path /var/log/apache2/access.log # Set the location of your log file
count_interval 3 # The time window for counting errors (in secs)
input_key code # The field to apply the regular expression
regexp ^5\d\d$ # The regular expression to be applied
threshold 1 # The minimum number of erros to trigger an alert
add_tag_prefix error_5xx # Generate tags like "error_5xx.apache.access"
<match error_5xx.apache.access>
@type stdout # Print to stdout for debugging
host smtp.gmail.com # Change this to your SMTP server host
port 587 # Normally 25/587/465 are used for submission
user USERNAME # Use your username to log in
password PASSWORD # Use your login password
enable_starttls_auto true # Use this option to enable STARTTLS
subject 'HTTP SERVER ERROR'
message Total 5xx error count: %s\n\nPlease check your Apache webserver ASAP
message_out_keys count # Use the "count" field to replace "%s" above