Breaking change since v10.12.0 with zlib

Version: v10.12.0
Platform: n/a
Subsystem: zlib

In particular the breaking change occurred with #23186.

Before this change, code like:

compress.write(data);
compress.flush(Z_PARTIAL_FLUSH, () => {
  // do something with `compress.read();`
});
compress.write(data);
compress.flush(Z_PARTIAL_FLUSH, () => {
  // do something with `compress.read();`
});
compress.write(data);
compress.flush(Z_PARTIAL_FLUSH, () => {
  // do something with `compress.read();`
});
// etc. ...

would result in compress.read() returning only the compressed portion of data written before each flush().

After the change, node now seems to buffer the compressed contents of all of the write()s and passes that to one of the callbacks as one big chunk. This broke at least the ssh2-streams module, which depends on getting only the compressed data for particular chunks because of the need to include them in separate packets.

I’m not sure that this qualifies as a bug, but if you are sure that this is something that we should address, the easiest way would probably be to not use a global 0-sized Buffer to convey flushing information, but rather create one zero-sized Buffer per .flush() call and attach the desired flush flag to it as a property.

zlib: do not coalesce multiple `.flush()` calls

@mscdex

@mscdex Feel free to take a look at #28520 and let me know what you think here, it should fully address this issue

zlib: do not coalesce multiple `.flush()` calls

Please ignore this msg (#1)

zlib: do not coalesce multiple `.flush()` calls

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Breaking change since v10.12.0 with zlib #28478

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Breaking change since v10.12.0 with zlib #28478

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addaleax commented on Jul 1, 2019

addaleax commented on Jul 11, 2019

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