Revision: Sun, 29 Mar 2020 14:49:18 GMT

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.

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:

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) {
    }
}

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, use Golang services to handle streaming and batch processing.

Generate the service

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

$ 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

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

$ php app.php grpc:generate proto/calculator.proto

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

declare(strict_types=1);

namespace App\Calculator;

use Spiral\GRPC;

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

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

Make sure that the service is available and activated via php app.php grpc:services:

+----------------+---------------------------+-------------------------------------------------+
| Service:       | Implementation:           | File:                                           |
+----------------+---------------------------+-------------------------------------------------+
| app.Calculator | App\Calculator\Calculator | .../grpc-test/app/src/Calculator/Calculator.php |
+----------------+---------------------------+--------------------------------------------------

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

grpc:
  listen: tcp://0.0.0.0:50051
  proto: "proto/calculator.proto"
  workers.command: "php app.php"
  tls.key:  "app.key"
  tls.cert: "app.crt"

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:

$ ./spiral serve -v -d

Run the grpcUI to observe the endpoint:

$ grpcui -insecure -import-path ./proto/ -proto calculator.proto localhost:50051

Read how to write PHP client in next article.

Metadata

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

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()
    ]);
}

Read more about auth practices here.

Response Headers

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

<?php

declare(strict_types=1);

namespace App\Calculator;

use Spiral\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/GRPC component provides a number of exceptions to indicate the server or request error:

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

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

Example:

<?php

declare(strict_types=1);

namespace App\Calculator;

use Spiral\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
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