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Date: Wed, 23 Jun 2010 17:23:47 +0100
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Subject: Recovering from failed compaction due to lack of disk space.
From: Robert Newson <robert.newson@gmail.com>
To: dev@couchdb.apache.org
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Couchdb can make a .compact file when the volume is almost out of disk
space and then crash before writing the header.

If you then clean some space and try to compact again, it won't ever work.

[Wed, 23 Jun 2010 16:11:59 GMT] [error] [emulator] Error in process
<0.1976.0> with exit value:
{{badmatch,no_valid_header},[{couch_db_updater,start_copy_compact,1}]}

The presence of the invalid .compact file prevents it, and needs to be
manually removed.

I think couchdb should handle this but it's clearly a dangerous area
to play with. My suggestion is to change the bit of code that tests
for the .compact file's presence to also verify that it's not 0 bytes
in length (and delete the file if it is). Is that dangerous? Should it
cover other similar cases?

B.