Apache Thrift

Thrift is an interface definition language that is used to define and create services for numerous languages.^[1] It is used as a remote procedure call (RPC) framework and was developed at Facebook for "scalable cross-language services development". It combines a software stack with a code generation engine to build services that work efficiently to a varying degree and seamlessly between C#, C++ (on POSIX-compliant systems^[2]), Cappuccino,^[3] Cocoa, Erlang, Go, Haskell, Java, OCaml, Perl, PHP, Python, Ruby, and Smalltalk.^[4] Although developed at Facebook, it is now an open source project in the Apache Software Foundation. The implementation was described in an April 2007 technical paper released by Facebook, now hosted on Apache.^[5] To put it simply, Apache Thrift is a binary communication protocol.^[6]

Architecture

Thrift includes a complete stack for creating clients and servers.^[7] The top part is generated code from the Thrift definition. The services generate from this file client and processor code. In contrast to built-in types, created data structures are sent as result in generated code. The protocol and transport layer are part of the runtime library. With Thrift, it is possible to define a service and change the protocol and transport without recompiling the code. Besides the client part, Thrift includes a server infrastructures to tie protocols and transports together, like blocking, non-blocking, and multi-threaded servers. The underlying I/O part of the stack is differently implemented for different languages.

Thrift supports a number of protocols:^[7]

• TBinaryProtocol – A straight-forward binary format, simple, but not optimized for space efficiency. Faster to process than the text protocol but more difficult to debug.
• TCompactProtocol – More compact binary format; typically more efficient to process as well
• TDebugProtocol – A human-readable text format to aid in debugging.
• TDenseProtocol – Similar to TCompactProtocol, striping off the meta information from what is transmitted.
• TJSONProtocol – Uses JSON for encoding of data.
• TSimpleJSONProtocol – A write-only protocol using JSON. Suitable for parsing by scripting languages.

The supported transports are:

• TFileTransport – This transport writes to a file.
• TFramedTransport – This transport is required when using a non-blocking server. It sends data in frames, where each frame is preceded by a length information.
• TMemoryTransport – Uses memory for I/O. The Java implementation uses a simple ByteArrayOutputStream internally.
• TSocket – Uses blocking socket I/O for transport.
• TZlibTransport – Performs compression using zlib. Used in conjunction with another transport. Not available in the Java implementation.

Thrift also provides a number of servers, which are

• TNonblockingServer – A multi-threaded server using non-blocking I/O (Java implementation uses NIO channels). TFramedTransport must be used with this server.
• TSimpleServer – A single-threaded server using std blocking io. Useful for testing.
• TThreadPoolServer – A multi-threaded server using std blocking io.

Benefits

Some stated benefits of Thrift include:

• Cross-language serialization with lower overhead than alternatives such as SOAP due to use of binary format
• A lean and clean library. No framework to code to. No XML configuration files.
• The language bindings feel natural. For example Java uses ArrayList<String>. C++ uses std::vector<std::string>.
• The application-level wire format and the serialization-level wire format are cleanly separated. They can be modified independently.
• The predefined serialization styles include: binary, HTTP-friendly and compact binary.
• Doubles as cross-language file serialization.
• Soft versioning of the protocol. Thrift does not require a centralized and explicit mechanism like major-version/minor-version. Loosely coupled teams can freely evolve RPC calls.
• No build dependencies or non-standard software. No mix of incompatible software licenses.

Creating a Thrift service

Thrift is written in C++, but can create code for a number of languages. To create a Thrift service, one has to write Thrift files that describe it, generate the code in the destination language, and write some code to start the server and call it from the client. Here is a code example of such a description file:

enum PhoneType {
 HOME,
 WORK,
 MOBILE,
 OTHER
}
 
struct Phone {
 1: i32 id,
 2: string number,
 3: PhoneType type
}

Thrift will generate the code out of this descriptive information. For instance, in Java, the PhoneType will be a simple enum inside the POJO for Phone class.

See also

• Apache Avro
• Abstract Syntax Notation One (ASN.1)
• Caucho's Hessian
• Cisco's Etch
• Google's Protocol Buffers
• Microsoft's "M"
• ZeroC's Internet Communications Engine (ICE)

References

External links

• Official website
• Thrift: The Missing Guide
• Thrift Ant task
• Thrift tutorial
• Thrift Installation Tutorial Spanish-Español