node-lbc

A node.js client library for LogicBlox. Allows you to connect to LogicBlox using pure JavaScript running in node.js.

It is the product of the LogicBlox Hackathon '13 and written by Zef Hemel. A 5 minute screencast explaining it can be seen here.

Why a node.js connector?

We now position LogicBlox as a database. Typically, a database is not enough to build complete applications. You typically have an application server of some kind that talks to the database and executes queries. On the Java platform you have JDBC for SQL databases. I already built a Clojure connector for LogicBlox before, so this time I thought I'd try building one for node.js.

The cool thing about node.js is

1. It's JavaScript -- awesome
2. It's asynchronous
3. It's a great platform for building efficient servers that primarily glue systems together

How to use it

The project contains a Vagrantfile:

$ vagrant up

Once done (this will take a while), login:

$ vagrant ssh

and then run npm install to intall dependencies:

$ npm install

To run the tests (in tests):

$ npm test

Connect

Import the module:

var lbConnect = require("lbc");

Connect to LB:

lbConnect(function(err, conn) {
    // Your code here
    // Close connection
    conn.close();
});

Disconnect:

conn.close(function(err) {
   ...
});

Schema management

Add a block:

conn.addBlock("myworkspace", "person(x) -> string(x).", function(err) {
   ...
});

Queries

Execute a block:

conn.exec("myworkspace", "+person(\"Zef\").", function(err) {
   ...
});

Query a predicate:

conn.query("myworkspace", "person", function(err, results) {
   console.log(results);
});

Execute a query:

conn.query("myworkspace", "_(p) <- person(p).", function(err, results) {
   console.log(results);
});

Workspace management

Create a workspace:

conn.createWorkspace("myworkspace", function(err) {
   ...
});

Export a workspace:

conn.exportWorkspace("myworkspace", "/tmp/myws", function(err) {
   ...
});

Import a workspace:

conn.importWorkspace("myworkspace2", "/tmp/myws", function(err) {
   ...
});

Remove a workspace:

conn.removeWorkspace("myworkspace2", function(err) {
   ...
});

Sample applications

The sample/ directory contains two samples:

• replserver.js: a server that could be used as a more secure connectblox implementation (used now at https://repl.logicblox.com).
• lb_api_server.js which is described in the next section.

LB API Server

Most, if not practically all databases that I know of have some sort of authentication and authorization system. LogicBlox does not. In fact, support for connecting to a LB database from another system is very limited.

The LB API server (samples/lb_api_server.js) exposes a LogicBlox server via a HTTP RESTful API and adds support for multiple users and authorization of users for specific workspaces, so you can create a user (as an admin) that can query a workspace, but not run 'exec' queries, or have access to other workspaces on the same server.

Documentation is limited due to time constraints, but the curl commands at the top of lb_api_server.js should help understanding the idea.

The users and their permissions are stored in a users workspace which is automatically created when the server is first started (and it does not already exist). The schema for this can be found under sample/api_server_schema.logic, as well as the initial data (for the admin user) in sample/api_server_init.logic.