While I was working on improving how Sarah gets information from Twitter and other sources, I decided to take some of that code and hack together this example. It shows how to make three Twitter web service requests concurrently — and then wait for their results before moving on — with Akka Futures.
Before sharing the entire class, the cool Akka Futures stuff is in these lines of code:
// get an ActorSystem in scope for the futures
implicit val system = ActorSystem("TwitterFutureSystem")
// get the desired info from twitter
val dailyTrendsFuture = Future { getDailyTrends(twitter) }
val usFuture = Future { getLocationTrends(twitter, woeidUnitedStates) }
val worldFuture = Future { getLocationTrends(twitter, woeidWorld) }
// wait for all of these before moving on
val dailyTrends = Await.result(dailyTrendsFuture, 5 seconds)
val usTrends = Await.result(usFuture, 5 seconds)
val worldTrends = Await.result(worldFuture, 5 seconds)
The three "get*Trends" methods happen to return strings, but they could return other object types.
Future and Await
I think this is the right way to make three Future calls and then wait for the results, but I could be wrong. I tried to follow the example shown in the Composing Futures section of the Akka docs.
The important thing from my perspective is that all three of these calls need to work before I move on any further in my code, so I wait for each of them with the Await.result calls. Here's a quick note from the Await class Scaladoc on how the result method works:
Blocks the current Thread to wait for the given awaitable to have a result. WARNING: Blocking operation, use with caution.
@throws( classOf[Exception] )
I can confirm that the code works, and I get the desired results, which I've shown below. (It also explodes as expected when I turn off my Wi-Fi connection.)
My main "driver" class
Given that brief intro, here's my complete main driver/test class:
import twitter4j.Twitter
import akka.dispatch.{ Await, Future }
import akka.util.duration._
import akka.actor.ActorSystem
object GetTrendsWithAkka extends TwitterBase {
val propertiesFile = "/Users/al/Projects/Scala/ScalaTwitterScripts/src/twitter.properties"
val woeidWorld = 1
val woeidUnitedStates = 23424977
val emailSubject = "Twitter Trends"
def main(args : Array[String]) {
populatePropertiesFromConfigFile(propertiesFile)
val twitter = getTwitterInstance
// get an ActorSystem in scope for the futures
implicit val system = ActorSystem("TwitterFutureSystem")
// get the desired info from twitter
val dailyTrendsFuture = Future { getDailyTrends(twitter) }
val usFuture = Future { getLocationTrends(twitter, woeidUnitedStates) }
val worldFuture = Future { getLocationTrends(twitter, woeidWorld) }
// wait for all of these before moving on
val dailyTrends = Await.result(dailyTrendsFuture, 5 seconds)
val usTrends = Await.result(usFuture, 5 seconds)
val worldTrends = Await.result(worldFuture, 5 seconds)
println(buildRawStringForSarah(dailyTrends, usTrends, worldTrends))
}
def buildRawStringForSarah(dailyTrends: String, usTrends: String, worldTrends: String): String = {
return "Daily trends:\n" +
dailyTrends +
"\nU.S. trends:\n" +
usTrends +
"\nWorld trends:\n" +
worldTrends;
}
def getDailyTrends(twitter: Twitter): String = {
var sb = new StringBuilder
val dailyTrends = twitter.getDailyTrends // ResponseList[Trends]
val trends = dailyTrends.get(1)
for (trend <- trends.getTrends) {
sb.append(trend.getName + "\n")
}
sb.toString
}
def getLocationTrends(twitter: Twitter, loc: Int): String = {
var sb = new StringBuilder
val dailyTrends = twitter.getLocationTrends(loc)
val trends = dailyTrends.getTrends
for (trend <- trends) {
sb.append(trend.getName + "\n")
}
sb.toString
}
} // end object
The TwitterBase class
As you saw in the code, that class extends my TwitterBase class. (This class may not make much sense in this example, so it may be helpful to know that I use it as the base class for a series of Twitter scripts I've created for Sarah and other purposes.)
import twitter4j.conf.ConfigurationBuilder
import twitter4j.Twitter
import twitter4j.TwitterFactory
/**
* A base class to do the basic things for each script.
*/
class TwitterBase {
// twitter
var consumerKey = ""
var consumerSecret = ""
var accessToken = ""
var accessTokenSecret = ""
var twitterUsername = ""
// email
var emailSendTo = ""
var emailFrom = ""
var emailSmtpHost = ""
def getTwitterInstance: Twitter = {
val cb = new ConfigurationBuilder()
cb.setDebugEnabled(true)
.setOAuthConsumerKey(consumerKey)
.setOAuthConsumerSecret(consumerSecret)
.setOAuthAccessToken(accessToken)
.setOAuthAccessTokenSecret(accessTokenSecret)
return new TwitterFactory(cb.build()).getInstance
}
def populatePropertiesFromConfigFile(propertiesFilename: String) {
val properties = Utils.loadPropertiesFile(propertiesFilename)
consumerKey = properties.getProperty("oauth.consumerKey")
consumerSecret = properties.getProperty("oauth.consumerSecret")
accessToken = properties.getProperty("oauth.accessToken")
accessTokenSecret = properties.getProperty("oauth.accessTokenSecret")
twitterUsername = properties.getProperty("twitter_username")
emailSendTo = properties.getProperty("email_send_to")
emailFrom = properties.getProperty("email_from")
emailSmtpHost = properties.getProperty("email_smtp_host")
}
}
The twitter.properties file
As you also saw, this code relies on a properties file. Here's my Twitter.properties file, without my secret Twitter keys. (Sorry, you have to get your own keys.)
debug=true oauth.consumerKey=KEY1 oauth.consumerSecret=KEY2 oauth.accessToken=KEY3 oauth.accessTokenSecret=KEY4 twitter_username=YOUR_USERNAME
Necessary libraries
You'll also need the Twitter4J and Akka libraries to make this work:
If putting all of that together is too much trouble, just leave a note in the Comments section below, and I can be a little less lazy and put a zip file out here, or create a Gist. (Reminder: You'll still need your own Twitter developer account to make this work.)
The output
When I ran this code late on Monday, June 25, 2012, the printed output looked like this:
Daily trends: #WhatReallyTurnsMeOn #SolteraOtraVez Lion King #FavouriteMovieQuotes Mufasa HBO Family Guy Cristina Simba Hakuna Matata Scar Teresa Project X Magic Mike Pânico Motoqueiro Fantasma Silvio Santos Puerto Rico Fantino Ice Age U.S. trends: #SingleLadies #RememberTheTime Lisa Raye #WWE Love & Hip Hop Kane Stevie J. Daniel Bryan Let It Shine Tiny World trends: #Raw Stevie J Single Ladies #LHHATL Joseline #RememberTheTime Mimi Mean Girls Lisa Raye Love & Hip Hop
Again, I think this is the right approach, though I'm not 100% positive (I'm sure I'll find out as I experiment more with Sarah). If you're new to Scala, concurrency, and Akka Futures, I also hope it's helpful.
books by alvin
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