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em-eventsource.rb
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em-eventsource.rb
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# encoding: utf-8
require "eventmachine"
require "em-http-request"
module EventMachine
# EventSource
# dev.w3.org/html5/eventsource/
class EventSource
# Get API url
attr_reader :url
# Get ready state
attr_reader :ready_state
# Get current retry value (in seconds)
attr_reader :retry
# Override retry value (in seconds)
attr_writer :retry
# Get value of last event id
attr_reader :last_event_id
# Get the inactivity timeout
attr_reader :inactivity_timeout
# Set the inactivity timeout
attr_writer :inactivity_timeout
# Ready state
# The connection has not yet been established, or it was closed and the user agent is reconnecting.
CONNECTING = 0
# The user agent has an open connection and is dispatching events as it receives them.
OPEN = 1
# The connection is not open, and the user agent is not trying to reconnect. Either there was a fatal error or the close() method was invoked.
CLOSED = 2
# Create a new stream
#
# url - the url as string
# query - the query string as hash
# headers - the headers for the request as hash
def initialize(url, query={}, headers={})
@conn = nil
@url = url
@query = query
@headers = headers
@ready_state = CLOSED
@last_event_id = nil
@retry = 3 # seconds
@inactivity_timeout = 60 # seconds
@opens = []
@errors = []
@messages = []
@on = {}
@middlewares = []
end
# Add open event handler
#
# Returns nothing
def open(&block)
@opens << block
end
# Add a specific event handler
#
# name - name of event
#
# Returns nothing
def on(name, &block)
@on[name] ||= []
@on[name] << block
end
# Add message event handler
#
# Returns nothing
def message(&block)
@messages << block
end
# Add error event handler
#
# Returns nothing
def error(&block)
@errors << block
end
# Add a middleware
#
# *args - the middleware class
#
# Returns nothing
def use(*args, &block)
block = args.pop if block.nil? && block_given?
@middlewares << [args, block]
end
# Start subscription
#
# Returns nothing
def start
@ready_state = CONNECTING
listen
end
# Cancel subscription
#
# Returns nothing
def close
@ready_state = CLOSED
@conn.close('requested') if @conn
end
protected
def listen
@conn, @req = prepare_request
@req.headers(&method(:handle_headers))
@req.errback(&method(:handle_reconnect))
@req.callback(&method(:handle_reconnect))
buffer = ""
@req.stream do |chunk|
unless chunk.valid_encoding?
chunk.scrub!('?')
end
buffer += chunk
while index = buffer.index(/\r\n\r\n|\n\n/)
stream = buffer.slice!(0..index)
handle_stream(stream)
end
end
end
def handle_reconnect(*args)
return if @ready_state == CLOSED
if @req.response_header.redirection?
@url = @req.response_header.location
listen
return
end
@ready_state = CONNECTING
@errors.each { |error| error.call("Connection lost. Reconnecting.") }
EM.add_timer(@retry) do
listen
end
end
def handle_headers(headers)
if headers.redirection?
@req.close
return
end
if headers.status != 200
close
@errors.each { |error| error.call("Unexpected response status #{headers.status}") }
return
end
if /^text\/event-stream/.match headers['CONTENT_TYPE']
@ready_state = OPEN
@opens.each { |open| open.call }
else
close
@errors.each { |error| error.call("The content-type '#{headers['CONTENT_TYPE']}' is not text/event-stream") }
end
end
def handle_stream(stream)
data = ""
name = nil
stream.split(/\r?\n/).each do |part|
/^data:(.+)$/.match(part) do |m|
data += m[1].strip
data += "\n"
end
/^id:(.+)$/.match(part) do |m|
@last_event_id = m[1].strip
end
/^event:(.+)$/.match(part) do |m|
name = m[1].strip
end
/^retry:(.+)$/.match(part) do |m|
if m[1].strip! =~ /^[0-9]+$/
@retry = m[1].to_i / 1000
end
end
end
return if data.empty?
data.chomp!
if name.nil?
@messages.each { |message| message.call(data) }
else
@on[name].each { |message| message.call(data) } unless @on[name].nil?
end
end
def prepare_request
conn = EM::HttpRequest.new(@url, {tls: {verify_peer: true}, inactivity_timeout: @inactivity_timeout})
@middlewares.each do |middleware, block|
if block
conn.use(*middleware, &block)
else
conn.use(*middleware)
end
end
headers = @headers.merge({'Cache-Control' => 'no-cache', 'Accept' => 'text/event-stream'})
headers.merge!({'Last-Event-Id' => @last_event_id }) unless @last_event_id.nil?
[conn, conn.get({ query: @query,
head: headers,
keepalive: true })]
end
end
end