plugins

README

Plugin Development

MarketStore exposes interfaces that allow for third-party Go plugin module integrations. The interfaces come in two flavors, a trigger plugin and a bgworker plugin.

Third-party plugins can be built as .so bundles, using the Go build command using the -buildmode=plugin flag and placed in the $GOPATH/bin directory. Once there, they can be referenced in the MarketStore YAML config file that is supplied to the marketstore startup cmd via the triggers or bgworkers flags.

Plugins, when included and configured in the MarketStore YAML config, are booted up on startup with the marketstore command. The included mkts.yml file shows some commented-out examples of configuration.

Trigger

Triggers are small applications that perform an action when data is written to the db that matches certain parameters. A trigger interface has to implement the following function -

NewTrigger(config map[string]interface{}) (Trigger, error)

The trigger instance returned by this function will be called on Fire() with the filePath (relative to root directory) and indexes that have been written (appended or updated). It is guaranteed that the new content has been written on disk when Fire() is called, so it is safe to read it from disk. Keep in mind that the trigger might be called on the startup, due to the WAL recovery.

Config example

triggers:
  - module: xxxTrigger.so
    on: "*/1Min/OHLCV"
    config: <according to the plugin>

The "on" value is matched with the file path to decide whether the trigger is fired or not. It can contain wildcard character "*". As of now, trigger fires only on the running state. Trigger on WAL replay may be added later.

Included

• On-disk-aggregation - updates the downsample data upon the writes on the underlying timeframe.
• Streaming - pushes data through MarketStore's streaming interface.

BgWorker

Small applications that run as independent processes in the background and can perform tick data transactions on the database. A bgworker interface has to implement the following function -

NewBgWorker(config map[string]interface{}) (BgWorker, error)

Background workers run under the MarketStore server by implementing the interface, started at the very beginning of the server lifecycle before the query interface starts. The MarketStore server does not handle panics that happen within the plugin. A plugin can recover from panics, but should be careful not to screw the MarketStore server state if touching internal API. It is often better to just let it go.

Config Example

bgworkers:
  - module: xxxWorker.so
    name: datafeed
    config: <according to the plulgin>

Included

• GDAXFeeder - fetches historical price data of cryptocurrencies from GDAX public API.
• Polygon - fetches historical price data of US stocks from Polygon's API.

Documentation

Index

• func Load(pluginName string) (pi *plugin.Plugin, err error)
• type SymbolLoader
  • func NewSymbolLoader(moduleName string) (*SymbolLoader, error)
  • func (l *SymbolLoader) LoadSymbol(symbolName string) (interface{}, error)

Functions

func Load

func Load(pluginName string) (pi *plugin.Plugin, err error)

Load loads plugin module. If pluginName is relative path name, it is loaded from one of the current GOPATH directories or current working directory. If the path is an absolute path, it loads from the path. err is nil if it succeeds.

Types

type SymbolLoader

type SymbolLoader struct {
	// contains filtered or unexported fields
}

func NewSymbolLoader

func NewSymbolLoader(moduleName string) (*SymbolLoader, error)

NewSymbolLoader creates a SymbolLoader that loads symbol from a particular module. moduleName can be a file name under one of $GOPATH directories or current working directory, or an absolute path to the file.

func (*SymbolLoader) LoadSymbol

func (l *SymbolLoader) LoadSymbol(symbolName string) (interface{}, error)

LoadSymbol looks up a symbol from the module. Plugin packages can accept this by defining an interface type without importing this package. It is important to note that each plugin package cannot import this plugins package since plugin module cannot import any packages that import built-in plugin package.