Core synchronous queue with an example worker

routes/calc-queue.js

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+const express = require('express')
+const statusCodes = require('http-status-codes').StatusCodes
+const calcQueueSvc = require('../src/services/calc-queue')
+const CalcQueueExceptions = require('../src/services/calc-queue/exceptions.js')
+
+const router = express.Router()
+
+// Return busy/not busy flag
+router.get('/busy', function(req, res) {
+  res.send({ busy: calcQueueSvc.isBusy() })
+})
+
+// Get the current queue of tasks
+router.get('/queue', function(req, res) {
+  res.send({ 'queue': calcQueueSvc.getQueue() })
+})
+
+// Add a calc task to the queue
+router.put('/queue/:id/:calcFn', function(req, res) {
+  try {
+    calcQueueSvc.enqueue(req.params.id, req.params.calcFn)
+    res.send({ success: true })
+  } catch(ex) {
+    if (ex instanceof CalcQueueExceptions.AlreadyQueued
+      || ex instanceof CalcQueueExceptions.AlreadyInProgress
+      || ex instanceof CalcQueueExceptions.CalculationUnknown) {
+      res.status(
+        statusCodes.BAD_REQUEST
+      ).send(
+        { success: false, error: ex.message }
+      )
+    } else {
+      throw ex
+    }
+  }
+})
+
+// Remove a task or collection of tasks from the queue
+router.delete('/queue/:id', function(req, res) {
+  calcQueueSvc.dequeue(req.params.id, null)
+  res.send({ success: true })
+})
+// Remove a task from the queue
+router.delete('/queue/:id/:calcFn', function(req, res) {
+  calcQueueSvc.dequeue(req.params.id, req.params.calcFn)
+  res.send({ success: true })
+})
+
+
+// Get the status of a task as a text string
+const processStatus = function(id, calcFn) {
+  if (calcQueueSvc.isInProgress(id, calcFn)) {
+    return 'in_progress'
+  } else if (calcQueueSvc.isQueued(id, calcFn)) {
+    return 'queued'
+  } else if (calcQueueSvc.isFinished(id, calcFn)) {
+    return 'finished'
+  } else {
+    return 'not_queued'
+  }
+}
+
+// Get the status of the queue and all tasks
+router.get('/status', function(req, res) {
+  res.status(statusCodes.OK).send({
+    'queued': calcQueueSvc.getQueue(),
+    'in_progress': calcQueueSvc.getInProgress(),
+    'finished': calcQueueSvc.getFinished()
+  })
+})
+
+// Get the status of all tasks with by id
+router.get('/status/:id', function(req, res) {
+  res.status(statusCodes.OK).send({
+    'id': req.params.id,
+    'status': processStatus(req.params.id, null)
+  })
+})
+
+// Get the status of an individual task
+router.get('/status/:id/:calcFn', function(req, res) {
+  res.status(statusCodes.OK).send({
+    'id': req.params.id,
+    'calcFn': req.params.calcFn,
+    'status': processStatus(req.params.id, req.params.calcFn)
+  })
+})
+
+module.exports = router

routes/index.js

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+const dotenv = require('dotenv')
+const express = require('express')
+const statusCodes = require('http-status-codes').StatusCodes
+const createError = require('http-errors')
+
+dotenv.config()
+
+const router = express.Router()
+
+// TODO: Add a mechanism for multiple clients/API keys
+const apiKeys = [
+  process.env.API_KEY
+]
+
+// Middleware to verify API access is granted
+router.use('/', function(req, res, next){
+  var key = req.query['api_key'];
+
+  // key isn't present
+  if (!key) {
+    return next(createError(statusCodes.BAD_REQUEST, 'api key required'))
+  }
+
+  // key is invalid
+  if (!~apiKeys.indexOf(key)) {
+    return next(createError(statusCodes.UNAUTHORIZED, 'invalid api key'))
+  }
+
+  // all good, store req.key for route access
+  req.key = key
+  next()
+})
+
+// Add API routes to default router
+router.use('/', require('./calc-queue.js'))
+
+module.exports = router