function is timing out when http-triggered

Question

What am I doing wrong? Why is the function timing out?

I have a blob triggered function which works totally fine:

const Jimp = require("jimp");

module.exports = function(context, myBlob) {
  const correlation = context.bindings.inputBlob.correlation;
  const inputImage = context.bindings.inputBlob.image;
  const imageName = context.bindings.inputBlob.imageName;

  context.log(
    correlation + "Attempting to convert this image to a tiff: " + imageName
  ); 
  Jimp.read(Buffer.from(inputImage, "base64"), function(err, image) {
    image.getBuffer(Jimp.MIME_TIFF, function(error, tiff) {
      const response = {
        myimage: tiff.toString("base64"),
        correlation: correlation
      };
      context.bindings.outputBlob = response
      context.log(
        correlation + "Successfully converted " + imageName + " to tiff."
      );
      context.done();
    });
  });
};

Here is the function.json file:

{
  "bindings": [
    {
      "name": "myBlob",
      "type": "blobTrigger",
      "direction": "in",
      "path": "images-in/{destination}/{name}",
      "connection": "AZURE_STORAGE_CONNECTION_STRING"
    },
    {
      "name": "inputBlob",
      "type": "blob",
      "direction": "in",
      "path": "images-in/{destination}/{name}",
      "connection": "AZURE_STORAGE_CONNECTION_STRING"
    },
    {
      "type": "blob",
      "name": "outputBlob",
      "path": "{destination}/{name}.tiff",
      "connection": "AZURE_STORAGE_CONNECTION_STRING",
      "direction": "out"
    }
  ],
  "disabled": false
}

The way it works:

1. drop a blob into a specific location
2. output blob will be generated by the function in another location (the whole process takes no longer than about 5 seconds).

I decided that I needed the function to be http-triggered, so I made the following changes:

const Jimp = require("jimp");

module.exports = function(context, req) {

  Jimp.read(Buffer.from(req.body, "base64"), function(err, image) {
    image.getBuffer(Jimp.MIME_TIFF, function(error, tiff) {
      const response = {
        myimage: tiff.toString("base64"),
        correlation: "yeeeeees"
      };


    });
      context.res = {
          body: response
      };
      context.done();
  });


};

function.json:

{
  "bindings": [
    {
      "authLevel": "anonymous",
      "type": "httpTrigger",
      "direction": "in",
      "name": "req",
      "methods": [
        "post"
      ]
    },
    {
      "type": "http",
      "direction": "out",
      "name": "res"
    }
  ]
}

However, I am getting a 500:

The telemetry is showing the following:

What am I doing wrong? Why is the function timing out?

I've made the following update to the function:

const Jimp = require("jimp");

module.exports = function (context, req) {
    const text = Buffer.from(req.body, "base64").toString("utf-8");

    Jimp.read(text, function(err, image) {
    if (err) {
      context.res = {
        body: err
      };
      context.done();
    }

    image.getBuffer(Jimp.MIME_TIFF, function(error, tiff) {
      if (error) {
        context.res = {
          body: error
        };
        context.done();
      }
      const response = {
        myimage: tiff.toString("base64"),
        correlation: "yeeeeees"
      };
      context.res = {
        body: response
      };
      context.done();
    });
  });
};

This yielded the following nonsensical response:

{
  "errno": -4058,
  "code": "ENOENT",
  "syscall": "open",
  "path": "D:\\home\\site\\wwwroot\\$R\u0005������{\u001av��r��Ū�O�$z�ނ)",
  "methodName": "constructor"
}

Answer 1

If you check your node.js logs in Azure, you would see an error like response is not defined because your scope where you defined response is different then where you used.

So basically you are not able to call context.done(); function and that is why your request throwing timeout exception.

Using async/await will help you to not have this kind of problems. Please check this code example to understand what could go wrong.

const Jimp = require("jimp");

module.exports = function(context, req) {

  Jimp.read(Buffer.from(req.body, "base64"), function(err, image) {

    if(err){
      context.res = {
          body: err
      };
      context.done();
    }

    image.getBuffer(Jimp.MIME_TIFF, function(error, tiff) {
      if(error){
        context.res = {
          body: error
        };
        context.done();
      }
      const response = {
        myimage: tiff.toString("base64"),
        correlation: "yeeeeees"
      };
      context.res = {
        body: response 
      };
      context.done();
    });
  });
};