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From REST to gRPC: Joe Runde IBM @joerunde Michael Keeling IBM @michaelkeeling An API Evolution Story
From REST to gRPC:
Joe Runde
IBM
@joerunde
Michael Keeling
IBM
@michaelkeeling
An API Evolution Story
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What is gRPC?
Open source Remote Procedure Call framework
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What is gRPC?
Open source Remote Procedure Call framework
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“… a modern, bandwidth and CPU efficient, low latency way to create massively distributed systems that span data centers”
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Why should we use gRPC?
Why is gRPC awesome?
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Performance
Performance Benefits
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HTTP / REST
Performance Benefits
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HTTP / REST gRPC
How does gRPC improve performance?
• HTTP/2 transport protocol
• Binary encodings via protocol buffers
• No more parsing text!
• Compression
• Streaming
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Why is gRPC awesome?
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Performance
Why is gRPC awesome?
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Performance
Remote Procedure Calls
REST setup is tedious
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headers = {}
headers.put(“X-FooBar-User”,
user.getFooBarID())
headers.put(“FooBarTransaction”,
app.getNextTxnIDAtomic())
headers.put(“FooBarAlgoType”,
ApproximateFoo.toHeaderString())
REST setup is tedious
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Public class Foo {
@JsonProperty(name=”foo_id”)
String id;
@JsonProperty(name=”bar”)
int bar;
...
}
REST setup is tedious
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Public class Foo {
...
public
Foo(@JsonProperty(“foo_id”,required=true)
String id,
@JsonProperty(“bar”,required=true)
int bar)
{ ... }
}
RPC setup is easy
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request = FooService.RequestBuilder()
.setId(foo.getId())
.setBar(foo.getBar())...
.build();
response = fooClient.DoFooBar(request);
Why is gRPC Awesome?
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Performance
Remote Procedure Calls
Why is gRPC Awesome?
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Performance
Remote Procedure Calls
Strategic Direction of our Platform
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<insert slick demo here>
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Just one problem…
Our current microservices
all use REST.
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Business Constraints
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The Transition Plan
• Phase 1: Design gRPC API
• Phase 2: Run REST and gRPC services
• Phase 3: Transition functional tests
• Phase 4: Remove REST functionality
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DESIGN THE APIPhase I
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Designing a gRPC API
gRPC:
rpc AddFoo(Foo)
returns FooID;
rpc GetFoo(FooID)
returns Foo;
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REST:
POST
/api/foo
GET
/api/foo/{foo_id}
Designing a gRPC API
gRPC:
message Foo {
FooID id = 1;
repeated Bar bars = 2;
}
message FooID {
string val = 1;
}
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REST:
POST
/api/foo
GET
/api/foo/{foo_id}
Designing a gRPC API
gRPC:
rpc AddBar(Bar)
returns BarID;
rpc GetFoo(BarID)
returns Bar;
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REST:
POST
/api/foo/{foo_id}/bar
GET
/api/foo/{foo_id}/bar/
{bar_id}
Designing a gRPC API
gRPC:
rpc AddBar(Bar)
returns BarID;
rpc GetFoo(BarID)
returns Bar;
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REST:
POST
/api/foo/{foo_id}/bar
GET
/api/foo/{foo_id}/bar/
{bar_id}
Designing a gRPC API
gRPC:message Bar{
BarID id = 1;
int baz = 2;
}
message BarID {
FooID foo_id = 1;
string bar_id = 2;
}
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REST:
POST
/api/foo/{foo_id}/bar
GET
/api/foo/{foo_id}/bar/
{bar_id}
Designing a gRPC API
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Bar service:
/api/foo/{foo_id}/bar/{bar_id}
Buzz service:
/api/foo/{foo_id}/buzz/{buzz_id}
SERVE REST AND GRPCPhase II
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Current: REST Only
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FooBar
Service
REST
Caller
Future: REST and gRPC
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FooBar
Service
REST
Caller
gRPC
Caller
We need to evolve our API without
damaging basic functionality.
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Code Package
is allowed to
use
Current: Layers View
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Rest Service
Business Logic
Datastore Access
Models
Models
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Code Package
is allowed to
use
Rest
Service
Business Logic
Datastore Access
gRPC
Service
Future: Layers View
Layer Pattern Rocks!
A code review comment:
"What's with the service layer? This just passes its inputs to our business logic functions, it's redundant cruft!"
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Evolving the code went really well…
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Things that suddenly became a problem
• Health Checks
• API Discovery
• No curl
• Headers?
• SSL?
• Simple community examples40
TRANSITION FUNCTIONAL TESTSPhase III
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Specification by Example
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Specification by Example- REST
Ruby metaprogramming
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Choice of programming language really paid off
request = Object::const_get(
”FooBar::#{message_name}").decode_json(json)
response = client.method(method_name.to_sym)
.call(request)
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Specification by Example- gRPC
200+ tests transitioned in 1 week
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Why did this go so well?
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• Expressiveness of spec by example
• Flexibility of Ruby
• gRPC can decode JSON
REMOVE REST FUNCTIONALITYPhase IV
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rm –rf src/*rest*
We need to retain some REST endpoints
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REST
Caller
gRPC
Caller
FooBar
Service
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Current Layered Architecture
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Models
Rest
Service
Business Logic
Datastore Access
gRPC
Service
FooBar
Service
Service
Layers Forked – Two Services
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ModelsBusiness Logic
Datastore Access
gRPC Service
FooBar
Service
gRPC Clients
REST ServiceFooBar
Proxy
Service
Evil wizards strike again!
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NOW WE’RE READY FOR RELEASE…?
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New problems we created
• Health Checks
• API Discovery
• No curl
• Headers?
• SSL?
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New problems we created
• Health Checks
• API Discovery
• No curl
• Headers?
• SSL?
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API Discovery
• REST – Ask the service!
• gRPC – Find the (correct) proto file?
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API Discovery
• REST – Ask the service!
• gRPC – Find the (correct) proto file?• Standard InfoService serves github url + version
• Snapshot proto files with releases
• Client vendors the proto files they use
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Tools support
• Basically Nonexistent
• Our solutions:• Hand roll mocks for testing
• Write new functional tests each time we wanted to use curl
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Adios,
REST!
INTERESTING THINGS WE LEARNED
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• The right kinds of abstractions promote
extensibility
• Focus on the domain model
• Create a specification by example
• Take care when choosing frameworks
• Deal with risks of technology adoption
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Would we do it again?
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Would we do it again?
• Super easy to integrate with a service
• Promotes small polyglot services
• Difficult to do bad things
• Performance is 🔥🔥🔥
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Yes.
Thank you!
Michael Keeling
@michaelkeeling
neverletdown.net
Joe Runde
@joerunde
Buy Design It! now at
http://bit.ly/2pJOrly
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BACKUP
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