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GRPC - Service Code

Unlike classic HTTP and REST endpoints GRPC enforce most strict request/response format driven by .proto files declaration and compiled into binary messages using protoc compiler.

Note
Use https://github.com/spiral/app-grpc as the base to speed up onboarding.

Define the Service

To declare our first service create a proto file in the desired direction. By default, the GRPC build proposes to create the proto files in /proto directory. Create file proto/calculator.proto:

json
syntax = "proto3";

option php_namespace = "App\\Calculator";
option php_metadata_namespace = "App\\GPBMetadata";

package app;

message Sum {
    int32 a = 1;
    int32 b = 2;
}

message Result {
    int32 result = 1;
}

service Calculator {
    rpc Sum (app.Sum) returns (app.Result) {
    }
}

Note
Make sure to use options php_namespace and php_metadata_namespace to properly configure PHP namespace. You can read more about GRPC service declaration here.

At the moment you can only create Unidirectional APIs.

Generate the service

You can generate the service code manually using the protoc compiler and php-grpc plugin.

Execute the command below:

protoc -I ./proto/ --php_out=app/src --php-grpc_out=app/src proto/calculator.proto

The default protoc compiler does not respect the location of the application namespaces. The code will be generated in the app/src/App/Calculator and app/src/App/GPBMetadata directories. Move the generated code to make it loadable:

  • app/src/Calculator
  • app/src/GPBMetadata

Generate Command

Put proto file into app/config/grpc.php

php
'services' => [
    __DIR__.'/../../proto/calculator.proto',
],

You can use the command embedded to the framework to simplify the service code generation, simply run:

php app.php grpc:generate

You should see the following output:

Compiling `proto/calculator.proto`:
• app/src/Calculator/CalculatorInterface.php
• app/src/Calculator/Result.php
• app/src/Calculator/Sum.php
• app/src/GPBMetadata/Calculator.php

The code will be moved into the proper place automatically.

Implement Service

Implement the CalculatorInterface located in app/src/Calculator in order to make your service work:

php
<?php

declare(strict_types=1);

namespace App\Calculator;

use Spiral\RoadRunner\GRPC;

class Calculator implements CalculatorInterface
{
    public function Sum(GRPC\ContextInterface $ctx, Sum $in): Result
    {
        return new Result([
            'result' => $in->getB() + $in->getA()
        ]);
    }
}

Note
You can not use the method injection with GRPC services at the moment. Stick to Prototype component.

Make sure to update the proto path in .rr.yaml:

yaml
grpc:
  listen: tcp://0.0.0.0:50051
  proto: "proto/calculator.proto"

Multiple Services

Use the import directive of proto declarations to combine multiple services in one application or store message declarations separately.

Test the Service

You can test your service now:

./rr serve

Metadata

Use Spiral\GRPC\ContextInterface to access the request metadata. There are number of system metadata properties you can read:

php
use Spiral\RoadRunner\GRPC;

public function Sum(GRPC\ContextInterface $ctx, Sum $in): Result
{
    dumprr($ctx->getValue(':authority'));
    dumprr($ctx->getValue(':peer.address'));
    dumprr($ctx->getValue(':peer.auth-type'));

    dumprr($ctx->getValue('user-agent'));
    dumprr($ctx->getValue('content-type'));

    return new Result([
        'result' => $in->getB() + $in->getA()
    ]);
}

Note
Read more about auth practices here.

Response Headers

You can add any custom metadata to response using Context-specific response headers:

php
<?php

declare(strict_types=1);

namespace App\Calculator;

use Spiral\RoadRunner\GRPC;

class Calculator implements CalculatorInterface
{
    public function Sum(GRPC\ContextInterface $ctx, Sum $in): Result
    {
        /** @var GRPC\ResponseHeaders $responseHeaders */
        $responseHeaders = $ctx->getValue(GRPC\ResponseHeaders::class);
        $responseHeaders->set('key', 'value');

        return new Result([
            'result' => $in->getB() + $in->getA()
        ]);
    }
}

Errors

spiral/roadrunner-grpc component provides a number of exceptions to indicate the server or request error:

Exception Error Code
Spiral\RoadRunner\GRPC\Exception\GRPCException UNKNOWN(2)
Spiral\RoadRunner\GRPC\Exception\InvokeException UNAVAILABLE(14)
Spiral\RoadRunner\GRPC\Exception\NotFoundException NOT_FOUND(5)
Spiral\RoadRunner\GRPC\Exception\ServiceException INTERNAL(13)
Spiral\RoadRunner\GRPC\Exception\UnauthenticatedException UNAUTHENTICATED(16)
Spiral\RoadRunner\GRPC\Exception\UnimplementedException UNIMPLEMENTED(12)

Note
See all status codes in Spiral\RoadRunner\GRPC\StatusCode. Read more about GRPC error codes here.

Example:

php
<?php

declare(strict_types=1);

namespace App\Calculator;

use Spiral\RoadRunner\GRPC;

class Calculator implements CalculatorInterface
{
    public function Sum(GRPC\ContextInterface $ctx, Sum $in): Result
    {
        if ($in->getA() < 0 || $in->getB() < 0) {
            throw new GRPC\Exception\GRPCException(
                "A and B arguments should be above zero",
                GRPC\StatusCode::INVALID_ARGUMENT
            );
        }

        return new Result([
            'result' => $in->getB() + $in->getA()
        ]);
    }
}

Best Practices

The recommended approach of designing the GRPC API for spiral application is to generate service code interfaces, messages, and client code in a separate repository.

Common:

  • Image-SDK - v1.2.0

Services:

  • Image-Service - implements Image-SDK v1.2.0
  • Account-Service - requires Image-SDK v1.1.0