I have a working Jhipster application, linked to a mysql database.
I would like to create a new application that I would connect to the first application database.
Is it possible? regarding to liquibase/entities/etc.
Why should this not be possible? MySQL itself is a multiuser DBMS, so it could handle multiple connections.
The only problem would be liquibase, because it checks if your database is valid against your changelogs. So, if your second app also uses liquibase and has not the same changelogs with same checksums, it will not start. So your second app should not use liquibase and you should remove the liquibase-stuff from the second app. The means: the first app is repsponsible for creating/updating the schema using liquibase and the second app just uses the same schema.
And you're right: the entities must be the same, because hibernate/JPA assumes the same column and entity/table names (which are given by the database)...
In my opinion, a better approach would be the microservice-way: the first application is the only who access the database directly and offers some interfaces for the entities via REST. Then, your second application simply uses the interface via a REST-Client. This also allows you to define other/modified entities via the REST-Service and your second app may not use exactly the same like in the first application.
Related
If one Nodejs app connects to a Mongo instance, and that app has defined a User schema with pre-save hooks, validation, etc.
And then another Nodejs app connects to the same database, and tries to register a User schema with different properties.
And then the second app saves a User
What happens?
I'm confused with how two Nodejs apps may communicate to the same database.
For example, it's very easy to see how one might want to have V2 of an api on a separate nodejs app developed by a separate team. But they will plug it into the same database and use the same Schema (or will they?), and I'm confused with how things are shared between the two apps.
Any help clarifying this in best-practices would be appreciated
I believe I've found the answer in the Documentation.
This connection object is then used to create and retrieve models. Models are always scoped to a single connection. docs
And
Models are fancy constructors compiled from our Schema definitions. docs
Which explains that a DB Connection 1's Schema Definitions (pre-save, etc), do not affect DB Connection 2's writes/etc.
Essentially, they are completely independent of validation and everything else. They only need to be OK in their own context.
I am trying out React-Starter-Kit for the first time and loving all the cutting edge features baked in (apollo/graphql-client in particular). A crucial part of any app for me is the database, and for that my understanding is the same author provides nodejs-api-starter which sets up a REST interface for accessing Postgres at localhost:5000 and has a graphql webui at localhost:5000/graphl.
That is about as far as I have been able to understand of the setup so far. I have changed the frontend code a little bit so a new Component "Counter" is loaded on the home page. I need to be able to make a new counter, fetch the latest counter, and increment decrement the counter. Write now the component just outputs the 'value' retrieved from the server at 5000.
I do not think I am accessing the 5000 server correctly, do I put the port in this url line somehow?
You can pull the repo down from : https://github.com/Falieson/react-starter-kit-crud-counter-demo
This is my first time setting up a nodejs api server, I am used to using MeteorJS which has pub/sub to MongoDB baked in. I am looking forward to the separation the RSK strategy (which seems more industry standard?) provides.
I've just done setting up the full site with Database from React-Stater-Kit, I'm also a newbie so I understand your frustration.
About this question, you don't need the NodeJS-API-Starter, it has enhanced function ( such as Redis cache ) and it's not suited for newbies. You should look deeper into the RSK, it already has the DB. If you ran the boilerplate and played around, change is you'll see file database.sqlite in your folder, it's the database. Here are the things you should learn:
Use SequelizeJS to connect the NodeJS server with database. Your database can be MySQL/MariaDB, PostgreSQL or SQLite. The connection is easy and there's tool to auto-generate Models from your database
How to create GraphQL's Types and Queries. If your queries need to search through the database, import Sequelize's models and use its functions.
Test your API via GraphQLi
Note: if you want to use MongoDB or other NoSQL, try Mongoose instead of Sequelize.
Does it create any major problems if we always create and populate a PouchDB database locally first, and then later sync/authenticate with a centralised CouchDB service like Cloudant?
Consider this simplified scenario:
You're building an accommodation booking service such as hotel search or airbnb
You want people to be able to favourite/heart properties without having to create an account, and will use PouchDB to store this list
i.e. the idea is to not break their flow by making them create an account when it isn't strictly necessary
If users wish to opt in, they can later create an account and receive credentials for a "server side" database to sync with
At the point of step 3, once I've created a per-user CouchDB database server-side and assigned credentials to pass back to the browser for sync/replication, how can I link that up with the PouchDB data already created? i.e.
Can PouchDB somehow just reuse the existing database for this sync, therefore pushing all existing data up to the hosted CouchDB database, or..
Instead do we need to create a new PouchDB database and then copy over all docs from the existing (non-replicated) one to this new (replicated) one, and then delete the existing one?
I want to make sure I'm not painting myself into any corner I haven't thought of, before we begin the first stage, which is supporting non-replicated PouchDB.
It depends on what kind of data you want to sync from the server, but in general, you can replicate a pre-existing database into a new one with existing documents, just so long as those document IDs don't conflict.
So probably the best idea for the star-rating model would be to create documents client-side with IDs like 'star_<timestamp>' to ensure they don't conflict with anything. Then you can aggregate them with a map/reduce function.
I'm trying to dynamically generate databases/collections on application startup, in case they do not exist yet. This works fine when working with the _system database. The thing is that it seems not to be allowed when trying to switch to other databases. From the docs:
db._useDatabase(name)
Changes the current database to the database specified by name. Note
that the database specified by name must already exist.
Changing the database might be disallowed in some contexts, for
example server-side actions (including Foxx).
Does this mean that Foxx applications can only create collections within the _system database? My manifest file sets the isSystem property to false. What is the meaning of such limitation?
A Foxx is included in one database context and has access to the collections there.
You can install Foxx apps in different databases.
f.E. you can run the following commands in arangosh to install the foxx app "example" in the database "myDB":
db._useDatabase("myDB")
fm.install("example","/example")
your app will than be reachable at (assuming standard configuration):
http://localhost:8529/_db/myDB/example
It is intentionally not possible to access a different database from within a Foxx app.
I am creating a WCF data service on top of a EF 4.1 code first data model that goes against a multi-tenant database. In order to enforce the rules of accessing the multi-tenancy I want to require a string id (that is required by all of our MVC-based REST services) be passed as part of the url route. So, for example, right now I have a service route like this:
http://mysample.net/mysamplesvc.svc/Users
That returns all users in the db w/o a filter. I want to partition this by client by requiring the client id be passed as part of the request like this:
http://mysample.net/mysamplesvc.svc/client123/Users
If it is not passed-in or is invalid I will handle it as required. However, I do not see any example like this anywhere. I think I must be searching incorrectly as this seems like a pretty common scenario.
TIA!
The sample service at http://services.odata.org/(S(readwrite))/OData/OData.svc/ does this (it creates a new instance of the data for each (S(...)) in the URL).
The service code is the last sample on this page: http://www.odata.org/ecosystem#samplecode