From 932330084fb50149ddbb711cfb653faeccdaea96 Mon Sep 17 00:00:00 2001 From: Tomas Doran Date: Sun, 13 Apr 2014 08:03:33 +0100 Subject: [PATCH] synapse etcd service watcher --- lib/synapse/service_watcher.rb | 2 + lib/synapse/service_watcher/etcd.rb | 154 ++++++++++++++++++++++++++++ synapse.gemspec | 1 + 3 files changed, 157 insertions(+) create mode 100644 lib/synapse/service_watcher/etcd.rb diff --git a/lib/synapse/service_watcher.rb b/lib/synapse/service_watcher.rb index 44227465..3af96864 100644 --- a/lib/synapse/service_watcher.rb +++ b/lib/synapse/service_watcher.rb @@ -3,6 +3,7 @@ module Synapse class ServiceWatcher + # the method which actually dispatches watcher creation requests def self.create(name, opts, synapse) opts['name'] = name @@ -24,3 +25,4 @@ def self.create(name, opts, synapse) end end end + diff --git a/lib/synapse/service_watcher/etcd.rb b/lib/synapse/service_watcher/etcd.rb new file mode 100644 index 00000000..dc4ec277 --- /dev/null +++ b/lib/synapse/service_watcher/etcd.rb @@ -0,0 +1,154 @@ +require "synapse/service_watcher/base" + +require 'etcd' + +module Synapse + class EtcdWatcher < BaseWatcher + NUMBERS_RE = /^\d+$/ + + def start + etcd_hosts = @discovery['host'] + + log.info "synapse: starting etcd watcher #{@name} @ host: #{@discovery['host']}, path: #{@discovery['path']}" + @should_exit = false + @etcd = ::Etcd.client(:host => @discovery['host'], :port => @discovery['port']) + + # call the callback to bootstrap the process + discover + @synapse.reconfigure! + @watcher = Thread.new do + watch + end + end + + def stop + log.warn "synapse: etcd watcher exiting" + + @should_exit = true + @etcd = nil + + log.info "synapse: etcd watcher cleaned up successfully" + end + + def ping? + @etcd.leader + end + + private + def validate_discovery_opts + raise ArgumentError, "invalid discovery method #{@discovery['method']}" \ + unless @discovery['method'] == 'etcd' + raise ArgumentError, "missing or invalid etcd host for service #{@name}" \ + unless @discovery['host'] + raise ArgumentError, "missing or invalid etcd port for service #{@name}" \ + unless @discovery['port'] + raise ArgumentError, "invalid etcd path for service #{@name}" \ + unless @discovery['path'] + end + + # helper method that ensures that the discovery path exists + def create(path) + log.debug "synapse: creating etcd path: #{path}" + @etcd.create(path, dir: true) + end + + def each_node(node) + begin + host, port, name = deserialize_service_instance(node.value) + rescue StandardError => e + log.error "synapse: invalid data in etcd node #{node.inspect} at #{@discovery['path']}: #{e} DATA #{node.value}" + nil + else + server_port = @server_port_override ? @server_port_override : port + + # find the numberic id in the node name; used for leader elections if enabled + numeric_id = node.key.split('/').last + numeric_id = NUMBERS_RE =~ numeric_id ? numeric_id.to_i : nil + + log.warn "synapse: discovered backend #{name} at #{host}:#{server_port} for service #{@name}" + { 'name' => name, 'host' => host, 'port' => server_port, 'id' => numeric_id} + end + end + + def each_dir(d) + new_backends = [] + d.children.each do |node| + if node.directory? + new_backends << each_dir(@etcd.get(node.key)) + else + backend = each_node(node) + if backend + new_backends << backend + end + end + end + new_backends.flatten + end + + # find the current backends at the discovery path; sets @backends + def discover + log.info "synapse: discovering backends for service #{@name}" + + d = nil + begin + d = @etcd.get(@discovery['path']) + rescue Etcd::KeyNotFound + create(@discovery['path']) + d = @etcd.get(@discovery['path']) + end + + new_backends = [] + if d.directory? + new_backends = each_dir(d) + else + log.warn "synapse: path #{@discovery['path']} is not a directory" + end + + if new_backends.empty? + if @default_servers.empty? + log.warn "synapse: no backends and no default servers for service #{@name}; using previous backends: #{@backends.inspect}" + false + else + log.warn "synapse: no backends for service #{@name}; using default servers: #{@default_servers.inspect}" + @backends = @default_servers + true + end + else + if @backends != new_backends + log.info "synapse: discovered #{new_backends.length} backends (including new) for service #{@name}" + @backends = new_backends + true + else + log.info "synapse: discovered #{new_backends.length} backends for service #{@name}" + false + end + end + end + + def watch + while !@should_exit + begin + @etcd.watch(@discovery['path'], :timeout => 60, :recursive => true) + rescue Timeout::Error + else + if discover + @synapse.reconfigure! + end + end + end + end + + # decode the data at a zookeeper endpoint + def deserialize_service_instance(data) + log.debug "synapse: deserializing process data" + decoded = JSON.parse(data) + + host = decoded['host'] || (raise ValueError, 'instance json data does not have host key') + port = decoded['port'] || (raise ValueError, 'instance json data does not have port key') + name = decoded['name'] || nil + + return host, port, name + end + end +end + diff --git a/synapse.gemspec b/synapse.gemspec index 86e238b3..4c23cae3 100644 --- a/synapse.gemspec +++ b/synapse.gemspec @@ -19,6 +19,7 @@ Gem::Specification.new do |gem| gem.add_runtime_dependency "aws-sdk", "~> 1.39" gem.add_runtime_dependency "docker-api", "~> 1.7.2" gem.add_runtime_dependency "zk", "~> 1.9.4" + gem.add_runtime_dependency "etcd", "~> 0.2.4" gem.add_development_dependency "rake" gem.add_development_dependency "rspec", "~> 3.1.0"