monitor provides basic runtime monitoring for Go programs. It is based on monitor.py, a Python module originally written to ensure a Bitcoin broker continued running even in the face of unanticipated exceptions.

The monitor.Monitor function takes a target function with the signature:

func target() error {}

It is assumed the target function will use configuration files, os.Args, environment variables, or some other mechanism to configure itself.

When the target function returns, monitor checks whether an error has occurred and whether a panic has occurred, and sends a notification in either case. If the function exits with no errors and hasn't panicked, monitor assumes the program exits normally. This behaviour may be changed by modifying the CanExit value in the package:

monitor.CanExit = false     // disable exit on clean return
monitor.CanExit = true      // enable exit on clean return

func target() {
        // self-contained main program code
}

func main() {
        monitor.Monitor(target)
}

monitor supports Pushover and email notifications. To enable either, you can load the configuration from a JSON file:

{"mail": 
    {"port": "<smtp-port>",
     "pass": "<smtp-password>", 
     "user": "<smtp-user>", 
     "address": "<from-address>", 
     "server": "<smtp-server>",
     "to": ["<dev@yourdomain.tld>, <otherdev@theirdomain.tld>"]}, 
 "pushover": 
    {"token": "<api-key>", 
     "user": "<user-key>"}}

You may include only one of the two sections to enable that type of notifications. By default, monitor looks for monitor.json in the same directory as the code is being run from.

        err := monitor.ConfigFromJson()
        if err != nil {
                fmt.Println("[!] error configuring monitor: ", err)
                os.Exit(1)
        }
        monitor.Monitor(target)

The configuration file can be set with the variable ConfigFile:

monitor.ConfigFile = "secret.json"

Alternatively, you can load the configuration from the environment. The environment variables support are:

• MAIL_SERVER
• MAIL_USER
• MAIL_PASS
• MAIL_ADDRESS
• MAIL_PORT
• MAIL_TO - this should be a comma separated list of address to email when notifications go out. For example, "dev1@example.com,dev2@example.com".
• PO_APIKEY
• PO_USER

To load the configuration, call ConfigFromEnv:

        monitor.ConfigFromEnv() 

        // check whether the notifications we expect to be enabled were enabled
        if monitor.PushoverEnabled() {
                log.Println("[!] pushover notifications not enabled!")
        }

        if monitor.EmailEnabled() {
                log.Println("[!] email notifications not enabled!")
        }