Using GMail with a Log4j SMTP Appender in Grails

I saw a plaintive wail on Twitter about using GMail as the smtp server to send error emails using a Log4j SMTPAppender in Grails. It turned out to be a little tricky (and a bigger solution than 140 characters would allow) so I thought I’d describe the process here.

Most of the properties are configurable as appender attributes (e.g. server name, auth username, etc.) but two important ones aren’t. SMTPAppender creates a Properties instance with System.getProperties() as the default values and adds smtp properties to that. But you need to specify the smtp port (it will default to 25 otherwise) and you need to tell it to send a STARTTLS command. Both are configurable via system properties:

System.setProperty 'mail.smtp.port', '587'
System.setProperty 'mail.smtp.starttls.enable', 'true'

and if you add those calls to Config.groovy before the appender is instantiated then it will have the values available when it configures its JavaMail Session:

import org.apache.log4j.Level
import org.apache.log4j.net.SMTPAppender

...

mail.error.server = 'smtp.gmail.com'
mail.error.port = 587
mail.error.username = 'your.email@gmail.com'
mail.error.password = 'yourpassword'
mail.error.to = 'to@yourapp.com'
mail.error.from = 'from@yourapp.com'
mail.error.subject = '[Application Error]'
mail.error.starttls = true
mail.error.debug = false

environments {
   production {
      grails.serverURL = "http://www.changeme.com"
   }
   development {
      grails.serverURL = "http://localhost:8080/${appName}"
   }
   test {
      grails.serverURL = "http://localhost:8080/${appName}"
   }
}

log4j = {

   System.setProperty 'mail.smtp.port', mail.error.port.toString()
   System.setProperty 'mail.smtp.starttls.enable', mail.error.starttls.toString()

   appenders {

      appender new SMTPAppender(name: 'smtp', to: mail.error.to, from: mail.error.from,
         subject: mail.error.subject, threshold: Level.ERROR,
         SMTPHost: mail.error.server, SMTPUsername: mail.error.username,
         SMTPDebug: mail.error.debug.toString(), SMTPPassword: mail.error.password,
         layout: pattern(conversionPattern:
            '%d{[ dd.MM.yyyy HH:mm:ss.SSS]} [%t] %n%-5p %n%c %n%C %n %x %n %m%n'))
   }

   error  'org.codehaus.groovy.grails.web.servlet',  //  controllers
          'org.codehaus.groovy.grails.web.pages', //  GSP
          'org.codehaus.groovy.grails.web.sitemesh', //  layouts
          'org.codehaus.groovy.grails.web.mapping.filter', // URL mapping
          'org.codehaus.groovy.grails.web.mapping', // URL mapping
          'org.codehaus.groovy.grails.commons', // core / classloading
          'org.codehaus.groovy.grails.plugins', // plugins
          'org.codehaus.groovy.grails.orm.hibernate', // hibernate integration
          'org.springframework',
          'org.hibernate',
          'net.sf.ehcache.hibernate'
   warn   'org.mortbay.log'

   root {
      error 'stdout', 'smtp'
      additivity = true
   }
}

I’ve parameterized the properties to make them configurable for each environment or using an external configuration file.

Note that GMail has a limit of 500 emails per day, so if you generate a lot of errors in your app you could hit that limit.

I saw a plaintive wail on Twitter about using GMail as the smtp server to send error emails using a Log4j SMTPAppender in Grails. It turned out to be a...