu, 25 Mar 2010 15:25:55 +0100
Message-ID: <op.u94nphyddopkj4@fozzie.gothenburg.osa>
On Thu, 25 Mar 2010 13:23:57 +0100, Olli Pettay <Olli.Pettay at helsinki.fi>  
wrote:

> On 3/25/10 12:08 PM, Niklas Beischer wrote:
>> On Thu, 25 Mar 2010 10:21:10 +0100, Olli Pettay
>> <Olli.Pettay at helsinki.fi> wrote:
>>
>>> On 3/25/10 12:08 AM, Olli Pettay wrote:
>>>> On 3/24/10 11:33 PM, Ian Hickson wrote:
>>>>> On Sun, 21 Feb 2010, Olli Pettay wrote:
>> [snip]
>>>>> I guess I'm unclear on whether bufferedAmount should return:
>>>>>
>>>>> 1. the sum of the count of characters sent?
>>>>> (what would we do when we add binary?)
>>>> I believe this is actually what we want.
>>>> If web developer sends a string which is X long,
>>>> bufferedAmount should report X.
>>>>
>>>> And when we add binary, if buffer which has size Y is
>>>> sent, that Y is added to bufferedAmount.
>>>
>>> Though, this is a bit ugly too.
>>> Mixing 16bit and 8bit data...
>>>
>>> One option is to remove bufferedAmount,
>>> and have just a boolean flag
>>> hasBufferedData.
>>>
>>> Or better could be that the API spec says that WebSocket.send()
>>> converts the data to UTF-8 and bufferedAmount
>>> indicates how much UTF-8 data is buffered.
>>> Then adding support for binary would be easy.
>>> And that way it doesn't matter whether the protocol
>>> actually sends the textual data as UTF-8 or as
>>> something else.
>>>
>>> This way web developer can still check what part of the
>>> data is still buffered. (S)he just have to convert
>>> UTF-16 to UTF-8 in JS, when needed.
>>
>> What about having bufferedAmount represent the number of bytes
>> (including overhead) buffered by the WebSocket,
> The problem here is that how can the API describe what the
> bufferedAmount actually is. And since the underlying protocol
> may change, the values in bufferedAmount may change.

Easy. The bufferedAmount is: "The amount of bytes waiting to be  
transferred, including protocol overhead". It is in this form purely  
informational and only intended to let the API user know if there is any  
point in trying to send more messages before waiting for more data to be  
transferred. Simply put, for flow control purposes.


>   for flow control
>> purposes, and adding a new indicator (bufferedMessages) representing the
>> number of messages that are not fully pushed to the network? Since the
>> API is message based there is, besides flow control, little reason to
>> specify how much of a particular message has been sent, right?
>
> Hmm, would it be enough to have just bufferedMessages, and remove
> bufferedAmount.

Well, yes. But that would leave it up to the API user to remember how big  
the messages sent were if he/she wants to add flow control and avoid  
having the buffers inside the WebSocket grow beyond reason.

BR,
  /niklas


>>>> The reason why I'd like it to work this way is that
>>>> IMO scripts should be able to check whether the data
>>>> they have posted is actually sent over the network.
>>>>
>>>>
>>>> -Olli
>>>>
>>>>
>>>>>
>>>>> 2. the sum of bytes after conversion to UTF-8?
>>>>>
>>>>> 3. the sum of bytes yet to be sent on the wire?
>>>>>
>>>>> I'm not sure how to pick a solution here. It sounds like WebKit  
>>>>> people
>>>>> want 3, and Opera and Mozilla are asking for 2. Is that right? I  
>>>>> guess
>>>>> I'll go with 2 unless more people have opinions.



-- 
Niklas Beischer
Software Developer
Opera Software
Received on Thursday, 25 March 2010 07:25:55 UTC

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