CODEWITHSUNDEEP
javascriptnode.jsmongodbexpress
Akila Uyanwatta
Akila Uyanwatta

Reputation: 603

Sequential HTTP post requests in node.js

I am pushing sensor data to a mongoDB server using node.js and express. I'm pushing data around 5 times a second (using HTTP post requests).

I send aggregated sensor data. My sensor data look like this

  transmission 1 - 1,2,3 
  transmission 2 - 4,5,6 
  transmission 3 - 7,8,9

After appending my data to database, it sometimes looks like this

data array - 1,2,3,7,8,9,4,5,6

As you can see 3rd transmission is appended before 2nd transmission

POST request handling parts of my server.js look like this

var app = require("express")();
app.post("/saveData", function(req, res){
  res.send("a");//sending acknowledgement  
      Data_From_NodeMCU = req.body.hello; //getting data from JSON object
      ////Some processing\\\\


      dbObject.updateOne(
      {name: "AKILA"}, 
      {'$push': {data :{$each: processed_data} }},
      function (err) {
                        if (err) 
                             {
                                console.log("DB error:");
                                console.log(err);
                              }                              
                      }
                        );        
    
});

It seems like what i want to achieve is, once app.post is called, stop it from executing again until database is updated. It maybe a basic problem but I'm new to this, any help would be very helpful

Upvotes: 0

Views: 487

Answers (1)

Josh Wulf
Josh Wulf

Reputation: 4877

You can use async's queue with a concurrency of 1. It will be something like this:

const app = require("express")();
const queue = require("async/queue");

const q = queue(function(task, cb) {
  dbObject.updateOne({name: "AKILA"}, 
    {'$push': {data :{$each: task.processed_data} }}, (err) => {
       if (err) console.log("DB error:", err);
       cb();
  });     
}, 1)

app.post("/saveData", function(req, res){
  res.send("a"); //sending acknowledgement  
  const Data_From_NodeMCU = req.body.hello; 
  const processed_data = processData(Data_From_NodeMCU);
  q.push({processed_data});   
});

Upvotes: 1

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