Let's be real, who's regularly browsing through megabytes of log files? Wouldn't it be nice, if important messages were delivered to you in time, and the log files just served the purpose of holding the details?
This package offers extended functionality for the zap logger, with the purpose of handling (some) log messages via (optionally signed and/or encrypted) SMTP mails.
We use this package to notice critical issues fast, so we can roll out a fix, before the user pushes the same buttons again. Yes, yes, alternatively, you can expand the turbine stack of your production environment by deploying, configuring and maintaining additional log management software.
As Golang only supports plain text SMTP mails natively, OpenSSL has to be installed if encryption and/or signature is
to be enabled. Other than that a simple go get is sufficient.
Because sending out a new mail for every single log message is not desirable in most cases, it is recommended to use
some kind of buffered Core. For this the delayedCore provided in this package can be used.
func Exmaple() {
// Prepare SMTP sink
sink, errSink := smtp.NewWriteSyncCloser(
conf.Server,
conf.Port,
conf.Subject,
conf.Sender, // mail.Address structs for the sender
conf.Recipients, // mail.Address structs for each recipient
conf.OpensslPath, // Can be omitted, if no e-mail signature nor encryption is desired
conf.SignatureCertPath, // Can be omitted, if no e-mail signature is desired
conf.SignatureKeyPath, // Can be omitted, if no e-mail signature is desired
conf.EncryptionCertPaths, // Can be omitted, if no e-mail encryption is desired
conf.TempDir, // If empty, the system's temporary directory will be used if needed
)
if errSink != nil {
fmt.Printf("Initializing SMTP sink failed: %s\n", errSink)
return
}
// Make sure logger is closed properly
defer func() {
if errClose := sink.Close(); errClose != nil {
fmt.Printf("Closing SMTP sink failed: %s\n", errClose)
}
}()
// Define the encoder
enc := zapcore.NewConsoleEncoder(zap.NewDevelopmentEncoderConfig())
// Initialize SMTP core
core, errCore := cores.NewDelayedCore(zapcore.WarnLevel, enc, sink, zapcore.ErrorLevel, time.Minute*1, time.Second*5)
if errCore != nil {
fmt.Printf("Initializing SMTP core failed: %s\n", errCore)
return
}
// Initialize Zap logger
logger := zap.New(core)
// Make sure logger is flushed before shutting down
defer func() { _ = logger.Sync() }()
// Log stuff
logger.Warn("Warn message, triggering email after 1 minute")
logger.Error("Error message, triggering email after 5 seconds") // Email sent after 5 seconds will include warning
}Note that even though the writeSyncCloser satisfies zap's Sink interface it is not recommended using it with
RegisterSink as this way only standard ioCores can be used.
Another example can be found in ./examples.
You can also visit Large-Scale Discovery to see it applied.
- When possible the
writeSyncClosershould be preferred over thewriteSyncer, as it will convert files only once and keep a reference to the resulting files untilCloseis called. - As encrypting and signing mails via OpenSSL is slow it is recommended to not log too frequently. This depends heavily on your use case though.
- Email signature and encryption needs certificate and key files in PEM format. The
writeSyncer(andwriteSyncCloser) also allows for DER format and will convert them internally. It's advised though to use PEM format if possible.