Attempt to send email should be retried if it fails

[dbseraf1]

Currently, if sending email fails because the email server is temporarily offline or overloaded, the only choice of action is to rerun the whole validation. This can be very expensive, and may require manual intervention if the program is running as part of an automatic workflow.

It would be better if the program detected the error in sending email and did its own wait-and-retry loop. This would be pretty cheap and much better than failing.

[colindean]

Great suggestion.

Quick notes for myself or whoever may pick this up:

• https://index.scala-lang.org/softwaremill/retry/retry/0.3.3?target=_2.11
• https://index.scala-lang.org/hipjim/scala-retry/scala-retry/0.2.4?target=_2.11

Add config for the retry here:

data-validator/src/main/scala/com/target/data_validator/Emailer.scala

Lines 11 to 18 in c17ec6a

	case class EmailConfig(
	smtpHost: String,
	subject: String,
	from: String,
	to: List[String],
	cc: Option[List[String]] = None,
	bcc: Option[List[String]] = None
	) extends EventLog with Substitutable {

Consume the config and handle the retry here:

data-validator/src/main/scala/com/target/data_validator/Emailer.scala

Lines 109 to 126 in c17ec6a

	def sendMessage(message: Message, body: String, mime: String): Boolean = {
	message.setContent(body, mime)
	val id = message.hashCode().toHexString
	try {
	logger.info(s"Sending email #$id [${message.getSubject}] to [${message.getAllRecipients.mkString(", ")}]")
	Transport.send(message)
	logger.info(s"Email #$id sent successfully to all recipients.")
	false
	}
	catch {
	case sfe: SendFailedException =>
	handleSendFailedException(id, sfe)
	true
	case me: MessagingException =>
	logger.error(s"Failure to send email #$id: $me")
	true
	}
	}

And document it in README.md here:

data-validator/README.md

Lines 74 to 83 in c17ec6a

	#### Email Config
	| Variable | Type | Required | Description |
	|:---|:---|:---|:---:
	| `smtpHost` | String | Yes | The smtp host to send email message through.
	| `subject` | String | Yes | Subject for email message.
	| `from` | String | Yes | Email address to appear in from part of message.
	| `to` | Array[String] | Yes | Must specify at least one email address to send the email report to.
	| `cc` | Array[String] | No | Optional list of email addresses to send message to via `cc` field in message.
	| `bcc` | Array[String] | No | Optional list of email addresses to send message to via `bcc` field in message.

[dougb]

@dbseraf1 You can save the output to a file or hdfs so you don't lose the results of the run if it fails to send the email.

If you can't wait for this issue to be resolved, you could also use the Pipe output option to specify a program to run which can read the jsonReport from stdin and send an email.