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< Erlang patches mailing list ~ log_mf_h can't store problem reports above 64K bytes (With p |
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 Posted: Tue Aug 21, 2007 11:50 am |
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Release: OTP-R11b-5
Operating system: All
Problem description:
When the STDLIB module log_mf_h stores a problem report in the on-disk round-robin database, it can't store a problem report above a size of 64Kilobytes[*]. The reason is that the format used is to encode the report is (bit-syntax notation)
<<Size:16/integer, Report/binary>>
So since 2^16 = 64K, trying to store a larger problem report fails. Then, when the SASL module 'rb' tries to read the problem report, it fails becase the report has the wrong size.
Problem solution:
The attached patch changes the code so it
** Uses bit syntax rather than old peek/poke
** Uses a 4 byte size field rather than a 2 byte size field.
Solution considerations:
The patch will make all old log_mf_h logs on-disk unreadable. There is no upgrade path incorporated.
With a 32-bit integer word, it is possible to write enormously large error-reports to disk. Several gigabytes at least.
Solution alternatives:
Use a 3-byte field. Not because of space, but because it is then a 8/16Mb report that can be written which makes the second consideration much more tolerable.
Use list_to_binary(Bin, [compressed]). We would save some space and trade Disk I/O for CPU cycles. However, I don't know how well that is supported in the system.
[*] Maybe this is only 32 kilobytes because of signedness
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