Add circuit breaker and adaptive timeout for provider resilience

lib/vmpooler/adaptive_timeout.rb

@@ -0,0 +1,130 @@
+# frozen_string_literal: true
+
+module Vmpooler
+  # Adaptive timeout that adjusts based on observed connection performance
+  # to optimize between responsiveness and reliability.
+  #
+  # Tracks recent connection durations and adjusts timeout to p95 + buffer,
+  # reducing timeout on failures to fail faster during outages.
+  class AdaptiveTimeout
+    attr_reader :current_timeout
+
+    # Initialize adaptive timeout
+    #
+    # @param name [String] Name for logging (e.g., "vsphere_connections")
+    # @param logger [Object] Logger instance
+    # @param metrics [Object] Metrics instance
+    # @param min [Integer] Minimum timeout in seconds
+    # @param max [Integer] Maximum timeout in seconds
+    # @param initial [Integer] Initial timeout in seconds
+    # @param max_samples [Integer] Number of recent samples to track
+    def initialize(name:, logger:, metrics:, min: 5, max: 60, initial: 30, max_samples: 100)
+      @name = name
+      @logger = logger
+      @metrics = metrics
+      @min_timeout = min
+      @max_timeout = max
+      @current_timeout = initial
+      @recent_durations = []
+      @max_samples = max_samples
+      @mutex = Mutex.new
+    end
+
+    # Get current timeout value (thread-safe)
+    # @return [Integer] Current timeout in seconds
+    def timeout
+      @mutex.synchronize { @current_timeout }
+    end
+
+    # Record a successful operation duration
+    # @param duration [Float] Duration in seconds
+    def record_success(duration)
+      @mutex.synchronize do
+        @recent_durations << duration
+        @recent_durations.shift if @recent_durations.size > @max_samples
+
+        # Adjust timeout based on recent performance
+        adjust_timeout if @recent_durations.size >= 10
+      end
+    end
+
+    # Record a failure (timeout or error)
+    # Reduces current timeout to fail faster on subsequent attempts
+    def record_failure
+      @mutex.synchronize do
+        old_timeout = @current_timeout
+        # Reduce timeout by 20% on failure, but don't go below minimum
+        @current_timeout = [(@current_timeout * 0.8).round, @min_timeout].max
+
+        if old_timeout != @current_timeout
+          @logger.log('d', "[*] [adaptive_timeout] '#{@name}' reduced timeout #{old_timeout}s → #{@current_timeout}s after failure")
+          @metrics.gauge("adaptive_timeout.current.#{@name}", @current_timeout)
+        end
+      end
+    end
+
+    # Reset to initial timeout (useful after recovery)
+    def reset
+      @mutex.synchronize do
+        @recent_durations.clear
+        old_timeout = @current_timeout
+        @current_timeout = [@max_timeout, 30].min
+
+        @logger.log('d', "[*] [adaptive_timeout] '#{@name}' reset timeout #{old_timeout}s → #{@current_timeout}s")
+        @metrics.gauge("adaptive_timeout.current.#{@name}", @current_timeout)
+      end
+    end
+
+    # Get statistics about recent durations
+    # @return [Hash] Statistics including min, max, avg, p95
+    def stats
+      @mutex.synchronize do
+        return { samples: 0 } if @recent_durations.empty?
+
+        sorted = @recent_durations.sort
+        {
+          samples: sorted.size,
+          min: sorted.first.round(2),
+          max: sorted.last.round(2),
+          avg: (sorted.sum / sorted.size.to_f).round(2),
+          p50: percentile(sorted, 0.50).round(2),
+          p95: percentile(sorted, 0.95).round(2),
+          p99: percentile(sorted, 0.99).round(2),
+          current_timeout: @current_timeout
+        }
+      end
+    end
+
+    private
+
+    def adjust_timeout
+      return if @recent_durations.empty?
+
+      sorted = @recent_durations.sort
+      p95_duration = percentile(sorted, 0.95)
+
+      # Set timeout to p95 + 50% buffer, bounded by min/max
+      new_timeout = (p95_duration * 1.5).round
+      new_timeout = [[new_timeout, @min_timeout].max, @max_timeout].min
+
+      # Only adjust if change is significant (> 5 seconds)
+      if (new_timeout - @current_timeout).abs > 5
+        old_timeout = @current_timeout
+        @current_timeout = new_timeout
+
+        @logger.log('d', "[*] [adaptive_timeout] '#{@name}' adjusted timeout #{old_timeout}s → #{@current_timeout}s (p95: #{p95_duration.round(2)}s)")
+        @metrics.gauge("adaptive_timeout.current.#{@name}", @current_timeout)
+        @metrics.gauge("adaptive_timeout.p95.#{@name}", p95_duration)
+      end
+    end
+
+    def percentile(sorted_array, percentile)
+      return 0 if sorted_array.empty?
+
+      index = (sorted_array.size * percentile).ceil - 1
+      index = [index, 0].max
+      index = [index, sorted_array.size - 1].min
+      sorted_array[index]
+    end
+  end
+end