class ActiveSupport::Cache::MemCacheStore

raw: true, will fail and return +nil+.
Incrementing a non-numeric value, or a value written without

cache.increment("baz") # => 6
cache.write("baz", 5, raw: true)

To set a specific value, call #write passing raw: true:

cache.increment("bar", 100) # => 100
cache.increment("foo") # => 1

If the key is unset or has expired, it will be set to +amount+:

Returns the updated value.
Increment a cached integer value using the memcached incr atomic operator.

def increment(name, amount = 1, options = nil)
  options = merged_options(options)
  instrument(:increment, name, amount: amount) do
    rescue_error_with nil do
      @data.with { |c| c.incr(normalize_key(name, options), amount, options[:expires_in], amount) }
    end
  end
end