Class: RightScale::DispatchedCache

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

Overview

Cache for requests that have been dispatched recently This cache is intended for use in checking for duplicate requests when there is only one server servicing a queue

Constant Summary collapse

MAX_AGE =

Maximum number of seconds to retain a dispatched request in cache This must be greater than the maximum possible retry timeout to avoid duplicate execution of a request

12 * 60 * 60

Instance Method Summary collapse

Constructor Details

#initialize(identity) ⇒ DispatchedCache

Initialize cache

Parameters

identity(String)

Serialized identity of agent



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# File 'lib/right_agent/dispatched_cache.rb', line 39

def initialize(identity)
  @identity = identity
  @cache = {}
  @lru = []
  @max_age = MAX_AGE
end

Instance Method Details

#serviced_by(token) ⇒ Object

Determine whether request has already been serviced

Parameters

token(String)

Generated message identifier

Return

(String|nil)

Identity of agent that already serviced request, or nil if none



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# File 'lib/right_agent/dispatched_cache.rb', line 75

def serviced_by(token)
  if @cache[token]
    @cache[token] = Time.now.to_i
    @lru.push(@lru.delete(token))
    @identity
  end
end

#size ⇒ Object

Get local cache size

Return

(Integer)

Number of cache entries



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# File 'lib/right_agent/dispatched_cache.rb', line 103

def size
  @cache.size
end

#stats ⇒ Object

Get local cache statistics

Return

stats(Hash|nil)

Current statistics, or nil if cache empty

“local total”(Integer)

Total number in local cache, or nil if none

“local max age”(String)

Time since oldest local cache entry created or updated



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# File 'lib/right_agent/dispatched_cache.rb', line 89

def stats
  if (s = size) > 0
    now = Time.now.to_i
    {
      "local total" => s,
      "local max age" => RightSupport::Stats.elapsed(now - @cache[@lru.first])
    }
  end
end

#store(token) ⇒ Object

Store dispatched request token in cache

Parameters

token(String)

Generated message identifier

Return

true

Always return true



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# File 'lib/right_agent/dispatched_cache.rb', line 53

def store(token)
  if token
    now = Time.now.to_i
    if @cache.has_key?(token)
      @cache[token] = now
      @lru.push(@lru.delete(token))
    else
      @cache[token] = now
      @lru.push(token)
      @cache.delete(@lru.shift) while (now - @cache[@lru.first]) > @max_age
    end
  end
  true
end