Class: SplitIoClient::Engine::ReconnectPolicy

Inherits:
Object
  • Object
show all
Defined in:
lib/splitclient-rb/engine/reconnect_policy.rb

Overview

Governs how aggressively streaming reconnects are attempted.

Extracted for FME-18143, where a customer's SDK reconnected up to ~64 times per second and accumulated ~10,000 threads. Two properties matter here:

* A connection only earns a back off reset if it stayed up long enough to count
as a genuine success. Resetting on every PUSH_CONNECTED meant a connection
that lived for milliseconds still produced a zero second retry.
* Only one reconnect may be in flight at a time, and errors describing an
already-replaced connection must not each start another one.

Constant Summary collapse

MIN_UPTIME_FOR_BACKOFF_RESET =

How long a connection must survive before it counts as stable.

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Instance Method Summary collapse

Constructor Details

#initialize(config, status_queue, back_off = nil) ⇒ ReconnectPolicy

Returns a new instance of ReconnectPolicy.



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# File 'lib/splitclient-rb/engine/reconnect_policy.rb', line 19

def initialize(config, status_queue, back_off = nil)
  @config = config
  @status_queue = status_queue
  @back_off = back_off || Engine::BackOff.new(1, 3)
  @connected_at = Concurrent::AtomicReference.new(nil)
  @reconnecting = Concurrent::AtomicBoolean.new(false)
end

Instance Method Details

#acquire ⇒ Object

Returns true only for the caller that acquired the right to reconnect; a concurrent caller gets false. AtomicBoolean#make_true is the compare-and-set: it returns true only for the transition from false to true.



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# File 'lib/splitclient-rb/engine/reconnect_policy.rb', line 52

def acquire
  @reconnecting.make_true
end

#actionable?(sse_connected, reconnect) ⇒ Boolean

Whether a disconnect should be acted on at all. Returns false for a disconnect of an already-disconnected stream, and for a reconnect when one is already in flight (typically driven by the token refresh thread) -- running two concurrently is what multiplied connection attempts.

Returns:

  • (Boolean) 


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# File 'lib/splitclient-rb/engine/reconnect_policy.rb', line 38

def actionable?(sse_connected, reconnect)
  unless sse_connected || reconnect
    log_debug('Streaming already disconnected.')
    return false
  end
  return true unless reconnect && !acquire

  log_debug('Streaming reconnect already in progress, ignoring.')
  false
end

#connected ⇒ Object

Monotonic clock: a backwards wall-clock jump (NTP correction, container migration) must not make uptime go negative and permanently block the back off reset.



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# File 'lib/splitclient-rb/engine/reconnect_policy.rb', line 30

def connected
  @connected_at.set(monotonic_now)
end

#discard_stale_errors ⇒ Object

Drops queued retryable errors, which refer to the connection just replaced. Acting on each of them would start one more reconnect apiece. Other statuses are preserved in order.



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# File 'lib/splitclient-rb/engine/reconnect_policy.rb', line 80

def discard_stale_errors
  kept = []
  discarded = 0

  until @status_queue.empty?
    status = @status_queue.pop(true)
    if status == Constants::PUSH_RETRYABLE_ERROR
      discarded += 1
    else
      kept << status
    end
  end

  kept.each { |kept_status| @status_queue.push(kept_status) }
  log_debug("Discarded #{discarded} stale streaming errors.") if discarded.positive?
  discarded
rescue ThreadError
  discarded
end

#interval ⇒ Object 



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# File 'lib/splitclient-rb/engine/reconnect_policy.rb', line 73

def interval
  @back_off.interval
end

#record_disconnect ⇒ Object

Resets the back off only if the connection that just dropped was stable, so a flapping connection keeps backing off instead of retrying immediately.



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# File 'lib/splitclient-rb/engine/reconnect_policy.rb', line 62

def record_disconnect
  connected_at = @connected_at.get_and_set(nil)
  return if connected_at.nil?

  uptime = monotonic_now - connected_at
  return if uptime < MIN_UPTIME_FOR_BACKOFF_RESET

  log_debug("Streaming connection was up for #{uptime.round(1)}s, resetting back off.")
  @back_off.reset
end

#release ⇒ Object 



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# File 'lib/splitclient-rb/engine/reconnect_policy.rb', line 56

def release
  @reconnecting.make_false
end