MEP 18 -- Support Milvus 2.0 C++ SDK

Current state: Accepted

ISSUE: https://github.com/milvus-io/milvus/issues/7713

PRs:

Keywords: C++ SDK

Released: with Milvus 2.1

Authors:

Summary

Deliver C++ SDK toolkit with full functionality for Milvus 2.0. Provide both static lib and dynamic lib for users.

Motivation

We've seen many users demands for C++ SDK, it is probably the most useful SDK which could be used in distributed systems.

Public Interfaces

Client interfaces declaration:

class MilvusClient {
 public:
    static std::shared_ptr<MilvusClient>
    Create();

    virtual Status
    Connect(const ConnectParam& connect_param) = 0;

    virtual Status
    Disconnect() = 0;

    virtual Status
    CreateCollection(const CollectionSchema& schema) = 0;

    virtual Status
    HasCollection(const std::string& collection_name, bool& has) = 0;

    virtual Status
    DropCollection(const std::string& collection_name) = 0;

    virtual Status
    LoadCollection(const std::string& collection_name, const TimeoutSetting* timeout) = 0;

    virtual Status
    ReleaseCollection(const std::string& collection_name) = 0;

    virtual Status
    DescribeCollection(const std::string& collection_name, CollectionDesc& collection_desc) = 0;

    virtual Status
    GetCollectionStatistics(const std::string& collection_name, bool do_flush, CollectionStat& collection_stat) = 0;

    virtual Status
    ShowCollections(const std::vector<std::string>& collection_names, CollectionsInfo& collection_desc) = 0;
};

Design Details

Project framework

The C++ sdk can be designed as two levels:

the orm classes: ConnectionInstance/Collection/Partition/Index/Schema/Parameters, and maybe ConnectionPool
the client implementation: a class to maintain grpc channel, a class to transfer parameters to rpc interface

CI Workflow

Use github ci process to run code lint, clang format check, compile project and run unittest.

Use mergify to automatically add ci-passed label.

Use code coverage tool to generate report and upload to codecov.io.

API Document

Add description for each class/method/constant, follow the Doxygen comment style.

ORM

To be determined.

C++ versions to support

Support C++ version above C++11. The Reason is:

Wider user range, as may organizations and devices support C++11.
Easy to maintain as it will get a large group of developer support.

OS platform to support

For the supported platform, need to be tested with mainstream distributions(e.g. Ubuntu 18.04+, CentOS 7+) using google tests.

Milvus cpp SDK 1.1 using cmake, and only build a shared library as output. In this new SDK for milvus 2, the user can choose which version to be built by setting cmake options. Quality gates such as clang-format, clang-tidy, cpplint are needed.

Code Style

A basic rule of C++ code style:

Namespace should use lower_case
Class name should use CamelCase
Class member name should use lower_case_ (with a underscore append)
Enum member name should use UPPER_CASE
The static/public Function name should use CamelCase, and the private/protected member Function name use camelBack

For more details, follow the Google C++ Style Guide.

Test Plan

Unit test
1. C++ SDK will implement a mock milvus for basic testing, need to be tested with mainstream distributions(e.g. Ubuntu 18.04+, CentOS 7+)
2. Start a standalone milvus complicated test.
CI test
1. Do we need to setup basic CI test for further improvement?
Examples
1. finish all the examples in user guide and make sure it works like https://milvus.io/docs/v2.0.0/example_code.md

References