Krug.EtsUtil (Krug v1.1.40) View Source

Utilitary module to secure handle ETS in memory data.

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Functions

Deletes a existing ets table whit received ets_key. Case the table don't exists, return true.

Creates a new ets table whit received ets_key and visibility. Case the table already exists, do not create a new, only return the existing ets_key.

Read a value relative to a key key stored in a ets table whit received ets_key. Case the table don't exists, return nil.

Delete a key/value par in ets table identified by received ets_key. Case the table don't exists, return true.

Store a key/value par in ets table identified by received ets_key. Case the table don't exists, return false.

Link to this section Functions

Deletes a existing ets table whit received ets_key. Case the table don't exists, return true.

The garbage collector do not destroy the ets tables. We need explicitly make it. Do not forget of call EtsUtil.delete(:my_key) before of terminate the proccess that has created it whit EtsUtil.new(...).

Doesn't acceppt string as key. EtsUtil.delete("key") will fail, as in :ets direct call.

Equivalent to :ets.delete(ets_key).

Examples

iex > EtsUtil.delete("echo")
** (ArgumentError) argument error
iex > EtsUtil.delete(:echo)
true
iex > EtsUtil.delete(:keyThatNotExists)
true
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new(ets_key, visibility \\ "public", read_concurrency \\ true)

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Creates a new ets table whit received ets_key and visibility. Case the table already exists, do not create a new, only return the existing ets_key.

SHOULD BE created in a process that act a task, living across the runtime of application. One good example is a Ecto repository.

defmodule MyApp.App.Repo do 
  
  use Ecto.Repo, otp_app: :my_app, adapter: Ecto.Adapters.MyXQL
  ...
  alias Krug.EtsUtil
  
  def init(_type, config) do
    ...
    EtsUtil.new(:my_ets_key_atom_identifier)
    {:ok, config}
  end

end
``

Visibility can be one of ["public","protected","private"] as 
in ets documentation. By default the value is "protected", as
defined in :ets machanism. If a not valid value for visibilty is received,
the default value is assumed.

Use "private" for the values be acessible only in module where the ETS table
is declared. Escope "protected" allows access to all modules in same
supervisor tree (a same Thread processes analogy), and "public"
allows access to any process of any supervisor tree (concurrent Threads
access equivalency). 

The garbage collector do not destroy the ets tables. We need
explicitly make it. Do not forget of call ```EtsUtil.delete(:my_key)```
before of terminate the proccess that has created it whit ```EtsUtil.new(...)```.

Equivalent to ```:ets.new(ets_key, [:set, :private, :named_table])```

Doesn't acceppt string as key. ```EtsUtil.new("key")``` will fail, as
in :ets direct call.

## Examples

iex > EtsUtil.new("echo") ** (ArgumentError) argument error

iex > EtsUtil.new(:echo) :echo

iex > EtsUtil.new(:echo,"protected") :echo

iex > EtsUtil.new(:echo,"private") :echo

iex > EtsUtil.new(:echo,"public") :echo

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read_from_cache(ets_key, key)

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Read a value relative to a key key stored in a ets table whit received ets_key. Case the table don't exists, return nil.

If the key don't exists, return nil.

Equivalent to :ets.lookup(ets_key,key) |> Tuple.to_list() |> Enum.at(1)

Examples

iex > EtsUtil.read_from_cache(:keyThatDontExists,"ping")
nil
iex > EtsUtil.new(:echo)
iex > EtsUtil.read_from_cache(:echo,"ping")
nil
iex > EtsUtil.new(:echo)
iex > EtsUtil.store_in_cache(:echo,"ping","pong")
iex > EtsUtil.read_from_cache(:echo,"ping")
"pong"
iex > EtsUtil.new(:echo)
iex > EtsUtil.store_in_cache(:echo,"ping","pong")
iex > EtsUtil.store_in_cache(:echo,"ping","foo")
iex > EtsUtil.read_from_cache(:echo,"ping")
"foo"
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remove_from_cache(ets_key, key)

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Delete a key/value par in ets table identified by received ets_key. Case the table don't exists, return true.

If the key don't exists in ets table or its value is nil, return true.

Equivalent to :ets.delete(ets_key,key)

Examples

iex > EtsUtil.remove_from_cache(:keyThatDontExists,"ping")
true
iex > EtsUtil.new(:echo)
iex > EtsUtil.remove_from_cache(:echo,"ping")
true
iex > EtsUtil.new(:echo)
iex > EtsUtil.store_in_cache(:echo,"ping","pong")
iex > EtsUtil.remove_from_cache(:echo,"ping")
true
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store_in_cache(ets_key, key, value)

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Store a key/value par in ets table identified by received ets_key. Case the table don't exists, return false.

If a old value exists and couldn't be replaced, return false.

Equivalent to :ets.insert(ets_key,{key,value}).

Examples

iex > EtsUtil.store_in_cache(:keyThatDontExists,"ping","pong")
false
iex > EtsUtil.new(:echo)
iex > EtsUtil.store_in_cache(:echo,"ping","pong")
true
iex > EtsUtil.new(:echo)
iex > EtsUtil.store_in_cache(:echo,"ping","pong")
iex > EtsUtil.store_in_cache(:echo,"ping","foo")
true