Reactive Scala Driver for MongoDB

Asynchronous & Non-Blocking

Failover Strategy

A FailoverStrategy defines if and how many times ReactiveMongo should retry the operations (DB resolution, query, insertion, command, etc.) that could fail for the following reasons.

The other causes (business errors, normal database errors, fatal errors, etc.) are not handled.

The default FailoverStrategy retries 5 times, with 500 ms between each attempt.

Let’s say that we want to define a FailoverStrategy that waits more time before a new attempt.

import scala.concurrent.duration._

import reactivemongo.api.FailoverStrategy

val strategy =
  FailoverStrategy(
    initialDelay = 500 milliseconds,
    retries = 5,
    delayFactor =
      attemptNumber => 1 + attemptNumber * 0.5
  )

This strategy retries at most 5 times, waiting for initialDelay * ( 1 + attemptNumber * 0.5 ) between each attempt (attemptNumber starting from 1). Here is the way the attempts will be run:

You can specify a strategy by giving it as a parameter to connection.database or database.collection:

import scala.concurrent.duration._
import scala.concurrent.ExecutionContext.Implicits.global

import reactivemongo.api.FailoverStrategy

val defaultStrategy = FailoverStrategy()

val customStrategy =
  FailoverStrategy(
    initialDelay = 500 milliseconds,
    retries = 5,
    delayFactor =
      attemptNumber => 1 + attemptNumber * 0.5
  )

def connection1: reactivemongo.api.MongoConnection = ???

// database-wide strategy
val db1 = connection1.db("dbname", customStrategy)

// collection-wide strategy
val db2 = connection1.db("dbname", defaultStrategy)
val collection = db2.collection("collname", customStrategy)