Thanks Lukasz, this is very helpful. I'll continue investigation with Andy and
then we'll see.
Matevz
On 10/03/14 06:39, Lukasz Janyst wrote:
> The "tried=" CGI was supposed to be a tool for the client to tell the server
> that it has tried a given host and failed and thus should not be sent to this
> host again. The client handles this CGI by calling
> XRootDMsgHandler::UpdateTriedCGI() which then results with a call to
> MessageUtils::MergeCGI() with "replace" parameter set to false:
>
> https://github.com/xrootd/xrootd/blob/master/src/XrdCl/XrdClMessageUtils.cc#L236
>
> This causes accumulation of all the values of a given CGI parameter, ie. it
> creates a comma-separated list of values.
>
> The CGI returned by the redirector is handled differently. Any new value
> returned by the server should supersede any previous value a given parameter
> had. The client handles this by calling
> XRootDMsgHandler::RewriteRequestRedirect(), which then calls
> MessageUtils::MergeCGI() with "replace" parameter set to true.
>
> The CGI is an integral part of the message being sent and never gets
> dropped. So everything in the client works exactly as intended.
>
> Why would the server want to tell the client that it (the client) has tried
> a certain other server and failed? This does not make a slightest sense!
>
> Cheers,
> Lukasz
>
>
> On 10/02/2014 06:24 PM, Matevz Tadel wrote:
>> The instances seem to be:
>>
>> ...00C0F.root?tried=+1213cmsxrootd1.fnal.gov1213xrootd.unl.edu
>>
>> and
>>
>> ...00C0F.root?hdfs_block_size=134217728&tried=xrootd.t2.ucsd.edu
>>
>> but maybe let's wait what Lukasz finds out from the client logs.
>>
>> The first one does seem rather strange to me though, it comes from the
>> DNS aliases on regional meta-managers in the US :)
>>
>> Matevz
>>
>> On 10/02/14 00:44, Andrew Hanushevsky wrote:
>>> Well, the onlyh time a redirector would ignore a tried is if the tried
>>> were
>>> malformed. It's pretty precise on how things get excluded. So, I would
>>> like to
>>> see an instance where the tried was ignored.
>>>
>>> Andy
>>>
>>> On Wed, 1 Oct 2014, Lukasz Janyst wrote:
>>>
>>>> On 10/01/2014 12:07 AM, Andrew Hanushevsky wrote:
>>>>> The issue here is that the redirector is under no obligation to re-pass
>>>>> opaque information. The only thing it can do is to add additional
>>>>> opaque
>>>>> information. It's the client's responsibility to maintain the "tried"
>>>>> history. I don't think the old client does this and drops the
>>>>> history at
>>>>> some point (so, yes, it's a bug). The new client did much the same but
>>>>> that is being corrected in 4.1.
>>>>
>>>> The new client does not drop any CGI, we observed sometimes the
>>>> redirector
>>>> would ignore the tried= cgi though. The old client is deprecated, so
>>>> if it
>>>> does not work, stop using it :)
>>>>
>>>> Lukasz
>>>>
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>
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