Execute shell command from AWS lambda

Question

I am trying to execute a shell command to migrate from the AWS lambda. The idea is that whenever we need to run the migration, we will call the lambda via AWS CLI. I am unable to make it run. The command to run migration never gets executed and it's always response with null. Any help would be greatly appreciated.

This is the code I have :

const exec = require("child_process").exec;
const { okResponse, errorResponse } = require('./response');

exports.handler = async (event) => {
    exec("node ./node_modules/db-migrate/bin/db-migrate up --config=./database.json", (error, stdout, stderr) => {
        if (error) {
            console.error(`error: ${error.message}`);
            return errorResponse(500, 'Error running migration.');
        }
        if (stderr) {
            console.log(`stderr: ${stderr}`);
            return errorResponse(500, 'Error running migration.');
        }
        console.log(`stdout: ${stdout}`);
        return okResponse(200, 'Migration successfully.');
    });
}

What happens when you put await before your command execution line await exec("node ./node_modules/db-migrate/bin/db-migrate up — Sohan
– Sohan, Commented Oct 28, 2020 at 9:36

Marcin · Accepted Answer · 2020-10-28 09:22:39Z

6

My guess is that because you are using async lambda handler your function finishes before exec has a chance to even run. Therefore, you could use promise, as shown in the linked docs, to solve this issue.

An example would be:

const exec = require("child_process").exec;
const { okResponse, errorResponse } = require('./response');

exports.handler = async (event) => {


    const promise = new Promise(function(resolve, reject) {
   
        exec("node ./node_modules/db-migrate/bin/db-migrate up --config=./database.json", (error, stdout, stderr) => {
            if (error) {
                console.error(`error: ${error.message}`);
                return errorResponse(500, 'Error running migration.');
            }
            if (stderr) {
                console.log(`stderr: ${stderr}`);
                return errorResponse(500, 'Error running migration.');
            }
            console.log(`stdout: ${stdout}`);
            return okResponse(200, 'Migration successfully.');
          })
    })

   return promise
}

Please note that I haven't run the code, and further changes may be required to make it work correctly.

answered Oct 28, 2020 at 9:22

Marcin

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1 Comment

IamGhale Over a year ago

Sorry for the late reply. I already solved it. And yes, a Promise was what I needed. Your answer matches the solution. I am going to accept your answer. Thank you for your time. Cheers

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