HIVE-26363: converting replLogger time format from epoch to readable UTC format

[Rakshith606]

What changes were proposed in this pull request?

Why are the changes needed?

Does this PR introduce any user-facing change?

How was this patch tested?

[cmunkey]

Are this timestamps going into the metrics table?
If so, others like CM are reading them, so you shouldn't change the type.
Also epoch seconds make doing time diffs easier.

[Rakshith606]

these don't go to metrics table, these are only logged to hive.log

[cmunkey]

LGTM.

[cmunkey]

Isn't there a way to have a custom mapper?

[cmunkey]

Maybe you can do the reverse of here:

https://stackoverflow.com/questions/69532856/serialize-java-time-duration-to-json-as-milliseconds-only-using-jackson

annotate the existing columns with custom mapper that maps as UTC time from epoch.

[cmunkey]

@JsonSerialize(using = UTCSerializer.class)
private Long dumpStartTime;

then

public class UTCSerializer extends JsonSerializer {

@Override
public void serialize(Long value, JsonGenerator gen, SerializerProvider serializers) throws IOException {
  LocalDateTime dateTime = LocalDateTime.ofEpochSecond(value, 0, ZoneOffset.UTC);
  // Might need to format here
  gen.writeString(dateTime.toString());
}

}

Then you just need to add annotation to all the State classes, and not change the type.

[cmunkey]

Add a unit test that serializes object and checks that the JSON string has a date and not epoch ms.

[cmunkey]

Since these are only logging messages, won't the log line already have the timestamp in readable format?
Won't it cause extra confusion if the log line and the message have a different times?
ReplState.log() does:

public void log(LogTag tag) {
try {
REPL_LOG.info("REPL::{}: {}", tag.name(), mapper.writeValueAsString(this));
} catch (Exception exception) {
REPL_LOG.error("Could not serialize REPL log: {}", exception.getMessage());
}
}
}

The object instance, BootstrapDumpBegin for instance, is created before the LOG.info(),
so could potentially have a different instance. Yes, converting from millis to seconds does
usually make them close, but log messages have:

2022-07-20 18:54:47,334 INFO

which is milliseconds.