RailsConf 2014 - Rails as an SOA Client by Pete Hodgson

PETE HODGSON: OK. So, thanks for coming.

Today I'm talking about Rails as an SOA client.

So, in the beginning, there was a Rails application.

And in the beginning, most of these Rails
applications

were pretty straight-forward.

Pretty simple things. They were normally

just talking to a single database.

And this is how most of our Rails applications
start.

They're green fields, and we're talking to

a single database.

Quite often, we, or pretty soon, particularly
now days,

we start talking to services. These might
be external

services like Twillo or Twitter, or they might
be

internal services that we're using as part
of doing

our job in a, in a more enterprise-y situation.

And as time has gone on, we've noticed, or

I've noticed, that our Rails applications
are depending more

and more on services. So, I think there's
kind

of two big forces in play here. Force number

one is, as time has grown and as Rails

has matured and our community's matured, our
Rails applications

have been kind of growing into these big monoliths,

mono Rails, these big, bloated applications,
and now there's

this kind of movement, quite a widespread
movement, meant

to break up our large, monolithic Rails apps
into,

into services and, obviously, something needs
to talk to

those services. And normally that is a Rails
app

fronting those services.

The second big force is, Rails applications,
which I

think started off mainly being used by start
ups,

have moved more and more into enterprise-y
places where

there are a lot, lot, lot of services. And

in these enterprise contexts, Rails apps are
normally talking

to a lot of services to get their job

done.

And this is, even goes to the extreme where

we have Rails app that don't actually have
any

local data storage at all, are not doing any

kind of persistence. All they're doing is,
is interacting

with services to do all of their work.

So, I, I built an application like this fairly

recently, and I'm gonna talk to you guys about

what we built, some of the techniques we used

to be successful in building these kind of
services

only application. Yup. So that's, that's gonna
be the

talk today.

My name is Pete. I work for this consulting

company called ThoughtWorks. So, we work with
clients to

help them build software and get better at
building

software. I've been with ThoughtWorks for
about four years.

As you can tell from my accent, I'm in

the San Francisco office.

I really am in the San Francisco office. And

I, I, in my time in ThoughtWorks, I've done

a lot of different things. I've done a fair

amount of Ruby and Rails, but I've also done

some Scala, some JavaScript, some, some iOS.
And I've

also worked in a lot of different contexts,
organizations.

So I've worked in really small start ups all

the way through to huge, lumbering banks.

And, one of the things that I love about

ThoughtWorks is I get to move in all these

different places. And one of the things that
I

think ThoughtWorks brings to its clients is
ideas from

one place applied in a different place. So,
what

we find ourselves doing a lot is taking ideas

from the Rails community and introducing them
to the

Scala community. Or taking ideas from mobile
applications and

introducing them to our client-side JavaScript
applications.

And, indeed, taking ideas from start ups and
taking

them to the enterprise. And so, shockingly
enough, vice

versa. So, that's part of what I'm gonna be

talking about today is, there's this subtext
of kind

of taking ideas from other communities that
are successful

and bringing them into the Rails community.

And so this is gonna be a kind of

a talk in two parts. The first part I'm

gonna talk about some kind of more hand wave-y,

how do we live in this ecosystem environment.
And

some tools and techniques that can help with
that,

particularly in the context of Rails. And
then I'm

gonna dive into some more kind of nitty gritty

kind of, how do we actually build these things

into our Rails applications?

So, first off. Co-dependence versus independence.
So, as I

said, I worked for a client. We were building

a large, we were building, actually, a pretty
small

Rails application in front of a very large
set

of services. We were building an online store
for,

for a large book retailer. They were going
to

a new market, and they didn't want to have

to keep working in Java. So they were taking

this as an opportunity to build a green-filled
Rails

app for a new market, which was still gonna

be using all of their existing services, which
were

implemented in a variety of languages.

So this is what the home page of this

application kind of looked like. There was
this kind

of list of all the products and prices and

descriptions and all that kind of stuff. And
then

across the top we had these kind of deals

of the day.

And the way that this worked was, was interesting

or, I, I suppose is, is interesting if you

haven't worked in like a large enterprise
like this.

But the information to power this page was
coming

from a lot of different places. And our Rails

app was really just responsible for stitching
that information

together. So, we had the product service that
was

kind of serving up product catalog data, and
then

we had the deals service that was kind of

telling us what the deals of the day were.

And, as I said, the Rails app was just

kind of there to kind of, go over here

and get some information. Go over here and
get

some information, and then kind of plug it
all

together. So when you're building an app like
this,

you get this interesting phenomenon, where
this app, on

its own, really can't do much at all. In

fact, it can't do anything. We, there wasn't,
there

was probably not a single page of this app

that would render if those services weren't
there.

So, what, this is what I mean by co-dependence.

This application was incredibly co-dependent
on the ecosystem of

services that it lived inside of. But ideally
we

don't want to be co-dependent, because we
want to

be able to run this thing in isolation, to

test it in isolation, to debug it in isolation.

So, we don't want to have to stand up

the entire enterprise on our laptops just
in order

to, to run this thing when we're, when we're

on a train or in a plane. So, we

want independence, but we're in a situation
of co-dependence.

And this gets even more interesting when you
start

thinking about it in terms of teams. So, in

our case, we had our team, let's call us

the red team. We're building the Rails application.
But

we weren't building any of these services.
The deals

services might have been maintained by the
green team

and the blue team, of course, were working
on

the product service.

And these teams were teams we sometimes, we
didn't

even know where they, where they were. We
had

vague ways of getting in contact with them,
but

we, we didn't have a very good relationship
with

them. And this leads to lots of interesting
side-effects.

So one thing that you might note here is

the shape of the teams. Lines up pretty closely

with the shape of the services. So this gets

to this thing called Conway's Law. Don't tell
DHH

that I'm talking about laws.

Conway's Law, coined in the 60s, says that
the

communication patterns of a software system
tend to mirror

the communication patterns of the people who
build that

system. How many people have heard of Conway's
Law,

by the way?

So, I'm trying to avoid calling it a law

but I'm not going to be able to do

that. I think Conway's Law is the most important

law for us to understand as software engineers.
Oh,

I said. As people. As software writers. Sorry.

Conway's Law says that how people work together
effects

system architecture. And, and the flip-side.
System architecture effects

how people work together. And, this isn't
kind of

a, a possible outcome. This is reality. This
is

empirically shown for fifty years, sixty years
almost. This

does happen. This is true.

So you can't, like, decide you don't want
it

to happen. But what you can do is you

can either wield Conway's Law to your advantage,
go

with the grain and, and use it to your

advantage, or you can kind of yield to Conway's

Law and have it beat you up.

So I'm gonna talk a little bit today about

how we wielded Conway's Law to our advantage
rather

than have it beat us up.

So, here's our three teams. One of the most

fun aspects of, of working in a system that

has more than one team is, is when you

find a bug. So let's say we've got our

deal, deals of the day section, and we've
noticed

that the prices are missing in some of the

deals section when we run the application.
So now

we start to play this game, it's called Who's

Bug is it Anyway?

Hands up if you've played this game. Awesome.
OK.

I wasn't sure if that was a cultural reference

that people wouldn't get. So, we know that
the

deals aren't loading correctly, but is that
the deal

service's fault? Maybe the product service
isn't returning the

right data for those deals. Maybe we're asking
it

the wrong questions. Or maybe we just have
a

bug in our rendering code.

The fundamental issue of all of these things
is

this tension between co-dependence and independence.
We are co-dependent.

We want to be independent. Some people solve
a

lot of these problems by embracing co-dependence.
So, if

our Rails app needs the services to be up

and running in order to run, we'll stand up

the services. You can do that. You can stand

up copies of the services locally on your
laptop.

This is more and more easy to do nowadays

cause we've got kind of trendy dev-ops things
like

Vagrant and Chef and Puppet.

That will only get you so far. Try standing

up a bank on your laptop. It's not happening.

Very, very common approach here is to, to
use

kind of shared services. So a shared dev environment.

A shared kind of staging environment. That
kind of

thing. And that, that works quite well. But,
for

our team, we decided to go the alternate route.

We wanted to, as much as possible, push for

independence. And, the main way we did that
was

by rem- replacing our dependency on services
with fake

services.

So, when we wanted to test our application,
we

wanted to test just our application in independence.
And

the way that we did that was, for each

of our dependent services, we replaced those
services with

kind of a fake version of that service. And

by doing that, we were allowed to run these

things that, that we called bounded integration
tests.

So, these were tests that tested the entire
stack

of our application, of our Rails application,
from top

to bottom, from kind of html all the way

down to the network. But, we weren't, we were

testing that in isolation. We weren't actually
hitting those

shared services.

And what's really interesting here is, do
you see

the, the boundary of those tests lines up
almost

perfectly with the boundary of our team. So
this

is a really good example of using Conway's
Law

to your advantage. Embracing Conway's Law
and shaping your

approach, shaping your software, with the
shape of your

team. And this was something that helped us
win.

So, if you want to build these fake services,

what are your options? Comes down to, to two

different kind of techniques, really. In-process
and out-of-process. So

in-process means you're kind of messing around
with the

actual Rails, running Rails process, and like
replacing the

network stack with a fake network stack maybe.

Out of process means you're standing up a
real

http server. It's an actual, you know, you
can

actually talk to it over http. And your application,

your Rails app, rather than pointing to a
real

deal service, it's going to point to this
fake

deal service. It's gonna look and smell like
a

deal service. You send it a request. It gives

you a response. It's not a real deals service.

It's a fake service that we have control over.

So, you can imagine if we wanted to test

unicode rendering, we could stand up a fake
product

service that returned a product tied tool
that was

all kind of snow man and that kind of

stuff. And, and that allows us to test how

we handle unicode titles without having, then,
to need

a unicode title.

So, in process, a couple of popular options,
vcr

and webmock. We actually used vcr quite heavily
on

this project that I'm talking about. So basically
it

just kind of sits, it kind of injects itself

in between your application and the network
layer and

records all the interactions between your
application and the

network, and then you can kind of flip it

into playback mode, and rather than, next
you time

you go and make a, make a network call,

it's not actually gonna call the network.
It's going

to just play back the previously recorded
interaction. So

that worked out well for us with some caveats.

Out of process, you've got a lot more options,

because you're not running out of process.
You don't

have to use Ruby. You can use whatever tool

makes the most sense. So mimic is a really

good option here. This is actually a Ruby
gem

written by Luke Redpath. It's a Sinatra application
that

pretends to be whatever you want it to be.

Outside of the Ruby community, or outside
of the

Ruby language, I suppose, there's a library
called moco.

It's quite powerful. Stubby is another one.
And then

there's this interesting one called montebank.
What makes montebank

interesting is it doesn't just fake out http,
it

will fake out whatever protocol you want.
So it

can fake out smtp to it, so you can

check emails. It'll fake out web sockets.
That kind

of stuff. So that's an interesting one to
look

at.

So now we've got these bounded integration
tests. And

that means we have some confidence that it
wasn't

us that, that's creating this bug. Because
our bounded

integration tests are passing. So all was
happy and

we can go on with our day.

Well, obviously not, because we actually still
don't know

where the bug is. And the goal here is

not for us to kind of, prove that we,

it's not our fault. The goal is to identify

the problem and fix it, because at the end

of the day it's a system. We're a part

of that system and we need to fix the

system and move on.

So, so we're left saying, OK. We know it's

not our fault. We'd like to help our, our

comrades on other teams figure out where the
problem

is. And for that we used a technique called

contract tests. So, contract tests, also sometimes
referred to

as consumer-driven contracts. The idea with
these is we

write test code that expresses what we expect
a

dependency, an external service to do, and
then we

run those tests against a real version of
that

service, and we find out if that service actually

does what we expect. Quite simple.

What's weird is we're testing someone else's
code. We're

not testing our code. We're, we're writing
tests, but

we're testing another team's services. So
here's, again, our

boundary, our bounded integration tests. And,
so we verified

that the way that the Rails app is, that

the Rails app does the right thing when it

talks to what we think these services are
doing.

Contract tests, once we add these, actually
verify that

what the service does is what we think it's

gonna do.

Cause it could be that there's a bug in

the service, and these tests will find those
bugs,

hopefully, because we'll ask it to do something
and

it won't do what we expect. There could be

a bug in our understanding of the service,
and

that's why these are called contract tests,
because they

define a contract between our team and the
other

team. Again, Conway's Law is coming in here.

How many of you have worked with an external

service where the, the Wiki page that documented
the

API was out of date? How many of you

have ever worked on a service where it wasn't

wrong? It's always wrong. And that's OK. Documentation
tends

to be stale. API documentation I think is
never

not stale. It just is born that way.

These contract tests are a way to, to, to

mitigate that. Because you're expressing your
expectations in code

rather than in words.

So we, on, on my, on my team, we

wrote contract tests for every single one
of our

dependencies. This was the most productive
thing we did

on this team is, in terms of improving efficiency

of, of us creating software. It really, really
helped

us nail down, whenever there was an issue,
where

that issue was. And it really helped us communicate

with, with our friends on other teams.

So, if you want to do these, you've got

a few different options for contract tests.
We actually

just did plain old RSpec. We just used standard

RSpec test runner to make network calls to
our

dependencies and then look at the results
and make

sure that things looked the way that we expected

them to look.

There's two more kind of sophisticated options
out there.

There's a gem called pacto and another gem
called

pact. And these are kind of like real power

tools. They're quite sophisticated. They're,
they're very fully-featured. If

you want to really kind of get into this,

into this mind set.

So once we had these bounded integration tests
and

these contract tests, we were left with this
kind

of CI dashboard that looked something like
this. So

whenever we checked in code, we'd run our
unit

tests, we'd run our functional tests. And
assuming those

passed, we'd run our kind of bounded integration
tests

up there at the top right.

Assuming those passed, we'd then run our end-to-end
tests.

So these were running, testing as much of
the

stack as we could possibly stand up. So, our

code, our team's code, maybe our team's dependency's
code.

So as much of the stack as possible. So

really verifying, from a user's point of view,
that

this, this system worked as we expected.

In theory, this was the picture. In reality
it

was almost never green. That was OK. So, this

is what things looked like a lot of the

time. Our tests were passing, the end-to-end
tests were

failing. If that was the end of the story,

we'd be left constantly fighting fires of,
why is

it not working in product- or, why is it

not working in staging? And is it the deals

service or the product service, blah, blah,
blah.

But we had these contract tests. So now we

can see here that service D's contract tests
seem

to be failing. So we've got some end-to-end
tests

that are failing. This contract is failing.
That's where

we can start looking for, for the cause of

this problem.

So this is what we spent a lot of

our time, not a lot of our time doing,

but this was a very frequent occurrence. The
build

would go red. We'd have a look at our

dashboard. Oh, it's service D, again. Service
D, you

guys.

So we go to our CI system and we

would look at the logs. We'd get the log

data that showed the request we were sending
the

response we, we got back. And we'd have a

look and say, yup. It looks like they've broken

it again. They forgot to turn on the database

after doing a deployment, again. And we would
write

an email to them saying, hey, I think it's

probably a bug in our code, but we've noticed

when we send this request we get back this

500 error from your service, I don't know
what's

going on there.

You can tell I'm a consultant.

And, things moved a lot smoother. It, it wasn't

all kind of rainbows and unicorns, but it
was

a lot better than if these tests hadn't have

been there. We would have still ended up telling

them and they would have fixed it, but it

would have sucked a lot more of our time.

So that's all the hand wave-y, let's all work

as teams stuff. Let's talk about how we're
actually

gonna build this, this inside of our team.

So I want to talk about this idea called

service gateways. The main thing I'm gonna
talk about

with service gateways is this gem called faraday.
And

in order to talk about this gem called faraday,

I need to talk about this other gem called

rack.

So, how many of you know what rack is?

Yeah, everyone knows what rack is. How many
of

you hate people that ask you raise your hands

when you're in the audience? I have all the

power. You guys have the power but don't realize

that.

So, rack is this awesome abstraction over
http servers.

And the main idea, the main thing that makes

rack awesome is, by abstracting over the concept
of

a request and the concept of a response, we

can kind of stack these middleware components
in between

our application, and the, the underlying http
server.

So, as a request comes in, from the outside

world, it travels through this stack of middleware.
So,

each piece of middleware can, as this request
is

traveling through, has the opportunity to
kind of modify,

modify the request and kind of transform it
in

some way, add some information to the request,
or

to kind of have some side-effect.

And then, a Rails app is gonna deal with

that request and then, and then send back
a

response. And, again, as that response is
traveling back

up through the pipeline, through the, the
middleware stacks,

again, each of those pieces of middleware
can modify

that request in some way, can add some information

to it or can have some side effect.

Rails loves rack. So this is the, the kind

of the stop stack of rack middlewares that
comes

when you, when you just do rails generate
new

project. So, yeah. Pretty, pretty popular.
And the reason

that this is popular is because the guys that

built rack are smart and the guys that, guys

and gals, excuse me, that built rack are smart

and, likewise, Rails. And they realized that
this is

a very powerful abstraction and so they're
really leveraging

this power.

So why was I talking about rack when I

was supposed to be talking about faraday?
Faraday is

the exact same idea of rack, but applied for

an http client. So, again, we have this abstraction

over request and response. This time in the
context

of making a request and receiving a response
rather

than receiving a request and sending back
a response.

And, again, we can stack these pieces of middleware

in between our application and the underlying
network library.

So, in this case, it's us making a request.

So, as we send the request out to the

network, again, that request travels through
all of these

middlewares, and these middlewares, again,
have the opportunity to

either modify that request in some way, have
a

side effect, add some information to the request.
Eventually

it gets on the wire. Eventually it gets to

our dependency. Hopefully not service D because
they'll probably

go down again.

And then service D hopefully sends a response,
and

again, as that response travels back through
the stack,

the stack is able to modify that, that response

as it comes through, add some information.
Have a

side effect.

So, how do we use this thing? So here's

a, this is a service gateway. This is a

class that represents a, a connection to the
outside

world. Here's us building a faraday middleware
stack. So

we're building a connection. We're saying
hey, new faraday.

Please use the instrumentation middleware
and do some JSON

stuff and follow redirects and do some logging.

And that's it. We've now got a faraday connection.

This is how we use a faraday connection. So,

we say, hey, faraday connection, hey, http
client, we

want to get this url, or this path. And

we get a response back. Pretty simple stuff.
I

would say this is readable code. DHH would
be

pleased with me.

And what's really nice, the real power of,
of

faraday, is there's all this extra stuff that
we

set up, this middleware, this technical junk
going on.

But our, the rest of our code doesn't have

to care about it. So we've kind of abstracted

over all of that stuff of JSON, following
redirects

and logging and caching.

So we used faraday a lot in these things

that, that I was calling service gateways.
So the,

as I said, the really nice thing about things

like rack and faraday is they allow us to

segregate the boring tech-y stuff, http, logging,
caching, instrumentation,

the stuff that computer people talk about
at conferences

like this, from the business domain, which
is the

stuff that people actually care about.

So, these service gateways acted as the place
where

we pushed all of the boring techy goop out

to the boundaries of our system, so the core

of our system, the core of our Rails application,

wasn't talking about JSON requests, urls,
caching, logging, deserialization.

It was talking about books and products and
prices.

Things that our application really should
be caring about.

So this is this idea of hexagonal architectures.
Push

all of the goopy boring techy stuff out to

the boundaries of your system, so that the
core

of your system can focus on the domain. The

stuff that you really care about. The stuff
that

makes your system valuable to other people.

So what kind of things did we put into

these? What kind of stuff, boring techy stuff
did

we isolate in these service gateways? One
thing that

we did was we isolated serialization. So,
serialization means

JSON parsing or, in our case, XML parsing,
cause

we were in an enterprise. Yay.

Comes down to the same thing actually. So,
when

we talk about parsing JSON or XML, we're actually

talking about two different things. And I
think often

we conflate these two. So, step one, is we

have this stream of bytes or this raw string,

and we want to turn it into this kind

of generic structure, like a hash of arrays
of,

of objects, right. So that's, that's something,
you know.

You do JSON dot parse or whatever and you

get this kind of generic data structure out.

But, if we are following the principles of
hexagonal

architecture, we don't want to deal with JSON
data

structures or generic data structures. We
want to deal

with products and books and deals. So the
next

step is to actually take that generic structure
and

map it into a domain object that we actually

want to work with.

Cause our goal here is to stop talking about

things like JSON as quickly as possible, at
the

boundaries of our system, and start talking
about products

and prices and deals. So this is two steps.

So, the other thing that you'll, I noticed
working

particularly in larger organizations, is these
responses that you

get back are huge. And really, often times,
you

only really care about a small subset of the

response you get back. So you get back this

big chunk of bytes. You turn it into this

big generic structure, and then you actually
just want

to pluck three or four or five or six

things out of that structure, that represent
the product

in your, in your domain.

You don't care about the, the short description.
You

certainly don't care about the response time.
Really all

you care about is the, you know, the title

or the author, you know, that kind of thing.

So there's some gems that can help you make

this easier. So, very popular one is this
thing

called hashie. Hashie will just make it a
little

bit easier for you to work with these generic

data structures. But at the end of the day,

they're still generic data structures.

The second step that we took was to take

all of that boring boiler plate that we were

doing of saying, you know, get this dot that

dot the other thing and get me the price.

And then this dot that dot the other thing,

get me the, the offer details. And turn that

into a declarative statement that we could
just make

at the top of a class that would make

these things.

So we turn that mapping, that boring boilerplate
mapping,

into something that was declarative rather
than imperative. We

actually ended up extracting that little library
that we

built into this thing called lazy_doc. There's
another couple

of gems that are very, that have very similar

goals. Embedded_doc is another one. And there's
this really

quite powerful one called representable, which
is very good.

It's, it's very powerful. It almost does too
many

things for my taste, but it's definitely,
definitely a

good option.

The reason, by the way, embedded_doc is called
embedded_doc

is cause it's, what we're kind of talking
about

here is this embedded document pattern. That's
the name

of the pattern. Sorry, now I'm talking about
patterns.

I'm really off-message.

So what else did we put in our faraday

stack? Caching. This is the most, for me,
the

most exciting thing to talk about. So let
me

talk about it. So, back to our example, let's

say we've got our Rails app. And we've got

our product service and we've got this pricing
service.

Fun fact that I didn't know before I worked

on this application. Prices can change, like,
multiple times

a minute in some of these systems. They're
really

trying to optimize for prices.

So, can't really cache pricing information.
Product information tends

to be pretty static. The author of a book

doesn't change very often. The title of a
book

doesn't change very often. But we're always
looking up

this product information, almost every single
request. So let's

cache that. Let's make this performant.

So, a lot of you are automatically starting
to

think about how we would implement this and,
well,

we would have a product cache, and then when

we need a product we'll go to the cache,

and if it's there, then we'll check the freshness.

And if the freshness is up to some configured

thing, then we'll get it. Otherwise we'll
go to

the network. And then when we get back from

network, put it in the cache, blah, blah,
blah.

All of this stuff, right. And we're, we're
back

to thinking about boring technical goop and
we're not

talking about our domain anymore. We didn't
want to

do this. I'm, honestly, bored with getting
caching wrong

over and over again in each of my applications.

And so, we just pretended to be a web

browser.

As web developers, we know that images are
very

cacheable, and we should put caching headers
on our,

on our images, so that the browser can do

the right thing and cache this so that every

time we want to get this image, if it's

already in the cache, we don't have to go

onto the network. Kind of very common practice.

We don't write JavaScript cache repositories
and then go

and check and see if the image is in

there and then, if it's not, we'll go to

the network and then put it in the cache

repository.

The web browser just does this for us. All

we need to do is set the caching headers

on this, this ping. So, my argument is, and

what we did was, just apply the same principle

to our API. So product dot, or product slash

wherever this is at - my pretend url for,

for this product. We had caching headers on
this

API call, that said this, this url is cacheable

for twenty minutes.

In our faraday stack, we had a caching middleware.

So, the first time that we requested that
url

for that product, first time we wanted that
product,

our Rails app would say to our service gateway,

I want this product. The service gateway would
say,

OK, it's at this url. I'm gonna make a

request through my faraday stack for that
url.

That request would go through our stack, and
the

response would go through our response on
the way

back, and the caching layer would say, oh
look

at that. There's this caching header on this
JSON

that says it's gonna be valid for twenty minutes.

Let me just put this response in my little

cache on disk here.

And, five minutes later, another user comes
in and

wants to, by chance, look at the same product.

Again, our service gateway, our code doesn't
do anything

different. It just says, hey, service gateway,
I want

this product. Our service gateway doesn't
do anything different.

It just says to faraday, hey, I want to

get this url.

The request comes through to the caching layer.
The

caching layer says, oh look. That's the same
url

I just pulled five minutes, and the, the caching

headers say it's valid for twenty minutes.
I'll just

return what I've got in my local cache. I

won't go on the network. I won't bother with

all that stuff. I'll just read it from the

disc.

This is what web browsers do all the time.

We can do this all this time with, literally,

a single line of code. Sorry. That's not a

single line. It's a single method call. Would
be

a single line, I guess everything could be
a

single line of code, right.

So, we've just said to our faraday stack,
hey,

add some caching middleware. Write it to disc
at

this location, and there we go. We, we've
now

got all the semantics of a web browser. And,

we didn't have to do any work apart from

this single method call. And what's really
powerful is

the team that knows the most about the data,

so the product team in this case, can define

the caching semantics of their data.

So, if they realized, like, you know what,
these,

this, the name of the author keeps on changing.

We need to drop down the caching freshness,
they

can just say, you know what, it's gonna be

ten minutes. And we just get that semantics,
we

just start, we change our caching rules. No,
no

code change. No configuration change. No redeployment.
It just

happens.

So, again, Conway's Law. The team that knows
the

most about the data has control over the caching

of that data. Really, really, really powerful
stuff.

This goes back to this principle that, that
I'm

really passionate about. I think a lot of
times

we, we, we, we think of ourselves as building

these systems on the web. We, we're building
our

stuff on top of http. I don't think we

should be doing that. I think we should be

building systems that are of the web.

So, we should be using principles like, like
REST,

like hypermedia, like caching, http caching,
because these, these

are the principles that have made the most
successful,

biggest distributed system in the world work.
It's really

messy, and sometimes it's a bit of a pain

to use, but it works really well, and it's

all done for us already. We don't have to

figure this stuff out ourselves. It's all
out there

and it's been working for decades.

We use it, in some cases, hypermedia is something

we're starting to understand more and more.
We can

use it in more places. Caching is, is an

example of that.

So, some principles. I could have talked about
all

this stuff for hours and hours and hours,
but

I don't have time to do that. So I'm

just gonna shove a bunch of words at the

end of this talk, and, and hope that, that

if they're new words to you that you go

out and, and research them.

Conway's Law is, is the big one. This is

something I'm really passionate about. If
you, software, building

software today is very much a team sport.
If

you don't understand how to work with other
teams,

then someone else is gonna do it better than

you. So this is important stuff.

Domain-Driven Design, I kind of touched on
this talking

about domain objects and talking about kind
of bounded

contexts. It's a really, really good book.
It's really,

really hard to read. Eric Evans is an incredibly

smart guy who's not necessarily the best at
kind

of succinctly expressing ideas.

If you do get this book, read the second

half before you read the first half. He himself

has said he got the order around wrong in

retrospect. The, the second half has loads
of really

good stuff in it. The first half does too.

But the second half, I think, is where the

real, the real, real great stuff is.

Postel's Law. I didn't really talk about this
at

all. But if you're building SOA systems, this
is

the way that you evolve these systems over
time,

without having to redeploy your entire enterprise
at once.

So, Postel's Law is very, very valuable. Another
reason

why the web has been so successful is Postel's

Law. html is incredibly permissive. It draws,
it causes

a bunch of pain, but it also is the

reason why html is the system that we still

use today.

Hexagonal architectures. Talked about this
a fair bit. This

is a really, really important principle. I'm
really excited

that the Rails community is starting to kind
of

get, to get excited about this. But it's been

around for awhile. There's loads of really
good talks

out there about hexagonal architectures as
they apply to

Rails. There's been a couple of talks at the

conference already.

There's a, there's a Birds of a Feather session

tonight about it, I believe. So there's loads
of

res- loads of good resources out there. Not
just

for Rails specifically, but just, hexagonal
architectures in general.

Because it is a general architectural principle.

Finally, we should be embracing the web. It's
been

around for a long time. The patterns are very

well understood, very well established. The
tooling is amazingly

powerful. We keep on reinventing wheels. Let's
not keep

reinventing this particular wheel. When it
makes sense to

make the web and the principles of the web,

we should be doing that.

Thank you.