N/A N/A
I took a look at this yesterday.
My assumption is that you are using a web page to display the _changes
feed delivered from couchdb (probably couchapps).
if this is the case then i do not think that you should be using the
continuous feed since my belief is that, by design this should be used
for decoupled systems (I also think that some browsers will struggle
with it) eg node.js / ruby /python.
What you should be using is the longpoll feed.
I began to write an example but found the perfect thing in jquery.couch.js
the function is changes (an example is worth a thousand words)
note I modded jquery.couch.js at around line 270 from
feed : "longpoll",
since : since,
to
feed : "longpoll",
since : since,
include_docs : true
not sure if this is the correct way to do things but did not look too deep.
<code>
<!DOCTYPE html>
<html>
<head>
<title>Couchdb continous feed test</title>
<script src="/_utils/script/jquery.js"></script>
<script src="/_utils/script/jquery.couch.js"></script>
</head>
<script>
var changes = $.couch.db("test").changes();
// Set up multiple callbacks (Nice!!)
changes.onChange(dbchanges);
changes.onChange(dbalert);
changes.onChange(dbrealtime);
// callback code examples for changes feed
// (1) console log
function dbchanges(response) {
console.log( " Database changes: ", response );
}
// (2) show a field (response is a json object)
function dbalert(response) {
alert(response.results[0].doc.address);
}
// (3) something more interesting display a real time list of changes
function dbrealtime(response) {
var now = new Date();
var month = now.getMonth() + 1;
var day = now.getDate();
var year = now.getFullYear();
var date = day + "/" + month + "/" + year;
var time = now.getHours() + ":" + now.getMinutes()
$("#tab1 > tbody:first").append("<tr><td>" + date +"</td><td>" +
time + "</td><td>" + response.results[0].doc.Surname +"</td><td>" +
response.results[0].doc.address +"</td></tr>");
}
</script>
<body>
<h1>Look at jquery.couch.js for changes feed</h1>
<table id=tab1 border="1">
<tr><th>Date</th><th>Time</th><th>Name</th><th>Address</th></tr>
<tbody></tbody>
</table>
</body>
</html>
</code>
best regards
Cliff
On 25/12/10 09:37, Johannes J. Schmidt wrote:
Hi,
You could check the length of req.responseText and call abort() if it
exceeds a limit. Or you can check for the number of revs the feed is
reporting and implement a limit of revs per connection.
Btw. Depending on your application you should query the database info
object (/dbname) to get the latest seq (update_seq).
Greetings
Johannes
Am Freitag, den 24.12.2010, 08:14 -0800 schrieb N/A N/A:
Hi,
Thank you! Hope you are well too...
Yes. First i'm doing changes poll without feed, so i can retrieve last_seq
key/value. Next i'm doing Ajax request like your with feed, heartbeat and even
include_docs.
This is working just fine. The code bellow is what i mean. There is function in
couch.js "CouchDB.request". I patched it a bit for my needs for continuous
_changes read.
I can post all of the function code later. But what i mean is this:
var req = CouchDB.newXhr();
if(uri.substr(0, "http://".length) != "http://";) {
uri = CouchDB.urlPrefix + uri
}
req.open(method, uri, true);
req.onreadystatechange = function () {
console.log(req.responseText);
}
responseText is read only. While the socket is open every
time onreadystatechange trigger, it only appends the result. So responseText is
growing really big and after N seconds/hours/days maybe ill be out of memory.
What to do, so i can avoid this? If something is not clear enough i'll post some
code later with some more explanations and logs.
Thanks
________________________________
From: Cliff Williams<[email protected]>
To: [email protected]
Sent: Fri, December 24, 2010 5:27:18 PM
Subject: Re: CouchDB _changes + continuous + Ajax
N/A N/A
I hope you are well and looking forward to Christmas
I am not sure that I fully understand but are you querying using last
sequence ?
I use
changesurl = "http://"+ host +":"+port.tostring+"/"+database+
"/_changes?feed=continuous&include_docs=true&heartbeat=10000
+"&since="+lastseq",
I can let you have a copy of a skeleton node.js program that I use if
you think that it would help.
best regards
cliff
On 24/12/10 14:04, N/A N/A wrote:
Hi there,
I am trying to use continuous changes of CouchDB + some java script. Using
couch.js, because it is nice and clean template for experiments i manage to
establish a connection to CouchDB and my webapp. Everything is working fine
except one thing. Because the socket is still open, my responseText in ajax is
just appending the JSON answers, so it is getting bigger and bigger and
bigger.
With heartbeat of 100, memory usage is growing pretty fast. JSON data transfer
could be really high sometimes and dataloss is not an option for me. One
solution for me was just to use websocket + node.js(or similar). Or maybe to
split() the answer in array and when it reach certain length to reopen the
socket with current sequence of _changes. But this solution is not for my
taste
and looks for me like a hack and not like solution. So, if someone is familiar
with continuous changes, is it possible to give me some advice how we can use
continuous changes + ajax without responseText getting so big? Any workaround
?
I prefer to not use websocket stuff(or something), because i prefer to keep
things clean and stick only with CouchDB.
Thanks in advance
