MongoDB Log Rotation

Note

Please handle MongoDB log rotation first. If mongodb.log is left unrotated for a long time and grows too large, VictoriaLogs collection and query pressure may increase significantly, and memory or CPU usage may even spike.

Log Rotation

Create the logrotate configuration directory and archive directory

mkdir -p /usr/local/logrotate-config
mkdir -p /data/logs/mongodb/oldlogs

Write the logrotate configuration file

cat > /usr/local/logrotate-config/mongodb <<EOF
/data/logs/mongodb/mongodb.log {
create 0644 mongodb mongodb
daily
dateext
dateformat -%Y-%m-%d
dateyesterday
rotate 180
missingok
ifempty
compress
delaycompress
olddir /data/logs/mongodb/oldlogs
sharedscripts
postrotate
    PID=$(pgrep -x mongod)
    [ -n "$PID" ] && /bin/kill -USR1 "$PID" || true
endscript
}
EOF

Run a dry-run check first

logrotate -d -f /usr/local/logrotate-config/mongodb

Add a scheduled task

(crontab -l ; echo "# Use logrotate to rotate MongoDB logs
0 0 * * * /usr/sbin/logrotate -f /usr/local/logrotate-config/mongodb >/dev/null 2>&1") | crontab -
crontab -l

Handling 0-Byte Log Files

If 0-byte log files appear after rotation, it is usually related to settings such as ifempty and delaycompress. You can use the script below to move 0-byte log files into a separate directory.

Create the script directory

mkdir /usr/local/mongodb/script/
cd /usr/local/mongodb/script/

Write the cleanup script

cat > move_empty_logs.sh << 'EOF'
#!/bin/bash
SOURCE_DIR="/data/logs/mongodb/"
DEST_DIR="/data/logs/mongodb/old-log-0"
MAX_DAYS=180

log_info() {
    echo "$(date +"%Y-%m-%d %H:%M:%S") INFO: $1"
}

log_error() {
    echo "$(date +"%Y-%m-%d %H:%M:%S") ERROR: $1"
}

move_empty_logs() {
    [[ ! -d "$DEST_DIR" ]] && mkdir -p "$DEST_DIR"
    log_info "Start moving 0-byte log files to $DEST_DIR"
    find "$SOURCE_DIR" -type f -name "mongodb.log.*" -size 0 -print0 | while IFS= read -r -d '' file; do
        local filename=$(basename "$file")
        log_info "Found 0-byte file: $filename, moving it to $DEST_DIR"
        mv "$file" "$DEST_DIR/$filename"
        log_info "File moved to $DEST_DIR/$filename"
    done
    log_info "Finished moving 0-byte log files."
}

cleanup_empty_logs() {
    local max_days=${1:-$MAX_DAYS}
    log_info "Start cleaning 0-byte log files, retention days: $max_days"
    find "$DEST_DIR" -type f -name "mongodb.log.*" -size 0 -mtime +$max_days -print -delete | while IFS= read -r file; do
        log_info "Deleted file: $file"
    done
    log_info "Cleanup finished."
}

move_empty_logs
cleanup_empty_logs "$1"
EOF

Set permissions and add a scheduled task

chown mongodb:mongodb -R /usr/local/mongodb/script/
chmod +x /usr/local/mongodb/script/move_empty_logs.sh
(crontab -l; echo "15 0 * * * /usr/local/mongodb/script/move_empty_logs.sh >/dev/null 2>&1") | crontab -
crontab -l

Log Rotation​

Handling 0-Byte Log Files​

Log Rotation

Handling 0-Byte Log Files