Internals
Background¶
Go Plugin¶
geth
is written in the Go programming language. Go 1.8 introduced a new plugin architecture
which allows for the creation of plugins (via plugin
build mode) and to use these plugins at runtime (via plugin
package).
In order to utilize this architecture, there are strict requirements in developing plugins.
By using the network RPC interface, the plugin is independently built and distributed without having to rebuild geth
.
Especially with gRPC interfaces, plugins can be written in different languages (see our examples).
This makes it easy for you to build a prototype feature or even a proprietary plugin for your organization’s internal use.
We use HashiCorp’s go-plugin
library as it fits our asks
and it has been proven in many plugin-based production systems.
Why we decided to use plugins¶
There are number of benefits:
- Dynamically-linked binaries (which you get when using plugins) are much smaller than statically compiled binaries.
- We value the ability to isolate failures. E.g.: Quorum client would continue mining/validating even if security plugin has crashed.
- Easily enables support for open source plugins written in languages other than Go.
Design¶
Discovery¶
The Quorum client reads the plugin settings file to determine which plugins are going to be loaded and searches for installed plugins
(<name>-<version>.zip
files) in the plugin baseDir
(defaults to <datadir>/plugins
). If the required plugin doesnt exist in the path, Quorum will attempt to use the configured plugin central
to download the plugin.
PluginManager¶
The PluginManager
manages the plugins being used inside geth
. It reads the configuration and builds a registry of plugins.
PluginManager
implements the standard Service
interface in geth
, hence being embedded into the geth
service life cycle, i.e.: expose service APIs, start and stop.
The PluginManager
service is registered as early as possible in the node lifecycle. This is to ensure the node fails fast if an issue is encountered when registering the PluginManager
, so as not to impact other services.
Plugin Reloading¶
The PluginManager
exposes an API (admin_reloadPlugin
) that allows reloading a plugin. This attempts to restart the current plugin process.
Any changes to the plugin config after initial node start will be applied when reloading the plugin.
This is demonstrated in the HelloWorld plugin example.