You can use the %maxLength{…}{N} pattern converter with PatternLayout at least. Unfortunately, I don’t think any other layouts support a similar option.
> On Jan 25, 2024, at 10:55, Gary D. Gregory <ggreg...@apache.org> wrote: > > Hi All, > > I'd like to ask how to if we can devise advice around an issue I ran into > this week. > > One of our test suites processes about 40K files of test fixtures. These > inputs are parsed, processed, and asserted. This randomly fails on a call to > Logger#debug(), randomly in that it happens usually once per build, somewhere > in a logging call. But it usually fails with a call that looks like this: > > logger.debug("This is fun" + myFunObject); > > To simplify things, let's say that it turns out that after an underlying > third party jar file version upgrade the call to myFunObject#toString() no > longer returns Object#toString() but rather (again to simplify) the contents > of the file that was parsed to create myFunObject. This toString() can be > megabytes. The solution is obvious: > > logger.debug("This is fun", myFunObject::toString) > > And our CI builds no longer randomly fail since our default logging does not > log at the debug level. > > A better solution could be: > > logger.debug("This is fun", () -> myFunObject.toString().substring(0, 100)) > > where I still want _some_ information better than making my own toString() > with System#identityHashCode(Object) or somesuch. Sure, .toString() is still > called but it does not make it down into logging. In my case the OOME > happened in myFunObject::toString so the substring() example would not have > worked. > > My question is: Should we document some general advice on this pattern and > what should the advice be? Would it make sense to have some features where we > truncate/reject Strings above a threshold. And yes, calling > myFunObject.toString() can still still get me in trouble. > > Gary >