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| 1 | +require "synapse/service_watcher/base" |
| 2 | + |
| 3 | +require 'etcd' |
| 4 | + |
| 5 | +module Synapse |
| 6 | + class EtcdWatcher < BaseWatcher |
| 7 | + NUMBERS_RE = /^\d+$/ |
| 8 | + |
| 9 | + def start |
| 10 | + etcd_hosts = @discovery['host'] |
| 11 | + |
| 12 | + log.info "synapse: starting etcd watcher #{@name} @ host: #{@discovery['host']}, path: #{@discovery['path']}" |
| 13 | + @should_exit = false |
| 14 | + @etcd = ::Etcd.client(:host => @discovery['host'], :port => @discovery['port']) |
| 15 | + |
| 16 | + # call the callback to bootstrap the process |
| 17 | + discover |
| 18 | + @synapse.reconfigure! |
| 19 | + @watcher = Thread.new do |
| 20 | + watch |
| 21 | + end |
| 22 | + end |
| 23 | + |
| 24 | + def stop |
| 25 | + log.warn "synapse: etcd watcher exiting" |
| 26 | + |
| 27 | + @should_exit = true |
| 28 | + @etcd = nil |
| 29 | + |
| 30 | + log.info "synapse: etcd watcher cleaned up successfully" |
| 31 | + end |
| 32 | + |
| 33 | + def ping? |
| 34 | + @etcd.leader |
| 35 | + end |
| 36 | + |
| 37 | + private |
| 38 | + def validate_discovery_opts |
| 39 | + raise ArgumentError, "invalid discovery method #{@discovery['method']}" \ |
| 40 | + unless @discovery['method'] == 'etcd' |
| 41 | + raise ArgumentError, "missing or invalid etcd host for service #{@name}" \ |
| 42 | + unless @discovery['host'] |
| 43 | + raise ArgumentError, "missing or invalid etcd port for service #{@name}" \ |
| 44 | + unless @discovery['port'] |
| 45 | + raise ArgumentError, "invalid etcd path for service #{@name}" \ |
| 46 | + unless @discovery['path'] |
| 47 | + end |
| 48 | + |
| 49 | + # helper method that ensures that the discovery path exists |
| 50 | + def create(path) |
| 51 | + log.debug "synapse: creating etcd path: #{path}" |
| 52 | + @etcd.create(path, dir: true) |
| 53 | + end |
| 54 | + |
| 55 | + def each_node(node) |
| 56 | + begin |
| 57 | + host, port, name = deserialize_service_instance(node.value) |
| 58 | + rescue StandardError => e |
| 59 | + log.error "synapse: invalid data in etcd node #{node.inspect} at #{@discovery['path']}: #{e} DATA #{node.value}" |
| 60 | + nil |
| 61 | + else |
| 62 | + server_port = @server_port_override ? @server_port_override : port |
| 63 | + |
| 64 | + # find the numberic id in the node name; used for leader elections if enabled |
| 65 | + numeric_id = node.key.split('/').last |
| 66 | + numeric_id = NUMBERS_RE =~ numeric_id ? numeric_id.to_i : nil |
| 67 | + |
| 68 | + log.warn "synapse: discovered backend #{name} at #{host}:#{server_port} for service #{@name}" |
| 69 | + { 'name' => name, 'host' => host, 'port' => server_port, 'id' => numeric_id} |
| 70 | + end |
| 71 | + end |
| 72 | + |
| 73 | + def each_dir(d) |
| 74 | + new_backends = [] |
| 75 | + d.children.each do |node| |
| 76 | + if node.directory? |
| 77 | + new_backends << each_dir(@etcd.get(node.key)) |
| 78 | + else |
| 79 | + backend = each_node(node) |
| 80 | + if backend |
| 81 | + new_backends << backend |
| 82 | + end |
| 83 | + end |
| 84 | + end |
| 85 | + new_backends.flatten |
| 86 | + end |
| 87 | + |
| 88 | + # find the current backends at the discovery path; sets @backends |
| 89 | + def discover |
| 90 | + log.info "synapse: discovering backends for service #{@name}" |
| 91 | + |
| 92 | + d = nil |
| 93 | + begin |
| 94 | + d = @etcd.get(@discovery['path']) |
| 95 | + rescue Etcd::KeyNotFound |
| 96 | + create(@discovery['path']) |
| 97 | + d = @etcd.get(@discovery['path']) |
| 98 | + end |
| 99 | + |
| 100 | + new_backends = [] |
| 101 | + if d.directory? |
| 102 | + new_backends = each_dir(d) |
| 103 | + else |
| 104 | + log.warn "synapse: path #{@discovery['path']} is not a directory" |
| 105 | + end |
| 106 | + |
| 107 | + if new_backends.empty? |
| 108 | + if @default_servers.empty? |
| 109 | + log.warn "synapse: no backends and no default servers for service #{@name}; using previous backends: #{@backends.inspect}" |
| 110 | + false |
| 111 | + else |
| 112 | + log.warn "synapse: no backends for service #{@name}; using default servers: #{@default_servers.inspect}" |
| 113 | + @backends = @default_servers |
| 114 | + true |
| 115 | + end |
| 116 | + else |
| 117 | + if @backends != new_backends |
| 118 | + log.info "synapse: discovered #{new_backends.length} backends (including new) for service #{@name}" |
| 119 | + @backends = new_backends |
| 120 | + true |
| 121 | + else |
| 122 | + log.info "synapse: discovered #{new_backends.length} backends for service #{@name}" |
| 123 | + false |
| 124 | + end |
| 125 | + end |
| 126 | + end |
| 127 | + |
| 128 | + def watch |
| 129 | + while !@should_exit |
| 130 | + begin |
| 131 | + @etcd.watch(@discovery['path'], :timeout => 60, :recursive => true) |
| 132 | + rescue Timeout::Error |
| 133 | + else |
| 134 | + if discover |
| 135 | + @synapse.reconfigure! |
| 136 | + end |
| 137 | + end |
| 138 | + end |
| 139 | + end |
| 140 | + |
| 141 | + # decode the data at a zookeeper endpoint |
| 142 | + def deserialize_service_instance(data) |
| 143 | + log.debug "synapse: deserializing process data" |
| 144 | + decoded = JSON.parse(data) |
| 145 | + |
| 146 | + host = decoded['host'] || (raise ValueError, 'instance json data does not have host key') |
| 147 | + port = decoded['port'] || (raise ValueError, 'instance json data does not have port key') |
| 148 | + name = decoded['name'] || nil |
| 149 | + |
| 150 | + return host, port, name |
| 151 | + end |
| 152 | + end |
| 153 | +end |
| 154 | + |
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