title: Overview - Pluggable Architecture - Smilo

The Smilo client is a modified geth client. One of the unique enhancements is the pluggable architecture which allows adding additional features as plugins to the core geth, providing extensibility, flexibility, and isolation of Smilo features.

↳ Benefits

This enhancement provides a number of benefits, including:

1. Allowing the implementation of certain components of the Smilo client to be changed at configuration time.
2. Supporting our community to improve the Smilo client with their own innovative implementations of the supported pluggable components.
3. Decoupling new Smilo-specific features from core geth thereby simplifying the process of pulling in changes from upstream geth.

↳ How it works?

Each plugin exposes an implementation for a specific plugin interface (or see Pluggable Architecture -> Plugins for more details) Plugins are executed as a separate process and communicate with the main Smilo client geth process over a gRPC interface.

The plugin implementation must adhere to certain gRPC services defined in a .proto file corresponding to the plugin interface. Plugins can be written in different languages as gRPC provides a mechanism to generate stub code from .proto files.

The network communication and RPC are handled automatically by the high-level plugin library.

↳ Installing Plugins

Currently plugins must be manually installed into a directory (defaults to plugins directory inside geth data directory - default can be overriden by setting baseDir in plugins settings).

↳ Using Plugins

Plugins settings file contains a JSON that describes what plugins to be used. Then start geth with --plugins as below:

geth ... \
     --plugins file:///<path>/<to>/plugins.json

↳ Plugin Integrity Verification

Plugin Central Server can be used to download and verify plugin integrity using PGP. The architecture enables the same verification process locally via --plugins.localverify and --plugins.publickey flags or remotely with custom plugin central - reference the Settings section for more information on how to support custom plugin central.

If the flag --plugins.skipverify is provided at runtime the plugin verification process will be disabled.

!!! warning Using --plugins.skipverify is not advised for production settings and it should be avoided as it introduces security risks.

↳ Example: HelloWorld plugin

The plugin interface is implemented in Go and Java. In this example, HelloWorld plugin exposes a JSON RPC endpoint to return a greeting message in the configured language. This plugin is reloadable. It means that the plugin can take changes from its JSON configuration.

↳ Build plugin distribution file

1. Clone plugin repository

   › git clone --recursive https://github.com/smilofoundation/Smilo-plugin-hello-world.git
   › cd Smilo-plugin-hello-world
   

2. Here we will use Go implementation of the plugin

   Smilo-plugin-hello-world› cd go
   Smilo-plugin-hello-world/go› make
   

   Smilo-plugin-hello-world-1.0.0.zip is now created in build directory. Noticed that there's a file hello-world-plugin-config.json which is the JSON configuration file for the plugin.

↳ Start Smilo with plugin support

1. Build Smilo

   › git clone https://github.com/smilofoundation/Smilo.git
   › cd Smilo
   Smilo› make geth
   

2. Copy HelloWorld plugin distribution file and its JSON configuration hello-world-plugin-config.json to build/bin
3. Create geth-plugin-settings.json

   Smilo› cat > build/bin/geth-plugin-settings.json <<EOF
   {
     "baseDir": "./build/bin",
     "providers": {
       "helloworld": {
         "name":"Smilo-plugin-hello-world",
         "version":"1.0.0",
         "config": "file://./build/bin/hello-world-plugin-config.json"
       }
     }
   }
   EOF
   

4. Run geth with plugin

   Smilo› PRIVATE_CONFIG=ignore \
   geth \
        --nodiscover \
        --verbosity 5 \
        --networkid 10 \
        --raft \
        --raftjoinexisting 1 \
        --datadir ./build/_workspace/test \
        --rpc \
        --rpcapi eth,debug,admin,net,web3,plugin@helloworld \
        --plugins file://./build/bin/geth-plugin-settings.json \
        --plugins.skipverify
   

   ps -ef | grep helloworld would reveal the HelloWorld plugin process

↳ Test the plugin

1. Call the JSON RPC

   Smilo› curl -X POST http://localhost:8545 \
        -H "Content-type: application/json" \
        --data '{"jsonrpc":"2.0","method":"plugin@helloworld_greeting","params":["Smilo Plugin"],"id":1}'
   {"jsonrpc":"2.0","id":1,"result":"Hello Smilo Plugin!"}
   

2. Update plugin config to support es language

   # update language to "es"
   Smilo› vi build/bin/hello-world-plugin-config.json
   

3. Reload the plugin

   Smilo› curl -X POST http://localhost:8545 \
        -H "Content-type: application/json" \
        --data '{"jsonrpc":"2.0","method":"admin_reloadPlugin","params":["helloworld"],"id":1}'
   {"jsonrpc":"2.0","id":1,"result":true}
   

4. Call the JSON RPC

   Smilo› curl -X POST http://localhost:8545 \
        -H "Content-type: application/json" \
        --data '{"jsonrpc":"2.0","method":"plugin@helloworld_greeting","params":["Smilo Plugin"],"id":1}'
   {"jsonrpc":"2.0","id":1,"result":"Hola Smilo Plugin!"}