Class: Mixpanel::Flags::LocalFlagsProvider

Inherits:
FlagsProvider show all
Defined in:
lib/mixpanel-ruby/flags/local_flags_provider.rb

Overview

Local feature flags provider Evaluates flags client-side with cached flag definitions

Constant Summary collapse

DEFAULT_CONFIG = 
{
  api_host: 'api.mixpanel.com',
  request_timeout_in_seconds: 10,
  enable_polling: true,
  polling_interval_in_seconds: 60,
  exposure_executor: nil
}.freeze

Instance Method Summary collapse

Methods inherited from FlagsProvider

#call_flags_endpoint, #track_exposure_event

Constructor Details

#initialize(token, config, tracker_callback, error_handler, credentials = nil) ⇒ LocalFlagsProvider

Returns a new instance of LocalFlagsProvider.

Parameters:

  • token (String) —

    Mixpanel project token

  • config (Hash) —

    Local flags configuration

  • tracker_callback (Proc) —

    Callback to track events

  • error_handler (Mixpanel::ErrorHandler) —

    Error handler

  • credentials (ServiceAccountCredentials, nil) (defaults to: nil) —

    Optional service account credentials



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# File 'lib/mixpanel-ruby/flags/local_flags_provider.rb', line 23

def initialize(token, config, tracker_callback, error_handler, credentials = nil)
  # compact: an explicit nil from the caller (e.g.
  # polling_interval_in_seconds: nil) must not override a sane default.
  # Both the previous sleep(nil) and the current
  # ConditionVariable#wait(mutex, nil) block indefinitely, which would
  # silently disable polling — fall back to the default instead.
  @config = DEFAULT_CONFIG.merge((config || {}).compact)

  interval = @config[:polling_interval_in_seconds]
  unless interval.is_a?(Numeric) && interval > 0
    raise ArgumentError,
          "polling_interval_in_seconds must be a positive number, got: #{interval.inspect}"
  end

  provider_config = {
    token: token,
    api_host: @config[:api_host],
    request_timeout_in_seconds: @config[:request_timeout_in_seconds],
    exposure_executor: @config[:exposure_executor],
    credentials: credentials
  }

  super(provider_config, '/flags/definitions', tracker_callback, 'local', error_handler)

  @flag_definitions = {}
  @polling_thread = nil
  @stop_polling = false
  @polling_mutex = Mutex.new
  @polling_condition = ConditionVariable.new
  # Separate from @polling_mutex: serializes the full start/stop lifecycle
  # (including the join inside stop) so a concurrent start can't observe a
  # mid-stop state and spawn a new polling thread before the old one
  # finishes exiting. We can't hold @polling_mutex across the join — the
  # polling thread needs it to wake from the condition wait.
  @lifecycle_mutex = Mutex.new
end

Instance Method Details

#get_all_variants(context) ⇒ Hash

Get all variants for user context Exposure events NOT tracked automatically

Parameters:

  • context (Hash) —

    Evaluation context

Returns:

  • (Hash) —

    Map of flag_key => SelectedVariant



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# File 'lib/mixpanel-ruby/flags/local_flags_provider.rb', line 200

def get_all_variants(context)
  variants = {}
  fallback = SelectedVariant.new(variant_value: nil)

  @flag_definitions.each_key do |flag_key|
    variant = get_variant(flag_key, fallback, context, report_exposure: false)
    variants[flag_key] = variant if variant.variant_source == VariantSource::LOCAL
  end

  variants
end

#get_variant(flag_key, fallback_variant, context, report_exposure: true) ⇒ SelectedVariant

Get complete variant information

Parameters:

  • flag_key (String) —

    Feature flag key

  • fallback_variant (SelectedVariant) —

    Fallback variant

  • context (Hash) —

    Evaluation context

  • report_exposure (Boolean) (defaults to: true) —

    Whether to track exposure event

Returns:



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# File 'lib/mixpanel-ruby/flags/local_flags_provider.rb', line 171

def get_variant(flag_key, fallback_variant, context, report_exposure: true)
  flag = @flag_definitions[flag_key]

  return fallback_variant.as_fallback(FallbackReason.flag_not_found) unless flag

  context_key = flag['context']
  unless context.key?(context_key) || context.key?(context_key.to_sym)
    return fallback_variant.as_fallback(FallbackReason.missing_context_key(context_key))
  end

  context_value = context[context_key] || context[context_key.to_sym]

  selected_variant = get_variant_override_for_test_user(flag, context)

  unless selected_variant
    rollout = get_assigned_rollout(flag, context_value, context)
    selected_variant = get_assigned_variant(flag, context_value, flag_key, rollout) if rollout
  end

  return fallback_variant.as_fallback(FallbackReason.no_rollout_match) unless selected_variant

  track_exposure_event(flag_key, selected_variant, context) if report_exposure
  selected_variant.with_source(VariantSource::LOCAL)
end

#get_variant_value(flag_key, fallback_value, context, report_exposure: true) ⇒ Object

Get variant value for a flag

Parameters:

  • flag_key (String) —

    Feature flag key

  • fallback_value (Object) —

    Fallback value if not in rollout

  • context (Hash) —

    Evaluation context

  • report_exposure (Boolean) (defaults to: true) —

    Whether to track exposure event

Returns:

  • (Object) —

    The variant value



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# File 'lib/mixpanel-ruby/flags/local_flags_provider.rb', line 155

def get_variant_value(flag_key, fallback_value, context, report_exposure: true)
  result = get_variant(
    flag_key,
    SelectedVariant.new(variant_value: fallback_value),
    context,
    report_exposure: report_exposure
  )
  result.variant_value
end

#is_enabled?(flag_key, context) ⇒ Boolean

Check if flag is enabled (for boolean flags)

Parameters:

  • flag_key (String) —

    Feature flag key

  • context (Hash) —

    Evaluation context (must include 'distinct_id')

Returns:

  • (Boolean) 


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# File 'lib/mixpanel-ruby/flags/local_flags_provider.rb', line 144

def is_enabled?(flag_key, context)
  value = get_variant_value(flag_key, false, context)
  value == true
end

#shutdown ⇒ Object 



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# File 'lib/mixpanel-ruby/flags/local_flags_provider.rb', line 136

def shutdown
  stop_polling_for_definitions!
end

#start_polling_for_definitions! ⇒ Object

Start polling for flag definitions Fetches immediately, then at regular intervals if polling enabled



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# File 'lib/mixpanel-ruby/flags/local_flags_provider.rb', line 62

def start_polling_for_definitions!
  # Clear @stop_polling BEFORE the initial fetch so a concurrent
  # stop_polling_for_definitions! arriving during the fetch can flip it
  # back to true and signal "abandon start". Under @polling_mutex, writes
  # to @stop_polling are linearized: whichever of {start's clear, stop's
  # set} happened latest is what we observe under the lifecycle lock
  # below — i.e. last-writer-wins semantics preserve stop's postcondition
  # (polling is off when stop returns) even across the unguarded fetch.
  @polling_mutex.synchronize { @stop_polling = false }

  # Initial fetch is intentionally outside @lifecycle_mutex: it's a
  # blocking HTTP call, and holding the lifecycle lock across it would
  # block a concurrent stop_polling_for_definitions! for the full request
  # timeout.
  #
  # A transient failure here (network blip, HTTP 500) should NOT prevent
  # the polling thread from spawning — the loop retries on the configured
  # interval. Without this inner rescue, the outer rescue below would
  # catch and return, leaving the SDK permanently without polling until
  # the caller manually retried.
  begin
    fetch_flag_definitions
  rescue StandardError => e
    safe_handle_error(e)
  end

  @lifecycle_mutex.synchronize do
    # If a stop arrived during/after our @stop_polling clear above, abort
    # — the user's stop "wins" because it's the most recent intent.
    stop_requested = @polling_mutex.synchronize { @stop_polling }

    # .alive? guards against a prior polling thread that died abnormally
    # (e.g. error_handler itself raised); without it @polling_thread would
    # be non-nil-but-dead and we'd silently refuse to restart polling.
    if !stop_requested && @config[:enable_polling] &&
       (@polling_thread.nil? || !@polling_thread.alive?)
      @polling_thread = Thread.new do
        loop do
          # Check @stop_polling INSIDE the mutex (before and after wait)
          # so a broadcast from stop_polling_for_definitions! can't be
          # lost if it arrives while we're outside the synchronized region
          # (e.g. during fetch_flag_definitions below).
          stopped = @polling_mutex.synchronize do
            next true if @stop_polling

            @polling_condition.wait(@polling_mutex, @config[:polling_interval_in_seconds])
            @stop_polling
          end
          break if stopped

          begin
            fetch_flag_definitions
          rescue StandardError => e
            safe_handle_error(e)
          end
        end
      end
    end
  end
rescue StandardError => e
  safe_handle_error(e)
end

#stop_polling_for_definitions! ⇒ Object 



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# File 'lib/mixpanel-ruby/flags/local_flags_provider.rb', line 125

def stop_polling_for_definitions!
  @lifecycle_mutex.synchronize do
    @polling_mutex.synchronize do
      @stop_polling = true
      @polling_condition.broadcast
    end
    @polling_thread&.join
    @polling_thread = nil
  end
end