Class: Restforce::DB::TimestampCache

Inherits:
Object
  • Object
show all
Defined in:
lib/restforce/db/timestamp_cache.rb

Overview

Restforce::DB::TimestampCache serves to cache the timestamps of the most recent known updates to records through the Restforce::DB system. It allows for more intelligent decision-making regarding what constitutes “stale” data during a synchronization.

While we can tell which user triggered the most recent changes to a record in Salesforce, we can’t tell if any modifications to that record were a result of a background Apex trigger or workflow (which apply any changes as if they were the user whose actions initiated the callback).

In order to distinguish between updates made by the worker and updates made _in response to_ changes by the worker, we have to check the record’s update timestamp against the timestamp of the last known update made by the system. This class serves as a mechanism to track the values for this comparison.

Instance Method Summary collapse

Constructor Details

#initialize ⇒ TimestampCache

Public: Initialize a new Restforce::DB::TimestampCache.



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# File 'lib/restforce/db/timestamp_cache.rb', line 23

def initialize
  reset
end

Instance Method Details

#cache_timestamp(instance) ⇒ Object

Public: Add a known update timestamp to the cache for the passed object.

instance - A Restforce::DB::Instances::Base.

Returns an Array of Restforce::DB::Instances::Base.



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# File 'lib/restforce/db/timestamp_cache.rb', line 32

def cache_timestamp(instance)
  @cache[key_for(instance)] = instance.last_update
end

#changed?(instance) ⇒ Boolean

Public: Has the passed instance been modified since the last known system-triggered update? This accounts for changes possibly introduced by callbacks and triggers.

instance - A Restforce::DB::Instances::Base.

Returns a Boolean.

Returns:

  • (Boolean) 


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# File 'lib/restforce/db/timestamp_cache.rb', line 55

def changed?(instance)
  return true unless instance.updated_internally?

  last_update = timestamp(instance)
  return true unless last_update

  instance.last_update > last_update
end

#dump_timestamps(io) ⇒ Object

Public: Dump the currently cached timestamps into the specified writable object.

io - An IO object opened for writing.

Returns nothing.



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# File 'lib/restforce/db/timestamp_cache.rb', line 90

def dump_timestamps(io)
  io.write(YAML.dump(@cache))
end

#load_timestamps(io) ⇒ Object

Public: Load the previous collection of cached timestamps from the passed readable object.

io - An IO object opened for reading.

Returns nothing.



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# File 'lib/restforce/db/timestamp_cache.rb', line 80

def load_timestamps(io)
  @cache = YAML.load(io.read) || {}
end

#reset ⇒ Object

Public: Reset the cache. Expires the previously-cached timestamps, and retires the currently-cached timestamps to ensure that they are only factored into the current synchronization run.

Returns nothing.



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# File 'lib/restforce/db/timestamp_cache.rb', line 69

def reset
  @retired_cache = @cache || {}
  @cache = {}
end

#timestamp(instance) ⇒ Object

Public: Get the most recently-stored timestamp for the passed object. Falls back to the retired timestamps to ensure that this run is aware of the modifications made during the previous run.

instance - A Restforce::DB::Instances::Base.

Returns a Time or nil.



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# File 'lib/restforce/db/timestamp_cache.rb', line 43

def timestamp(instance)
  key = key_for(instance)
  @cache.fetch(key) { @retired_cache[key] }
end