SSL + file upload = lots of memory
I'm using lighttpd (1.4.15) in an embedded device, and attempting to upload a file (~6MB). Without SSL enabled, lighttpd doesn't use much more than 6-7MB (lighttpd process grows by <1MB, ~6MB are written to /tmp). With SSL enabled, lighttpd's memory usage quickly jumps to over 26MB (lighttpd process grows to 20+MB, ~6MB are written to /tmp), exhausting all available memory and bringing the device to a grinding halt.
I also noticed that the <1MB of extra size on a non-SSL upload goes away once the upload is complete; in contrast, if I upload a smaller file (900kB) via SSL, the process size grows by ~7MB and stays that large, even after the connection is closed. However, uploading a similarly-sized file again does not cause it to grow any larger, i.e. the memory doesn't seem to be permanently leaked.
I found this ticket:
which sounds somewhat similar, but no additional information was ever posted about a potential cause. Any ideas? Thanks!
use SSL_MODE_RELEASE_BUFFERS (OpenSSL >= 1.0.0) to free buffers
as they are used, to potentially reduce memory footprint of
idle SSL connections
"memory usage when ssl.engine used and large data uploaded through CGI"
"SSL + file upload = lots of memory"
"Memory usage increases when proxy+ssl+large file"
- Description updated (diff)
- Status changed from Wontfix to Patch Pending
- Target version changed from 1.5.0 to 1.4.40
New: asynchronous, bidirectional streaming support for request and response
Submitted pull request: https://github.com/lighttpd/lighttpd1.4/pull/66
included in the pull request are flags to openssl (SSL_MODE_RELEASE_BUFFERS) to release memory buffers when finished with them, instead of holding onto the buffers.
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