Sally Kleinfeldt and Aaron VanDerlip describe ore.bigfile, a minimalist solution to the problem of uploading, downloading, and versioning very large files in Plone.

1. Large Files
Without the Trials
Aaron VanDerlip and Sally Kleinfeldt
Plone Symposium East 2010
Thursday, June 3, 2010

2. Acknowledgments
• Bioneers provides environmental education
and social connectivity through
conferences, radio and TV, books, and online
materials
• Engaged Jazkarta to build a file asset server
based on Plone to help them organize,
capture, and store multimedia and textual
content with files as large as 5 GB.
Thursday, June 3, 2010

3. Acknowledgments
• Aaron VanDerlip - Project Manager
• Kapil Thangavelu - Developer
Thursday, June 3, 2010

4. What is a Big File?
• Anything that makes you wait...
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5. Plone Problems with
Big Files
1.Uploading/Downloading
2.Versioning
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6. Uploading Big Files
• Both the user and a Zope thread are
waiting for the file transfer
Thursday, June 3, 2010

7. Thursday, June 3, 2010

8. Uploading Big Files
• Browser encodes file in multipart mime
format
• Zope must undo this encoding
• CPU and memory intensive, and SLOW
• Zope thread is blocked during this process
Thursday, June 3, 2010

9. Downloading Big Files
• ...the same thing happens in reverse
Thursday, June 3, 2010

10. Learning from Rails
• Get file encoding/unencoding and read/
write operations out of Plone
• Web servers are really good at this -
Apache, Nginx, and Lighttpd
• Our implementation uses Apache
• Apache file streaming is fast and threads
are cheap
Thursday, June 3, 2010

11. Learning from Rails
• Uploads: Apache plus mod_porter
http://therailsway.com/tags/porter
• Downloads: Apache plus mod_xsendfile
http://john.guen.in/past/2007/4/17/
send_files_faster_with_xsendfile/
• ...and of course ZODB Blob storage
Thursday, June 3, 2010

12. Mod Porter
• Parses the multipart mime data
• Writes the file to disk
• Changes the Request to contain a pointer
to the temp file on disk
• All done efficiently in C code inside your
Apache process
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13. Mod Porter
Thursday, June 3, 2010

14. Apache Config for
Mod Porter
LoadModule apreq_module /usr/lib/Apache2/modules/mod_apreq2.so
LoadModule porter_module /usr/lib/Apache2/modules/mod_porter.so
# Apache has a default read limit of 64MB, set it higher
APREQ2_ReadLimit 2G
...
Porter On
# Files below this size will not be handled by mod-porter
PorterMinSize 14M
# Where the uploaded files are stored
PorterDir /mnt/uploads-Apache
Thursday, June 3, 2010

15. X-Sendfile
• HTTP header
• Set an X-Sendfile header and the path of a
file on your response
• Apache does the rest
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16. Apache Config for
X-Sendfile
LoadModule xsendfile_module /usr/lib/Apache2/modules/mod_xsendfile.so
...
EnableSendfile On
XSendFile on
# Config to send file resources directly from blob storage
XSendFilePath /mnt/bioneers/var/blobstorage
Thursday, June 3, 2010

17. Using X-Sendfile
from Python
def download(self, response, file_path):
response.setHeader("X-Sendfile",
file_path)
Thursday, June 3, 2010

18. Blob Storage
• Uploads
• Blob.consumeFile moves file from
Apache’s temp area to blob storage
(ZODB/blob.py)
• Uses os.rename, file never enters Plone
• Downloads
• Served directly from blob storage
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19. Upload Process
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20. What About Really
Really Big Files?
• Use FTP
• Supports continuation and batching
• Handles files too large for browser limits
• Content editors use FTP to transfer files to
an upload directory
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21. UI
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22. Uploading with FTP
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23. ore.bigfile
• Minimally intrusive, works with the grain of
Plone
• Provides Big File content type
• IFrontendFileServer interface defines two
methods that provide web server support
for upload and download
• Apache and Nginx implementations
provided
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24. ore.bigfile
Limitations
• Upload directory is hardcoded
• Possibility of error on very large images
which Mod Porter intercepts
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25. Versioning Big Files
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26. Solution
• Bypass CMFEditions - no file size limitation
• Create a new version only when file
changes (not metadata)
• Allow old versions to be purged
• Version information stored on Big File
object using annotations
Thursday, June 3, 2010

27. UI
Thursday, June 3, 2010

28. Conclusion
• ore.bigfile solves the Big File problem for a
particular use case, not feature complete
• It does so by taking advantage of mature
web server technology
• The code is minimally intrusive
• It provides a strategy for implementation
we can learn from as we improve Plone’s
Big File story
Thursday, June 3, 2010

29. http://svn.objectrealms.net/
view/public/browser/ore.bigfile
Questions
Thursday, June 3, 2010