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Original file line number | Diff line number | Diff line change |
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require 'concurrent/atomics' | ||
require 'json' | ||
require 'yaml' | ||
require 'pathname' | ||
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module LaunchDarkly | ||
# To avoid pulling in 'listen' and its transitive dependencies for people who aren't using the | ||
# file data source or who don't need auto-updating, we only enable auto-update if the 'listen' | ||
# gem has been provided by the host app. | ||
@@have_listen = false | ||
begin | ||
require 'listen' | ||
@@have_listen = true | ||
rescue | ||
end | ||
def self.have_listen? | ||
@@have_listen | ||
end | ||
|
||
# | ||
# Provides a way to use local files as a source of feature flag state. This would typically be | ||
# used in a test environment, to operate using a predetermined feature flag state without an | ||
# actual LaunchDarkly connection. | ||
# | ||
# To use this component, call `FileDataSource.factory`, and store its return value in the | ||
# `update_processor_factory` property of your LaunchDarkly client configuration. In the options | ||
# to `factory`, set `paths` to the file path(s) of your data file(s): | ||
# | ||
# factory = FileDataSource.factory(paths: [ myFilePath ]) | ||
# config = LaunchDarkly::Config.new(update_processor_factory: factory) | ||
# | ||
# This will cause the client not to connect to LaunchDarkly to get feature flags. The | ||
# client may still make network connections to send analytics events, unless you have disabled | ||
# this with Config.send_events or Config.offline. | ||
# | ||
# Flag data files can be either JSON or YAML. They contain an object with three possible | ||
# properties: | ||
# | ||
# - "flags": Feature flag definitions. | ||
# - "flagValues": Simplified feature flags that contain only a value. | ||
# - "segments": User segment definitions. | ||
# | ||
# The format of the data in "flags" and "segments" is defined by the LaunchDarkly application | ||
# and is subject to change. Rather than trying to construct these objects yourself, it is simpler | ||
# to request existing flags directly from the LaunchDarkly server in JSON format, and use this | ||
# output as the starting point for your file. In Linux you would do this: | ||
# | ||
# curl -H "Authorization: {your sdk key}" https://app.launchdarkly.com/sdk/latest-all | ||
# | ||
# The output will look something like this (but with many more properties): | ||
# | ||
# { | ||
# "flags": { | ||
# "flag-key-1": { | ||
# "key": "flag-key-1", | ||
# "on": true, | ||
# "variations": [ "a", "b" ] | ||
# } | ||
# }, | ||
# "segments": { | ||
# "segment-key-1": { | ||
# "key": "segment-key-1", | ||
# "includes": [ "user-key-1" ] | ||
# } | ||
# } | ||
# } | ||
# | ||
# Data in this format allows the SDK to exactly duplicate all the kinds of flag behavior supported | ||
# by LaunchDarkly. However, in many cases you will not need this complexity, but will just want to | ||
# set specific flag keys to specific values. For that, you can use a much simpler format: | ||
# | ||
# { | ||
# "flagValues": { | ||
# "my-string-flag-key": "value-1", | ||
# "my-boolean-flag-key": true, | ||
# "my-integer-flag-key": 3 | ||
# } | ||
# } | ||
# | ||
# Or, in YAML: | ||
# | ||
# flagValues: | ||
# my-string-flag-key: "value-1" | ||
# my-boolean-flag-key: true | ||
# my-integer-flag-key: 1 | ||
# | ||
# It is also possible to specify both "flags" and "flagValues", if you want some flags | ||
# to have simple values and others to have complex behavior. However, it is an error to use the | ||
# same flag key or segment key more than once, either in a single file or across multiple files. | ||
# | ||
# If the data source encounters any error in any file-- malformed content, a missing file, or a | ||
# duplicate key-- it will not load flags from any of the files. | ||
# | ||
class FileDataSource | ||
# | ||
# Returns a factory for the file data source component. | ||
# | ||
# @param options [Hash] the configuration options | ||
# @option options [Array] :paths The paths of the source files for loading flag data. These | ||
# may be absolute paths or relative to the current working directory. | ||
# @option options [Boolean] :auto_update True if the data source should watch for changes to | ||
# the source file(s) and reload flags whenever there is a change. Auto-updating will only | ||
# work if all of the files you specified have valid directory paths at startup time. | ||
# Note that the default implementation of this feature is based on polling the filesystem, | ||
# which may not perform well. If you install the 'listen' gem (not included by default, to | ||
# avoid adding unwanted dependencies to the SDK), its native file watching mechanism will be | ||
# used instead. However, 'listen' will not be used in JRuby 9.1 due to a known instability. | ||
# @option options [Float] :poll_interval The minimum interval, in seconds, between checks for | ||
# file modifications - used only if auto_update is true, and if the native file-watching | ||
# mechanism from 'listen' is not being used. The default value is 1 second. | ||
# | ||
def self.factory(options={}) | ||
return Proc.new do |sdk_key, config| | ||
FileDataSourceImpl.new(config.feature_store, config.logger, options) | ||
end | ||
end | ||
end | ||
|
||
class FileDataSourceImpl | ||
def initialize(feature_store, logger, options={}) | ||
@feature_store = feature_store | ||
@logger = logger | ||
@paths = options[:paths] || [] | ||
if @paths.is_a? String | ||
@paths = [ @paths ] | ||
end | ||
@auto_update = options[:auto_update] | ||
if @auto_update && LaunchDarkly.have_listen? && !options[:force_polling] # force_polling is used only for tests | ||
# We have seen unreliable behavior in the 'listen' gem in JRuby 9.1 (https://github.com/guard/listen/issues/449). | ||
# Therefore, on that platform we'll fall back to file polling instead. | ||
if defined?(JRUBY_VERSION) && JRUBY_VERSION.start_with?("9.1.") | ||
@use_listen = false | ||
else | ||
@use_listen = true | ||
end | ||
end | ||
@poll_interval = options[:poll_interval] || 1 | ||
@initialized = Concurrent::AtomicBoolean.new(false) | ||
@ready = Concurrent::Event.new | ||
end | ||
|
||
def initialized? | ||
@initialized.value | ||
end | ||
|
||
def start | ||
ready = Concurrent::Event.new | ||
|
||
# We will return immediately regardless of whether the file load succeeded or failed - | ||
# the difference can be detected by checking "initialized?" | ||
ready.set | ||
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||
load_all | ||
|
||
if @auto_update | ||
# If we're going to watch files, then the start event will be set the first time we get | ||
# a successful load. | ||
@listener = start_listener | ||
end | ||
|
||
ready | ||
end | ||
|
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def stop | ||
@listener.stop if !@listener.nil? | ||
end | ||
|
||
private | ||
|
||
def load_all | ||
all_data = { | ||
FEATURES => {}, | ||
SEGMENTS => {} | ||
} | ||
@paths.each do |path| | ||
begin | ||
load_file(path, all_data) | ||
rescue => exn | ||
Util.log_exception(@logger, "Unable to load flag data from \"#{path}\"", exn) | ||
return | ||
end | ||
end | ||
@feature_store.init(all_data) | ||
@initialized.make_true | ||
end | ||
|
||
def load_file(path, all_data) | ||
parsed = parse_content(IO.read(path)) | ||
(parsed[:flags] || {}).each do |key, flag| | ||
add_item(all_data, FEATURES, flag) | ||
end | ||
(parsed[:flagValues] || {}).each do |key, value| | ||
add_item(all_data, FEATURES, make_flag_with_value(key.to_s, value)) | ||
end | ||
(parsed[:segments] || {}).each do |key, segment| | ||
add_item(all_data, SEGMENTS, segment) | ||
end | ||
end | ||
|
||
def parse_content(content) | ||
# We can use the Ruby YAML parser for both YAML and JSON (JSON is a subset of YAML and while | ||
# not all YAML parsers handle it correctly, we have verified that the Ruby one does, at least | ||
# for all the samples of actual flag data that we've tested). | ||
symbolize_all_keys(YAML.load(content)) | ||
end | ||
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||
def symbolize_all_keys(value) | ||
# This is necessary because YAML.load doesn't have an option for parsing keys as symbols, and | ||
# the SDK expects all objects to be formatted that way. | ||
if value.is_a?(Hash) | ||
value.map{ |k, v| [k.to_sym, symbolize_all_keys(v)] }.to_h | ||
elsif value.is_a?(Array) | ||
value.map{ |v| symbolize_all_keys(v) } | ||
else | ||
value | ||
end | ||
end | ||
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||
def add_item(all_data, kind, item) | ||
items = all_data[kind] | ||
raise ArgumentError, "Received unknown item kind #{kind} in add_data" if items.nil? # shouldn't be possible since we preinitialize the hash | ||
key = item[:key].to_sym | ||
if !items[key].nil? | ||
raise ArgumentError, "#{kind[:namespace]} key \"#{item[:key]}\" was used more than once" | ||
end | ||
items[key] = item | ||
end | ||
|
||
def make_flag_with_value(key, value) | ||
{ | ||
key: key, | ||
on: true, | ||
fallthrough: { variation: 0 }, | ||
variations: [ value ] | ||
} | ||
end | ||
|
||
def start_listener | ||
resolved_paths = @paths.map { |p| Pathname.new(File.absolute_path(p)).realpath.to_s } | ||
if @use_listen | ||
start_listener_with_listen_gem(resolved_paths) | ||
else | ||
FileDataSourcePoller.new(resolved_paths, @poll_interval, self.method(:load_all), @logger) | ||
end | ||
end | ||
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def start_listener_with_listen_gem(resolved_paths) | ||
path_set = resolved_paths.to_set | ||
dir_paths = resolved_paths.map{ |p| File.dirname(p) }.uniq | ||
opts = { latency: @poll_interval } | ||
l = Listen.to(*dir_paths, opts) do |modified, added, removed| | ||
paths = modified + added + removed | ||
if paths.any? { |p| path_set.include?(p) } | ||
load_all | ||
end | ||
end | ||
l.start | ||
l | ||
end | ||
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||
# | ||
# Used internally by FileDataSource to track data file changes if the 'listen' gem is not available. | ||
# | ||
class FileDataSourcePoller | ||
def initialize(resolved_paths, interval, reloader, logger) | ||
@stopped = Concurrent::AtomicBoolean.new(false) | ||
get_file_times = Proc.new do | ||
ret = {} | ||
resolved_paths.each do |path| | ||
begin | ||
ret[path] = File.mtime(path) | ||
rescue Errno::ENOENT | ||
ret[path] = nil | ||
end | ||
end | ||
ret | ||
end | ||
last_times = get_file_times.call | ||
@thread = Thread.new do | ||
while true | ||
sleep interval | ||
break if @stopped.value | ||
begin | ||
new_times = get_file_times.call | ||
changed = false | ||
last_times.each do |path, old_time| | ||
new_time = new_times[path] | ||
if !new_time.nil? && new_time != old_time | ||
changed = true | ||
break | ||
end | ||
end | ||
reloader.call if changed | ||
rescue => exn | ||
Util.log_exception(logger, "Unexpected exception in FileDataSourcePoller", exn) | ||
end | ||
end | ||
end | ||
end | ||
|
||
def stop | ||
@stopped.make_true | ||
@thread.run # wakes it up if it's sleeping | ||
end | ||
end | ||
end | ||
end |
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