Add support for plugins in fnext

api/agent/agent.go

@@ -109,7 +109,7 @@ type agent struct {
 	shutWg   *common.WaitGroup
 	shutonce sync.Once
 
-	callOverrider CallOverrider
+	callOverrider fnext.CallOverrider
 	// deferred actions to call at end of initialisation
 	onStartup []func()
 }
@@ -203,7 +203,7 @@ func WithDockerDriver(drv drivers.Driver) Option {
 }
 
 // WithCallOverrider registers register a CallOverrider to modify a Call and extensions on call construction
-func WithCallOverrider(fn CallOverrider) Option {
+func WithCallOverrider(fn fnext.CallOverrider) Option {
 	return func(a *agent) error {
 		if a.callOverrider != nil {
 			return errors.New("lb-agent call overriders already exists")

api/agent/call.go

@@ -39,9 +39,6 @@ type Call interface {
 	End(ctx context.Context, err error) error
 }
 
-// Interceptor in GetCall
-type CallOverrider func(*models.Call, map[string]string) (map[string]string, error)
-
 // TODO build w/o closures... lazy
 type CallOpt func(c *call) error
 

api/agent/lb_agent.go

@@ -24,7 +24,7 @@ type lbAgent struct {
 	callListeners []fnext.CallListener
 	rp            pool.RunnerPool
 	placer        pool.Placer
-	callOverrider CallOverrider
+	callOverrider fnext.CallOverrider
 	shutWg        *common.WaitGroup
 }
 
@@ -71,7 +71,7 @@ func WithLBAgentConfig(cfg *Config) LBAgentOption {
 }
 
 // LB agents can use this to register a CallOverrider to modify a Call and extensions
-func WithLBCallOverrider(fn CallOverrider) LBAgentOption {
+func WithLBCallOverrider(fn fnext.CallOverrider) LBAgentOption {
 	return func(a *lbAgent) error {
 		if a.callOverrider != nil {
 			return errors.New("lb-agent call overriders already exists")

fnext/listeners.go

@@ -57,7 +57,7 @@ type FnListener interface {
 	AfterFnDelete(ctx context.Context, fnID string) error
 }
 
-//// TriggerListener enables callbacks around Trigger events
+// TriggerListener enables callbacks around Trigger events
 type TriggerListener interface {
 	// BeforeTriggerCreate called before trigger created in the datastore
 	BeforeTriggerCreate(ctx context.Context, trigger *models.Trigger) error
@@ -68,9 +68,9 @@ type TriggerListener interface {
 	// AfterTriggerUpdate called after trigger updated in datastore
 	AfterTriggerUpdate(ctx context.Context, trigger *models.Trigger) error
 	// BeforeTriggerDelete called before trigger deleted from the datastore
-	BeforeTriggerDelete(ctx context.Context, triggerId string) error
+	BeforeTriggerDelete(ctx context.Context, triggerID string) error
 	// AfterTriggerDelete called after trigger deleted from the datastore
-	AfterTriggerDelete(ctx context.Context, triggerId string) error
+	AfterTriggerDelete(ctx context.Context, triggerID string) error
 }
 
 // CallListener enables callbacks around Call events.

fnext/overrider.go

@@ -0,0 +1,8 @@
+package fnext
+
+import (
+	"github.com/fnproject/fn/api/models"
+)
+
+// CallOverrider is an interceptor in GetCall which can modify Call and extensions
+type CallOverrider func(*models.Call, map[string]string) (map[string]string, error)

fnext/plugin.go

@@ -0,0 +1,98 @@
+package fnext
+
+import (
+	"fmt"
+	"plugin"
+)
+
+const (
+	listenerSymbolName   = "Listener"
+	middlewareSymbolName = "Handle"
+	overriderSymbolName  = "Overrider"
+)
+
+func symbolFromPlugin(path, symbolName string) (plugin.Symbol, error) {
+	plugin, err := plugin.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	return plugin.Lookup(symbolName)
+}
+
+// NewPluginMiddleware creates an Fn Middleware from a Golang plugin
+func NewPluginMiddleware(path string) (Middleware, error) {
+	handleSymbol, err := symbolFromPlugin(path, middlewareSymbolName)
+	if err != nil {
+		return nil, err
+	}
+	handler, ok := handleSymbol.(*MiddlewareFunc)
+	if !ok {
+		return nil, fmt.Errorf("%s is not a valid middleware function in plugin: %s", middlewareSymbolName, path)
+	}
+	return handler, nil
+}
+
+// NewPluginAppListener creates an Fn AppListener from a Golang plugin
+func NewPluginAppListener(path string) (AppListener, error) {
+	listenerSymbol, err := symbolFromPlugin(path, listenerSymbolName)
+	if err != nil {
+		return nil, err
+	}
+	callListener, ok := listenerSymbol.(AppListener)
+	if !ok {
+		return nil, fmt.Errorf("%s is not a AppListener", listenerSymbolName)
+	}
+	return callListener, nil
+}
+
+// NewPluginFnListener creates an Fn FnListener from a Golang plugin
+func NewPluginFnListener(path string) (FnListener, error) {
+	listenerSymbol, err := symbolFromPlugin(path, listenerSymbolName)
+	if err != nil {
+		return nil, err
+	}
+	callListener, ok := listenerSymbol.(FnListener)
+	if !ok {
+		return nil, fmt.Errorf("%s is not a FnListener", listenerSymbolName)
+	}
+	return callListener, nil
+}
+
+// NewPluginTriggerListener creates an Trigger TriggerListener from a Golang plugin
+func NewPluginTriggerListener(path string) (TriggerListener, error) {
+	listenerSymbol, err := symbolFromPlugin(path, listenerSymbolName)
+	if err != nil {
+		return nil, err
+	}
+	callListener, ok := listenerSymbol.(TriggerListener)
+	if !ok {
+		return nil, fmt.Errorf("%s is not a TriggerListener", listenerSymbolName)
+	}
+	return callListener, nil
+}
+
+// NewPluginCallListener creates an Fn CallListener from a Golang plugin
+func NewPluginCallListener(path string) (CallListener, error) {
+	listenerSymbol, err := symbolFromPlugin(path, listenerSymbolName)
+	if err != nil {
+		return nil, err
+	}
+	callListener, ok := listenerSymbol.(CallListener)
+	if !ok {
+		return nil, fmt.Errorf("%s is not a CallListener", listenerSymbolName)
+	}
+	return callListener, nil
+}
+
+// NewPluginCallOverrider creates an Fn CallOverrider from a Golang plugin
+func NewPluginCallOverrider(path string) (CallOverrider, error) {
+	overriderSymbol, err := symbolFromPlugin(path, overriderSymbolName)
+	if err != nil {
+		return nil, err
+	}
+	callOverrider, ok := overriderSymbol.(*CallOverrider)
+	if !ok {
+		return nil, fmt.Errorf("%s is not a valid call overrider in plugin: %s", overriderSymbolName, path)
+	}
+	return *callOverrider, nil
+}