/usr/lib/ruby/vendor_ruby/fog/core/cache.rb is in ruby-fog-core 1.45.0-1.
This file is owned by root:root, with mode 0o644.
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require "fileutils"
require "yaml"
require "tmpdir"
module Fog
# A generic cache mechanism for fog resources. This can be for a server, security group, etc.
#
# Currently this is a on-disk cache using yml files per-model instance, however
# there is nothing in the way of extending this to use various other cache
# backends.
#
# == Basic functionality
#
# set the namespace where this cache will be stored:
#
# Fog::Cache.namespace_prefix = "service-account-foo-region-bar"
#
# cache to disk:
#
# # after dumping, there will be a yml file on disk:
# resouce.cache.dump
#
# # you can load cached data in from a different session
# Fog::Cache.load(Fog::Compute::AWS::Server, compute)
#
# # you can also expire cache (removes cached data assocaited with the resources of this model associated to the service passed in).
# Fog::Cache.expire_cache!(Fog::Compute::AWS::Server, compute)
#
# == More detailed flow/usage
#
# Normally, you would have a bunch of resources you want to cache/reload from disk.
# Every fog model has a +cache+ object injected to accomplish this. So in order to cache a server for exmaple
# you would do something like this:
#
# # note this is necessary in order to segregate usage of cache between various providers regions and accounts.
# # if you are using one account/region/etc only, you still must set it. 'default' will do.
# Fog::Cache.namespace_prefix = "prod-emea-eu-west-1"
#
# s = security_groups.sample; s.name # => "default"
# s.cache.dump # => 2371
#
# Now it is on disk:
#
# shai@adsk-lappy ~ % tree ~/.fog-cache/prod-emea-eu-west-1/
#
# /Users/shai/.fog-cache/prod-emea-eu-west-1/
# └── fog_compute_aws_real
# └── fog_compute_aws_securitygroup
# ├── default-90928073d9d5d9b4e7545e88aee7ec4f.yml
#
# You can do the same with a SecurityGroup, Instances, Elbs, etc.
#
# Note that when loading cache from disk, you need to pass the appropriate model class, and service associated with it.
# +Service+ is passed in is so that the service/connection details can be loaded into the loaded instances so they can be re-queried, etc.
# +Model+ is passed in so we can find the cache data associated to that model in the namespace of cache this session is using:
# Will try to load all resources associated to those. If you had 1 yml file, or 100, it would load whatever it could find.
# As such, the normal usage of dumping would be do it on a collection:
#
# load_balancers.each {|elb| elb.cache.dump }
#
# In order to load the cache into a different session with nothing but the service set up, use like so:
# As mentioned, will load all resources associated to the +model_klass+ and +service+ passed in.
#
# instances = Fog::Cache.load(Fog::Compute::AWS::Server, compute)
# instances.first.id # => "i-0569a70ae6f47d229"
#
# Note that if there is no cache located for the +model+ class and +service+ passed to `Fog::Cache.load`
# you will get an exception you can handle (for example, to load the resources for the fisrt time):
#
# Fog::Cache.expire_cache!(Fog::Compute::AWS::SecurityGroup, compute)
# # ... now there is no SecurityGroup cache data. So, if you tried to load it, you would get an exception:
#
# Fog::Cache.load(Fog::Compute::AWS::SecurityGroup, compute)
# rescue Fog::Cache::CacheNotFound => e
# puts "could not find any cache data for security groups on #{compute}"
# get_resources_and_dump
#
# == Extending cache backends
#
# Currently this is on-disk using yml. If need be, this could be extended to other cache backends:
#
# Find references of yaml in this file, split out to strategy objects/diff backends etc.
class Cache
# cache associated not found
class CacheNotFound < StandardError; end
# cache directory problem
class CacheDir < StandardError; end
# where different caches per +service+ api keys, regions etc, are stored
# see the +namespace_prefix=+ method.
SANDBOX = ENV["HOME"] ? File.expand_path("~/.fog-cache") : File.expand_path(".fog-cache")
# when a resource is used such as `server.cache.dump` the model klass is passed in
# so that it can be identified from a different session.
attr_reader :model
# Loads cache associated to the +model_klass+ and +service+ into memory.
#
# If no cache is found, it will raise an error for handling:
#
# rescue Fog::Cache::CacheNotFound
# set_initial_cache
#
def self.load(model_klass, service)
cache_files = Dir.glob("#{namespace(model_klass, service)}/*")
raise CacheNotFound if cache_files.empty?
# collection_klass and model_klass should be the same across all instances
# choose a valid cache record from the dump to use as a sample to deterine
# which collection/model to instantiate.
sample_path = cache_files.detect{ |path| valid_for_load?(path) }
model_klass = const_get_compat(load_cache(sample_path)[:model_klass])
collection_klass = const_get_compat(load_cache(sample_path)[:collection_klass]) if load_cache(sample_path)[:collection_klass]
# Load the cache data into actual ruby instances
loaded = cache_files.map do |path|
model_klass.new(load_cache(path)[:attrs]) if valid_for_load?(path)
end.compact
# Set the collection and service so they can be reloaded/connection is set properly.
# See https://github.com/fog/fog-aws/issues/354#issuecomment-286789702
loaded.each do |i|
i.collection = collection_klass.new(:service => service) if collection_klass
i.instance_variable_set(:@service, service)
end
# uniqe-ify based on the total of attributes. duplicate cache can exist due to
# `model#identity` not being unique. but if all attributes match, they are unique
# and shouldn't be loaded again.
uniq_loaded = uniq_w_block(loaded) { |i| i.attributes }
if uniq_loaded.size != loaded.size
Fog::Logger.warning("Found duplicate items in the cache. Expire all & refresh cache soon.")
end
# Fog models created, free memory of cached data used for creation.
@memoized = nil
uniq_loaded
end
# :nodoc: compatability for 1.8.7 1.9.3
def self.const_get_compat(strklass)
# https://stackoverflow.com/questions/3163641/get-a-class-by-name-in-ruby
strklass.split('::').inject(Object) do |mod, class_name|
mod.const_get(class_name)
end
end
# :nodoc: compatability for 1.8.7 1.9.3
def self.uniq_w_block(arr)
ret, keys = [], []
arr.each do |x|
key = block_given? ? yield(x) : x
unless keys.include? key
ret << x
keys << key
end
end
ret
end
# method to determine if a path can be loaded and is valid fog cache format.
def self.valid_for_load?(path)
data = load_cache(path)
if data && data.is_a?(Hash)
if [:identity, :model_klass, :collection_klass, :attrs].all? { |k| data.keys.include?(k) }
return true
else
Fog::Logger.warning("Found corrupt items in the cache: #{path}. Expire all & refresh cache soon.\n\nData:#{File.read(path)}")
return false
end
end
end
# creates on-disk cache of this specific +model_klass+ and +@service+
def self.create_namespace(model_klass, service)
FileUtils.mkdir_p(self.namespace(model_klass, service))
end
# Expires cache - this does not expire all cache associated.
# Instead, this will remove all on-disk cache of this specific +model_klass+ and and +@service+
def self.expire_cache!(model_klass, service)
FileUtils.rm_rf(namespace(model_klass, service))
end
# cleans the `SANDBOX` - specific any resource cache of any namespace,
# and any metadata associated to any.
def self.clean!
FileUtils.rm_rf(SANDBOX)
end
# loads yml cache from path on disk, used
# to initialize Fog models.
def self.load_cache(path)
@memoized ||= {}
return @memoized[path] if @memoized[path]
@memoized[path] = YAML.load(File.read(path))
end
def self.namespace_prefix=(name)
@namespace_prefix = name
end
def self.namespace_prefix
@namespace_prefix
end
# write any metadata - +hash+ information - specific to the namespaced cache in the session.
#
# you can retrieve this in other sessions, as long as +namespace_prefix+ is set
# you can overwrite metadata over time. see test cases as examples.
def self.write_metadata(h)
if namespace_prefix.nil?
raise CacheDir.new("Must set an explicit identifier/name for this cache. Example: 'serviceX-regionY'") unless namespace_prefix
elsif !h.is_a?(Hash)
raise CacheDir.new("metadta must be a hash of information like {:foo => 'bar'}")
end
mpath = File.join(SANDBOX, namespace_prefix, "metadata.yml")
to_write = if File.exist?(mpath)
YAML.dump(YAML.load(File.read(mpath)).merge!(h))
else
YAML.dump(h)
end
mdir = File.join(SANDBOX, namespace_prefix)
FileUtils.mkdir_p(mdir) if !File.exist?(mdir)
File.open(mpath, "w") { |f| f.write(to_write) }
end
# retrive metadata for this +namespace+ of cache. returns empty {} if none found.
def self.metadata
mpath = File.join(SANDBOX, namespace_prefix, "metadata.yml")
if File.exist?(mpath)
metadata = YAML.load(File.read(mpath))
return metadata
else
return {}
end
end
# The path/namespace where the cache is stored for a specific +model_klass+ and +@service+.
def self.namespace(model_klass, service)
raise CacheDir.new("Must set an explicit identifier/name for this cache. Example: 'serviceX-regionY'") unless namespace_prefix
ns = File.join(SANDBOX, namespace_prefix, service.class.to_s, model_klass.to_s)
ns = safe_path(ns)
end
def self.safe_path(klass)
klass.to_s.gsub("::", "_").downcase
end
def initialize(model)
@model = model
end
# Dump a Fog::Model resource. Every fog model/instance now has a +cache+ method/object injected in.
# as such you can use the #dump method to save the attributes and metadata of that instance as cache
# which can be re-used in some other session.
def dump
if !File.exist?(self.class.namespace(model.class, model.service))
self.class.create_namespace(model.class, model.service)
end
data = { :identity => model.identity,
:model_klass => model.class.to_s,
:collection_klass => model.collection && model.collection.class.to_s,
:attrs => model.attributes }
File.open(dump_to, "w") { |f| f.write(YAML.dump(data)) }
end
# the location of where to save this fog model/instance to.
def dump_to
# some fog models have an identity field that is duplicate.
# duplicate identities can mean the cache for that already exists.
# this means cache duplication is possible.
#
# see "dumping two models that have duplicate identity" test case.
"#{self.class.namespace(model.class, model.service)}/#{model.identity}-#{SecureRandom.hex}.yml"
end
end
end
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