Class: LaunchDarkly::RedisFeatureStore

Inherits:
Object
  • Object
show all
Defined in:
lib/ldclient-rb/redis_feature_store.rb

Overview

An implementation of the LaunchDarkly client’s feature store that uses a Redis instance. Feature data can also be further cached in memory to reduce overhead of calls to Redis.

To use this class, you must first have the redis, connection-pool, and moneta gems installed. Then, create an instance and store it in the feature_store property of your client configuration.

Constant Summary collapse

INIT_KEY = 
:"$initialized"

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(opts = {}) ⇒ RedisFeatureStore

Constructor for a RedisFeatureStore instance.

Options Hash (opts):

  • :redis_url (String) —

    URL of the Redis instance (shortcut for omitting redis_opts)

  • :redis_opts (Hash) —

    options to pass to the Redis constructor (if you want to specify more than just redis_url)

  • :prefix (String) —

    namespace prefix to add to all hash keys used by LaunchDarkly

  • :logger (Logger) —

    a Logger instance; defaults to Config.default_logger

  • :max_connections (Integer) —

    size of the Redis connection pool

  • :expiration (Integer) —

    expiration time for the in-memory cache, in seconds; 0 for no local caching

  • :capacity (Integer) —

    maximum number of feature flags to cache locally

  • :pool (Object) —

    custom connection pool, used for testing only



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# File 'lib/ldclient-rb/redis_feature_store.rb', line 40

def initialize(opts = {})
  if !REDIS_ENABLED
    raise RuntimeError.new("can't use RedisFeatureStore because one of these gems is missing: redis, connection_pool, moneta")
  end
  @redis_opts = opts[:redis_opts] || Hash.new
  if opts[:redis_url]
    @redis_opts[:url] = opts[:redis_url]
  end
  if !@redis_opts.include?(:url)
    @redis_opts[:url] = RedisFeatureStore.default_redis_url
  end
  max_connections = opts[:max_connections] || 16
  @pool = opts[:pool] || ConnectionPool.new(size: max_connections) do
    Redis.new(@redis_opts)
  end
  @prefix = opts[:prefix] || RedisFeatureStore.default_prefix
  @logger = opts[:logger] || Config.default_logger
  @features_key = @prefix + ':features'

  @expiration_seconds = opts[:expiration] || 15
  @capacity = opts[:capacity] || 1000
  # We're using Moneta only to provide expiration behavior for the in-memory cache.
  # Moneta can also be used as a wrapper for Redis, but it doesn't support the Redis
  # hash operations that we use.
  if @expiration_seconds > 0
    @cache = Moneta.new(:LRUHash, expires: true, threadsafe: true, max_count: @capacity)
  else
    @cache = Moneta.new(:Null)  # a stub that caches nothing
  end

  @stopped = Concurrent::AtomicBoolean.new(false)

  with_connection do |redis|
    @logger.info("RedisFeatureStore: using Redis instance at #{redis.connection[:host]}:#{redis.connection[:port]} \
and prefix: #{@prefix}")
  end
end

Class Method Details

.default_prefix ⇒ Object

Default value for the prefix constructor parameter.



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# File 'lib/ldclient-rb/redis_feature_store.rb', line 89

def self.default_prefix
  'launchdarkly'
end

.default_redis_url ⇒ Object

Default value for the redis_url constructor parameter; points to an instance of Redis running at localhost with its default port.



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# File 'lib/ldclient-rb/redis_feature_store.rb', line 82

def self.default_redis_url
  'redis://localhost:6379/0'
end

Instance Method Details

#all ⇒ Object 



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# File 'lib/ldclient-rb/redis_feature_store.rb', line 120

def all
  fs = {}
  with_connection do |redis|
    begin
      hashfs = redis.hgetall(@features_key)
    rescue => e
      @logger.error("RedisFeatureStore: could not retrieve all flags from Redis with error: #{e}; returning none")
      hashfs = {}
    end
    hashfs.each do |k, jsonFeature|
      f = JSON.parse(jsonFeature, symbolize_names: true)
      if !f[:deleted]
        fs[k.to_sym] = f
      end
    end
  end
  fs
end

#clear_local_cache ⇒ Object

exposed for testing



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# File 'lib/ldclient-rb/redis_feature_store.rb', line 203

def clear_local_cache()
  @cache.clear
end

#delete(key, version) ⇒ Object 



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# File 'lib/ldclient-rb/redis_feature_store.rb', line 139

def delete(key, version)
  with_connection do |redis|
    f = get_redis(redis, key)
    if f.nil?
      put_redis_and_cache(redis, key, { deleted: true, version: version })
    else
      if f[:version] < version
        f1 = f.clone
        f1[:deleted] = true
        f1[:version] = version
        put_redis_and_cache(redis, key, f1)
      else
        @logger.warn("RedisFeatureStore: attempted to delete flag: #{key} version: #{f[:version]} \
  with a version that is the same or older: #{version}")
      end
    end
  end
end

#get(key) ⇒ Object 



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# File 'lib/ldclient-rb/redis_feature_store.rb', line 93

def get(key)
  f = @cache[key.to_sym]
  if f.nil?
    @logger.debug("RedisFeatureStore: no cache hit for #{key}, requesting from Redis")
    f = with_connection do |redis|
      begin
        get_redis(redis,key.to_sym)
      rescue => e
        @logger.error("RedisFeatureStore: could not retrieve feature #{key} from Redis, with error: #{e}")
        nil
      end
    end
    if !f.nil?
      put_cache(key.to_sym, f)
    end
  end
  if f.nil?
    @logger.warn("RedisFeatureStore: feature #{key} not found")
    nil
  elsif f[:deleted]
    @logger.warn("RedisFeatureStore: feature #{key} was deleted, returning nil")
    nil
  else
    f
  end
end

#init(fs) ⇒ Object 



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# File 'lib/ldclient-rb/redis_feature_store.rb', line 158

def init(fs)
  @cache.clear
  with_connection do |redis|
    redis.multi do |multi|
      redis.del(@features_key)
      fs.each { |k, f| put_redis_and_cache(multi, k, f) }
    end
  end
  put_cache(INIT_KEY, true)
  @logger.info("RedisFeatureStore: initialized with #{fs.count} feature flags")
end

#initialized? ⇒ Boolean 



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# File 'lib/ldclient-rb/redis_feature_store.rb', line 182

def initialized?
  if @cache[INIT_KEY].nil?
    if with_connection { |redis| redis.exists(@features_key) }
      put_cache(INIT_KEY, true)
      true
    else
      false
    end
  else
    put_cache(INIT_KEY, true)  # reset TTL
  end
end

#stop ⇒ Object 



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# File 'lib/ldclient-rb/redis_feature_store.rb', line 195

def stop
  if @stopped.make_true
    @pool.shutdown { |redis| redis.close }
    @cache.clear
  end
end

#upsert(key, feature) ⇒ Object 



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# File 'lib/ldclient-rb/redis_feature_store.rb', line 170

def upsert(key, feature)
  with_connection do |redis|
    redis.watch(@features_key) do
      old = get_redis(redis, key)
      if old.nil? || (old[:version] < feature[:version])
        put_redis_and_cache(redis, key, feature)
      end
      redis.unwatch
    end
  end
end