CODEWITHSUNDEEP
javascriptnode.jses6-promise
MANOJ
MANOJ

Reputation: 736

how to wait till DB connection is made and queries are executed for each database in an array

A file contains json data with details of database. For each database connection, a series of queries need to be executed. Currently, the map function is waiting for the database connection.

Below is the start function

function start() {
 console.log('function initiated');
  try {
    let jsonData = fs.readFileSync('../request.json');
    let jsonString = JSON.parse(jsonData);

    //jsonString['request'].forEach(async function(json) {
    jsonString['request'].map(async json => {
      dbdetails = json.dbdetails;
      //dbdetails.forEach(async function(db){
      await dbbdetails.map(async db => {
        console.log('pdbdetails: ' + db);
        connString = json.connString;

        //makes the DB connection
        await connectDB(db.userId, db.Password, connString)
          .then(async conn => {
            await execution(conn, pdbDetails, vmUser, vmPassword, ip);
          })
          .catch(err => {
            console.log(err);
          });
        console.log('after each execution');
        //}
      });
    });
  } catch (err) {
    console.log(err.message);
    return;
  }
}

Below function is to make a database connection and return the connection

function connectDB(oUser, oPassword, connString) {
  console.log('inside connectDB');
  return new Promise((resolve, reject) => {
    oracledb.getConnection(
      {
        user: oUser,
        password: oPassword,
        connectString: connString
      },
      function(err, connection) {
        if (err) {
          console.error(err.message);
          reject(err);
          //throw err;
        }
        console.log('returning connection');
        //console.log(connection);
        resolve(connection);
        //return connection;
      }
    );
  });
}

below is the function which executes servies of queries on database

  function execution() {
     /// series of sql query execution
    }

Upvotes: 1

Views: 526

Answers (1)

Ben West
Ben West

Reputation: 4596

Not sure what you’re trying to do exactly, but sounds like the problem is that .map doesn’t wait for your async functions. If you have to do them one at a time, use a for loop:

for ( var item of array ) {
    await item.something();
}

To do them all at once:

var results = await Promise.all( array.map( item => item.something() )

Upvotes: 1

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