Created
November 12, 2021 13:39
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Elixir redis cache
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defmodule Toolkit.Cache do | |
@moduledoc """ | |
Cache provide some helper method to do the cache thing | |
Backend could be any. Currently using Redis via :redix library | |
""" | |
# TODO: move this to config | |
@redix_conn :octosells_cache | |
# 512kb | |
@max_cache_size 512 * 1024 | |
@doc """ | |
Cache a value with given key | |
""" | |
@spec set(String.t(), String.t()) :: :ok | {:error, any()} | |
def set(key, value, timeout_sec \\ nil) do | |
if timeout_sec do | |
set_ttl(key, value, timeout_sec) | |
else | |
with {:ok, value} <- serialize_data(value), | |
{:ok, _} <- Redix.command(@redix_conn, ["SET", key, value]) do | |
:ok | |
end | |
end | |
end | |
@doc """ | |
Cache a value with given key and timeout(in second) | |
""" | |
@spec set(String.t(), String.t(), timeout_sec :: integer()) :: :ok | {:error, any()} | |
def set_ttl(key, value, timeout_sec) do | |
with {:ok, value} <- serialize_data(value), | |
{:ok, _} <- Redix.command(@redix_conn, ["SETEX", key, timeout_sec, value]) do | |
:ok | |
end | |
end | |
@doc """ | |
Get cached value by key | |
""" | |
@spec get(String.t()) :: {:ok, String.t()} | {:error, :not_found} | {:error, any()} | |
def get(key) do | |
case Redix.command(@redix_conn, ["GET", key]) do | |
{:ok, nil} -> {:error, :not_found} | |
{:ok, value} -> deserialize_data(value) | |
error -> error | |
end | |
end | |
@doc """ | |
Get cached value by key. If key is not cached, then execute given function, cache new value and return the value. | |
""" | |
@spec get_or_set(String.t(), function(), timeout_sec :: integer()) :: | |
{:ok, String.t()} | {:error, any()} | |
def get_or_set(key, func, ttl \\ nil) when is_function(func) do | |
case get(key) do | |
{:error, _} -> | |
case func.() do | |
{:ok, value} = rs -> | |
set(key, value, ttl) | |
rs | |
{:error, _} = error -> | |
error | |
value -> | |
set(key, value, ttl) | |
{:ok, value} | |
end | |
{:ok, value} -> | |
{:ok, value} | |
end | |
end | |
@doc """ | |
Delete a cache value by key | |
""" | |
def delete(key) do | |
Redix.command(@redix_conn, ["DEL", key]) | |
end | |
# we remove struct and meta to reduce size | |
defp serialize_data(value) do | |
value = | |
if is_map(value) do | |
Map.drop(value, [:__struct__, :__meta__]) | |
else | |
value | |
end | |
data = :erlang.term_to_binary(value) | |
if byte_size(data) > @max_cache_size do | |
{:error, "Not allow cache value > 512kb"} | |
else | |
{:ok, data} | |
end | |
end | |
defp deserialize_data(data) do | |
try do | |
{:ok, :erlang.binary_to_term(data)} | |
rescue | |
_ -> {:error, "Bad data"} | |
end | |
end | |
end |
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