commit | c04c573fb3ef294362d193b84249498eb4c8ef91 | [log] [tgz] |
---|---|---|
author | Thomas Wouters <thomas@python.org> | Thu Feb 19 13:37:08 2015 -0800 |
committer | Thomas Wouters <thomas@python.org> | Fri Feb 20 06:20:36 2015 -0800 |
tree | 631b694932154c3108fb1764e38d6f1725c675d8 | |
parent | 2efc1cbd7e7645edabd56a07c0d0ee3c10c322f5 [diff] |
Clean up Python C API use in src/python/src/grpc/_adapter/*.c. Specifically: - Use METH_O and METH_NOARGS where appropriate, modifying the C functions appropriately. METH_O is for functions that take a single PyObject, and it's passed directly instead of 'args'. METH_NOARGS is for functions that take no arguments, and they get called with just one argument ('self'.) - In PyArg_ParseTuple*() calls, specify the callable's name for more descriptive exception messages. - For tp_init functions (which always take keyword arguments) introduce keyword argument parsing (using the C local variables as keywords, although I don't know if they're the best names to use.) This is mostly as a way to show how keyword arguments are done in C. An alternative method is to use _PyArg_NoKeywords(kwds) (see https://hg.python.org/cpython/file/70a55b2dee71/Python/getargs.c#l1820, but unfortunately it's not part of the official API,) or check manually that the dict is empty. - Check the return value of Python API functions that can return an error indicator (NULL or -1.) PyFloat_AsDouble is also one of these, but we don't check the return type (we would have to compare the result to 1.0 with ==, which is not a thing you should do) so just call PyErr_Occurred unconditionally. - Change Py_BuildValue() calls with just "O" formats into PyTuple_Pack calls. It requires less runtime checking. - Replace Py_BuildValue()/PyObject_CallObject pairs with PyObject_CallFunctionObjArgs (since all of them have just PyObject* arguments.) If the Py_BuildValue formats had included other types, PyObject_CallFunction() would have been easier, but no need in these cases. - Replace Py_BuildValue("f", ...) with PyFloat_FromDouble(...). Less runtime checking and parsing necessary, and more obvious in what it does. - In the PyType structs, replace "PyObject_HEAD_INIT(NULL) 0" with "PyVarObject_HEAD_INIT(NULL, 0)". Anything with an ob_size struct member is a PyVarObject, although the distinction isn't all that import; it's just a more convenient macro. - Assign tp_new in the PyType structs directly, like all other struct members, rather than right before the PyType_Ready() call. - Remove PyErr_SetString() calls in places that already have a (meaningful) exception set. - Add a PyErr_Format() for an error return that wasn't setting an exception (PyObject_TypeCheck() doesn't set an exception.) - Remove NULL assignments to struct members in the error paths of the tp_init functions. PyObject structs are always zeroed after allocation, guaranteed. (If there's a way for them to already contain an object you'd use Py_CLEAR() to clear them, but that can't happen in these cases.) - Remove a few unnecessary parentheses.
Copyright 2015 Google Inc.
#Installation
See grpc/INSTALL for installation instructions for various platforms.
#Repository Structure
This repository contains source code for gRPC libraries for multiple lanugages written on top of shared C core library [src/core] (src/core).
Java source code is in [grpc-java] (http://github.com/grpc/grpc-java) repository. Go source code is in [grpc-go] (http://github.com/grpc/grpc-go) repository.
#Documentation
You can find more detailed documentation and examples in the grpc-common repository.
#Current Status of libraries
Libraries in different languages are in different state of development. We are seeking contributions for all of these libraries.
#Overview
Remote Procedure Calls (RPCs) provide a useful abstraction for building distributed applications and services. The libraries in this repository provide a concrete implementation of the gRPC protocol, layered over HTTP/2. These libraries enable communication between clients and servers using any combination of the supported languages.
##Interface
Developers using gRPC typically start with the description of an RPC service (a collection of methods), and generate client and server side interfaces which they use on the client-side and implement on the server side.
By default, gRPC uses Protocol Buffers as the Interface Definition Language (IDL) for describing both the service interface and the structure of the payload messages. It is possible to use other alternatives if desired.
###Surface API Starting from an interface definition in a .proto file, gRPC provides Protocol Compiler plugins that generate Client- and Server-side APIs. gRPC users typically call into these APIs on the Client side and implement the corresponding API on the server side.
Synchronous RPC calls, that block until a response arrives from the server, are the closest approximation to the abstraction of a procedure call that RPC aspires to.
On the other hand, networks are inherently asynchronous and in many scenarios,
it is desirable to have the ability to start RPCs without blocking the current thread.
The gRPC programming surface in most languages comes in both synchronous and asynchronous flavors.
gRPC supports streaming semantics, where either the client or the server (or both) send a stream of messages on a single RPC call. The most general case is Bidirectional Streaming where a single gRPC call establishes a stream where both the client and the server can send a stream of messages to each other. The streamed messages are delivered in the order they were sent.
#Protocol
The gRPC protocol specifies the abstract requirements for communication between clients and servers. A concrete embedding over HTTP/2 completes the picture by fleshing out the details of each of the required operations.
A gRPC RPC comprises of a bidirectional stream of messages, initiated by the client. In the client-to-server direction, this stream begins with a mandatory Call Header
, followed by optional Initial-Metadata
, followed by zero or more Payload Messages
. The server-to-client direction contains an optional Initial-Metadata
, followed by zero or more Payload Messages
terminated with a mandatory Status
and optional Status-Metadata
(a.k.a.,Trailing-Metadata
).
The abstract protocol defined above is implemented over HTTP/2. gRPC bidirectional streams are mapped to HTTP/2 streams. The contents of Call Header
and Initial Metadata
are sent as HTTP/2 headers and subject to HPACK compression. Payload Messages
are serialized into a byte stream of length prefixed gRPC frames which are then fragmented into HTTP/2 frames at the sender and reassembled at the receiver. Status
and Trailing-Metadata
are sent as HTTP/2 trailing headers (a.k.a., trailers).
gRPC inherits the flow control mechanisms in HTTP/2 and uses them to enable fine-grained control of the amount of memory used for buffering in-flight messages.