Class: Mudis

Inherits:
Object
  • Object
show all
Defined in:
lib/mudis.rb

Overview

Mudis is a thread-safe, in-memory, sharded, LRU cache with optional compression and expiry. It is designed for high concurrency and performance within a Ruby application.

Defined Under Namespace

Classes: LRUNode

Class Attribute Summary collapse

Class Method Summary collapse

Class Attribute Details

.compress ⇒ Object

Returns the value of attribute compress.



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# File 'lib/mudis.rb', line 24

def compress
  @compress
end

.default_ttl ⇒ Object

Returns the value of attribute default_ttl.



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# File 'lib/mudis.rb', line 24

def default_ttl
  @default_ttl
end

.hard_memory_limit ⇒ Object

Returns the value of attribute hard_memory_limit.



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# File 'lib/mudis.rb', line 24

def hard_memory_limit
  @hard_memory_limit
end

.max_bytes ⇒ Object

Returns the value of attribute max_bytes.



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# File 'lib/mudis.rb', line 25

def max_bytes
  @max_bytes
end

.max_ttl ⇒ Object

Returns the value of attribute max_ttl.



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# File 'lib/mudis.rb', line 24

def max_ttl
  @max_ttl
end

.max_value_bytes ⇒ Object

Returns the value of attribute max_value_bytes.



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# File 'lib/mudis.rb', line 25

def max_value_bytes
  @max_value_bytes
end

.serializer ⇒ Object

Returns the value of attribute serializer.



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# File 'lib/mudis.rb', line 24

def serializer
  @serializer
end

Class Method Details

.all_keys ⇒ Object

Returns an array of all cache keys



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# File 'lib/mudis.rb', line 376

def all_keys
  keys = []
  buckets.times do |idx|
    mutex = @mutexes[idx]
    store = @stores[idx]
    mutex.synchronize { keys.concat(store.keys) }
  end
  keys
end

.apply_config! ⇒ Object

Applies the current configuration to Mudis



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# File 'lib/mudis.rb', line 39

def apply_config! # rubocop:disable Metrics/AbcSize,Metrics/MethodLength
  validate_config!

  self.serializer = config.serializer
  self.compress = config.compress
  self.max_value_bytes = config.max_value_bytes
  self.hard_memory_limit = config.hard_memory_limit
  self.max_bytes = config.max_bytes
  self.max_ttl = config.max_ttl
  self.default_ttl = config.default_ttl

  if config.buckets # rubocop:disable Style/GuardClause
    @buckets = config.buckets
    reset!
  end
end

.bucket_index(key) ⇒ Object

Computes which bucket a key belongs to



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# File 'lib/mudis.rb', line 190

def bucket_index(key)
  key.hash % buckets
end

.buckets ⇒ Object

Number of cache buckets (shards). Default: 32

Raises:

  • (ArgumentError) 


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# File 'lib/mudis.rb', line 144

def self.buckets
  return @buckets if @buckets

  val = config.buckets || ENV["MUDIS_BUCKETS"]&.to_i || 32
  raise ArgumentError, "bucket count must be > 0" if val <= 0

  @buckets = val
end

.cleanup_expired! ⇒ Object

Removes expired keys across all buckets



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# File 'lib/mudis.rb', line 362

def cleanup_expired!
  now = Time.now
  buckets.times do |idx|
    mutex = @mutexes[idx]
    store = @stores[idx]
    mutex.synchronize do
      store.keys.each do |key| # rubocop:disable Style/HashEachMethods
        evict_key(idx, key) if store[key][:expires_at] && now > store[key][:expires_at]
      end
    end
  end
end

.clear(key, namespace: nil) ⇒ Object

Clears a specific key from the cache, a semantic synonym for delete This method is provided for clarity in usage It behaves the same as delete



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# File 'lib/mudis.rb', line 325

def clear(key, namespace: nil)
  delete(key, namespace: namespace)
end

.clear_namespace(namespace:) ⇒ Object

Clears all keys in a specific namespace

Raises:

  • (ArgumentError) 


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# File 'lib/mudis.rb', line 395

def clear_namespace(namespace:)
  raise ArgumentError, "namespace is required" unless namespace

  prefix = "#{namespace}:"
  buckets.times do |idx|
    mutex = @mutexes[idx]
    store = @stores[idx]

    mutex.synchronize do
      keys_to_delete = store.keys.select { |key| key.start_with?(prefix) }
      keys_to_delete.each { |key| evict_key(idx, key) }
    end
  end
end

.config ⇒ Object

Returns the current configuration object



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# File 'lib/mudis.rb', line 34

def config
  @config ||= MudisConfig.new
end

.configure {|config| ... } ⇒ Object

Configures Mudis with a block, allowing customization of settings

Yields:



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# File 'lib/mudis.rb', line 28

def configure
  yield(config)
  apply_config!
end

.current_memory_bytes ⇒ Object

Returns total memory used across all buckets



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# File 'lib/mudis.rb', line 429

def current_memory_bytes
  @current_bytes.sum
end

.delete(*a, **k) ⇒ Object

rubocop:disable Naming/MethodParameterName,Style/GlobalVars



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# File 'lib/mudis.rb', line 296

def delete(key, namespace: nil)
  key = namespaced_key(key, namespace)
  idx = bucket_index(key)
  mutex = @mutexes[idx]

  mutex.synchronize do
    evict_key(idx, key)
  end
end

.exists?(key, namespace: nil) ⇒ Boolean

Checks if a key exists and is not expired

Returns:

  • (Boolean) 


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# File 'lib/mudis.rb', line 195

def exists?(key, namespace: nil)
  key = namespaced_key(key, namespace)
  !!read(key)
end

.fetch(*a, **k, &b) ⇒ Object

rubocop:disable Naming/MethodParameterName,Style/GlobalVars



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# File 'lib/mudis.rb', line 310

def fetch(key, expires_in: nil, force: false, namespace: nil)
  key = namespaced_key(key, namespace)
  unless force
    cached = read(key)
    return cached if cached
  end

  value = yield
  write(key, value, expires_in: expires_in)
  value
end

.inspect(key, namespace: nil) ⇒ Object

Inspects a key and returns all meta data for it



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# File 'lib/mudis.rb', line 340

def inspect(key, namespace: nil) # rubocop:disable Metrics/MethodLength
  key = namespaced_key(key, namespace)
  idx = bucket_index(key)
  store = @stores[idx]
  mutex = @mutexes[idx]

  mutex.synchronize do
    entry = store[key]
    return nil unless entry

    {
      key: key,
      bucket: idx,
      expires_at: entry[:expires_at],
      created_at: entry[:created_at],
      size_bytes: key.bytesize + entry[:value].bytesize,
      compressed: compress
    }
  end
end

.keys(namespace:) ⇒ Object

Returns all keys in a specific namespace

Raises:

  • (ArgumentError) 


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# File 'lib/mudis.rb', line 387

def keys(namespace:)
  raise ArgumentError, "namespace is required" unless namespace

  prefix = "#{namespace}:"
  all_keys.select { |key| key.start_with?(prefix) }.map { |key| key.delete_prefix(prefix) }
end

.least_touched(n = 10) ⇒ Object

Returns the least-touched keys across all buckets



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# File 'lib/mudis.rb', line 411

def least_touched(n = 10) # rubocop:disable Metrics/MethodLength,Naming/MethodParameterName
  keys_with_touches = []

  buckets.times do |idx|
    mutex = @mutexes[idx]
    store = @stores[idx]

    mutex.synchronize do
      store.each do |key, entry|
        keys_with_touches << [key, entry[:touches] || 0]
      end
    end
  end

  keys_with_touches.sort_by { |_, count| count }.first(n)
end

.max_memory_bytes ⇒ Object

Returns configured maximum memory allowed



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# File 'lib/mudis.rb', line 434

def max_memory_bytes
  @max_bytes
end

.metrics ⇒ Object

rubocop:disable Style/GlobalVars



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# File 'lib/mudis.rb', line 71

def metrics # rubocop:disable Metrics/MethodLength
  @metrics_mutex.synchronize do
    {
      hits: @metrics[:hits],
      misses: @metrics[:misses],
      evictions: @metrics[:evictions],
      rejected: @metrics[:rejected],
      total_memory: current_memory_bytes,
      least_touched: least_touched(10),
      buckets: buckets.times.map do |idx|
        {
          index: idx,
          keys: @stores[idx].size,
          memory_bytes: @current_bytes[idx],
          lru_size: @lru_nodes[idx].size
        }
      end
    }
  end
end

.read(*a, **k) ⇒ Object

rubocop:disable Naming/MethodParameterName,Style/GlobalVars



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# File 'lib/mudis.rb', line 201

def read(key, namespace: nil) # rubocop:disable Metrics/MethodLength,Metrics/AbcSize,Metrics/CyclomaticComplexity,Metrics/PerceivedComplexity
  key = namespaced_key(key, namespace)
  raw_entry = nil
  idx = bucket_index(key)
  mutex = @mutexes[idx]
  store = @stores[idx]

  mutex.synchronize do
    raw_entry = @stores[idx][key]
    if raw_entry && raw_entry[:expires_at] && Time.now > raw_entry[:expires_at]
      evict_key(idx, key)
      raw_entry = nil
    end

    store[key][:touches] = (store[key][:touches] || 0) + 1 if store[key]

    metric(:hits) if raw_entry
    metric(:misses) unless raw_entry
  end

  return nil unless raw_entry

  value = decompress_and_deserialize(raw_entry[:value])
  promote_lru(idx, key)
  value
end

.replace(key, value, expires_in: nil, namespace: nil) ⇒ Object

Replaces the value for a key if it exists, otherwise does nothing This is useful for updating values without needing to check existence first It will write the new value and update the expiration if provided If the key does not exist, it will not create a new entry



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# File 'lib/mudis.rb', line 333

def replace(key, value, expires_in: nil, namespace: nil)
  return unless exists?(key, namespace: namespace)

  write(key, value, expires_in: expires_in, namespace: namespace)
end

.reset! ⇒ Object

rubocop:disable Style/GlobalVars



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# File 'lib/mudis.rb', line 100

def reset!
  stop_expiry_thread

  @buckets = nil
  b = buckets

  @stores        = Array.new(b) { {} }
  @mutexes       = Array.new(b) { Mutex.new }
  @lru_heads     = Array.new(b) { nil }
  @lru_tails     = Array.new(b) { nil }
  @lru_nodes     = Array.new(b) { {} }
  @current_bytes = Array.new(b, 0)

  reset_metrics!
end

.reset_metrics! ⇒ Object

rubocop:disable Style/GlobalVars



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# File 'lib/mudis.rb', line 93

def reset_metrics!
  @metrics_mutex.synchronize do
    @metrics = { hits: 0, misses: 0, evictions: 0, rejected: 0 }
  end
end

.start_expiry_thread(interval: 60) ⇒ Object

Starts a thread that periodically removes expired entries



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# File 'lib/mudis.rb', line 168

def start_expiry_thread(interval: 60)
  return if @expiry_thread&.alive?

  @stop_expiry = false
  @expiry_thread = Thread.new do
    loop do
      break if @stop_expiry

      sleep interval
      cleanup_expired!
    end
  end
end

.stop_expiry_thread ⇒ Object

Signals and joins the expiry thread



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# File 'lib/mudis.rb', line 183

def stop_expiry_thread
  @stop_expiry = true
  @expiry_thread&.join
  @expiry_thread = nil
end

.update(key, namespace: nil) ⇒ Object

Atomically updates the value for a key using a block



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# File 'lib/mudis.rb', line 269

def update(key, namespace: nil) # rubocop:disable Metrics/AbcSize,Metrics/MethodLength
  key = namespaced_key(key, namespace)
  idx = bucket_index(key)
  mutex = @mutexes[idx]
  store = @stores[idx]

  raw_entry = nil
  mutex.synchronize do
    raw_entry = store[key]
    return nil unless raw_entry
  end

  value = decompress_and_deserialize(raw_entry[:value])
  new_value = yield(value)
  new_raw = serializer.dump(new_value)
  new_raw = Zlib::Deflate.deflate(new_raw) if compress

  mutex.synchronize do
    old_size = key.bytesize + raw_entry[:value].bytesize
    new_size = key.bytesize + new_raw.bytesize
    store[key][:value] = new_raw
    @current_bytes[idx] += (new_size - old_size)
    promote_lru(idx, key)
  end
end

.validate_config! ⇒ Object

Validates the current configuration, raising errors for invalid settings

Raises:

  • (ArgumentError) 


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# File 'lib/mudis.rb', line 57

def validate_config! # rubocop:disable Metrics/AbcSize,Metrics/CyclomaticComplexity,Metrics/PerceivedComplexity
  if config.max_value_bytes && config.max_value_bytes > config.max_bytes
    raise ArgumentError,
          "max_value_bytes cannot exceed max_bytes"
  end

  raise ArgumentError, "max_value_bytes must be > 0" if config.max_value_bytes && config.max_value_bytes <= 0

  raise ArgumentError, "buckets must be > 0" if config.buckets && config.buckets <= 0
  raise ArgumentError, "max_ttl must be > 0" if config.max_ttl && config.max_ttl <= 0
  raise ArgumentError, "default_ttl must be > 0" if config.default_ttl && config.default_ttl <= 0
end

.with_namespace(namespace) ⇒ Object

Executes a block with a specific namespace, restoring the old namespace afterwards



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# File 'lib/mudis.rb', line 439

def with_namespace(namespace)
  old_ns = Thread.current[:mudis_namespace]
  Thread.current[:mudis_namespace] = namespace
  yield
ensure
  Thread.current[:mudis_namespace] = old_ns
end

.write(*a, **k) ⇒ Object

rubocop:disable Naming/MethodParameterName,Style/GlobalVars



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# File 'lib/mudis.rb', line 229

def write(key, value, expires_in: nil, namespace: nil) # rubocop:disable Metrics/MethodLength,Metrics/CyclomaticComplexity,Metrics/AbcSize,Metrics/PerceivedComplexity
  key = namespaced_key(key, namespace)
  raw = serializer.dump(value)
  raw = Zlib::Deflate.deflate(raw) if compress
  size = key.bytesize + raw.bytesize
  return if max_value_bytes && raw.bytesize > max_value_bytes

  if hard_memory_limit && current_memory_bytes + size > max_memory_bytes
    metric(:rejected)
    return
  end

  # Ensure expires_in respects max_ttl and default_ttl
  expires_in = effective_ttl(expires_in)

  idx = bucket_index(key)
  mutex = @mutexes[idx]
  store = @stores[idx]

  mutex.synchronize do
    evict_key(idx, key) if store[key]

    while @current_bytes[idx] + size > (@threshold_bytes / buckets) && @lru_tails[idx]
      evict_key(idx, @lru_tails[idx].key)
      metric(:evictions)
    end

    store[key] = {
      value: raw,
      expires_at: expires_in ? Time.now + expires_in : nil,
      created_at: Time.now,
      touches: 0
    }

    insert_lru(idx, key)
    @current_bytes[idx] += size
  end
end