Nimbus logs are written to the console, and optionally to a file. Writing to a file for a long-running process may lead to difficulties when the file grows large. This is typically solved with a log rotator. A log rotator is responsible for switching the written to file, as well as compressing and removing old logs.
To set up file-based log rotation, an application such as rotatelogs is used -
rotatelogs is available on most servers and can be used with
systemd and manual setups to write rotated logs files.
In particular, when using
systemd and its accompanying
journald log daemon, this setup avoids clogging the the system log by keeping the Nimbus logs in a separate location.
rotatelogs works by reading stdin and redirecting it to a file based on a name pattern. Whenever the log is about to be rotated, the application invokes a shell script with the old and new log files. Our aim is to compress the log file to save space. repo provides a helper script to do so:
# Create a rotation script for rotatelogs cat << EOF > rotatelogs-compress.sh #!/bin/sh # Helper script for Apache rotatelogs to compress log files on rotation - `$2` contains the old log file name if [ -f "$2" ]; then # "nice" prevents hogging the CPU with this low-priority task nice gzip -9 "$2" fi EOF chmod +x rotatelogs-compress.sh
Logs in files generally don't benefit from colors. To avoid colors being written to the file, additional flags can be added to the Nimbus build process -- these flags are best saved in a build script to which one can add more options. Future versions of Nimbus will support disabling colors at runtime.
# Build nimbus with colors disabled cat << EOF > build-nbc-text.sh #!/bin/bash make NIMFLAGS="-d:chronicles_colors=off -d:chronicles_sinks=textlines" nimbus_beacon_node EOF
The final step is to redirect logs to
rotatelogs using a pipe when starting Nimbus:
build/nimbus_beacon_node \ --network:pyrmont \ --web3-url="$WEB3URL" \ --data-dir:$DATADIR | rotatelogs -L "$DATADIR/nbc_bn.log" -p "/path/to/rotatelogs-compress.sh" -D -f -c "$DATADIR/log/nbc_bn_%Y%m%d%H%M%S.log" 3600
The options used in this example do the following:
-L nbc_bn.log- symlinks to the latest log file, for use with
-p "/path/to/rotatelogs-compress.sh"- runs
rotatelogs-compress.shwhen rotation is about to happen
-D- creates the
logdirectory if needed
-f- opens the log immediately when starting
-c "$DATADIR/log/nbc_bn_%Y%m%d%H%M%S.log"- includes timestamp in log filename
3600- rotates logs every hour (3600 seconds)