Mongoose and multiple database in single node js project

Question

I m doing a Node js project that contains sub projects  One sub project will have one Mongodb database and Mongoose will be use for wrapping and querying db  But the problem is    Mongoose doesn t allow to use multiple databases in single mongoose instance as the models are build on one connection  To use multiple mongoose instances  Node js doesn t allow multiple module instances as it has caching system in require    I know disable module caching in Node js but I think it is not the good solution as it is only need for mongoose    I ve tried to use createConnection   and openSet   in mongoose  but it was not the solution   I ve tried to deep copy the mongoose instance  http   blog imaginea com deep-copy-in-javascript   to pass new mongoose instances to the sub project  but it throwing RangeError  Maximum call stack size exceeded     I want to know is there anyways to use multiple database with mongoose or any workaround for this problem  Because I think mongoose is quite easy and fast  Or any other modules as recommendations

User · Answer

A bit optimized for me atleast  solution  write this to a file db js and require this to wherever required and call it with a function call and you are good to go      const MongoClient   require  mongodb   MongoClient      async function getConnections url db           return new Promise  resolve reject   gt               MongoClient connect url    useUnifiedTopology  true   function err  client                    if err    console error err                       resolve false                                     else                      resolve client db db                                                            module exports   async function            let dbs                    dbs  db1         await getConnections  mongodb   localhost 27017    db1            dbs  db2         await getConnections  mongodb   localhost 27017    db2            return dbs

User · Answer

One thing you can do is  you might have subfolders for each projects  So  install mongoose in that subfolders and require   mongoose from own folders in each sub applications  Not from the project root or from global  So one sub project  one mongoose installation and one mongoose instance   -app root  --foo app  ---db access js ---foo db connect js ---node modules  ----mongoose  --bar app  ---db access js ---bar db connect js ---node modules  ----mongoose    In foo db connect js  var mongoose   require  mongoose    mongoose connect  mongodb   localhost foo db    module exports   exports   mongoose    In bar db connect js  var mongoose   require  mongoose    mongoose connect  mongodb   localhost bar db    module exports   exports   mongoose    In db access js files  var mongoose   require    foo db connect js       bar db connect js for bar app   Now  you can access multiple databases with mongoose

User · Answer

As an alternative approach  Mongoose does export a constructor for a new instance on the default instance  So something like this is possible   var Mongoose   require  mongoose   Mongoose   var instance1   new Mongoose    instance1 connect  foo     var instance2   new Mongoose    instance2 connect  bar      This is very useful when working with separate data sources  and also when you want to have a separate database context for each user or request  You will need to be careful  as it is possible to create a LOT of connections when doing this  Make sure to call disconnect   when instances are not needed  and also to limit the pool size created by each instance

User · Answer

According to the fine manual  createConnection   can be used to connect to multiple databases   However  you need to create separate models for each connection database   var conn        mongoose createConnection  mongodb   localhost testA    var conn2       mongoose createConnection  mongodb   localhost testB        stored in  testA  database var ModelA      conn model  Model   new mongoose Schema     title     type   String  default    model in testA database             stored in  testB  database var ModelB      conn2 model  Model   new mongoose Schema     title     type   String  default    model in testB database           I m pretty sure that you can share the schema between them  but you have to check to make sure

User · Answer

Pretty late but this might help someone  The current answers assumes you are using the same file for your connections and models   In real life  there is a high chance that you are splitting your models into different files  You can use something like this in your main file   mongoose connect  mongodb   localhost default     const db   mongoose connection   db on  error   console error bind console   connection error      db once  open        gt      console log  connected          which is just how it is described in the docs  And then in your model files  do something like the following   import mongoose    Schema   from  mongoose    const userInfoSchema   new Schema     createdAt        type  Date      required  true      default  new Date                 other fields      const myDB   mongoose connection useDb  myDB     const UserInfo   myDB model  userInfo   userInfoSchema    export default UserInfo    Where myDB is your database name

User · Answer

Mongoose and multiple database in single node js project use useDb to solve this issue example   product databse const myDB   mongoose connection useDb  product    module exports   myDB model  quot Snack quot   snackSchema     user databse const myDB   mongoose connection useDb  user    module exports   myDB model  quot User quot   userSchema

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