zlib errors after upgrading

[Timo Sirainen]

zstd support was added in v2.3.11 (not v2.3.12 like I mistakenly tried to say in the earlier mail).

> On 28. Aug 2020, at 16.36, Robert Nowotny <rnowotny at rotek.at> wrote:
> 
> 
> ok, I did install zstd (zstd command line interface 64-bits v1.4.4, by Yann Collet)
> 
> reconfigured & compiled dovecot 2.3.10.1  again with option : with-zstd
> 
> changed the configuration file to : 
> 
> zlib_save = zstd
> 
> and restarted dovecot - 
> 
> now I have following log file errors : 
> 
> Aug 28 16:17:39 lxc-imap dovecot: imap(rnowotny)<237930><H1kft/CtENRUclcc>: Error: zlib_save: Unknown handler: zstd
> Aug 28 16:17:44 lxc-imap dovecot: imap(rprager)<237939><p5hst/Ct8evAqKhu>: Error: zlib_save: Unknown handler: zstd
> Aug 28 16:17:44 lxc-imap dovecot: imap(rprager)<237940><Vp5st/Ct8uvAqKhu>: Error: zlib_save: Unknown handler: zstd
> Aug 28 16:17:44 lxc-imap dovecot: imap(rprager)<237941><U31tt/Ct8+vAqKhu>: Error: zlib_save: Unknown handler: zstd
> ...
> 
> 
> what I do wrong here ? 
> 
> 
> 
> 
> Am 28.08.2020 um 13:15 schrieb Timo Sirainen:
>> On 28. Aug 2020, at 12.10, Robert Nowotny <rnowotny at rotek.at <mailto:rnowotny at rotek.at>> wrote:
>>> 
>>> unfortunately after re-installing 2.3.11.3, those broken-pipe errors appear again. (on different, new files) 
>>> so for sure there is something broken with zlib.
>>> I will go back to 2.3.10.1 now.
>>> attached is the configuration file, though it did not change between 2.3.10.1 and 2.3.11.3
>> 
>> Oh, this is with xz, not with gz like we first thought. There are some known problems with xz, which is why we are planning on removing it entirely. I'm not sure why v2.3.11 breaks it, although there are some changes related to it but it might be coincidence. I can't reproduce this problem though.
>> 
>> In any case, I'd recommend switching to zlib or to zstd in v2.3.12. (In theory you could leave the existing mails xz-compressed, but best would be to re-compress everything via dsync so old mails can be read when we eventually remove xz support.)
>> 
> 

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