API Tools

A collection of tools we use in our Golang APIs

The gRPC field mask hook

This field mask hook check the request to the server if it has a field mask available. If the mask is available in the request it is applied to the response. The field mask is not validated in the hook, that needs to be done by the user, something like this:

if valid := request.GetFieldMask().IsValid(&SomeResponse{}); !valid {
    return nil, fmt.Errorf("not valid")
}

If the request implements a field mask with the name field_mask like this, the mask will be applied to the response:

message SomeRequest {
    google.protobuf.FieldMask field_mask = 1;
}

Add the hook like this when you create the gRPC server:

opts := []grpc.ServerOption{
    grpc.UnaryInterceptor(grpc_middleware.ChainUnaryServer(
        fieldmaskx.UnaryServerInterceptor(),
    )),
    grpc.StreamInterceptor(grpc_middleware.ChainStreamServer(
        fieldmaskx.StreamServerInterceptor(),
    )),
}

The gRPC notification hook

The gRPC notification hook package can be used to send messages on different channels when an endpoint is called. It can be restricted to only send notifications when an error, or only when specific errors, occurred.

The default for endpoints is to send notifications on all errors, and not on successful requests.

notificationChannels := []notification.Sender{} // Add the channels where you want to send notifications
grpcServer := grpc.NewServer(
    grpc.UnaryInterceptor(grpc_middleware.ChainUnaryServer(
        grpchook.UnaryNotificationInterceptor(notificationChannels, grpchook.Endpoint("gRPCEndpointName", ...), ...),
    )),
    grpc.StreamInterceptor(grpc_middleware.ChainStreamServer(
        grpchook.StreamNotificationInterceptor(notificationChannels, grpchook.Endpoint("gRPCStreamEndpointName", ...), ...),
    )),
)

It is possible to add options for each endpoint to change the default behaviour. Available options for an endpoint: NotifyOnlyOn(codeList []codes.Code)
DoNotifyOnSuccess(b bool)
DoNotifyOnError(b bool)
UseCustomDecisionFunction(f DecisionFunc)

The function that decides if a notification should be sent or not is called DecisionFunc. You can add your own for each endpoint if you want to make the decision based on something else than the configurations available. The decision function signature looks like this.

type DecisionFunc func(ctx context.Context, respError error) bool

Examples

Add options to an endpoint:

grpchook.UnaryNotificationInterceptor(notificationChannels, grpchook.Endpoint("gRPCEndpointName", grpchook.NotifyOnlyOn([]codes.Code{codes.Internal, codes.InvalidArgument}), ...))

Add more endpoint configurations:

grpchook.UnaryNotificationInterceptor(notificationChannels, grpchook.Endpoint("oneEndpoint", ...), grpchook.Endpoint("anotherEndpoint", ...), ...)

KeyVault interface

// Todo: Add update certificate functionality so we don't have to create new certificates as soon as the old expire
type KeyVault interface {
	// GetCertificate downloads a certificate and key from an Azure key vault
	GetCertificate(ctx context.Context, certName string, secretVersion string, certPassword string) (*x509.Certificate, *rsa.PrivateKey, error)

	// UploadCertificate uploads a given certificate and key as certName to an Azure key vault
	UploadCertificate(ctx context.Context, cert *x509.Certificate, key *rsa.PrivateKey, certName string, certPassword string) error
}