My task is to copy few redshift tables from cluster one to a new cluster. For this I am writing a script in nodejs. I am using aws-sdk RedshiftData api to fetch the data. I have two separate queries which I want to run in parallel. Following is my code
class syncRedShiftNodes {
constructor(){ ... }
readDataOne(){
let newSqlQuery = `select * from ${this.tableName} limit 10`;
const params = {
ClusterIdentifier: clusterIdentifier,
Sql: newSqlQuery,
Database: database,
DbUser: dbUser
};
return new Promise((resolve, reject)=>{
return awsRedshift.executeStatement(params, function(err, res){
if (err) console.log(err, err.stack); // an error occurred
else{
return awsRedshift.getStatementResult({Id:res.Id}, function(error, data){
if (error) console.log(error, error.stack); // an error occurred
else return data;
});
}
});
});
}
readDataTwo(){ ...//identical to above function except the query }
main(){
return Promise.all([this.readDataOne(), this.readDataTwo()])
.spread((data1, data2)=>{
console.log("promise resolved!!");
return true;
}
}
The problem is that my code is never reaching the "promise resolved" log. If I put a log in the callback of the redshift getStatementResult, that is being printed correctly but my handle is never reaching the promise.all().then statement which I am not able to understand why so.
Another question I had in mind was is it a good practice to use such a pattern inside a class?
You didn't resolve or reject your promise inside the class.
Example below
class syncRedShiftNodes {
constructor() {}
readDataOne() {
let newSqlQuery = `select * from ${this.tableName} limit 10`;
const params = {
ClusterIdentifier: clusterIdentifier,
Sql: newSqlQuery,
Database: database,
DbUser: dbUser,
};
return new Promise((resolve, reject) => {
awsRedshift.executeStatement(params, function (err, res) {
if (err) {
console.log(err, err.stack);
reject(err);
} else {
awsRedshift.getStatementResult(
{ Id: res.Id },
function (error, data) {
if (error) {
console.log(error, error.stack);
reject(error);
} else {
resolve(data);
}
}
);
}
});
});
}
readDataTwo() {}
async main() {
try {
const result = await Promise.all([
this.readDataOne(),
this.readDataTwo(),
]);
return result;
} catch (err) {
console.log(err);
}
}
}