Added Loadbalancer based on request count. Ref #14 issue

Added a min-heap based Loadbalancer to balance based on request count.

dispatch_system/constants.json

@@ -3,5 +3,6 @@
     "master_port": 8080,
     "master_address": "localhost",
     "kafka_host": "10.129.6.5:9092",
+    "grunt_host": "https://www.namandixit.net/lovecraftian_nightmares/grunt",
     "log_channel": "LOG_COMMON"
 }
\ No newline at end of file

dispatch_system/dispatch_daemon/index.js

@@ -56,7 +56,7 @@ libSupport.makeTopic(node_id).then(() => {
 /**
  * download and start grunt
  */
-libSupport.download(host_url + '/repository/grunt', "grunt").then(() => {
+libSupport.download(constants.grunt_host, "grunt").then(() => {
     logger.info("Downloaded grunt binary from repository")
     fs.chmod('grunt', 0o555, (err) => {
         logger.info("grunt made executable. Starting grunt")

dispatch_system/dispatch_manager/index.js

@@ -7,6 +7,7 @@ const constants = require('.././constants.json')
 const fs = require('fs')
 const { spawn } = require('child_process');
 const morgan = require('morgan')
+const heap = require('heap')
 
 const app = express()
 const libSupport = require('./lib')
@@ -14,11 +15,11 @@ const logger = libSupport.logger
 let date = new Date();
 let log_channel = constants.log_channel
 
-let functionToResource = new Map(), // TODO: make the resource a list for horizontal scale out
-    usedPort = new Map(), // TODO: remove after integration with RM
+let usedPort = new Map(), // TODO: remove after integration with RM
     rmQueue = new Map(), // queue holding requests for which DM is waiting for RM allocation
-    db = new Map(),
-    resourceMap = new Map()
+    db = new Map(), // queue holding request to be dispatched
+    resourceMap = new Map(), // map between resource_id and resource details like node_id, port, associated function etc
+    functionToResource = new Map()
 
 let kafka = require('kafka-node'),
     Producer = kafka.Producer,
@@ -163,15 +164,19 @@ function deployContainer(path, imageName) {
  */
 app.post('/serverless/execute/:id', (req, res) => {
     let runtime = req.body.runtime
-    if (functionToResource.has(req.params.id + runtime)) {
+    let id = req.params.id + runtime
+    if (functionToResource.has(id)) {
         /**
          * Bypass deployment pipeline if resource available
          */
-        let forwardTo = functionToResource.get(req.params.id + runtime) 
+        let forwardTo = heap.pop(functionToResource.get(id), libSupport.compare)
         let resource = resourceMap.get(forwardTo.resource_id)
-        logger.info("resource found " + JSON.stringify(forwardTo) + 
-            " forwarding via reverse proxy to: " + JSON.stringify(resource));
+        logger.info(`Choosing resource ${JSON.stringify(forwardTo.resource_id)}` + 
+            "\n forwarding via reverse proxy to: " + JSON.stringify(resource));
         libSupport.reverseProxy(req, res, `http://${resource.node_id}:${resource.port}/serverless/function/execute`)
+        forwardTo.metric += 1
+        functionToResource.get(id).push(forwardTo)
+        console.log(functionToResource.get(id));
         
     } else {
         /**
@@ -281,9 +286,29 @@ consumer.on('message', function (message) {
         
         if (db.has(message.resource_id)) {
             let { req, res } = db.get(message.resource_id)
-            functionToResource.set(message.functionHash + message.runtime, {
-                resource_id: message.resource_id
-            })
+            if (functionToResource.has(message.functionHash + message.runtime)) {
+                let resourceHeap = functionToResource.get(message.functionHash + message.runtime)
+                heap.push(resourceHeap, {
+                    resource_id: message.resource_id,
+                    metric: 0
+                }, libSupport.compare)
+                console.log("adding to list", functionToResource.get(message.functionHash + message.runtime));
+                
+            } else {
+                /**
+                * function to resource map - holds a min heap of resources associated with a function
+                * the min heap is sorted based on a metric [TBD] like CPU usage, request count, mem usage etc
+                * TODO: decide on metric to use for sorting.
+                */
+                let resourceHeap = []
+                heap.push(resourceHeap, {
+                    resource_id: message.resource_id,
+                    metric: 0
+                }, libSupport.compare)
+                functionToResource.set(message.functionHash + message.runtime, resourceHeap)
+                console.log("creating new heap", functionToResource.get(message.functionHash + message.runtime));
+                
+            }
             let resource = resourceMap.get(message.resource_id)
             let confirmRM = [{
                 topic: log_channel,
@@ -308,6 +333,7 @@ consumer.on('message', function (message) {
                     db.delete(message.resource_id)
                 })
         }
+
     } else if (topic == "removeWorker") {
         logger.info("Worker blown: Removing Metadata " + message);
         try {
@@ -316,10 +342,27 @@ consumer.on('message', function (message) {
             // process.exit(0)
         }
         usedPort.delete(message.port)
-        let resource = functionToResource.get(message.functionHash + message.runtime)
+        if (functionToResource.has(message.functionHash + message.runtime)) {
+            let resourceArray = functionToResource.get(message.functionHash + message.runtime)
+            for (let i = 0; i < resourceArray.length; i++)
+                if (resourceArray[i].resource_id === message.resource_id) {
+                    console.log("splicing");
+                    
+                    resourceArray.splice(i, 1);
+                    break;
+                }
+
+            heap.heapify(resourceArray, libSupport.compare)
+            console.log(functionToResource.get(message.functionHash + message.runtime));
+            
+            resourceMap.delete(message.resource_id)
+            if (resourceArray.length == 0)
                 functionToResource.delete(message.functionHash + message.runtime)
-        if (resource != null)
-            resourceMap.delete(resource.resource_id)
+            console.log(resourceArray);
+            
+        }
+        
+
     } else if (topic == "RESPONSE_RM_2_DM") {
         
         logger.info("Response from RM: " + message);

dispatch_system/dispatch_manager/lib.js

@@ -112,6 +112,10 @@ const logger = winston.createLogger({
    ]
 });
 
+function compare(a, b) {
+   return a.metric - b.metric
+}
+
  module.exports = {
-    makeid, generateExecutor, reverseProxy, getPort, logger
+    makeid, generateExecutor, reverseProxy, getPort, logger, compare
  }
\ No newline at end of file

dispatch_system/dispatch_manager/package.json

@@ -13,6 +13,7 @@
     "body-parser": "^1.19.0",
     "express": "^4.17.1",
     "express-fileupload": "^1.1.6",
+    "heap": "^0.2.6",
     "isolated-vm": "^3.0.0",
     "kafka-node": "^5.0.0",
     "morgan": "^1.9.1",