Hyperledger Fabric 2.5.4开发之“定义功能需求”问题

说明

本文描述了一个不再使用“系统通道”的网络（以前该通道由排序服务引导，并且由排序服务专门控制）。自Fabric v2.3发布以来，在创建通道的过程方法中，使用系统通道现在被视为遗留方案。

在通道配置（在通道的最新配置区块中找到）中，可以为每个通道定义功能需求。通道配置包含三个位置，每个位置定义了不同类型的功能。

功能设置

功能设置是通道配置的一部分（要么作为初始配置，要么作为重新配置的一部分）。

有关如何更新通道配置的更多信息，请查看更新通道配置。

初始配置中的功能

在最新下载安装的Fabric（V2.5.4）的目录fabric-samples中的config子目录下的 configtx.yaml 文件中，有一个 Capabilities 部分，列举了每种功能类型（通道、排序节点和应用程序）的可能功能。

Capabilities:

    # Channel capabilities apply to both the orderers and the peers and must be

    # supported by both.

    # Set the value of the capability to true to require it.

    Channel: &ChannelCapabilities

        # V2.0 for Channel is a catchall flag for behavior which has been

        # determined to be desired for all orderers and peers running at the v2.0.0

        # level, but which would be incompatible with orderers and peers from

        # prior releases.

        # Prior to enabling V2.0 channel capabilities, ensure that all

        # orderers and peers on a channel are at v2.0.0 or later.

        V2_0: true

    # Orderer capabilities apply only to the orderers, and may be safely

    # used with prior release peers.

    # Set the value of the capability to true to require it.

    Orderer: &OrdererCapabilities

        # V1.1 for Orderer is a catchall flag for behavior which has been

        # determined to be desired for all orderers running at the v1.1.x

        # level, but which would be incompatible with orderers from prior releases.

        # Prior to enabling V2.0 orderer capabilities, ensure that all

        # orderers on a channel are at v2.0.0 or later.

        V2_0: true

    # Application capabilities apply only to the peer network, and may be safely

    # used with prior release orderers.

    # Set the value of the capability to true to require it.

    Application: &ApplicationCapabilities

        # V2.5 for Application enables the new non-backwards compatible

        # features of fabric v2.5, namely the ability to purge private data.

        # Prior to enabling V2.5 application capabilities, ensure that all

        # peers on a channel are at v2.5.0 or later.

        V2_5: true

请注意， Capabilities 在根级别（用于通道功能）和 Orderer 级别（用于排序节点功能）各有一个定义部分。上边的示例使用 YAML 引用了在 YAML 文件底部定义的功能。

定义排序服务通道的时候没有 Application 部分，它在创建应用通道的时候会被创建。

这里，Application 部分有一个新元素 Capabilities，引用了 YAML 最后部分的 ApplicationCapabilities。

参考

• https://hyperledger-fabric.readthedocs.io/en/latest/capability_requirements.html
• https://hyperledger-fabric.readthedocs.io/en/latest/config_update.html
• https://hyperledger-fabric.readthedocs.io/en/latest/channel_update_tutorial.html