Should backtraces be logged by Syslog module? Syslog seems historically oriented around short log messages, and by default (as of PHP 7.3 and later), a new syslog message is created when a newline is encountered. Note, the syslog.filter PHP setting can be configured to not split syslog messages at newlines, see https://www.php.net/manual/en/errorfunc.configuration.php#ini.syslog.filter
If backtraces should be logged by Syslog, this is currently missing from some important places. For events logged by ExceptionLoggingSubscriber, watchdog_exception() and friends, which do not include it in the log message, it could be pulled from the context array.
If backtraces should not be logged by Syslog, we could remove @backtrace_string from the log message in core/includes/errors.inc and core/lib/Drupal/Core/Config/Entity/ConfigEntityUpdater.php
If desired, we could also add a config toggle to choose between not logging the @backtrace_string or pulling it from the context array.
Throw an exception from a controller method, or log it using watchdog_exception(); syslog will not log the @backtrace_string.
To be determined.
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