## README.org

```
# Goldrush #
Goldrush is a small Erlang app that provides fast event stream processing
# Features #
* Event processing compiled to a query module
- per module protected event processing statistics
- query module logic can be combined for any/all filters
- query module logic can be reduced to efficiently match event processing
* Complex event processing logic
- match input events with greater than (gt) logic
- match input events with less than (lt) logic
- match input events with equal to (eq) logic
- match input events with wildcard (wc) logic
- match input events with notfound (nf) logic
- match no input events (null blackhole) logic
- match all input events (null passthrough) logic
* Handle output events
- Once a query has been composed the output action can be overriden
with an erlang function. The function will be applied to each
output event from the query.
* Usage
To use goldrush in your application, you need to define it as a rebar dep or
include it in erlang's path.
Before composing modules, you'll need to define a query. The query syntax
matches any number of `{erlang, terms}' and is composed as follows:
* Simple Logic
- Simple logic is defined as any logic matching a single event filter
Select all events where 'a' exists and is greater than 0.
#+BEGIN_EXAMPLE
glc:gt(a, 0).
#+END_EXAMPLE
Select all events where 'a' exists and is equal to 0.
#+BEGIN_EXAMPLE
glc:eq(a, 0).
#+END_EXAMPLE
Select all events where 'a' exists and is less than 0.
#+BEGIN_EXAMPLE
glc:lt(a, 0).
#+END_EXAMPLE
Select all events where 'a' exists.
#+BEGIN_EXAMPLE
glc:wc(a).
#+END_EXAMPLE
Select all events where 'a' does not exist.
#+BEGIN_EXAMPLE
glc:nf(a).
#+END_EXAMPLE
Select no input events. User as a black hole query.
#+BEGIN_EXAMPLE
glc:null(false).
#+END_EXAMPLE
Select all input events. Used as a passthrough query.
#+BEGIN_EXAMPLE
glc:null(true).
#+END_EXAMPLE
* Combined Logic
- Combined logic is defined as logic matching multiple event filters
Select all events where both 'a' AND 'b' exists and are greater than 0.
#+BEGIN_EXAMPLE
glc:all([glc:gt(a, 0), glc:gt(b, 0)]).
#+END_EXAMPLE
Select all events where 'a' OR 'b' exists and are greater than 0.
#+BEGIN_EXAMPLE
glc:any([glc:gt(a, 0), glc:gt(b, 0)]).
#+END_EXAMPLE
Select all events where 'a' AND 'b' exists where 'a' is greater than 1 and 'b' is less than 2.
#+BEGIN_EXAMPLE
glc:all([glc:gt(a, 1), glc:lt(b, 2)]).
#+END_EXAMPLE
Select all events where 'a' OR 'b' exists where 'a' is greater than 1 and 'b' is less than 2.
#+BEGIN_EXAMPLE
glc:any([glc:gt(a, 1), glc:lt(b, 2)]).
#+END_EXAMPLE
* Reduced Logic
- Reduced logic is defined as logic which can be simplified to improve efficiency.
Select all events where 'a' is equal to 1, 'b' is equal to 2 and 'c' is equal to 3 and collapse any duplicate logic.
#+BEGIN_EXAMPLE
glc_lib:reduce(
glc:all([
glc:any([glc:eq(a, 1), glc:eq(b, 2)]),
glc:any([glc:eq(a, 1), glc:eq(c, 3)])])).
#+END_EXAMPLE
The previous example will produce and is equivalent to:
#+BEGIN_EXAMPLE
glc:all([glc:eq(a, 1), glc:eq(b, 2), glc:eq(c, 3)]).
#+END_EXAMPLE
# Composing Modules #
To compose a module you will take your Query defined above and compile it.
#+BEGIN_EXAMPLE
glc:compile(Module, Query).
#+END_EXAMPLE
- At this point you will be able to handle an event using a compiled query.
Begin by constructing an event list.
#+BEGIN_EXAMPLE
Event = gre:make([{'a', 2}], [list]).
#+END_EXAMPLE
Now pass it to your query module to be handled.
#+BEGIN_EXAMPLE
glc:handle(Module, Event).
#+END_EXAMPLE
* Handling output events
- You can override the output action with an erlang function.
Write all input events as info reports to the error logger.
#+BEGIN_EXAMPLE
glc:with(glc:null(true), fun(E) ->
error_logger:info_report(gre:pairs(E)) end).
#+END_EXAMPLE
Write all input events where `error_level' exists and is less than 5 as info reports to the error logger.
#+BEGIN_EXAMPLE
glc:with(glc:lt(error_level, 5), fun(E) ->
error_logger:info_report(gre:pairs(E)) end).
#+END_EXAMPLE
# Event Processing Statistics #
Return the number of input events for this query module.
#+BEGIN_EXAMPLE
glc:input(Module).
#+END_EXAMPLE
Return the number of output events for this query module.
#+BEGIN_EXAMPLE
glc:output(Module).
#+END_EXAMPLE
Return the number of filtered events for this query module.
#+BEGIN_EXAMPLE
glc:filter(Module).
#+END_EXAMPLE
* Build
#+BEGIN_EXAMPLE
$ ./rebar compile
#+END_EXAMPLE
or
#+BEGIN_EXAMPLE
$ make
#+END_EXAMPLE
* CHANGELOG
0.1.6
- Add notfound event matching
0.1.5
- Rewrite to make highly crash resilient
- per module supervision
- statistics data recovery
- Add wildcard event matching
- Add reset counters
```