Frossie Economou requests that we tackle this within the first couple of months of S17.

Comments about the use of the fine grained trace debugging are with DM-8356.

Since meas_modelfit uses the old debug<n> template for n = 10, 8, and 7, I have translated those into trace levels 5,4, and 3. They can be enabled using lsst.log.utils.traceSetAt(component_name, level). All traces <= level are enabled by this method.

The old pex_logging enabling mechanism was to call lsst.pex.logging.Debug(name, n) with n = 1, ..., 10. This method sets the debug level for name and anything higher on the hierarchy. For examble, lsst.pex.logging.Debug("meas.modelfit.optimizer", 10) seems to enable not only that level, but also "meas.modelfit.optimizer.Optimizer". I don't think that traceSetAt() has this same ability to set up the tree.

Hsin-Fang Chiang, can you confirm that this is true, that the trace for the individual level must be set individually?

log can handle the logger hierarchy too, with or without the fine grained trace debugging scheme. For example, lsst.log.utils.traceSetAt("afw.math",4) enables all of its descendant loggers up to TRACE4 as well, unless specified otherwise.

Do you mind doing this review? You may be one of the only people who knows this code.

You are correct that the setTraceAt applies to the entire tree. Strange, but I'm sure I tested it. Might have been before I knew about some of the other gotchas.

This mistakenly got pushed into "In Review"

This is ready to review under tickets/DM-8357

In terms of usage, this patch looks fine to me. Minor comments on the PR.

As mentioned in DM-8356, I'm not sure if meas_modelfit really needs to use the fine-level tracing scheme. Each logger of its unique name uses up to two debug levels, so using simply DEBUG and TRACE could be enough too. But I guess the intent may be to add more debug messages in the future using more fine levels? I'll leave the decision to you and Jim Bosch.

I don't anticipate turning on this logging in production code, so Hsin-Fang Chiang may be right; I'm not sure about the implications of that change to really know. It is important that we maintain the ability to turn on or off any of the name+level combinations that currently exist without turning off the others. It is not important that these have the same name or level, or that levels across different names are kept consistent.