Fwd: [squid-users] negotiate_kerberos_auth helpers stay busy

On Wed, Jul 31, 2013 at 6:59 AM, Amos Jeffries <squid3_at_treenet.co.nz> wrote:
> On 31/07/2013 9:18 a.m., Klaus Walter wrote:
>> strace shows me that this helpers are blocked during a read-command:
>> ....
>> read(0, "r", 1) = 1
>> read(0, "r", 1) = 1
>> read(0, "7", 1) = 1
>> read(0, "+", 1) = 1
>> read(0, "a", 1) = 1
>> read(0, "G", 1) = 1
>> read(0, <unfinished ...>
>>
>> After this the process is never continued.
>
>
> That does not look blocked to me. The value arriving is changing, just
> vvvveeerrrryyyy ssslloowwwlllyyy, one byte per I/O cycle to be exact. Since
> kerberos credentials can be up to 32 KB large its easy to see why they are
> stuck in BUSY state for such long times.

I see the helper is reading one byte at a time.
The code for the kerberos explicitly disables buffering:

setbuf(stdout, NULL);
setbuf(stdin, NULL);

As a test, I removed setbuf(stdin, NULL), and it works well: the
helper no longer reads one byte at a time, but the whole thing at
once.

I tried to take it further and enable buffering for stdout as well,
but it doesn't work: the helpers don't write anything until the buffer
is full, so it just hangs. I think glibc only flushes stdout on
newline when stdout is a terminal. So I added explicit calls to
fflush() after each fprintf(stdout, ...), and now it works like a
charm.

I haven't measured the performance improvement with this, and I'm sure
it doesn't solve Klaus' issue, but I am very interested in improving
performance in every possible way, even if its a small improvement.

If anybody is interested, please see the attached patch against Squid 3.3.8.

Best regards,

Alan

----
I'm resending this message because it was rejected due to the attachment.
If you are interested in the patch, please run:
echo 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
| perl -MCompress::Zlib -MMIME::Base64 -e 'print
Compress::Zlib::memGunzip(decode_base64(<>))' >
/tmp/negotiate_kerberos_auth-buffering.patch