Module: Iriq::Reducer

Defined in:
lib/iriq/reducer.rb

Overview

Reducers consume the Event stream emitted by Corpus#observe and update the storage backend’s materialized views. Each Reducer is a callable that takes (event, storage) and applies the appropriate storage operation; non-applicable events are no-ops via the EVENT_TYPES gate.

Adding a new metric is: define a new Event subtype, write a Reducer that handles it, register it in DEFAULTS — no other module changes.

Constant Summary collapse

DEFAULTS =

Each entry: { event_class => [lambda(event, storage) -> result] }. Lambdas may return the result of the underlying storage call so callers (Corpus#observe) can pick up the cluster they need to return.

{
  Event::HostSeen        => [->(e, s) { s.increment_host(e.host) }],
  Event::PathLengthSeen  => [->(e, s) { s.increment_path_length(e.length) }],
  Event::RawShapeSeen    => [->(e, s) { s.increment_raw_shape(e.shape) }],
  Event::FingerprintSeen => [->(e, s) { s.increment_fingerprint(e.shape) }],
  Event::PositionSeen    => [->(e, s) { s.observe_position(e.position, e.value, e.type) }],
  Event::ClusterAddition => [->(e, s) { s.add_to_cluster(e.key, e.host, e.scheme, e.shape, e.identifier) }],
}.freeze

Class Method Summary collapse

Class Method Details

.apply(event, storage, reducers: DEFAULTS) ⇒ Object

Apply the event to the storage via all Reducers registered for its type. Returns the last non-nil reducer result — used by Corpus#observe to pick up the Cluster created/updated by Event::ClusterAddition.



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# File 'lib/iriq/reducer.rb', line 27

def apply(event, storage, reducers: DEFAULTS)
  results = reducers.fetch(event.class, [])
  result  = nil
  results.each do |r|
    rv = r.call(event, storage)
    result = rv unless rv.nil?
  end
  result
end