grpc_server.py

import grpc

from consistent_storage.pb.consistent_storage_pb2 import *
from consistent_storage.pb.consistent_storage_pb2_grpc import ConsistentStorageServicer
from lib.consistent_storage import BaseStorageBackend


class GrpcProxyServer(ConsistentStorageServicer):
    """
    Consistent storage proxy server that exposes a gRPC interface.

    This might be inane to translate a protobuf message to a Python dict and then back to a protobuf,
    especially if the backend is also a gRPC server. However,
    """
    def __init__(self, backend: BaseStorageBackend):
        self.backend = backend

    def Get(self, request, context):
        res = self.backend.get(request.key)

        value = res.get('value')
        if not value:
            value = ''
        value = value.encode('utf-8')

        return GetResponse(
            exists=res.get('exists', False),
            value=value,
            isOwner=res.get('is_owner', False),
            owner=res.get('owner', ''),
        )

    def Put(self, request, context):
        res = self.backend.put(request.key, request.value)
        return PutResponse(
            ok=res.get('ok', False),
            owner=res.get('owner', ''),
        )

    def Remove(self, request, context):
        res = self.backend.remove(request.key)

        error = res.get('error', '')
        if error == 'Key does not exist':
            error = REMOVE_KEY_ERROR
        elif error == 'Not owner of key':
            error = REMOVE_NOT_OWNER
        else:
            error = REMOVE_KEY_ERROR  # Default error, not accurate.

        return RemoveResponse(
            removed=res.get('removed', False),
            error=error,
        )