I need to create a lambda function to act as the middleman between a mobile Java app and an AWS RDS MySQL database. The idea is to submit queries from the mobile app and then send them off to the lambda function, which will then return the query. I have a basic MySQL query set up in my AWS lambda:
var mysql = require('mysql');
var config = require('./config.json');
var pool = mysql.createPool({
host : config.dbhost,
user : config.dbuser,
password : config.dbpassword,
database : config.dbname
});
exports.handler = (event, context, callback) -> {
context.callbackWaitsForEmptyEventLoop = false;
pool.getConnection(function(err, connection) {
if (err) throw err; // not connected!
// Use the connection
connection.query('select Album from record', function (error, results, fields) {
// When done with the connection, release it.
connection.release();
// Handle error after the release.
if (error) callback(error);
else callback(null, results[0].Album);
// Don't use the connection here, it has been returned to the pool.
});
});
};
And all that I am currently trying to do is get this code to run and output what the query will return. I've seen tutorials where people seem to just click test and have the code run, but it keeps asking me to create a test, and I'm not sure what exactly I would need to do to test this function.
EDIT: I realized I was missing a small change in my lambda uploaded code, but I am now getting an error on line 10 saying there is an unexpected token >.
I'm not sure what's wrong here, as the tutorial I watched seems to have the same exact thing.
Since you're not passing in any parameters through the context, you can just create a test with the defaults or an empty object {}, and click Test in the console. It will invoke your Lambda function as if it had been called from your mobile app, and you can debug from there.
Related
I have an Azure Function that connects to a MySQL DB outside of Azure. The DB connection is working, I am able to run INSERT queries without issue. The problem is that when I try to do a SELECT query and try to print the returned DB records to the console it shows as undefined. Below is the relevant code:
const mysql = require('mysql');
module.exports = async function (context, req) {
context.log('JavaScript HTTP trigger function processed a request.');
var connection = mysql.createConnection({
...
});
connection.connect();
let result;
const selectQuery = `SELECT * FROM emails WHERE email_address = 'tester#email.com'`;
await connection.query(selectQuery, async function (error, results, fields) {
if (error) throw error;
// This log doesn't work, it shows an error (see below code)
context.log(`Result: ${results}`)
result = results;
});
// Logging result here shows as undefined.
context.log(result);
connection.end();
context.log('Disconnected.');
The log inside the connection.query call results in this warning: Warning: Unexpected call to 'log' on the context object after function execution has completed. Please check for asynchronous calls that are not awaited or calls to 'done' made before function execution completes.
Then I try to save the result to a variable and log it after the query function, it returns as undefined. My guess is that I'm using await wrong for this, but I can't figure out how to get it right.
Warning: Unexpected call to 'log' on the context
object after function execution has completed.
Please check for asynchronous calls that are not
awaited or calls to 'done' made before function
execution completes.
The reason for the above warning and why you get undefined ? is because when assigning the variable, the statements of console logging the variable are executed before the connection.query can finish execution.
Now the work around for this would be that all the processing related to the variable i.e., result of the query must be done inside the call back function itself.
Here I have a NodeJS script which will run the query and console.log the result.
var mysql = require('mysql');
var connection = mysql.createConnection({
...
});
connection.connect();
connection.query('SELECT L FROM NEWTABLE WHERE P=1 ', function (error, results, fields) {
console.log("Logging inside the callback function");
if (error) throw error;
console.log(results);
});
connection.end();
output:
you can also set the context.res for your httptriggred function inside the callback function.
I am trying to set up an alexa skill that calls MySQL Querys when a certain question gets asked. Nothing I tried seemed to work because I either get an error or nothing happens at all.
I am using/what I am working with:
Alexa Developer Console
Cloud9 as IDE(which uploads the code to AWS Lambda, where I defined the environmental variables used in my code)
AWS Lambda, NodeJS
Amazon RDS, which hosts my DB instance
MySQL Workbench (where I created a few tables to test the database, which works fine)
I tried several ways to solve my problem, like creating a connection or a pool, but I think it has to be handled differently, because Alexa has to wait for the response.
const GetOeffnungszeiten_Handler = {
canHandle(handlerInput) {
const request = handlerInput.requestEnvelope.request;
return request.type === 'IntentRequest' && request.intent.name === 'GetOeffnungszeiten' ;
},
handle(handlerInput) {
const request = handlerInput.requestEnvelope.request;
const responseBuilder = handlerInput.responseBuilder;
let sessionAttributes = handlerInput.attributesManager.getSessionAttributes();
let say = 'OUTPUT: ';
var mysql = require('mysql');
var connection = mysql.createPool({
host : process.env.MYSQL_HOSTNAME,
user : process.env.MYSQL_USERNAME,
password : process.env.MYSQL_PASSWORD,
database : process.env.MYSQL_DATABASE,
port : process.env.MYSQL_PORT
});
exports.handler = (event, context, callback) => {
context.callbackWaitsForEmptyEventLoop = false;
pool.getConnection(function(err, connection) {
connection.query('select name from persons where id=1', function (error, results, fields) {
connection.release();
if (error) {
callback(error);
say=say+'0';
} else {
callback(null,results[0].name);
say=say+' 1';
}
});
});
};
return responseBuilder
.speak(say)
.reprompt('try again, ' + say)
.getResponse();
},
};
I expect the output to either be "OUTPUT: 1" or "OUTPUT: 0" but it is "OUTPUT: "
With output I refer to the say variable.
Your function is returning responseBuilder...getResponse() before the SQL connection finishes and callback is called.
I would suggest to refactor your code using async and await to make it easier to read and to understand. (read https://stormacq.com/2019/06/22/async-js.html for help)
Be sure to return the Alexa response only when your call to MySQL returns, and not before. Remember that Alexa timeout is 8 secs, so your code need to return before that. Be sure that the AWS Lambda timeout is aligned to the Alexa timeout too (put it at 7 secs)
Finally, I would advise against using MySQL for Alexa skills. Because each Lambda invocation might be served by different containers, your code will create a connection pool for each interaction between customers and your skill, creating a significant delay to bring a response to customers. DynamoDB and Elastic Cache are much better suited to Alexa skills.
How to use mysql connection with serverless framework.connection should be available in my component functions without creating mysql connection each time in component function
Tried like this
var mysql = require('mysql');
module.exports.respond = function(event, cb) {
var pool = mysql.createPool({
connectionLimit : 100,
host : 'hostname',
user : 'username',
password : 'password',
database : 'databasename',
debug : false
});
var message='';
pool.getConnection(function(err,connection){
if(err) {
message='Could not connect to database';
} else {
message="Database is connected";
}
var response = {
message: message
};
return cb(null, response);
});
};
but above code will be only available for current function,want to make common thing for mysql connection in serverless framework,can not find proper document about how to use mysql in serverless framework
I am writing answer of my own question
make database.js file in component/lib folder
code of database.js
var mysql = require('mysql');
var connection = mysql.createConnection({
host : 'hostname',
user : 'username',
password : 'password',
database : 'databasename'
});
connection.connect();
module.exports = connection;
created object like this in component/lib/index.js file
var connection = require("../lib/database.js");
Can use connection variable to write mysql query like this in component/lib/index.js
module.exports.respond = function(event, cb) {
var query="SELECT * from table_name";
connection.query(query,function(err,rows) {
})
};
I believe you have a Component created in your Serverless Framework based project that contains multiple lambda functions. And now you want to write the MySQL connection code such that this code block is available for re-use in all your lambda functions of that component.
If this is the ask, then Serverless does provide a "lib" folder inside your Component directory, which you can utilize to write common code logic to be re-used. Since you have a NodeJS-based runtime for your component, there should be an "index.js" file inside your Component folder -
your_serverless_project_directory/component_name/lib/index.js
The first thing you want to do is to add the MySQL connection code logic to a function/method in index.js.
Serverless should have already included for you this entire lib/ folder in all your lambda function's handler.js code like this -
var lib = require('../../lib');
Therefore, the next/final thing you want to do is re-use your connection function/method (in all the lambda functions belonging inside your Component) like this -
module.exports.handler = function(event, context) {
lib.mySQLConnection();
};
Hope this helps, let me know how it goes.
To build off of Normal Goswami's answer:
You've specified the database here in the connection. My lambdas each need different databases, so in the connection code just leave off the database:
var mysql = require('mysql');
var connection = mysql.createConnection({
host : 'hostname',
user : 'username',
password : 'password'
// no database here
});
connection.connect();
module.exports = connection;
And then use an oddly named function to change the database in each lambda function:
connection.changeUser({database: database}, function(err) {
if (err) { throw err; }
});
connection.query(sql, function(err, rows, fields) {
// etc
}
You could also look into using a database connection pool.
you have to make connection out of function, as we are doing it with mongodb
we are making mongodb connection out side of Lambda Function.
my code snippet from https://github.com/malikasinger1/serverles-practice/tree/master/mongodb-connection:
var mongoose = require("mongoose");
var dbURI = 'mongodb://localhost/mydatabase';
mongoose.connect(dbURI);
mongoose.connection.on('connected', function () {//connected
console.log("Mongoose is connected");
// process.exit(1);
});
module.exports.signup = (event, context, cb) => {
//doing signup here
}
in your cace it will be something like this most probably:
var mysql = require('mysql');
//make connection here
var pool = mysql.createPool({
...
});
pool.getConnection(function(err,connection){
...
});
module.exports.respond = function(event, cb) {
//use connection here
};
I am assuming you are using serverless framework on AWS.
Although you can create a connection and assign it to a frozen variable, it's not guaranteed that your lambda won't create a new connection. Here is why:
The best way so far (in my personal opinion) is to create a separate lambda function for db related operations and invoke this function through other lambdas. Here is the flow:
client -> registerUserLambda -> dbLambda -> DATABASE
However, the thing about lambdas is that when there are too many requests, there will be new containers created to handle other requests. That is, new connections will be created. Therefore the concept of connection pools does not work well for now on serverless lambdas.
I am using Express 4.9.0 and express-generator. Executed this command:
express --hbs projectname
Installed following modules with NPM:
mysql
express-myconnection
I want to make todo application. I have created separate file under routes/todo.js and created get/post routes for creating todos in that file using router.get and router.post.
i have following code in app.js:
// mysql connection
var connection = require('express-myconnection');
var mysql = require('mysql');
app.use(
connection(mysql, {
host : config.db.host,
user : config.db.user,
password : config.db.password,
database : config.db.database,
debug : false //set true if you wanna see debug logger
}, 'request')
);
// end of mysql connection
Where should i place mysql config and connection code? Inside todo.js? I still don't get concept of organisation file structure and where to place database queries.
I don't know if you eventually found the answer, but I thought it might help out others who accidentally stumbled on your question:
After you've setup like mentioned above, you can call the connection from the request object using the getConnection method like this:
exports.index = function(req, res) {
req.getConnection(function (err, connection) {
connection.query('select * from table_name', function(err, rows, fields){
if (err) {
return res.status(400).send({
message: errorHandler.getErrorMessage(err)
});
} else {
res.jsonp(rows);
}
});
});
};
This should print out a json with the content of your table all nice an pretty.
Hope this comes in handy.
i'm new to NodeJS (duh!).
I know it executes functions asynchronous but I still cannot see what causes this phenomenon:
I am using the express and mysql modules and trying to execute an SQL query based on request parameters. It is supposed to be a simple validation API feature where the server is going to lookup a user in a database by listening on a specific URL for two request parameters (user and passwd).
The problem is that the SQL query always returns an empty object as result when I do this using the request parameters in the query.
However, if i hard code the query and run it outside the app.get(...) I get the desired result! But I need this to work on demand by request...
(I'm not intending to use GET-request later on, this example is for debugging purposes :))
What am i doing wrong here?
Here's my code:
// Server and Mysql setup here
var app = require('express').createServer(),
SERVER_PORT = 8080;
var Client = require('mysql').Client,
client = new Client(),
...
// User, password and database setup here, cropped out from this example //
// ...
function validateUser(user, passwd, callback) {
client.query('SELECT date FROM '+CUSTOMERS_TABLE+' WHERE email="'+user+'" AND passwd="'+passwd+'";',
function selectCb(err, results, fields) {
if (err) {
throw err;
}
console.log(fields);
callback(results);
});
}
app.get('/', function(req, res){
var url_parts = url.parse(req.url, true);
var query = url_parts.query;
if((typeof query[REQ_PARAM_USER] != 'undefined' && typeof query[REQ_PARAM_PASSWD] != 'undefined')
&& (query[REQ_PARAM_USER] != '' && query[REQ_PARAM_PASSWD] != '')) {
validateUser(REQ_PARAM_USER, REQ_PARAM_PASSWD, function(results) {
console.log(results);
});
}
res.end("End")
});
app.listen(SERVER_PORT);
console.log('Server running at port '+SERVER_PORT);
Oh, and by the way, console.log(fields) outputs the correct fields! But why not the results?
You are passing the wrong parameters to validateUser:
validateUser(REQ_PARAM_USER, REQ_PARAM_PASSWD, // ...
What you really want:
validateUser(query[REQ_PARAM_USER], query[REQ_PARAM_PASSWD], // ...
Edit: A few other issues with your code:
You don't have to parse the url. Express does this for you, and the query is available as req.query.
You shouldn't throw in asynchronous code. It will give unexpected results. Instead, stick to the nodejs paradigm of passing (err, results) to all callbacks, and do proper error checking where you can -- i.e., in your verifyUser, pass along the error with the callback and check for errors in your get handler. Either res.send(500) (or something) when you get an error, or pass it along to the express error handler by calling next(err).
validateUser(query[REQ_PARAM_USER], query[REQ_PARAM_PASSWD], function(err, results) {
if(err) {
console.error(err);
res.send(500);
} else {
console.log(results);
res.send(results);
}
});
Never pass query parameters directly to something like an SQL query. Instead, use parameters for your SQL query:
client.query('SELECT date FROM '+CUSTOMERS_TABLE+' WHERE email=? AND passwd=?', [user, passwd], // ...