Module: Cache

Defined in:
lib/memcache_util.rb

Overview

A utility wrapper around the MemCache client to simplify cache access. All methods silently ignore MemCache errors.

Class Method Summary collapse

Class Method Details

.add(key, value, expiry = 0) ⇒ Object

Sets value in the cache at key, with an optional expiry time in seconds. If key already exists in cache, returns nil.



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# File 'lib/memcache_util.rb', line 66

def self.add(key, value, expiry = 0)
  start_time = Time.now
  response = CACHE.add key, value, expiry
  elapsed = Time.now - start_time
  logger.debug('MemCache Add (%0.6f)  %s' % [elapsed, key])
  (response == "STORED\r\n") ? value : nil
rescue MemCache::MemCacheError => err
  ActiveRecord::Base.logger.debug "MemCache Error: #{err.message}"
  nil
end

.delete(key, delay = nil) ⇒ Object

Deletes key from the cache in delay seconds.



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# File 'lib/memcache_util.rb', line 80

def self.delete(key, delay = nil)
  start_time = Time.now
  CACHE.delete key, delay
  elapsed = Time.now - start_time
  logger.debug('MemCache Delete (%0.6f)  %s' %
                                  [elapsed, key])
  nil
rescue MemCache::MemCacheError => err
  logger.debug "MemCache Error: #{err.message}"
  nil
end

.get(key, expiry = 0) ⇒ Object

Returns the object at key from the cache if successful, or nil if either the object is not in the cache or if there was an error attermpting to access the cache.

If there is a cache miss and a block is given the result of the block will be stored in the cache with optional expiry, using the add method rather than set.



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

def self.get(key, expiry = 0)
  start_time = Time.now
  value = CACHE.get key
  elapsed = Time.now - start_time
  logger.debug('MemCache Get (%0.6f)  %s' % [elapsed, key])
  if value.nil? and block_given? then
    value = yield
    add key, value, expiry
  end
  value
rescue MemCache::MemCacheError => err
  logger.debug "MemCache Error: #{err.message}"
  if block_given? then
    value = yield
    put key, value, expiry
  end
  value
end

.logger ⇒ Object

Try to return a logger object that does not rely on ActiveRecord for logging.



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# File 'lib/memcache_util.rb', line 10

def self.logger
  @logger ||= if defined? Rails.logger # Rails 2.1 +
    Rails.logger
  elsif defined? RAILS_DEFAULT_LOGGER # Rails 1.2.2 +
    RAILS_DEFAULT_LOGGER
  else
    ActiveRecord::Base.logger # ... very old Rails.
  end
end

.put(key, value, expiry = 0) ⇒ Object

Sets value in the cache at key, with an optional expiry time in seconds.



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# File 'lib/memcache_util.rb', line 51

def self.put(key, value, expiry = 0)
  start_time = Time.now
  CACHE.set key, value, expiry
  elapsed = Time.now - start_time
  logger.debug('MemCache Set (%0.6f)  %s' % [elapsed, key])
  value
rescue MemCache::MemCacheError => err
  ActiveRecord::Base.logger.debug "MemCache Error: #{err.message}"
  nil
end

.reset ⇒ Object

Resets all connections to MemCache servers.



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# File 'lib/memcache_util.rb', line 95

def self.reset
  CACHE.reset
  logger.debug 'MemCache Connections Reset'
  nil
end