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 19

def compress
  @compress
end

.max_value_bytes ⇒ Object

Returns the value of attribute max_value_bytes.



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# File 'lib/mudis.rb', line 19

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 19

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 193

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

.bucket_index(key) ⇒ Object

Computes which bucket a key belongs to



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# File 'lib/mudis.rb', line 77

def bucket_index(key)
  key.hash % buckets
end

.buckets ⇒ Object

Number of cache buckets (shards). Default: 32



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# File 'lib/mudis.rb', line 38

def self.buckets
  @buckets ||= (ENV['MUDIS_BUCKETS']&.to_i || 32)
end

.cleanup_expired! ⇒ Object

Removes expired keys across all buckets



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# File 'lib/mudis.rb', line 177

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

.current_memory_bytes ⇒ Object

Returns total memory used across all buckets



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# File 'lib/mudis.rb', line 204

def current_memory_bytes
  @current_bytes.sum
end

.delete(key) ⇒ Object

Deletes a key from the cache



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# File 'lib/mudis.rb', line 167

def delete(key)
  idx = bucket_index(key)
  mutex = @mutexes[idx]

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

.exists?(key) ⇒ Boolean

Checks if a key exists and is not expired

Returns:

  • (Boolean) 


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# File 'lib/mudis.rb', line 82

def exists?(key)
  !!read(key)
end

.max_memory_bytes ⇒ Object

Returns configured maximum memory allowed



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# File 'lib/mudis.rb', line 209

def max_memory_bytes
  @max_bytes
end

.metrics ⇒ Object

Returns a snapshot of metrics (thread-safe)



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# File 'lib/mudis.rb', line 22

def metrics
  @metrics_mutex.synchronize { @metrics.dup }
end

.read(key) ⇒ Object

Reads and returns the value for a key, updating LRU and metrics



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# File 'lib/mudis.rb', line 87

def read(key)
  raw_entry = nil
  idx = bucket_index(key)
  mutex = @mutexes[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

    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

.start_expiry_thread(interval: 60) ⇒ Object

Starts a thread that periodically removes expired entries



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# File 'lib/mudis.rb', line 56

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 70

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

.update(key) ⇒ Object

Atomically updates the value for a key using a block



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# File 'lib/mudis.rb', line 141

def update(key)
  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

.write(key, value, expires_in: nil) ⇒ Object

Writes a value to the cache with optional expiry and LRU tracking



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# File 'lib/mudis.rb', line 111

def write(key, value, expires_in: nil)
  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

  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
    }

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