feat(app): Add Custom Trigger Example

Introduce an example for the custom trigger functionality introduced to
the SDK in edgexfoundry/app-functions-sdk-go#587

Signed-off-by: Alex Ullrich <alexullrich@technotects.com>

application-services/custom/cloud-event/main.go

@@ -93,37 +93,7 @@ func gotEvent(ctx context.Context, event cloudevents.Event) {
 	var readingData string
 	event.DataAs(&readingData)
 	fmt.Printf("CloudEvent received reading value: %v\n", readingData)
-}
-
-// App function to send the cloudevent to the receiver
-func sendCloudEvents(edgexcontext *appcontext.Context, params ...interface{}) (bool, interface{}) {
-	edgexcontext.LoggingClient.Info("sendCloudEvent")
-	if len(params) < 1 {
-		return false, errors.New("No Event Received")
-	}
-
-	events, ok := params[0].([]cloudevents.Event)
-	if !ok {
-		return false, errors.New("Cloud event not received")
-	}
-	ctx := cloudevents.ContextWithTarget(context.Background(), "http://localhost:8080/")
-	ctx = cloudevents.ContextWithHeader(ctx, "demo", "header value")
-	c, err := cloudevents.NewDefaultClient()
-	if err != nil {
-		edgexcontext.LoggingClient.Error(fmt.Sprintf("failed to create client, %v", err))
-		return false, nil
-	}
-	for _, cloudevent := range events {
-		if _, resp, err := c.Send(ctx, cloudevent); err != nil {
-			edgexcontext.LoggingClient.Error(fmt.Sprintf("failed to send: %v", err))
-			return false, nil
-		} else if resp != nil {
-			// don't need a response back, in this example we aren't expecting/sending one
-			edgexcontext.LoggingClient.Info(fmt.Sprintf("got back a response: %s", resp))
-		}
-	}
-	return true, events
-}
+}z
 
 func printToConsole(edgexcontext *appcontext.Context, params ...interface{}) (bool, interface{}) {
 	edgexcontext.LoggingClient.Info("PrintToConsole")

application-services/custom/custom-trigger/Dockerfile

@@ -0,0 +1,46 @@
+#
+# Copyright (c) 2019 Intel Corporation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+FROM golang:1.15-alpine AS builder
+
+LABEL license='SPDX-License-Identifier: Apache-2.0' \
+  copyright='Copyright (c) 2019: Intel'
+
+# add git for go modules
+RUN apk update && apk add --no-cache make git gcc libc-dev libsodium-dev zeromq-dev
+WORKDIR /custom-trigger
+
+COPY go.mod .
+
+RUN go mod download
+
+COPY . .
+RUN apk info -a zeromq-dev
+
+RUN make build
+
+# Next image - Copy built Go binary into new workspace
+FROM alpine
+
+LABEL license='SPDX-License-Identifier: Apache-2.0' \
+  copyright='Copyright (c) 2019: Intel'
+
+RUN apk --no-cache add zeromq
+
+COPY --from=builder /custom-trigger/res /res
+COPY --from=builder /custom-trigger/app-service /custom-trigger
+
+CMD [ "/custom-trigger", "--confdir=/res"]

application-services/custom/custom-trigger/Makefile

@@ -0,0 +1,17 @@
+.PHONY: build clean
+
+GO=CGO_ENABLED=1 GO111MODULE=on go
+
+build:
+	$(GO) build -o app-service
+
+docker:
+	docker build \
+	--build-arg http_proxy \
+	--build-arg https_proxy \
+	-f Dockerfile \
+	-t edgexfoundry/docker-custom-trigger-example:dev \
+	.
+
+clean:
+	rm -f app-service

application-services/custom/custom-trigger/README.md

@@ -0,0 +1,11 @@
+# Custom-Trigger
+
+Custom-Trigger provides an example for using a custom trigger with the app functions SDK.
+
+## Overview
+
+In this example we introduce a trigger that listens for input on os.Stdin and sends it through the function pipeline.  The function pipeline is a single function that introduce a slight delay based on the length of the input string and then print it to the console.
+
+To run:
+
+`make docker && docker run -it edgexfoundry/docker-custom-trigger-example:dev`

application-services/custom/custom-trigger/go.mod

@@ -0,0 +1,10 @@
+module custom-trigger
+
+go 1.15
+
+require (
+	github.com/cloudevents/sdk-go v1.1.2
+	github.com/edgexfoundry/app-functions-sdk-go v1.3.1-dev.16
+	github.com/edgexfoundry/go-mod-core-contracts v0.1.112
+	github.com/stretchr/testify v1.6.1
+)

application-services/custom/custom-trigger/main.go

@@ -0,0 +1,141 @@
+//
+// Copyright (c) 2019 Intel Corporation
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+package main
+
+import (
+	"bufio"
+	"context"
+	"fmt"
+	"github.com/edgexfoundry/app-functions-sdk-go/appcontext"
+	"github.com/edgexfoundry/app-functions-sdk-go/appsdk"
+	"github.com/edgexfoundry/app-functions-sdk-go/pkg/util"
+	"github.com/edgexfoundry/go-mod-bootstrap/bootstrap"
+	"github.com/edgexfoundry/go-mod-messaging/pkg/types"
+	"os"
+	"strings"
+	"sync"
+	"time"
+)
+
+const (
+	serviceKey = "customTrigger"
+)
+
+type stdinTrigger struct{
+	tc appsdk.TriggerConfig
+}
+
+func (t *stdinTrigger) Initialize(wg *sync.WaitGroup, ctx context.Context, background <-chan types.MessageEnvelope) (bootstrap.Deferred, error) {
+	msgs := make(chan []byte)
+
+	ctx, cancel := context.WithCancel(context.Background())
+
+	receiveMessage := true
+
+	go func() {
+		fmt.Print("> ")
+		rdr := bufio.NewReader(os.Stdin)
+		for receiveMessage {
+			s, err := rdr.ReadString('\n')
+			s = strings.TrimRight(s, "\n")
+
+			if err != nil {
+				t.tc.Logger.Error(err.Error())
+				continue
+			}
+
+			msgs <- []byte(s)
+		}
+	}()
+
+	for receiveMessage {
+		select {
+		case <- ctx.Done():
+			receiveMessage = false
+		case m := <- msgs:
+			go func() {
+				env := types.MessageEnvelope{
+					Payload: m,
+				}
+
+				ctx := t.tc.ContextBuilder(env)
+
+				err := t.tc.MessageProcessor(ctx, env)
+
+				if err != nil {
+					t.tc.Logger.Error(err.Error())
+				}
+			}()
+		}
+
+
+	}
+	return func() {
+		cancel()
+	}, nil
+}
+
+func main() {
+	// turn off secure mode for examples. Not recommended for production
+	os.Setenv("EDGEX_SECURITY_SECRET_STORE", "false")
+	// First thing to do is to create an instance of the EdgeX SDK and initialize it.
+	edgexSdk := &appsdk.AppFunctionsSDK{ServiceKey: serviceKey, TargetType: &[]byte{} }
+
+	if err := edgexSdk.Initialize(); err != nil {
+		edgexSdk.LoggingClient.Error(fmt.Sprintf("SDK initialization failed: %v\n", err))
+		os.Exit(-1)
+	}
+
+	edgexSdk.RegisterCustomTriggerFactory("custom-stdin", func(config appsdk.TriggerConfig) (appsdk.Trigger, error) {
+		return &stdinTrigger{
+			tc: config,
+		}, nil
+	})
+
+	edgexSdk.SetFunctionsPipeline(
+		printToConsole,
+	)
+
+	// Lastly, we'll go ahead and tell the SDK to "start" and begin listening for events
+	err := edgexSdk.MakeItRun()
+	if err != nil {
+		edgexSdk.LoggingClient.Error("MakeItRun returned error: ", err.Error())
+		os.Exit(-1)
+	}
+
+	// Do any required cleanup here
+	os.Exit(0)
+}
+
+func printToConsole(edgexcontext *appcontext.Context, params ...interface{}) (bool, interface{}) {
+	input, err := util.CoerceType(params[0])
+
+	if err != nil {
+		edgexcontext.LoggingClient.Error(err.Error())
+		return false, err
+	}
+
+	wait := time.Millisecond * time.Duration(len(input))
+
+	time.Sleep(wait)
+
+	edgexcontext.LoggingClient.Info("PrintToConsole")
+
+	os.Stdout.WriteString(fmt.Sprintf("'%s' received %s ago\n>", string(input), wait.String()))
+
+	return false, nil
+}

application-services/custom/custom-trigger/res/configuration.toml

@@ -0,0 +1,25 @@
+[Writable]
+LogLevel = 'INFO'
+
+[Service]
+BootTimeout = '30s'
+ClientMonitor = '15s'
+CheckInterval = '10s'
+Host = 'localhost'
+Port = 48095
+Protocol = 'http'
+ReadMaxLimit = 100
+StartupMsg = 'Cloud Event Transforms'
+Timeout = '5s'
+
+[Registry]
+Host = 'localhost'
+Port = 8500
+Type = 'consul'
+
+[Logging]
+EnableRemote = false
+File = ''
+
+[Binding]
+Type="custom-stdin"