Adding time zone without config might break scripts parsing the logs. I think it's risky.

I'd prefer that we allow some config to select time format, either a custom format string or an enum of some pre-defined formats where some of them include time zone, but the default one doesn't.

A problem with a custom format string for strftime is that milliseconds can't be included, so perhaps an enum with some predifined formats is preferable. A limited number of formats may also be easier to handle for scripts attempting to be independent of this config.

As stated in #12932 (comment), I think the issues with strftime() are in my opinion:

• strftime format specification differences between operating systems
• strftime usually does not allow fractional seconds/ milliseconds / microseconds

But I fully agree that the default log format should be kept as is today otherwise scripts, and log shippers like fluentd, fluentbit, logstash, etc will stop working on the new redis version, the default must be backwards compatible

If I have any say on this , one of the predefined formats should be iso8601_with_utcoffset which should contain microseconds (not truncated) and a UTC offset in the form +HH:MM as for example 2023-12-08T15:03:26.246333+00:00 and it should always be 32 chars.

I have seen implementations where the fractional seconds are omitted if they are zeros (which is legal by iso 8601) like .246000 gets truncated to .246, so please add a testcase to make sure you don't truncate the zeroes in that case.

Predefined formats that I think are useful

• iso8601utc: 2023-12-08T15:03:26.246Z, milliseconds and Z (zulu) timezone
• iso8601_with_utcoffset: 2023-12-08T15:03:26.24600+01:00, microsends and full utc offset.

Predefined formats that I think are useful (...) iso8601utc, iso8601_with_utcoffset

@ecerulm Are these ISO 8601 variants defined anywhere?

@zuiderkwast , You mean the names iso8601utc and iso8601_with_utcoffset? I made the names up I don’t think there are standardized names for them.

The format that I called iso8601utc is what JavaScript calls “isotring” (toISOString)

the format that I called iso8601_with_utcoffset is what python calls “isoformat” (datetime.isoformat())

Adding time zone without config might break scripts parsing the logs. I think it's risky.

I don't think this is a problem. Redis has gone through multiple versions, and its log format has also evolved. Different versions have different log formats. For example:

2.8: [pid] day month h:m:s.ms level message
4.0: pid:role day month h:m:s.ms level message
6.0: pid:role day month year h:m:s.ms level message

So scripts need to have different handling methods for different versions of Redis. In the next major version, displaying time zone information is also something that the script should adapt to.

If we finally decide there will be a backwards compatibility problem, we can have a new configuration item to control whether to display time zone, and by default it is off.

The point is, we want to keep everything as simple as it can.

I don't think this is a problem. Redis has gone through multiple versions, and its log format has also evolved. Different versions have different log formats.

@soloestoy, I think redis has the same log format since Redis 3.x and now we are in Redis 7.2, so it has been the same log format for 8 years. right? correct me if I'm wrong.

You can take a look at the example I provided. We made modifications to the log format in both versions 4.0 and 6.0.

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