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Subject: Re: EventSource periodically dumps db contents.
From: Stephen Bartell <snbartell@gmail.com>
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Date: Wed, 17 Apr 2013 22:28:02 -0700
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To: dev@couchdb.apache.org

Thanks for the summary Robert. That clears it all up :)

Ok so now I'm going to risk looking like a tool.  Besides the underlying =
mechanism, what is the difference between eventsource and continuous?  =
In other words, what does ES bring to the table that continuous does =
not?  I was originally excited about event source because for some =
reason i had it in my head that  multiple event source subscriptions =
would use the same connection, thus circumventing the open connection =
limits on browsers.

Best
Stephen

On Apr 17, 2013, at 4:31 AM, Robert Newson <rnewson@apache.org> wrote:

> Setting timeout and heartbeat to the same value is going to lead to
> exactly what you're seeing.
>=20
> The timeout setting is how long, without an event, the connection will
> stay open.
>=20
> The heartbeat setting is how long to wait, without an event, before
> sending a newline character to keep the connection from timing out.
>=20
> What you're seeing is that the timeout happens before the heartbeat,
> since both are happening approximately simultaneously.
>=20
> Just set heartbeat=3D5000 and rely on the timeout default of 1 minute,
> or specify timeout to whatever multiple of heartbeat you find useful
> (as long as it's more than one).
>=20
> Summary: timeout =3D=3D heartbeat is not going to keep the connection =
alive.
>=20
> B.
>=20
>=20
>=20
>=20
>=20
> On 17 April 2013 10:29, Stephen Bartell <snbartell@gmail.com> wrote:
>> Ok heres a test script.  Have a couch serving localhost:5984 in admin =
party mode.
>>=20
>> git clone https://github.com/snbartell/couch-es-test.git
>> cd couch-es-test
>> npm install
>> node index.js
>>=20
>> My theory of a second source crashing couch was wrong.
>>=20
>> I think I know whats going on.  My script above acts just like the =
browser does.  When the `timeou`t is reached and `heartbeat` !=3D=3D =
`timeout`, the EventSource module (whether its the browser or the node =
package) will restart the feed.  This is why every `timeout` ms the feed =
__appears__ to by dumping all the docs since `since`.
>>=20
>> curling works fine. Try this after running the above script and =
leaving the test db in place.  I expect this behavior.
>>     curl =
"http://localhost:5984/source1/_changes?since=3D2&feed=3Dcontinuous&timeou=
t=3D5000&heartbeat=3D5000"
>>=20
>> So then it comes to using this in Chrome console.  If you go to the =
couch you ran the script against,  open the console, and paste the =
following:
>> var source1 =3D new =
EventSource('/source1/_changes?feed=3Deventsource&timeout=3D5000&heartbeat=
=3D5000')
>>=20
>> Watch the Network panel.  It looks like EventSource does not pass the =
query params.  I'm probably being an idiot and not calling it correctly. =
 I googled around and couldn't find the api.  Does someone have a link?
>>=20
>> Still though, if I call EventSource without `timeout` and =
`heartbeat`, then couchdb will use the defaults of 60000 each.  Then, =
with `timeout` =3D=3D=3D `heartbeat`, the connection should be kept =
alive, right?
>>=20
>> Thanks guys,
>>=20
>> Stephen
>>=20
>>=20
>> On Apr 16, 2013, at 11:17 PM, Stephen Bartell <snbartell@gmail.com> =
wrote:
>>=20
>>>=20
>>> On Apr 16, 2013, at 11:13 PM, Benoit Chesneau <bchesneau@gmail.com> =
wrote:
>>>=20
>>>> On Wed, Apr 17, 2013 at 7:55 AM, Stephen Bartell =
<snbartell@gmail.com> wrote:
>>>>>=20
>>>>> But for what I was doing, no, I wasn't specifying since.  I would =
expect the fundamentals to be the same as well.  What I was see is that =
even without `since` given, no changes would come through until that =
second source was added.  Once the second source is added, then all =
sources periodically dump.
>>>>>=20
>>>>=20
>>>> Hi Stephen,
>>>>=20
>>>> Can you provide a clear way to reproduce what you're doing and the
>>>> result you're expecting. It's not clear for me right now if you :
>>>=20
>>> Yep, Im actually working on it now :)
>>>=20
>>>>=20
>>>> 1. the reauest results when giving the since parameter without any
>>>> changes  , did you try using curl?
>>> no.  I only did it from the browser console.
>>>=20
>>>> 2. If it's a javascript error
>>> nope. its a couch thing.
>>>=20
>>>> 3. ?
>>>>=20
>>>> - benoit
>>>=20
>>=20