simple-squiggle

A restricted subset of Squiggle
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server.js (1985B)

      1 /**
      2  * This example demonstrates how to run math.js in a child process with limited
      3  * execution time.
      4  *
      5  * Prerequisites:
      6  *
      7  *     npm install express workerpool
      8  *
      9  * Start the server:
     10  *
     11  *     node ./server.js
     12  *
     13  * Make a request to the server:
     14  *
     15  *     GET http://localhost:8080/mathjs?expr=sqrt(16)
     16  *
     17  * Note that the query parameter `expr` should be properly url encoded.
     18  */
     19 const path = require('path')
     20 
     21 let express
     22 let workerpool
     23 try {
     24   express = require('express')
     25   workerpool = require('workerpool')
     26 } catch (err) {
     27   console.log('Error: To run this example, install express and workerpool first via:\n\n' +
     28       '    npm install express workerpool\n')
     29   process.exit()
     30 }
     31 
     32 const app = express()
     33 const pool = workerpool.pool(path.join(__dirname, '/math_worker.js'))
     34 
     35 const TIMEOUT = 10000 // milliseconds
     36 
     37 /**
     38  * GET /mathjs?expr=...
     39  */
     40 app.get('/mathjs', function (req, res) {
     41   const expr = req.query.expr
     42   if (expr === undefined) {
     43     return res.status(400).send('Error: Required query parameter "expr" missing in url.')
     44   }
     45 
     46   pool.exec('evaluate', [expr])
     47     .timeout(TIMEOUT)
     48     .then(function (result) {
     49       res.send(result)
     50     })
     51     .catch(function (err) {
     52       res.status(400).send(formatError(err))
     53     })
     54 })
     55 
     56 /**
     57  * Format error messages as string
     58  * @param {Error} err
     59  * @return {String} message
     60  */
     61 function formatError (err) {
     62   if (err instanceof workerpool.Promise.TimeoutError) {
     63     return 'TimeoutError: Evaluation exceeded maximum duration of ' + TIMEOUT / 1000 + ' seconds'
     64   } else {
     65     return err.toString()
     66   }
     67 }
     68 
     69 // handle uncaught exceptions so the application cannot crash
     70 process.on('uncaughtException', function (err) {
     71   console.log('Caught exception: ' + err)
     72   console.trace()
     73 })
     74 
     75 // start the server
     76 const PORT = process.env.PORT || 8080
     77 app.listen(PORT, function () {
     78   console.log('Listening at http://localhost:' + PORT)
     79   console.log('Example request:\n    GET http://localhost:' + PORT + '/mathjs?expr=sqrt(16)')
     80 })