Implement support of date/time format specifiers in log and error log file names

[sirvickr]

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• New Feature

Changelog entry (a user-readable short description of the changes that goes to CHANGELOG.md):

Added the possibility to use date and time format specifiers in log and error log file names, either in config files (log and errorlog tags) or command line arguments (--log-file and --errorlog-file)

Documentation entry for user-facing changes

• Documentation is written (mandatory for new features)

[robot-ch-test-poll2]

This is an automated comment for commit e592c7c with description of existing statuses. It's updated for the latest CI running
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The overall status of the commit is 🟢 success

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[rvasin]

Hi, could anyone be assigned to this PR? So Victor could start working on reviewers suggestions.

[alexey-milovidov]

LGTM.

The localtime_r and stringstream usage was suspicious to me while reviewing, but it looks like we cannot support all these format substitutions easier, and the method will be called very rarely, and it is static (buried deep enough).

[amosbird]

This breaks relative path configuration for non-daemon servers. Consider the following example:

    <logger>
        <level>trace</level>
        <log>logs/clickhouse-server.log</log>
        <errorlog>logs/clickhouse-server.err.log</errorlog>
        <size>1000M</size>
        <count>10</count>
    </logger>

The log path will be modified as logs/logs/clickhouse-server.log.

cc @sirvickr

[sirvickr]

That's the exact reason why those format specifiers currently do not apply to the "path" part - only to the file name.

[sirvickr]

@amosbird, path.replace_filename() does the trick.
If someone decides another day to apply the specifiers to the full path, they will have to take into consideration this issue about non-daemon servers.

[amosbird]

That's the exact reason why those format specifiers currently do not apply to the "path" part - only to the file name.

@sirvickr I'm confused. If that's the expected behavior, why not do the following:

    ss << std::put_time(&buf, path.filename().c_str());

[sirvickr]

@amosbird, you are right, my code looks like an ugly typo, to say the least. This one is more concise, clear and correct:

ss << std::put_time(&buf, path.filename().c_str());

It looks like it should be amended.

[sirvickr]

I guess, replace_filename() extracts the file name from its argument, otherwise it wouldn't work properly.

[sirvickr]

And thank you for noticing.
I'm thinking of creating a "follow-up" PR to clean up this line of code. Or may be you'd rather amend this code by yourself?

[amosbird]

And thank you for noticing.

No problem!

I'm thinking of creating a "follow-up" PR to clean up this line of code.

Perfect. Please go ahead for amending it :)