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Posted to user@couchdb.apache.org by Jens Alfke <je...@mooseyard.com> on 2011/06/06 07:27:54 UTC
Issue: _changes feed's Content-Encoding is wrong
I’ve been trying to figure out why my Cocoa code can’t read the db/_changes feed. It acts as though it never makes a connection to the server. I’ve finally concluded that it’s because CouchDB’s HTTP response is, to put it bluntly, lying:
> $ curl -i 'http://127.0.0.1:5984/testdb/_changes?feed=continuous'
> HTTP/1.1 200 OK
> Transfer-Encoding: chunked
> Server: CouchDB/1.1.1 (Erlang OTP/R14B)
> Date: Mon, 06 Jun 2011 05:12:42 GMT
> Content-Type: text/plain;charset=utf-8
> Cache-Control: must-revalidate
>
> {"seq":1,"id":"cf8a2e561cccbc5570ec8f391d041cce","changes":[{"rev":"1-4fad6ccf08b52a49a65734784296dcdd"}]}
> {"seq":2,"id":"cf8a2e561cccbc5570ec8f391d0428c6","changes":[{"rev":"1-a1eee1babb5545b9b45d4aaf1b55eb75"}]}
> …
Note the header “Transfer-Encoding: chunked”. The problem is, the body of the response is *not* in chunked format as defined by the HTTP spec [1]. Chunked format consists of a sequence of ‘chunks’, each of which is prefixed by an ASCII chunk size. The actual body doesn’t have those, it’s just a normal unencoded response.
What I’m assuming is that Cocoa’s NSURLConnection code sees the header and expects to read a chunk header, then gets confused when it doesn’t find one. (What I see is that it never calls me back with any response data). Other CouchDB requests are working fine for me, but they don’t include the Transfer-Encoding header.
Has anyone else run into trouble with this? Is there a way to disable that header short of modifying the CouchDB source code?
[1] http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.6.1
Re: Issue: _changes feed's Content-Encoding is wrong
Posted by Jens Alfke <je...@mooseyard.com>.
On Jun 5, 2011, at 10:54 PM, Pasi Eronen wrote:
> Curl normally hides the chunked transfer encoding from the user. If
> you add the "--raw" option (requires Curl >=7.16.2), the chunk
> prefixes will be visible, too.
Ah, you’re right (and it makes sense, in hindsight, that curl does that.) Hm, I’ll have to search for another explanation of why my code isn’t working. But it was so easy to blame someone else :(
—Jens
$ curl -i --raw 'http://127.0.0.1:5984/demo-addresses/_changes?feed=normal'
HTTP/1.1 200 OK
Transfer-Encoding: chunked
Server: CouchDB/1.1.1 (Erlang OTP/R14B)
Etag: "1H2QIKQ2E49Q68SEOZB1CBFFF"
Date: Mon, 06 Jun 2011 16:27:34 GMT
Content-Type: text/plain;charset=utf-8
Cache-Control: must-revalidate
d
{"results":[
6a
{"seq":2,"id":"3aaa5e74e5d96db3b2248fb1c404f888","changes":[{"rev":"1-422bdffd6eef915859d46a18bf373d74"}]}
6c
,
{"seq":8,"id":"3aaa5e74e5d96db3b2248fb1c404eb65","changes":[{"rev":"7-7e833e1c2ee3db8e4ae3f615c20ca592"}]}
12
],
"last_seq":8}
1
0
Re: Issue: _changes feed's Content-Encoding is wrong
Posted by Pasi Eronen <er...@gmail.com>.
Curl normally hides the chunked transfer encoding from the user. If
you add the "--raw" option (requires Curl >=7.16.2), the chunk
prefixes will be visible, too.
Best regards,
Pasi
On Mon, Jun 6, 2011 at 08:27, Jens Alfke <je...@mooseyard.com> wrote:
> I’ve been trying to figure out why my Cocoa code can’t read the db/_changes feed. It acts as though it never makes a connection to the server. I’ve finally concluded that it’s because CouchDB’s HTTP response is, to put it bluntly, lying:
>
>> $ curl -i 'http://127.0.0.1:5984/testdb/_changes?feed=continuous'
>> HTTP/1.1 200 OK
>> Transfer-Encoding: chunked
>> Server: CouchDB/1.1.1 (Erlang OTP/R14B)
>> Date: Mon, 06 Jun 2011 05:12:42 GMT
>> Content-Type: text/plain;charset=utf-8
>> Cache-Control: must-revalidate
>>
>> {"seq":1,"id":"cf8a2e561cccbc5570ec8f391d041cce","changes":[{"rev":"1-4fad6ccf08b52a49a65734784296dcdd"}]}
>> {"seq":2,"id":"cf8a2e561cccbc5570ec8f391d0428c6","changes":[{"rev":"1-a1eee1babb5545b9b45d4aaf1b55eb75"}]}
>> …
>
>
> Note the header “Transfer-Encoding: chunked”. The problem is, the body of the response is *not* in chunked format as defined by the HTTP spec [1]. Chunked format consists of a sequence of ‘chunks’, each of which is prefixed by an ASCII chunk size. The actual body doesn’t have those, it’s just a normal unencoded response.
>
> What I’m assuming is that Cocoa’s NSURLConnection code sees the header and expects to read a chunk header, then gets confused when it doesn’t find one. (What I see is that it never calls me back with any response data). Other CouchDB requests are working fine for me, but they don’t include the Transfer-Encoding header.
>
> Has anyone else run into trouble with this? Is there a way to disable that header short of modifying the CouchDB source code?
>
> [1] http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.6.1