Introduction to Finagle

class: center, middle

# Introduction to Finagle

<h2 class="title-title"><a href="https://twitter.com/travisbrown">@travisbrown</a><br/><span class="title-org">Twitter, Inc.</span>
</h2>
<h2 class="title-venue"><span>BASE</span>, September 2015</h2>

---

layout: true

<div class="footer">
  <div class="footer-title">
    <h1><span class="blue">Introduction to Finagle</span> | <a href="https://twitter.com/travisbrown">@travisbrown</a></h1>
  </div>
</div>

---

.left-column[
  ## Intro
]
.right-column[
### What is Finagle?

From the [Finagle guide](https://twitter.github.io/finagle/):

> Finagle is an extensible <hi class="blue">remote procedure call</hi> system for the JVM, used to construct high-concurrency servers. Finagle implements <hi class="blue">uniform client and server APIs</hi> for several protocols, and is designed for high performance and concurrency. Most of Finagle's code is <hi class="blue">protocol agnostic</hi>, simplifying the implementation of new protocols.

]

---

.left-column[
  ## Intro
]
.right-column[
### What is Finagle?

From the [Finagle guide](https://twitter.github.io/finagle/):

"several" protocols is modest:

* [Thrift](https://github.com/twitter/finagle/tree/develop/finagle-thriftmux) and [Protobuf](https://github.com/finagle/finagle-protobuf)
* [HTTP](https://github.com/twitter/finagle/tree/develop/finagle-httpx) and [WebSocket](https://github.com/finagle/finagle-websocket)
* Database clients: [MySQL](https://github.com/twitter/finagle/tree/develop/finagle-mysql), [Postgres](https://github.com/finagle/finagle-postgres), [Redis](https://github.com/twitter/finagle/tree/develop/finagle-redis)
* [ZooKeeper](https://github.com/finagle/finagle-zookeeper), [SMTP](https://github.com/finagle/finagle-smtp), [IRC](https://github.com/finagle/finagle-irc), etc.

]

---

.left-column[
  ## Intro
  ## History
]
.right-column[

### Twitter before Finagle

]
---

.left-column[
  ## Intro
  ## History
]
.right-column[

<blockquote class="twitter-tweet" lang="en" width="550"><p lang="en" dir="ltr">.<a href="https://twitter.com/stuhood">@stuhood</a> at <a href="https://twitter.com/hashtag/SFScala?src=hash">#SFScala</a> on the "symbolic" birthday of Finagle: August 2010. <a href="http://t.co/hexSDIixf0">pic.twitter.com/hexSDIixf0</a></p>— Finagle (@finagle) <a href="https://twitter.com/finagle/status/567885703180259328">February 18, 2015</a></blockquote>

]

---

.left-column[
  ## Intro
  ## History
]
.right-column[

### Finagle at Twitter now

* Almost all services are now written in Finagle
* The "Monorail" is fully retired

<blockquote class="twitter-tweet" lang="en" width="550"><p lang="en" dir="ltr">I've decided to transition into a role heading up special projects.</p>— The Monorail (@monorail_repo) <a href="https://twitter.com/monorail_repo/status/614186349810221056">June 25, 2015</a></blockquote>

<blockquote class="twitter-tweet" lang="en" width="550"><p lang="en" dir="ltr">I have decided to transition to an advisory role.</p>— The Monorail (@monorail_repo) <a href="https://twitter.com/monorail_repo/status/643509383989694465">September 14, 2015</a></blockquote>

]

---

.left-column[
  ## Intro
  ## History
  ## Open source
]
.right-column[

### [Finagle outside of Twitter](https://github.com/twitter/finagle/blob/master/ADOPTERS.md)

* Box
* EA DICE
* Foursquare
* Nest
* The National Center for Biotechnology Information
* The New York Times
* PagerDuty
* Pinterest
* Rdio
* Sabre Labs
* SoundCloud
* SproutSocial
* StumbleUpon
* Strava
]

---

.left-column[
  ## Intro
  ## History
  ## Open source
]
.right-column[

### Finagle on GitHub

* [Twitter Util](https://github.com/twitter/util)
* [Finagle](https://github.com/twitter/finagle)
* [Finatra](https://github.com/twitter/finatra)
* [Finagle organization projects](https://github.com/finagle)

]
---

.left-column[
  ## Intro
  ## History
  ## Open source
  ## Core ideas
]
.right-column[

```scala
class Service[-Req, +Rep] extends (Req => Future[Rep])
```
]
---

.left-column[
  ## Intro
  ## History
  ## Open source
  ## Core ideas
]
.right-column[

```scala
class Service[-Req, +Rep] extends (Req => Future[Rep])
```

* [`Service`](https://twitter.github.io/finagle/docs/index.html#com.twitter.finagle.Service) is protocol and network agnostic
* A [`Server`](https://twitter.github.io/finagle/docs/index.html#com.twitter.finagle.Server) makes a `Service` available on the network

]

---

.left-column[
  ## Intro
  ## History
  ## Open source
  ## Core ideas
]
.right-column[

### Services and servers in action

```scala
import com.twitter.finagle.{ Httpx, Service }
import com.twitter.finagle.httpx._
import com.twitter.util.Future

val myHttpService: Service[Request, Response] =
  Service.mk(_ => Future(Response()))

val server = Httpx.serve(":8080", myHttpService)
```

]

---

.left-column[
  ## Intro
  ## History
  ## Open source
  ## Core ideas
]
.right-column[

### Services and clients

```scala
import com.twitter.finagle.{ Httpx, Service }
import com.twitter.finagle.httpx._
import com.twitter.util.Future

val myHttpService: Service[Request, Response] =
  Service.mk(_ => Future(Response()))

val server = Httpx.serve(":8080", myHttpService)
```

Clients _are_ services

```scala
val myHttpClient: Service[Request, Response] =
  Httpx.newService("meta.plasm.us:80")
```

]
---

.left-column[
  ## Intro
  ## History
  ## Open source
  ## Core ideas
]
.right-column[

### Services and clients

```scala
import com.twitter.finagle.{ Httpx, Service }
import com.twitter.finagle.httpx._
import com.twitter.util.Future

val myHttpService: Service[Request, Response] =
  Service.mk(_ => Future(Response()))

val server = Httpx.serve(":8080", myHttpService)
```

Clients _are_ services

```scala
val myHttpClient: Service[Request, Response] =
  Httpx.newService("meta.plasm.us:80")

val proxy = Httpx.serve(":8080", myHttpClient)
```

This is a functioning HTTP proxy:

```bash
wget --header="Host: meta.plasm.us" \
  http://localhost:8080/posts/2015/07/11/roll-your-own-scala/
```

]

---

.left-column[
  ## Intro
  ## History
  ## Open source
  ## Core ideas
]
.right-column[

### The second core idea: filters

```scala
class Filter[-ReqIn, +RepOut, +ReqOut, -RepIn]
  extends (ReqIn, Service[ReqOut, RepIn]) => Future[RepOut]
```

Filters wrap services to modify inputs or outputs (or both)

]
---

.left-column[
  ## Intro
  ## History
  ## Open source
  ## Core ideas
]
.right-column[

### The second core idea: filters

```scala
class Filter[-ReqIn, +RepOut, +ReqOut, -RepIn]
  extends (ReqIn, Service[ReqOut, RepIn]) => Future[RepOut]
```

Filters wrap services to modify inputs or outputs (or both)

### What filters can do

* Retries
* Logging
* Serialization
* Authentication
* Retries
* Timeouts
* etc.

]
---
.left-column[
  ## Intro
  ## History
  ## Open source
  ## Core ideas
]
.right-column[

### Creating a timeout filter

```scala
import com.twitter.conversions.time._
import com.twitter.finagle.util.DefaultTimer
import com.twitter.finagle.service.TimeoutFilter

val myTimeoutFilter = new TimeoutFilter[String, Int](
  1.second,
  DefaultTimer.twitter
)
```
]

---
.left-column[
  ## Intro
  ## History
  ## Open source
  ## Core ideas
]
.right-column[

### Creating a timeout filter

```scala
import com.twitter.conversions.time._
import com.twitter.finagle.util.DefaultTimer
import com.twitter.finagle.service.TimeoutFilter

val myTimeoutFilter = new TimeoutFilter[String, Int](
  1.second,
  DefaultTimer.twitter
)
```

### Using our filter

```scala
import com.twitter.util.FuturePool

val slowParserService = new Service[String, Int] {
  def apply(request: String) = FuturePool.unboundedPool {
    Thread.sleep(5000); request.toInt
  }
}

val myService = myTimeoutFilter andThen slowParserService
```
]
---

.left-column[
  ## Intro
  ## History
  ## Open source
  ## Core ideas
]
.right-column[

### Why filters?

* The abstraction is protocol and network agnostic
* Generic filters can be used across our (your) stack
* We provide a lot of useful ones for you
* Clean, declarative composition:

```scala
recordHandletime     andThen
traceRequest         andThen
collectJvmStats      andThen
parseRequest         andThen
logRequest           andThen
recordClientStats    andThen
sanitize             andThen
respondToHealthCheck andThen
applyTrafficControl  andThen
virtualHostServer
```

]
---

.left-column[
  ## Intro
  ## History
  ## Open source
  ## Core ideas
  ## Two futures
]
.right-column[

### Two futures

```scala
import scala.concurrent.{ Future => FutureS }
import scala.concurrent.ExecutionContext.Implicits.global

val foo = FutureS { Thread.sleep(5000); "foo" }
```
]

---

.left-column[
  ## Intro
  ## History
  ## Open source
  ## Core ideas
  ## Two futures
]
.right-column[

### Two futures

```scala
import scala.concurrent.{ Future => FutureS }
import scala.concurrent.ExecutionContext.Implicits.global

val foo = FutureS { Thread.sleep(5000); "foo" }
```

No implicit execution context:

```scala
import com.twitter.util.Future

val bar = Future { Thread.sleep(5000); "bar" }
```
]

---

.left-column[
  ## Intro
  ## History
  ## Open source
  ## Core ideas
  ## Two futures
]
.right-column[

### Two futures

```scala
import scala.concurrent.{ Future => FutureS }
import scala.concurrent.ExecutionContext.Implicits.global

val foo = FutureS { Thread.sleep(5000); "foo" }
```

No implicit execution context:

```scala
import com.twitter.util.{ Future, FuturePool }

val bar = Future { Thread.sleep(5000); "bar" }

val pool = FuturePool.unboundedPool
val baz: Future[String] = pool { Thread.sleep(5000); "baz" }
```
]

---

.left-column[
  ## Intro
  ## History
  ## Open source
  ## Core ideas
  ## Two futures
]
.right-column[

### More about futures

Where does this operation run?

```scala
val f = pool(0).map(expensiveOperation)
```

]
---

.left-column[
  ## Intro
  ## History
  ## Open source
  ## Core ideas
  ## Two futures
]
.right-column[

### More about futures

Where does this operation run?

```scala
val f = pool(0).map(expensiveOperation)
```

* It's undefined: the API doesn't specify
* Use future pools when you need control
* In general you let the scheduler decide

]

---

.left-column[
  ## Intro
  ## History
  ## Open source
  ## Core ideas
  ## Two futures
]
.right-column[

### Why two futures?

* History: developed in parallel
* Inspiration in both directions
* Differences:
  * Our scheduler better at avoiding context switches
  * Cancellability
  * `ThreadLocal`-like variables via `Local`

]

---

.left-column[
  ## Intro
  ## History
  ## Open source
  ## Core ideas
  ## Two futures
]
.right-column[
### Future convergence?

* We may adopt `scala.util.Try`
* `Future` is much trickier, convergence is unlikely
* Officially supported converters in [Bijection](https://github.com/twitter/bijection)
* Many Finagle adopters happily use both

]

---
.left-column[
  ## Intro
  ## History
  ## Open source
  ## Core ideas
  ## Two futures
  ## Starting points
]
.right-column[

### [Finatra](https://github.com/twitter/finatra)

* v2.0 recently released
* Huge performance improvements over v1.6
* Battle-tested in production at Twitter

### [Finch](https://github.com/finagle/finch)

* Small FP-flavored toolkit for building web services
* Generic derivation, other functionality via [Shapeless](https://meta.plasm.us/slides/finagle/finch-and-shapeless/)

### [Finagle Serial](https://github.com/finagle/finagle-serial)

* Simple binary services without IDLs
* Serialization via [scodec](http://scodec.org/)
* Turn arbitrary functions into serve-able services
* Supports multiplexing via [Mux](http://twitter.github.io/finagle/guide/Protocols.html)

]

---
.left-column[
  ## Intro
  ## History
  ## Open source
  ## Core ideas
  ## Two futures
  ## Starting points
  ## The future
]
.right-column[

### The future

* [FinagleCon](https://finagle.github.io/finaglecon/) videos will be up any day
* Netty 4 is [coming soon](https://twitter.com/finagle/status/648576503832297472)
* Scala 2.12 builds aren't too far off
* Constantly ongoing performance improvements

### Adoption and contributing

* Get in touch on [the Finaglers mailing list](https://groups.google.com/forum/#!forum/finaglers)
* We're looking for [Finagle org](https://github.com/finagle) project co-owners
* [Finatra](https://github.com/twitter/finatra) and [Finch](https://github.com/finagle/finch) are very active
* Finagle more slow-moving, but there's lots to do
]

---
.left-column[
  ## Intro
  ## History
  ## Open source
  ## Core ideas
  ## Two futures
  ## Starting points
  ## The future
  ## Resources
]
.right-column[

### Resources

* [Finagle on GitHub](https://github.com/twitter/finagle)
* [Finagle on Twitter](https://twitter.com/finagle)
* [Finagle on Gitter](https://gitter.im/twitter/finagle)
* [The Finagle blog](https://finagle.github.io/blog/)
* [The Finagle organization](https://github.com/finagle)
* [The Finaglers mailing list](https://groups.google.com/forum/#!forum/finaglers)

### Thanks!
]