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Add SMTP email alerting channel (#42)
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,161 @@ | ||
| package alert | ||
|
|
||
| import ( | ||
| "context" | ||
| "crypto/tls" | ||
| "io" | ||
| "net" | ||
| "net/smtp" | ||
| "time" | ||
|
|
||
| "github.com/pkg/errors" | ||
| ) | ||
|
|
||
| var ( | ||
| _ Channel = (*SmtpChannel)(nil) | ||
| ) | ||
|
|
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| type SmtpConfig struct { | ||
| Host string // SMTP endpoint and port | ||
| From string // Sender address | ||
| To []string // Receipt addresses | ||
| Password string // SMTP password | ||
| } | ||
|
|
||
| // SmtpChannel represents a SMTP email notification channel | ||
| type SmtpChannel struct { | ||
| Formatter Formatter // Formatter is used to format the notification message | ||
| ID string // ID is the identifier of the channel | ||
| Config SmtpConfig // Config contains the configuration for the SMTP server | ||
| } | ||
|
|
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| // NewSmtpChannel creates a new SMTP channel with the given ID, formatter, and configuration | ||
| func NewSmtpChannel(chID string, fmtter Formatter, conf SmtpConfig) *SmtpChannel { | ||
| return &SmtpChannel{ID: chID, Formatter: fmtter, Config: conf} | ||
| } | ||
|
|
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| // Name returns the ID of the channel | ||
| func (c *SmtpChannel) Name() string { | ||
| return c.ID | ||
| } | ||
|
|
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| // Type returns the type of the channel, which is SMTP | ||
| func (c *SmtpChannel) Type() ChannelType { | ||
| return ChannelTypeSMTP | ||
| } | ||
|
|
||
| // Send sends a notification using the SMTP channel | ||
| func (c *SmtpChannel) Send(ctx context.Context, note *Notification) error { | ||
| // Format the notification message | ||
| msg, err := c.Formatter.Format(note) | ||
| if err != nil { | ||
| return errors.WithMessage(err, "failed to format alert msg") | ||
| } | ||
| // Send the formatted message | ||
| return c.send(ctx, msg) | ||
| } | ||
|
|
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| // send sends a message using the SMTP channel | ||
| func (c *SmtpChannel) send(ctx context.Context, msg string) error { | ||
| // Dial the SMTP server | ||
| client, err := c.dial(ctx) | ||
| if err != nil { | ||
| return errors.WithMessage(err, "failed to dial smtp server") | ||
| } | ||
|
|
||
| // Close the client when done | ||
| defer client.Close() | ||
|
|
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| // Authenticate with the SMTP server if it supports authentication | ||
| if ok, _ := client.Extension("AUTH"); ok { | ||
| auth := smtp.PlainAuth("", c.Config.From, c.Config.Password, c.Config.Host) | ||
| if err := c.doWithDeadlineCheck(ctx, func() error { return client.Auth(auth) }); err != nil { | ||
| return errors.WithMessage(err, "failed to authenticate smtp server") | ||
| } | ||
| } | ||
|
|
||
| // Set the sender | ||
| if err := c.doWithDeadlineCheck(ctx, func() error { return client.Mail(c.Config.From) }); err != nil { | ||
| return errors.WithMessage(err, "failed to set sender") | ||
| } | ||
|
|
||
| // Add the recipients | ||
| for _, addr := range c.Config.To { | ||
| if err := c.doWithDeadlineCheck(ctx, func() error { return client.Rcpt(addr) }); err != nil { | ||
| return errors.WithMessagef(err, "failed to add recipient %s", addr) | ||
| } | ||
| } | ||
|
|
||
| // Write the message | ||
| var w io.WriteCloser | ||
| if err := c.doWithDeadlineCheck(ctx, func() error { w, err = client.Data(); return err }); err != nil { | ||
| return errors.WithMessage(err, "failed to open data writer") | ||
| } | ||
|
|
||
| if err := c.doWithDeadlineCheck(ctx, func() error { _, err = w.Write([]byte(msg)); return err }); err != nil { | ||
| return errors.WithMessage(err, "failed to write data") | ||
| } | ||
|
|
||
| // Close the writer | ||
| if err := w.Close(); err != nil { | ||
| return errors.WithMessage(err, "failed to close data writer") | ||
| } | ||
|
|
||
| // Quit the SMTP session | ||
| if err := c.doWithDeadlineCheck(ctx, func() error { return client.Quit() }); err != nil { | ||
| return errors.WithMessage(err, "failed to quit smtp session") | ||
| } | ||
|
|
||
| return nil | ||
| } | ||
|
|
||
| // doWithDeadlineCheck checks if the deadline has been exceeded before performing an operation | ||
| func (c *SmtpChannel) doWithDeadlineCheck(ctx context.Context, op func() error) error { | ||
| if deadlineExceeded(ctx) { | ||
| return context.DeadlineExceeded | ||
| } | ||
|
|
||
| if err := op(); err != nil { | ||
| return err | ||
| } | ||
|
|
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| return nil | ||
| } | ||
|
|
||
| // deadlineExceeded checks if the deadline of the context has been exceeded | ||
| func deadlineExceeded(ctx context.Context) bool { | ||
| if _, ok := ctx.Deadline(); ok { | ||
| select { | ||
| case <-ctx.Done(): | ||
| return true | ||
| default: | ||
| } | ||
| } | ||
| return false | ||
| } | ||
|
|
||
| // dial dials the SMTP server and returns a new SMTP client | ||
| func (c *SmtpChannel) dial(ctx context.Context) (*smtp.Client, error) { | ||
| var dialer *net.Dialer | ||
|
|
||
| // Check if a deadline has been set | ||
| deadline, ok := ctx.Deadline() | ||
| if ok { // deadline set? | ||
| timeout := time.Until(deadline) | ||
| if timeout < 0 { // timeout exceeded | ||
| return nil, context.DeadlineExceeded | ||
| } | ||
| dialer = &net.Dialer{Timeout: timeout} | ||
| } else { | ||
| dialer = new(net.Dialer) | ||
| } | ||
|
|
||
| // Dial the SMTP server | ||
| conn, err := tls.DialWithDialer(dialer, "tcp", c.Config.Host, nil) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
|
||
| // Create a new SMTP client | ||
| return smtp.NewClient(conn, c.Config.Host) | ||
| } |
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