feat: Empty and Dump methods on cache

lib/ditty/services/cache.rb

@@ -1,20 +1,23 @@
 # frozen_string_literal: true
 
 require 'dalli'
+require 'net/telnet'
 
 module Ditty
   module Services
     class Cache
       attr_writer :store
       attr_accessor :ttl
+      attr_accessor :namespace
 
-      def initialize(store: nil, ttl: 3_600)
+      def initialize(store: nil, ttl: 3_600, namespace: 'Ditty')
         @store = store
         @ttl = ttl
+        @namespace = namespace
       end
 
       def store
-        @store ||= Dalli::Client.new(ENV.fetch('CACHE_URL'), namespace: 'Ditty')
+        @store ||= Dalli::Client.new(ENV.fetch('CACHE_URL'), namespace: namespace)
       end
 
       def set(key, obj)
@@ -24,6 +27,9 @@ def set(key, obj)
 
       def get(key)
         store.get(key)
+      rescue Memcached::ServerIsMarkedDead => e
+        logger.warn "Could not retrieve cache key #{key}: #{e.message}"
+        nil
       end
 
       def clear(key)
@@ -33,6 +39,64 @@ def clear(key)
       def delete(key)
         store.delete(key)
       end
+
+      def dump
+        cache_items.map do |key, expires_at|
+          {
+            key: key,
+            value: get(key),
+            expires_at: expires_at
+          }
+        end
+      end
+
+      def empty
+        count = 0
+        cache_items.keys.each do |key|
+          delete(key)
+          count = count + 1
+        end
+        count
+      end
+
+      private
+
+      def cache_uri
+        @cache_uri ||= URI("memcached://#{ENV.fetch('CACHE_URL')}")
+      end
+
+      def connection
+        @connection ||= Net::Telnet::new("Host" => cache_uri.host, "Port" => cache_uri.port, "Timeout" => 30)
+      end
+
+      def slab_ids
+        slab_ids = []
+        connection.cmd('String' => 'stats items', 'Match' => /^END/) do |result|
+          slab_ids = result.scan(/STAT items:(\d+):/).flatten.uniq
+        end
+        slab_ids
+      end
+
+      def cache_items
+        items = {}
+        slab_ids.each do |slab_id|
+          connection.cmd("String" => "stats cachedump #{slab_id} 100", "Match" => /^END/) do |result|
+            matches = result.scan(/^ITEM (.+?) \[(\d+) b; (\d+) s\]$/).each do |key_data|
+              (cache_key, bytes, expires_time) = key_data
+              humanized_expires_time = Time.at(expires_time.to_i).to_s
+              items[cache_key.sub(/^#{namespace}:/, '')] = Time.at(expires_time.to_i)
+            end
+          end
+        end
+        items
+      end
     end
   end
 end
+
+module URI
+  class Memcached < Generic
+    DEFAULT_PORT = 11211
+  end
+  @@schemes['Memcached'] = Memcached
+end