Mentat v0.6.0 Mentat View Source
Provides a basic cache with ttls.
Usage
A cache must be given a name when its started.
Mentat.start_link(name: :my_cache)After its been started you can store and retrieve values:
Mentat.put(:my_cache, user_id, user)
user = Mentat.get(:my_cache, user_id)TTLs
Both put and fetch operations allow you to specify the key's TTL. If no
TTL is provided then the TTL is set to :infinity. TTL times are always
in milliseconds.
Mentat.put(:my_cache, :key, "value", [ttl: 5_000])
Mentat.fetch(:my_cache, :key, [ttl: 5_000], fn key ->
{:commit, "value"}
end)Limits
Mentat supports optional limits per cache.
Mentat.start_link(name: LimitedCache, limit: [size: 100])When the limit is reached, the janitor will asynchronously reclaim a percentage of the keys
Telemetry
Mentat publishes multiple telemetry events.
[:mentat, :get]- executed after retrieving a value from the cache. Measurements are::status- Can be either:hitor:missdepending on if the key was found in the cache.
Metadata are:
:key- The key requested:cache- The cache name
[:mentat, :put]- executed when putting a key into the cache. No measurements are provided. Metadata are::key- The key requested:cache- The name of the cache
[:mentat, :janitor, :cleanup]- executed after old keys are cleaned from the cache. Measurements are::duration- the time it took to clean up the old keys. Time is in:nativeunits.total_removed_keys- The count of keys removed from the cache.
Metadata are:
cache- The cache name.
Link to this section Summary
Functions
Returns a specification to start this module under a supervisor.
Deletes a key from the cache
Fetches a value or executes the fallback function. The function can return
either {:commit, term()} or {:ignore, term()}. If {:commit, term()} is
returned, the value will be stored in the cache before its returned. See the
"TTLs" section for a list of options.
Retrieves a value from a the cache. Returns nil if the key is not found.
Callback implementation for Supervisor.init/1.
Returns a list of all keys.
Removes all keys from the cache.
Puts a new key into the cache. See the "TTLs" section for a list of options.
Starts a new cache.
Updates a keys inserted at time. This is useful in conjunction with limits when you want to evict the oldest keys.
Link to this section Functions
Returns a specification to start this module under a supervisor.
See Supervisor.
Deletes a key from the cache
Fetches a value or executes the fallback function. The function can return
either {:commit, term()} or {:ignore, term()}. If {:commit, term()} is
returned, the value will be stored in the cache before its returned. See the
"TTLs" section for a list of options.
Example
Mentat.fetch(:cache, user_id, fn user_id ->
case get_user(user_id) do
{:ok, user} ->
{:commit, user}
error ->
{:ignore, error}
end
end)Retrieves a value from a the cache. Returns nil if the key is not found.
Callback implementation for Supervisor.init/1.
Returns a list of all keys.
Removes all keys from the cache.
Puts a new key into the cache. See the "TTLs" section for a list of options.
Starts a new cache.
Options:
:name- Required.:cleanup_interval- How often the janitor process will remove old keys. The default value is5000.:ets_args- Additional arguments to pass to:ets.new/2. The default value is[].:limit- false Limits to the number of keys a cache will store. The default value is[].:ttl- false Default ttl in milliseconds to use for all keys The default value is:infinity.
Updates a keys inserted at time. This is useful in conjunction with limits when you want to evict the oldest keys.