500 (Internal Server Error) on GET, POST requests to Function App Azure

Question

I created the Function App, I created a Function named HttpTrigger and provided the code in the index.js file which is the following:

const { performance, promisify } = require('perf_hooks');
const fs = require('fs');
const readline = require('readline');
const multer = require('multer');
const upload = multer();
const readFileAsync = promisify(fs.readFile);
const writeFileAsync = promisify(fs.writeFile);

const processingData = [];
let sortingRequests = 0;

module.exports = async function (context, req) {
    context.res = {
        headers: {
            'Content-Type': 'application/json'
        },
    };


    if (req.method === 'POST') {
        if (req.query.action === 'sort') {
            try {
                const inputFile = await processFileUpload(req);

                const startTime = performance.now();
                let requestsCounter = 0;

                const fileContent = await readFileAsync(inputFile.path, 'utf8');
                const dateArray = fileContent.split('\n');

                dateArray.sort((a, b) => {
                    requestsCounter++;
                    return new Date(b) - new Date(a);
                });

                const sortedDateArray = dateArray.join('\n');

                const data = {
                    requests: requestsCounter,
                    processingTime: performance.now() - startTime,
                };

                processingData.push(data);
                sortingRequests += requestsCounter;

                const filePath = `${context.executionContext.functionDirectory}/uploads/result.txt`;

                await writeFileAsync(filePath, sortedDateArray, 'utf8');

                context.res = {
                    status: 200,
                    body: { message: 'File sorted and saved as result.txt', processingData },
                };
            } catch (error) {
                context.res = {
                    status: 500,
                    body: { error: 'Internal Server Error', details: error.message },
                };
            }
        }
    } else if (req.method === 'GET') {
    if (req.query.action === 'download') {
        // Handle file download
        try {
            const filePath = `${context.executionContext.functionDirectory}/uploads/result.txt`;
            context.res = {
                status: 200,
                body: fs.readFileSync(filePath, 'utf8'),
                headers: {
                    'Content-Type': 'text/plain',
                    'Content-Disposition': 'attachment; filename=result.txt',
                },
            };
            context.done();
        } catch (error) {
            context.res = {
                status: 500,
                body: { error: 'Error downloading file' },
            };
            context.done();
        }
    } else if (req.query.action === 'sortingInfo') {
    
        // Handle sorting information request
        try {
            const sortingInfo = {
                requests: sortingRequests,
                processingData: processingData,
            };
            context.res = {
                status: 200,
                body: sortingInfo,
            };
            context.done();
        } catch (error) {
            context.res = {
                status: 500,
                body: { error: 'Internal Server Error' },
            };
            context.done();
        }
    } else {
        // Handle other GET requests as needed
        try {
            const greetingMessage = 'Hello from Azure Function!';
            context.res = {
                status: 200,
                body: { message: greetingMessage },
            };
            context.done();
        } catch (error) {
            context.res = {
                status: 500,
                body: { error: 'Internal Server Error' },
            };
            context.done();
        }
    }

} else {
        context.res = {
            status: 405,
            body: { error: 'Method Not Allowed' },
        };
        context.done();
    }
};
async function processFileUpload(req) {
    return new Promise((resolve, reject) => {
        upload.single('inputFile')(req, {}, (err) => {
            if (err) {
                console.error('Error processing file upload:', err);
                reject(new Error('Error processing file upload'));
            } else {
                resolve(req.file);
            }
        });
    });
}

Whenever I try to send a POST or GET request to the url provided by the function I keep getting 500 (Internal Server Error).

I tried logging the error but it is always the same thing, and I can't figure out where I'm getting the code wrong because both the client-side and the server-side runs perfectly when I run it locally but it fails when I run it as a function. Does anyone have any suggestions in order to debug the code and adjust it and solve the problem?

Answer 1

Below is the modified code with your code to sort the dates using the Multer package in an Azure function.

Code :

const { performance } = require('perf_hooks');
const fs = require('fs');
const { promisify } = require('util');
const multer = require('multer');
const upload = multer();
const readFileAsync = promisify(fs.readFile);
const writeFileAsync = promisify(fs.writeFile);

const processingData = [];
let sortingRequests = 0;

module.exports = async function (context, req) {
    context.res = {
        headers: {
            'Content-Type': 'application/json'
        },
    };

    try {
        if (req.method === 'POST') {
            if (req.query.action === 'sort') {
                const filePath = req.body && req.body.filePath;
                if (!filePath) {
                    throw new Error('No file path provided');
                }

                const fileContent = await readFileAsync(filePath, 'utf8');
                const dateArray = fileContent.split('\n');

                const startTime = Date.now();
                let requestsCounter = 0;

                dateArray.sort((a, b) => {
                    requestsCounter++;
                    return new Date(b) - new Date(a);
                });

                const sortedDateArray = dateArray.join('\n');
                const data = {
                    requests: requestsCounter,
                    processingTime: Date.now() - startTime,
                };

                processingData.push(data);
                sortingRequests += requestsCounter;

                const resultFilePath = `${context.executionContext.functionDirectory}/uploads/result.txt`;
                await writeFileAsync(resultFilePath, sortedDateArray, 'utf8');

                context.res = {
                    status: 200,
                    body: { message: 'File sorted and saved as result.txt', processingData },
                };
            }
        } else if (req.method === 'GET') {
            if (req.query.action === 'download') {
                try {
                    const filePath = `${context.executionContext.functionDirectory}/uploads/result.txt`;
                    const fileContent = fs.readFileSync(filePath, 'utf8');

                    context.res = {
                        status: 200,
                        body: fileContent,
                        headers: {
                            'Content-Type': 'text/plain',
                            'Content-Disposition': 'attachment; filename=result.txt',
                        },
                    };
                } catch (error) {
                    context.res = {
                        status: 500,
                        body: { error: 'Error downloading file' },
                    };
                }
            } else if (req.query.action === 'sortingInfo') {
                const sortingInfo = {
                    requests: sortingRequests,
                    processingData: processingData,
                };
                context.res = {
                    status: 200,
                    body: sortingInfo,
                };
            } else {
                const greetingMessage = 'Hello from Azure Function!';
                context.res = {
                    status: 200,
                    body: { message: greetingMessage },
                };
            }
        } else {
            context.res = {
                status: 405,
                body: { error: 'Method Not Allowed' },
            };
        }
    } catch (error) {
        context.res = {
            status: 500,
            body: { error: 'Internal Server Error', details: error.message },
        };
    }
};

async function processFileUpload(req) {
    return new Promise((resolve, reject) => {
        upload.single('inputFile')(req, {}, (err) => {
            if (err) {
                console.error('Error processing file upload:', err);
                reject(new Error('Error processing file upload'));
            } else {
                resolve(req.file);
            }
        });
    });
}

Output in Postman :

http://localhost:7071/api/HttpTrigger1?action=sort

json body:

{
    "filePath": "C:/Users/xxxxxxxxx/Documents/xxxxxxxxx/HttpTrigger1/uploads/dates.txt"
}

{
  "message": "File sorted and saved as result.txt",
  "processingData": [
    {
      "requests": 6,
      "processingTime": 1
    }
  ]
}

Browser Output :

localhost:7071/api/HttpTrigger1?action=sortingInfo

{
  "requests": 6,
  "processingData": [
    {
      "requests": 6,
      "processingTime": 1
    }
  ]
}

http://localhost:7071/api/HttpTrigger1?action=download

result.txt file is downloaded using GET method in browser as below.

Output :

It ran successfully as below,

 *  Executing task: func host start 

Azure Functions Core Tools
Core Tools Version:       4.0.5030 Commit hash: N/A  (64-bit)
Function Runtime Version: 4.15.2.20177

[2024-02-13T05:16:28.613Z] Debugger listening on ws://127.0.0.1:9229/aa5f50b2xxxxxxxxxxxxxx
[2024-02-13T05:16:28.618Z] For help, see: https://nodejs.org/en/docs/inspector

Functions:

        HttpTrigger1: [GET,POST] http://localhost:7071/api/HttpTrigger1

For detailed output, run func with --verbose flag.
[2024-02-13T05:16:29.634Z] Worker process started and initialized.
[2024-02-13T05:16:29.786Z] Debugger attached.
[2024-02-13T05:16:35.501Z] Host lock lease acquired by instance ID '0000000000xxxxxxxxxxxx'.
[2024-02-13T05:16:55.643Z] Executing 'Functions.HttpTrigger1' (Reason='This function was programmatically called via the host APIs.', Id=831c04cbxxxxxxxxxxxx)
[2024-02-13T05:16:56.038Z] Executed 'Functions.HttpTrigger1' (Succeeded, Id=831c04cbxxxxxxxxxxx, Duration=465ms)
[2024-02-13T05:17:23.955Z] Executing 'Functions.HttpTrigger1' (Reason='This function was programmatically called via the host APIs.', Id=2df554b2xxxxxxxxxxxxxxxx)
[2024-02-13T05:17:23.982Z] Executed 'Functions.HttpTrigger1' (Succeeded, Id=2df554b2xxxxxxxxxxx, Duration=28ms)
[2024-02-13T05:17:34.554Z] Executing 'Functions.HttpTrigger1' (Reason='This function was programmatically called via the host APIs.', Id=39d2374dxxxxxxxxxxxxx)
[2024-02-13T05:17:34.595Z] Executed 'Functions.HttpTrigger1' (Succeeded, Id=39d2374d-1e81-4f21-b52a-d39eef10a5fd, Duration=41ms)
[2024-02-13T05:17:50.464Z] Executing 'Functions.HttpTrigger1' (Reason='This function was programmatically called via the host APIs.', Id=70b272d7xxxxxxxxxxxxxx)
[2024-02-13T05:17:50.487Z] Executed 'Functions.HttpTrigger1' (Succeeded, Id=70b272d7xxxxxxxxxxxxx, Duration=24ms)

Before sort :

After sort :