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Rescuing legacy
codebases with
GraphQL
@nettofarah
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Netto Farah
@nettofarah
Eng. Manager at
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Context
• Millions of users
• Billions of API calls every day
• Website, iOS app, Android app
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Tech Stack (at the time)
• Seasoned Rails 3 monolith app
• APIs v1, v2, v3, dev_api…
• Challenging to deploy/iterate/run tests
• sole web dev
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Challenge:
Build an entirely new product
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With a 9 months
deadline
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We knew we needed
to make some changes
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Majestic Monoliths
vs
Micro-services
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Not a binary
decision
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A hybrid approach:
Rich API + specific clients
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How can we make our
frontend and backend
apps communicate?
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Through the
database?
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Why are database-driven
integrations tempting?
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Why are database-driven
integrations challenging?
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What about APIs?
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Challenges with
Traditional APIs
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Multiple use cases
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Different access pattern
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Ambiguity
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Solved with documentation
or conventions
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[',(,)..*] => ✅
,
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,
[-] =>
ask me later…
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How can we
solve a few of these
challenges with APIs ?
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Types
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Ability to load just what
we need
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Always get predictable
results
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You know where
I’m going with this, right?
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TYPES +
PREDICTABLE RESULTS +
COMPOSABLE QUERIES
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= GraphQL ❤
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We built a GraphQL API
on top of our monolith
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GraphQL API
as an integration layer
for multiple (not so micro) services
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GraphQL API
———
MonoRail
☁
A
P
I
G
A
T
E
W
A
Y
Service A
Service B
Service C
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GraphQL API
———
MonoRail
⛈
A
P
I
G
A
T
E
W
A
Y
Service A
Service B
Service C
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GraphQL (and Rails) in
production
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Challenge #1
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N+1 queries
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query {
recipes {
title
ingredients {
name
vendor { name }
}
}
}
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SELECT "recipes".* FROM “recipes"
SELECT "ingredients".* FROM "ingredients" WHERE "ingredients"."recipe_id" = 1
SELECT "vendors".* FROM "vendors" WHERE "vendors"."id" = 1
SELECT "vendors".* FROM "vendors" WHERE "vendors"."id" = 2
SELECT "vendors".* FROM "vendors" WHERE "vendors"."id" = 3
SELECT "vendors".* FROM "vendors" WHERE "vendors"."id" = 4
SELECT "ingredients".* FROM "ingredients" WHERE "ingredients"."recipe_id" = 2
SELECT "vendors".* FROM "vendors" WHERE "vendors"."id" = 5
SELECT "vendors".* FROM "vendors" WHERE "vendors"."id" = 6
SELECT "ingredients".* FROM "ingredients" WHERE "ingredients"."recipe_id" = 3
SELECT "vendors".* FROM "vendors" WHERE "vendors"."id" = 7
SELECT "vendors".* FROM "vendors" WHERE "vendors"."id" = 8
SELECT "vendors".* FROM "vendors" WHERE "vendors"."id" = 9
SELECT "ingredients".* FROM "ingredients" WHERE "ingredients"."recipe_id" = 4
SELECT "vendors".* FROM "vendors" WHERE "vendors"."id" = 10
SELECT "vendors".* FROM "vendors" WHERE "vendors"."id" = 11
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SELECT "ingredients".* FROM "ingredients" WHERE
"ingredients"."recipe_id" = 1
SELECT * FROM "vendors" WHERE "id" = 1
SELECT * FROM "vendors" WHERE "id" = 2
SELECT * FROM "vendors" WHERE "id" = 3
SELECT * FROM "vendors" WHERE "id" = 4
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How do people
usually solve this problem?
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DataLoader
but that’s a javascript only tool
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GraphQL-Batch
resolve -> (obj, args, context) do
Loader.for(Product).load(args["id"]).then do |p|
Loader.for(Image).load(p.image_id)
end
end
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Let’s take a second
look at our data models
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Recipe.all.includes({
ingredients: 'vendor'
})
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query {
recipes {
title
ingredients {
name
vendor
}
}
}
Recipe.all.includes({
ingredients: 'vendor'
})
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SELECT "recipes".* FROM "recipes"
SELECT "ingredients".* FROM “ingredients”
WHERE “ingredients"."recipe_id"
IN (1, 2, 3, 4)
SELECT "vendors".* FROM “vendors"
WHERE “vendors"."id"
IN (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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github.com/nettofarah/graphql-query-resolver
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~60% reduction
in database IOPS
=
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Selectively choosing
our Database environment
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if includes_mutation?(query)
DatabaseSelection.use_main_database do
GraphQL.execute_query(query)
end
else
DatabaseSelection.use_readonly_replica do
GraphQL.execute_query(query)
end
end
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☠ Eliminated
contention locks
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Lessons
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#1 Figure out
batching as early
as you can
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#2 Leverage
GraphQL types
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Challenge #2
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Monitoring and
Errors
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This is not really useful
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What’s up with my
errors?
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#2 Leverage
GraphQL types
(again)
Lesson
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# At the field level
new_resolver = -> (obj, args, ctx) {
name = [“GraphQL/field/#{type.name}.#{field.name}"]
NewRelic.trace_execution_scoped(name) do
old_resolver.call(obj, args, ctx)
end
}
# At the query level
NewRelic::Agent.set_transaction_name(query_name)
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http://bit.ly/gql-rb-nr
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#3 Proper monitoring
is as important as
good performance
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#4 GraphQL is
awesome