Add message queue trigger support (#218)

Adds support for message queue triggers based on the NATS-Streaming message queue.

This lets the user map a queue topic to a function, and optionally send the function's response into another queue topic.

The message queue trigger manager is designed to be message queue independent, so we should be able add support for more queues by adding implementations for the relatively simple mqtrigger.MessageQueue interface.

test/mqtrigger/test.sh

@@ -0,0 +1,45 @@
+#!/bin/bash
+
+set -e
+
+clusterID="fissionMQTrigger"
+topic="foo.bar"
+resptopic="foo.foo"
+expectedRespOutput="[foo.foo]: 'Hello, World!'"
+FISSIONDIR=$GOPATH"/src/github.com/fission/fission"
+
+if [[ -z $NATS_STREAMING_URL ]]; then
+    echo "'NATS_STREAMING_URL' must not be empty. For example: export NATS_STREAMING_URL=nats://192.168.0.1:4222"
+    exit 1
+fi
+
+if [[ -z $FISSION_URL ]]; then
+    echo "'FISSION_URL' must not be empty. For example: export FISSION_URL=http://10.10.10.10"
+    exit 1
+fi
+
+cd $FISSIONDIR"/fission/"
+go build
+mv fission $FISSIONDIR"/test/mqtrigger"
+cd $FISSIONDIR"/test/mqtrigger"
+
+./fission env create --name nodejs --image fission/node-env
+./fission fn create --name hello1 --env nodejs --code main.js --method GET
+./fission route create --method GET --url /h1 --function hello1
+./fission mqtrigger create --name h1 --function hello1 --mqtype "nats-streaming" --topic "foo.bar" --resptopic "foo.foo"
+
+# wait until nats trigger is created
+sleep 5
+
+go run ./stan-pub.go -s $NATS_STREAMING_URL -c $clusterID -id clientPub $topic "" || exit 1
+
+response=$(go run ./stan-sub.go --last -s $NATS_STREAMING_URL -c $clusterID -id clientSub $resptopic 2>&1)
+
+if [[ "$response" != "$expectedRespOutput" ]]; then
+    echo "$response is not equal to $expectedRespOutput"
+    exit 1
+fi
+
+echo "Subscriber received expected response: $response"
+
+exit 0