e2 example: mydb

An e2 demo multi-user socket-based database

Introduction

The code in this project is an LFE port of Garrett Smith's fabulous e2 tutorial, quite possibly one of the best Erlang tutorials available on the internets.

The code in this repo differs from that which is presented in the tutorial in several ways:

• It's in LFE, so it's all Lisp syntax (i.e., no syntax!).
• The standard Lisp naming conventions are used for functions and variables.
• Some of the module names are different (but a quick comparison should make the differences intuitively obvious).
• Configuration for different environments is done in mydb.app.src instead of separate config files.
• Since this was written against 17.3, appmon is not available; observer is used instead.

Use

$ git clone https://github.com/billota/e2-mydb-example.git mydb
$ cd mydb
$ make compile
$ make repl-no-deps

Then, from the repl:

> (mydb:start)
ok
> (observer:start)
ok

Then, from a separate terminal window:

$ telnet 127.0.0.1 3456
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
PUT msg hello
+OK
GET msg
+hello
DEL msg
+OK
GET msg
-ERROR

This can be repeated from many different terminal windows, and you will see the branches from the handler supervisor node in observer grow in number.