Mountpoint for Amazon S3 uses the tracing ecosystem for logging. This makes it easy to configure the verbosity and target of log output. By default we output minimal log information, but for reporting issues or debugging application problems, you may want to customize this logging behavior.
By default, Mountpoint for Amazon S3 outputs logs to the ~/.mountpoint-s3/ directory, creating it if it doesn't exist. This destination can be changed using the -l, --log-directory command-line argument.
A new log file is created for each execution of mount-s3. Log files are never automatically rotated or cleaned up.
When running in foreground mode (-f, --foreground), mount-s3 also emits the same log information to stdout.
By default, we output minimal (error-level) information to the log file. For reporting issues or debugging application problems, it can be helpful to increase this verbosity. We use the common RUST_LOG environment variable for controlling log verbosity and subjects.
To control the log verbosity, set the RUST_LOG environment variable. If unset, it defaults to error to enable only error-level log messages. Verbosity can be increased by instead setting RUST_LOG to warn, info, debug, or trace.
RUST_LOG can also control the subjects that are included in the log output. By default, all subjects are included, but verbosity can be configured on a per-subject basis. For example, setting RUST_LOG to trace,awscrt=off turns on trace-level logging for all subjects except awscrt. See the tracing documentation for more details on how to configure RUST_LOG.
For interactive debugging, we often set RUST_LOG=debug,awscrt=off to enable debug-level errors for everything except the AWS Common Runtime (the awscrt subject). The Common Runtime logging is more verbose, so it's helpful to filter those messages out interactively.
For reporting issues, we suggest RUST_LOG=trace,awscrt=debug as a good default choice.