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XROOTD-L  May 2021

XROOTD-L May 2021

Subject:

Re: http ingest using xcache fails

From:

"Yang, Wei" <[log in to unmask]>

Reply-To:

Support use of xrootd by HEP experiments <[log in to unmask]>

Date:

Tue, 11 May 2021 08:43:34 +0000

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (1 lines)

From my pass experience:

Xcache fetch data blocks by blocks. This translate to HTTP range request in XrdCl::Http. We have seen examples where web servers don't like HTTP range header and ignoring it. For this reason, we built something in XcacheH to handle this situation. But web servers can behave in other weird ways. I think we have run in to a similar issue (maybe not so similar - we don't know) and I don't know we ever understand whther the problem is solved or not.

regards,
--
Wei Yang  |  [log in to unmask]  |  650-926-3338(O)

-----Original Message-----
From: Bertrand RIGAUD <[log in to unmask]>
Date: Monday, May 10, 2021 at 3:07 AM
To: Wei Yang <[log in to unmask]>
Cc: xrootd-l <[log in to unmask]>
Subject: Re: http ingest using xcache fails

    Hello,
    
    well I don't think XcacheH is related to this issue. It's the same behaviour whether or not XcacheH is activated
    
    in xcache data folder, I have the file but the size is just under the entire size (the last chunk is missing)
    it depends on the pfc.blocksize I choose.
    
    let's say I have a file of 10MB and a pfc.blocksize set to 4MB, my downloaded file (in xcache data folder and by extension on the client machine) will be 8MB, and, in the xcache logs, I will have two 4MB chunks OK, and the last chunk will be failed and it will be mentionned that the rest (2MB) can't be downloaded because it cannot be read.
    
    [2021-05-10 10:30:18.127994 +0200][Error  ][XrdClHttp         ] Could not read URL: http://u23@source_server:8000//path/to/the/file?, error: [ERROR] Internal error: no such device or address: Result Invalid Read in request after 3 attempts
    
    
    
    I performed another test:
    
    I downloaded the file from the source server using curl. I have the fully downloaded file (same amount of bytes that is told by curl "Content-Length" attribute).
    I copied this file on a simple VM at our site and expose it through a basic http server (python -m SimpleHTTPServer 80)
    I downloaded the entire file through xcache! No error message in xcache logs, file is fully downloaded on xcache data folder and on client machine.
    
    So,
    
    there is no problem with the file itself
    there is no problem when downloading from the source server using curl or wget
    there is no problem between xcache and my basic http server
    but there is a problem between xcache and the source server
    
    What in the communication between xcache and the source server can prevents from reading the last chunk of a file?
    
    regards,
    
    Bertrand Rigaud
    
    Centre de Calcul de l'IN2P3 - CNRS
    21 avenue Pierre de Coubertin
    69627 Villeurbanne CEDEX
    Tél : 04.78.93.08.80
    
    ----- Mail original -----
    De: "Yang, Wei" <[log in to unmask]>
    À: "Bertrand RIGAUD" <[log in to unmask]>, "xrootd-l" <[log in to unmask]>
    Envoyé: Samedi 8 Mai 2021 00:46:50
    Objet: Re: http ingest using xcache fails
    
    Hmm, I think XcacheH is still more or less experimental. That said, it should still work. Can you go inside the cache directory to find a file name http/path/to/my/file and see if that file is fully cache (size, checksum) ?
    
    regards,
    --
    Wei Yang  |  [log in to unmask]  |  650-926-3338(O)
    
    -----Original Message-----
    From: <[log in to unmask]> on behalf of Bertrand RIGAUD <[log in to unmask]>
    Date: Thursday, May 6, 2021 at 4:47 AM
    To: <[log in to unmask]>
    Subject: http ingest using xcache fails
    
        Hi,
        
        Trying to deploy this architecture (https://cvmfs.readthedocs.io/en/stable/_images/xcache2.svg), I'm facing a problem when downloading a file through http.
        
        Everythting works well till the last chunk is downloaded.
        
        As an example, here is a simple curl performed from the client machine (and this is the same behaviour with cvmfs client) :
        
        ### Through xcache server ###
        
        $ curl -v -o file1  http://my_xcache_server:1094//http://path/to/my/file
          % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                         Dload  Upload   Total   Spent    Left  Speed
          0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0* About to connect() to my_xcache_server port 1094 (#0)
        *   Trying xxx.xxx.xxx.xxx...
        * Connected to my_xcache_server (xxx.xxx.xxx.xxx) port 1094 (#0)
        > GET //http://path/to/my/file HTTP/1.1
        > User-Agent: curl/7.29.0
        > Host: my_xcache_server:1094
        > Accept: */*
        > 
        < HTTP/1.1 200 OK
        < Connection: Keep-Alive
        < Content-Length: 506173152
        < 
        { [data not shown]
         99  482M   99  480M    0     0  57.9M      0  0:00:08  0:00:08 --:--:-- 29.9M* transfer closed with 2856672 bytes remaining to read
         99  482M   99  480M    0     0  57.7M      0  0:00:08  0:00:08 --:--:-- 11.5M
        * Closing connection 0
        curl: (18) transfer closed with 2856672 bytes remaining to read
        
        
        ### Direct download ###
        
        curl -v -o file2 http://path/to/my/file
          % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                         Dload  Upload   Total   Spent    Left  Speed
          0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0* About to connect() to source_server port 8000 (#0)
        *   Trying 145.146.100.30...
        * Connected to source_server (xxx.xxx.xxx.xxx) port 8000 (#0)
        > GET path/to/my/file HTTP/1.1
        > User-Agent: curl/7.29.0
        > Host: source_server:8000
        > Accept: */*
        > 
        < HTTP/1.1 200 OK
        < Connection: Keep-Alive
        < Content-Length: 506173152
        < 
        { [data not shown]
        100  482M  100  482M    0     0   101M      0  0:00:04  0:00:04 --:--:--  101M
        * Connection #0 to host source_server left intact
        
        ### Xcache server logs (last chunk) ###
        
        210506 08:53:05 155627 sysXrdHttp:  XrdHttpReq::Data! final=1
        210506 08:53:05 155627 unknown.2:23@clientmachine sysXrdHttp: PostProcessHTTPReq req: 2 reqstate: 481
        210506 08:53:05 155627 unknown.2:23@clientmachine sysXrdHttp: Got data vectors to send:1
        210506 08:53:05 155627 sysXrdHttp: Sending 1048576 bytes
        210506 08:53:05 155627 unknown.2:23@clientmachine sysXrdHttp:  Process. lp:0 reqstate: 481
        210506 08:53:05 155627 unknown.2:23@clientmachine sysXrdHttp: Process is exiting rc:0
        210506 08:53:05 155627 XrdPfc_IO: dump Read() 0x7fc1d00019f0 off: 503316480 size: 1048576 [log in to unmask]:8000/http/source.server:8000/path/to/file" target="_blank">http:[log in to unmask]:8000/http/source.server:8000/path/to/file?
        210506 08:53:05 155627 XrdPfc_File: dump Read() idx 120 http/source.server:8000/path/to/file
        210506 08:53:05 155627 XrdPfc_File: dump inc_ref_count 0x7fc1a0403530 refcnt  1 http/source.server:8000/path/to/file
        210506 08:53:05 155627 XrdPfc_File: dump Read() 0x7fc1f0028000inc_ref_count for existing block 0x7fc1a0403530 idx = 120 http/source.server:8000/path/to/file
        XcacheH: stagein list snapshot: available workers: 10, list length: 0
        [2021-05-06 08:53:09.092614 +0200][Error  ][XrdClHttp         ] Could not read URL: [log in to unmask]:8000//path/to/file?" target="_blank">http:[log in to unmask]:8000//path/to/file?, error: [ERROR] Internal error: no such device or address: Result Invalid Read in request after 3 attempts
        210506 08:53:09 155645 XrdPfc_File: dump Prefetch enter to check download status http/source.server:8000/path/to/file
        210506 08:53:09 155645 XrdPfc_File: debug Prefetch file is complete, stopping prefetch. http/source.server:8000/path/to/file
        210506 08:53:09 155626 XrdPfc_File: dump ProcessBlockResponse block=0x7fc1a0403530, idx=120, off=503316480, res=-6 http/source.server:8000/path/to/file
        210506 08:53:09 155626 XrdPfc_File: debug ProcessBlockResponse after failed prefetch on io 0x7fc1d00019f0 disabling prefetching on this io. http/source.server:8000/path/to/file
        210506 08:53:09 155626 XrdPfc_File: error ProcessBlockResponse block 0x7fc1a0403530, idx=120, off=503316480 error=-6 http/source.server:8000/path/to/file
        210506 08:53:09 155627 XrdPfc_File: dump Read() requested block finished 0x7fc1a0403530, is_failed()=True http/source.server:8000/path/to/file
        210506 08:53:09 155627 XrdPfc_File: error Read() io 0x7fc1d00019f0, block 120 finished with error 6 no such device or address http/source.server:8000/path/to/file
        210506 08:53:09 155627 XrdPfc_File: dump Read() dec_ref_count 0x7fc1a0403530 idx = 120 http/source.server:8000/path/to/file
        210506 08:53:09 155627 XrdPfc_File: dump free_block block 0x7fc1a0403530  idx =  120 http/source.server:8000/path/to/file
        210506 08:53:09 155627 XrdPfc_IO: warning Read() error in File::Read(), exit status=-6, error=no such device or address [log in to unmask]:8000/http/source.server:8000/path/to/file" target="_blank">http:[log in to unmask]:8000/http/source.server:8000/path/to/file?
        210506 08:53:09 155627 ofs_read: unknown.2:23@clientmachine Unable to read /http:/source.server:8000/path/to/file; no such device or address
        210506 08:53:09 155627 sysXrdHttp:  XrdHttpReq::Error
        210506 08:53:09 155627 unknown.2:23@clientmachine sysXrdHttp: PostProcessHTTPReq req: 2 reqstate: 482
        210506 08:53:09 155627 unknown.2:23@clientmachine sysXrdHttp: PostProcessHTTPReq mapping Xrd error [3005] to status code [500]
        210506 08:53:09 155627 unknown.2:23@clientmachine sysXrdHttp: Stopping request because more data is expected but no data has been read.
        210506 08:53:09 155627 sysXrdHttp:  XrdHttpReq request ended.
        210506 08:53:09 155627 sysXrdHttp:  Cleanup
        210506 08:53:09 155627 sysXrdHttp:  Reset
        210506 08:53:09 155627 sysXrdHttp:  XrdHttpReq request ended.
        210506 08:53:09 155627 XrootdXeq: unknown.2:23@clientmachine disc 0:00:09 (send failure)
        210506 08:53:09 155627 XrdPfc_File: debug ioActive start for io 0x7fc1d00019f0 http/path/to/file
        210506 08:53:09 155627 XrdPfc_File: info ioActive for io 0x7fc1d00019f0, active_prefetches 0, allow_prefetching False, ioactive_false_reported False, ios_in_detach 0
        210506 08:53:09 155627 XrdPfc_File: info 	io_map.size() 1, block_map.size() 0, file http/path/to/file
        210506 08:53:09 155627 XrdPfc_File: info ioActive for io 0x7fc1d00019f0 returning False, file http/path/to/file
        210506 08:53:09 155627 XrdPfc_IO: info DetachFinalize() 0x7fc1d00019f0
        210506 08:53:09 155627 XrdPfc_Cache: debug ReleaseFile http/path/to/file, io 0x7fc1d00019f0
        210506 08:53:09 155627 XrdPfc_File: debug RemoveIO() io = 0x7fc1d00019f0 http/path/to/file
        210506 08:53:09 155627 XrdPfc_Cache: debug dec_ref_cnt http/path/to/file, cnt at entry = 1
        210506 08:53:09 155627 XrdPfc_File: debug FinalizeSyncBeforeExit requesting sync to write detach stats http/path/to/file
        210506 08:53:09 155627 XrdPfc_Cache: debug dec_ref_cnt http/path/to/file, scheduling final sync
        210506 08:53:09 155627 XrdPfc_IO: debug ~IOEntireFile() 0x7fc1d00019f0 [log in to unmask]:8000/http/path/to/file" target="_blank">http:[log in to unmask]:8000/http/path/to/file?
        210506 08:53:09 155627 Posix_PrepIODisable: Disabling defered open [log in to unmask]:8000//path/to/file" target="_blank">http:[log in to unmask]:8000//path/to/file?
        210506 08:53:09 160872 XrdPfc_File: dump Sync() http/path/to/file
        210506 08:53:09 160872 XrdPfc_File: dump Sync 0 blocks written during sync http/path/to/file
        210506 08:53:09 160872 XrdPfc_Cache: debug dec_ref_cnt http/path/to/file, cnt at entry = 1
        210506 08:53:09 160872 XrdPfc_File: debug FinalizeSyncBeforeExit sync not required http/path/to/file
        210506 08:53:09 160872 XrdPfc_Cache: debug dec_ref_cnt http/path/to/file, cnt after sync_check and dec_ref_cnt = 0
        210506 08:53:09 160872 XrdPfc_File: debug ~File() close info  http/path/to/file
        210506 08:53:09 160872 XrdPfc_File: debug ~File() close output   http/path/to/file
        210506 08:53:09 160872 XrdPfc_File: debug ~File() ended, prefetch score = 3.95238 http/path/to/file
        210506 08:53:11 155631 Posix_DDestroy: DLY destory of 1 objects; 0 already lost.
        210506 08:53:11 155631 Posix_DDestroy: DLY destory end; 0 objects deferred and 0 lost.
        
        ### Xcache config ###
        
        all.role     proxy server
        
        all.export /http:/
        all.export /https:/
        
        ofs.osslib      libXrdPss.so
        
        xrootd.seclib /usr/lib64/libXrdSec.so
        
        pss.origin =http,https
        
        # US data servers
        pss.permit      source.server
        pss.permit      source.server
        pss.permit      source.server
        pss.permit      source.server
        pss.permit      source.server
        pss.permit      source.server
        pss.permit      source.server
        # EU data servers
        pss.permit      source.server
        pss.permit      source.server
        pss.permit      source.server
        
        pss.cachelib    libXrdPfc.so
        pss.config streams 8
        
        # XcacheH
        pss.namelib -lfncachesrc+ /usr/lib64/XrdName2NameXcacheH.so cacheLife=1d cacheBlockSize=4m
        pss.ccmlib /usr/lib64/XrdName2NameXcacheH.so
        
        oss.localroot   /xcache/ns
        
        # Metadata directories (cinfo files)
        oss.space meta /xcache/meta
        
        # Data directories
        oss.space data /xcache/data
        
        # Xcache spaces assignement
        pfc.spaces data meta
        
        if exec xrootd
          xrd.protocol http:1094 libXrdHttp.so
        fi
        
        pfc.diskusage 0.90 0.95
        
        pfc.ram 6g
        pfc.blocksize 4M
        pfc.prefetch 32
        
        pfc.trace dump
        http.trace   all
        pss.trace  all
        pss.debug
        
        ### xrootd version: 5.1.1 ###
        
        As a result, I got an almost file downloaded on client side, and also in xcache server, cached data is an almost file. Just this last chunk missing.
        
        Are there directives missing in congig file?
        
        Thank you,
        
        Bertrand Rigaud
        
        Centre de Calcul de l'IN2P3 - CNRS
        21 avenue Pierre de Coubertin
        69627 Villeurbanne CEDEX
        Tél : 04.78.93.08.80
        
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