Cachex (Cachex v3.4.0) View Source

Cachex provides a straightforward interface for in-memory key/value storage.

Cachex is an extremely fast, designed for caching but also allowing for more general in-memory storage. The main goal of Cachex is achieve a caching implementation with a wide array of options, without sacrificing performance. Internally, Cachex is backed by ETS, allowing for an easy-to-use interface sitting upon extremely well tested tools.

Cachex comes with support for all of the following (amongst other things):

  • Time-based key expirations
  • Maximum size protection
  • Pre/post execution hooks
  • Statistics gathering
  • Multi-layered caching/key fallbacks
  • Transactions and row locking
  • Asynchronous write operations
  • Syncing to a local filesystem
  • User command invocation

All features are optional to allow you to tune based on the throughput needed. See start_link/2 for further details about how to configure these options and example usage.

Link to this section Summary

Functions

Returns a specification to start this module under a supervisor.

Removes all entries from a cache.

Retrieves the number of unexpired records in a cache.

Decrements an entry in the cache.

Removes an entry from a cache.

Serializes a cache to a location on a filesystem.

Determines whether a cache contains any entries.

Executes multiple functions in the context of a cache.

Determines whether an entry exists in a cache.

Places an expiration time on an entry in a cache.

Updates an entry in a cache to expire at a given time.

Exports all entries from a cache.

Fetches an entry from a cache, generating a value on cache miss.

Retrieves an entry from a cache.

Retrieves and updates an entry in a cache.

Imports an export set into a cache.

Increments an entry in the cache.

Inspects various aspects of a cache.

Invokes a custom command against a cache entry.

Retrieves a list of all entry keys from a cache.

Deserializes a cache from a location on a filesystem.

Removes an expiration time from an entry in a cache.

Triggers a cleanup of all expired entries in a cache.

Places an entry in a cache.

Places a batch of entries in a cache.

Refreshes an expiration for an entry in a cache.

Resets a cache by clearing the keyspace and restarting any hooks.

Deprecated implementation delegate of put/4.

Deprecated implementation delegate of put_many/3.

Retrieves the total size of a cache.

Creates a new Cachex cache service tree.

Creates a new Cachex cache service tree, linked to the current process.

Retrieves statistics about a cache.

Takes an entry from a cache.

Updates the last write time on a cache entry.

Executes multiple functions in the context of a transaction.

Retrieves the expiration for an entry in a cache.

Updates an entry in a cache.

Link to this section Types

Specs

cache() :: atom() | Spec.cache()

Specs

status() :: :ok | :error

Link to this section Functions

Returns a specification to start this module under a supervisor.

See Supervisor.

Link to this function

clear(cache, options \\ [])

View Source

Specs

clear(cache(), Keyword.t()) :: {status(), integer()}

Removes all entries from a cache.

The returned numeric value will contain the total number of keys removed from the cache. This is equivalent to running size/2 before running the internal clear operation.

Examples

iex> Cachex.put(:my_cache, "key", "value")
iex> Cachex.get(:my_cache, "key")
iex> Cachex.size(:my_cache)
{ :ok, 1 }

iex> Cachex.clear(:my_cache)
{ :ok, 1 }

iex> Cachex.size(:my_cache)
{ :ok, 0 }
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count(cache, options \\ [])

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Specs

count(cache(), Keyword.t()) :: {status(), number()}

Retrieves the number of unexpired records in a cache.

Unlike size/2, this ignores keys which should have expired. Due to this taking potentially expired keys into account, it is far more expensive than simply calling size/2 and should only be used when the distinction is completely necessary.

Examples

iex> Cachex.put(:my_cache, "key1", "value1")
iex> Cachex.put(:my_cache, "key2", "value2")
iex> Cachex.put(:my_cache, "key3", "value3")
iex> Cachex.count(:my_cache)
{ :ok, 3 }
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decr(cache, key, amount \\ 1, options \\ [])

View Source

Specs

decr(cache(), any(), integer(), Keyword.t()) :: {status(), integer()}

Decrements an entry in the cache.

This will overwrite any value that was previously set against the provided key.

Options

  • :initial

    An initial value to set the key to if it does not exist. This will take place before the decrement call. Defaults to 0.

Examples

iex> Cachex.put(:my_cache, "my_key", 10)
iex> Cachex.decr(:my_cache, "my_key")
{ :ok, 9 }

iex> Cachex.put(:my_cache, "my_new_key", 10)
iex> Cachex.decr(:my_cache, "my_new_key", 5)
{ :ok, 5 }

iex> Cachex.decr(:my_cache, "missing_key", 5, initial: 2)
{ :ok, -3 }
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del(cache, key, options \\ [])

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Specs

del(cache(), any(), Keyword.t()) :: {status(), boolean()}

Removes an entry from a cache.

This will return { :ok, true } regardless of whether a key has been removed or not. The true value can be thought of as "is key no longer present?".

Examples

iex> Cachex.put(:my_cache, "key", "value")
iex> Cachex.get(:my_cache, "key")
{ :ok, "value" }

iex> Cachex.del(:my_cache, "key")
{ :ok, true }

iex> Cachex.get(:my_cache, "key")
{ :ok, nil }
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dump(cache, path, options \\ [])

View Source

Specs

dump(cache(), binary(), Keyword.t()) :: {status(), any()}

Serializes a cache to a location on a filesystem.

This operation will write the current state of a cache to a provided location on a filesystem. The written state can be used alongside the load/3 command to import back in the future.

It is the responsibility of the user to ensure that the location is able to be written to, not the responsibility of Cachex.

Options

  • :compression

    Specifies the level of compression to apply when serializing (0-9). This will default to level 1 compression, which is appropriate for most dumps. Using a compression level of 0 will disable compression completely. This will result in a faster serialization but at the cost of higher space.

Examples

iex> Cachex.dump(:my_cache, "/tmp/my_default_backup")
{ :ok, true }

iex> Cachex.dump(:my_cache, "/tmp/my_custom_backup", [ compressed: 0 ])
{ :ok, true }
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empty?(cache, options \\ [])

View Source

Specs

empty?(cache(), Keyword.t()) :: {status(), boolean()}

Determines whether a cache contains any entries.

This does not take the expiration time of keys into account. As such, if there are any unremoved (but expired) entries in the cache, they will be included in the returned determination.

Examples

iex> Cachex.put(:my_cache, "key1", "value1")
iex> Cachex.empty?(:my_cache)
{ :ok, false }

iex> Cachex.clear(:my_cache)
iex> Cachex.empty?(:my_cache)
{ :ok, true }
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execute(cache, operation, options \\ [])

View Source

Specs

execute(cache(), function(), Keyword.t()) :: {status(), any()}

Executes multiple functions in the context of a cache.

This can be used when carrying out several cache operations at once to avoid the overhead of cache loading and jumps between processes.

This does not provide a transactional execution, it simply avoids the overhead involved in the initial calls to a cache. For a transactional implementation, please see transaction/3.

To take advantage of the cache context, ensure to use the cache instance provided when executing cache calls. If this is not done you will see zero benefits from using execute/3.

Examples

iex> Cachex.put(:my_cache, "key1", "value1")
iex> Cachex.put(:my_cache, "key2", "value2")
iex> Cachex.execute(:my_cache, fn(worker) ->
...>   val1 = Cachex.get!(worker, "key1")
...>   val2 = Cachex.get!(worker, "key2")
...>   [val1, val2]
...> end)
{ :ok, [ "value1", "value2" ] }
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exists?(cache, key, options \\ [])

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Specs

exists?(cache(), any(), Keyword.t()) :: {status(), boolean()}

Determines whether an entry exists in a cache.

This will take expiration times into account, meaning that expired entries will not be considered to exist.

Examples

iex> Cachex.put(:my_cache, "key", "value")
iex> Cachex.exists?(:my_cache, "key")
{ :ok, true }

iex> Cachex.exists?(:my_cache, "missing_key")
{ :ok, false }
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expire(cache, key, expiration, options \\ [])

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Specs

expire(cache(), any(), number() | nil, Keyword.t()) :: {status(), boolean()}

Places an expiration time on an entry in a cache.

The provided expiration must be a integer value representing the lifetime of the entry in milliseconds. If the provided value is not positive, the entry will be immediately evicted.

If the entry does not exist, no changes will be made in the cache.

Examples

iex> Cachex.put(:my_cache, "key", "value")
iex> Cachex.expire(:my_cache, "key", :timer.seconds(5))
{ :ok, true }

iex> Cachex.expire(:my_cache, "missing_key", :timer.seconds(5))
{ :ok, false }
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expire_at(cache, key, timestamp, options \\ [])

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Specs

expire_at(cache(), any(), number(), Keyword.t()) :: {status(), boolean()}

Updates an entry in a cache to expire at a given time.

Unlike expire/4 this call uses an instant in time, rather than a duration. The same semantics apply as calls to expire/4 in that instants which have passed will result in immediate eviction.

Examples

iex> Cachex.put(:my_cache, "key", "value")
iex> Cachex.expire_at(:my_cache, "key", 1455728085502)
{ :ok, true }

iex> Cachex.expire_at(:my_cache, "missing_key", 1455728085502)
{ :ok, false }
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export(cache, options \\ [])

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Specs

export(cache(), Keyword.t()) :: {status(), [Spec.entry()]}

Exports all entries from a cache.

This provides a raw read of the entire backing table into a list of cache records for export purposes.

This function is very heavy, so it should typically only be used when debugging and/or exporting of tables (although the latter case should really use dump/3).

## Examples

iex> Cachex.put(:my_cache, "key", "value")
iex> Cachex.export(:my_cache)
{ :ok, [ { :entry, "key", 1538714590095, nil, "value" } ] }
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fetch(cache, key, fallback \\ nil, options \\ [])

View Source

Specs

fetch(cache(), any(), function() | nil, Keyword.t()) ::
  {status() | :commit | :ignore, any()}

Fetches an entry from a cache, generating a value on cache miss.

If the entry requested is found in the cache, this function will operate in the same way as get/3. If the entry is not contained in the cache, the provided fallback function will be executed.

A fallback function is a function used to lazily generate a value to place inside a cache on miss. Consider it a way to achieve the ability to create a read-through cache.

A fallback function should return a Tuple consisting of a :commit or :ignore tag and a value. If the Tuple is tagged :commit the value will be placed into the cache and then returned. If tagged :ignore the value will be returned without being written to the cache. If you return a value which does not fit this structure, it will be assumed that you are committing the value.

If a fallback function has an arity of 1, the requested entry key will be passed through to allow for contextual computation. If a function has an arity of 2, the :provide option from the global :fallback cache option will be provided as the second argument. This is to allow easy state sharing, such as remote clients. If a function has an arity of 0, it will be executed without arguments.

If a cache has been initialized with a default fallback function in the :fallback option at cache startup, the third argument to this call becomes optional.

Examples

iex> Cachex.put(:my_cache, "key", "value")
iex> Cachex.fetch(:my_cache, "key", fn(key) ->
...>   { :commit, String.reverse(key) }
...> end)
{ :ok, "value" }

iex> Cachex.fetch(:my_cache, "missing_key", fn(key) ->
...>   { :ignore, String.reverse(key) }
...> end)
{ :ignore, "yek_gnissim" }

iex> Cachex.fetch(:my_cache, "missing_key", fn(key) ->
...>   { :commit, String.reverse(key) }
...> end)
{ :commit, "yek_gnissim" }
Link to this function

get(cache, key, options \\ [])

View Source

Specs

get(cache(), any(), Keyword.t()) :: {atom(), any()}

Retrieves an entry from a cache.

Examples

iex> Cachex.put(:my_cache, "key", "value")
iex> Cachex.get(:my_cache, "key")
{ :ok, "value" }

iex> Cachex.get(:my_cache, "missing_key")
{ :ok, nil }
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get_and_update(cache, key, update_function, options \\ [])

View Source

Specs

get_and_update(cache(), any(), function(), Keyword.t()) ::
  {:commit | :ignore, any()}

Retrieves and updates an entry in a cache.

This operation can be seen as an internal mutation, meaning that any previously set expiration time is kept as-is.

This function accepts the same return syntax as fallback functions, in that if you return a Tuple of the form { :ignore, value }, the value is returned from the call but is not written to the cache. You can use this to abandon writes which began eagerly (for example if a key is actually missing).

Examples

iex> Cachex.put(:my_cache, "key", [2])
iex> Cachex.get_and_update(:my_cache, "key", &([1|&1]))
{ :commit, [1, 2] }

iex> Cachex.get_and_update(:my_cache, "missing_key", fn
...>   (nil) -> { :ignore, nil }
...>   (val) -> { :commit, [ "value" | val ] }
...> end)
{ :ignore, nil }
Link to this function

import(cache, entries, options \\ [])

View Source

Specs

import(cache(), [Spec.entry()], Keyword.t()) :: {status(), any()}

Imports an export set into a cache.

This provides a raw import of a previously exported cache via the use of the export/2 command.

## Examples

iex> Cachex.put(:my_cache, "key", "value")
iex> Cachex.import(:my_cache, [ { :entry, "key", 1538714590095, nil, "value" } ])
{ :ok, true }
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incr(cache, key, amount \\ 1, options \\ [])

View Source

Specs

incr(cache(), any(), integer(), Keyword.t()) :: {status(), integer()}

Increments an entry in the cache.

This will overwrite any value that was previously set against the provided key.

Options

  • :initial

    An initial value to set the key to if it does not exist. This will take place before the increment call. Defaults to 0.

Examples

iex> Cachex.put(:my_cache, "my_key", 10)
iex> Cachex.incr(:my_cache, "my_key")
{ :ok, 11 }

iex> Cachex.put(:my_cache, "my_new_key", 10)
iex> Cachex.incr(:my_cache, "my_new_key", 5)
{ :ok, 15 }

iex> Cachex.incr(:my_cache, "missing_key", 5, initial: 2)
{ :ok, 7 }
Link to this function

inspect(cache, option, options \\ [])

View Source

Specs

inspect(cache(), atom() | tuple(), Keyword.t()) :: {status(), any()}

Inspects various aspects of a cache.

These operations should be regarded as debug tools, and should really only happen outside of production code (unless absolutely) necessary.

Accepted options are only provided for convenience and should not be heavily relied upon. They are not part of the public interface (despite being documented) and as such may be removed at any time (however this does not mean that they will be).

Please use cautiously. inspect/2 is provided mainly for testing purposes and so performance isn't as much of a concern. It should also be noted that inspect/2 will always operate locally.

Options

  • :cache

    Retrieves the internal cache record for a cache.

  • { :entry, key }

    Retrieves a raw entry record from inside a cache.

  • { :expired, :count }

    Retrieves the number of expired entries which currently live in the cache but have not yet been removed by cleanup tasks (either scheduled or lazy).

  • { :expired, :keys }

    Retrieves the list of expired entry keys which current live in the cache but have not yet been removed by cleanup tasks (either scheduled or lazy).

  • { :janitor, :last }

    Retrieves metadata about the last execution of the Janitor service for the specified cache.

  • { :memory, :bytes }

    Retrieves an approximate memory footprint of a cache in bytes.

  • { :memory, :binary }

    Retrieves an approximate memory footprint of a cache in binary format.

  • { :memory, :words }

    Retrieve an approximate memory footprint of a cache as a number of machine words.

Examples

iex> Cachex.inspect(:my_cache, :cache)
{:ok,
  {:cache, :my_cache, %{}, {:expiration, nil, 3000, true}, {:fallback, nil, nil},
    {:hooks, [], []}, {:limit, nil, Cachex.Policy.LRW, 0.1, []}, false, []}}

iex> Cachex.inspect(:my_cache, { :entry, "my_key" } )
{ :ok, { :entry, "my_key", 1475476615662, 1, "my_value" } }

iex> Cachex.inspect(:my_cache, { :expired, :count })
{ :ok, 0 }

iex> Cachex.inspect(:my_cache, { :expired, :keys })
{ :ok, [ ] }

iex> Cachex.inspect(:my_cache, { :janitor, :last })
{ :ok, %{ count: 0, duration: 57, started: 1475476530925 } }

iex> Cachex.inspect(:my_cache, { :memory, :binary })
{ :ok, "10.38 KiB" }

iex> Cachex.inspect(:my_cache, { :memory, :bytes })
{ :ok, 10624 }

iex> Cachex.inspect(:my_cache, { :memory, :words })
{ :ok, 1328 }
Link to this function

invoke(cache, cmd, key, options \\ [])

View Source

Specs

invoke(cache(), atom(), any(), Keyword.t()) :: any()

Invokes a custom command against a cache entry.

The provided command name must be a valid command which was previously attached to the cache in calls to start_link/2.

Examples

iex> import Cachex.Spec
iex>
iex> Cachex.start_link(:my_cache, [
...>    commands: [
...>      last: command(type: :read, execute: &List.last/1)
...>    ]
...> ])
{ :ok, _pid }

iex> Cachex.put(:my_cache, "my_list", [ 1, 2, 3 ])
iex> Cachex.invoke(:my_cache, :last, "my_list")
{ :ok, 3 }
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keys(cache, options \\ [])

View Source

Specs

keys(cache(), Keyword.t()) :: {status(), [any()]}

Retrieves a list of all entry keys from a cache.

The order these keys are returned should be regarded as unordered.

Examples

iex> Cachex.put(:my_cache, "key1", "value1")
iex> Cachex.put(:my_cache, "key2", "value2")
iex> Cachex.put(:my_cache, "key3", "value3")
iex> Cachex.keys(:my_cache)
{ :ok, [ "key2", "key1", "key3" ] }

iex> Cachex.clear(:my_cache)
iex> Cachex.keys(:my_cache)
{ :ok, [] }
Link to this function

load(cache, path, options \\ [])

View Source

Specs

load(cache(), binary(), Keyword.t()) :: {status(), any()}

Deserializes a cache from a location on a filesystem.

This operation will read the current state of a cache from a provided location on a filesystem. This function will only understand files which have previously been created using dump/3.

It is the responsibility of the user to ensure that the location is able to be read from, not the responsibility of Cachex.

Options

  • :trusted

    Allow for loading from trusted or untrusted sources; trusted sources can load atoms into the table, whereas untrusted sources cannot. Defaults to true.

Examples

iex> Cachex.put(:my_cache, "my_key", 10)
iex> Cachex.dump(:my_cache, "/tmp/my_backup")
{ :ok, true }

iex> Cachex.size(:my_cache)
{ :ok, 1 }

iex> Cachex.clear(:my_cache)
iex> Cachex.size(:my_cache)
{ :ok, 0 }

iex> Cachex.load(:my_cache, "/tmp/my_backup")
{ :ok, true }

iex> Cachex.size(:my_cache)
{ :ok, 1 }
Link to this function

persist(cache, key, options \\ [])

View Source

Specs

persist(cache(), any(), Keyword.t()) :: {status(), boolean()}

Removes an expiration time from an entry in a cache.

Examples

iex> Cachex.put(:my_cache, "key", "value", ttl: 1000)
iex> Cachex.persist(:my_cache, "key")
{ :ok, true }

iex> Cachex.persist(:my_cache, "missing_key")
{ :ok, false }
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purge(cache, options \\ [])

View Source

Specs

purge(cache(), Keyword.t()) :: {status(), number()}

Triggers a cleanup of all expired entries in a cache.

This can be used to implement custom eviction policies rather than relying on the internal Janitor service. Take care when using this method though; calling purge/2 manually will result in a purge firing inside the calling process.

Examples

iex> Cachex.purge(:my_cache)
{ :ok, 15 }
Link to this function

put(cache, key, value, options \\ [])

View Source

Specs

put(cache(), any(), any(), Keyword.t()) :: {status(), boolean()}

Places an entry in a cache.

This will overwrite any value that was previously set against the provided key, and overwrite any TTLs which were already set.

Options

  • :ttl

    An expiration time to set for the provided key (time-to-live), overriding any default expirations set on a cache. This value should be in milliseconds.

Examples

iex> Cachex.put(:my_cache, "key", "value")
{ :ok, true }

iex> Cachex.put(:my_cache, "key", "value", ttl: :timer.seconds(5))
iex> Cachex.ttl(:my_cache, "key")
{ :ok, 5000 }
Link to this function

put_many(cache, pairs, options \\ [])

View Source

Specs

put_many(cache(), [{any(), any()}], Keyword.t()) :: {status(), boolean()}

Places a batch of entries in a cache.

This operates in the same way as put/4, except that multiple keys can be inserted in a single atomic batch. This is a performance gain over writing keys using multiple calls to put/4, however it's a performance penalty when writing a single key pair due to some batching overhead.

Options

  • :ttl

    An expiration time to set for the provided keys (time-to-live), overriding any default expirations set on a cache. This value should be in milliseconds.

Examples

iex> Cachex.put_many(:my_cache, [ { "key", "value" } ])
{ :ok, true }

iex> Cachex.put_many(:my_cache, [ { "key", "value" } ], ttl: :timer.seconds(5))
iex> Cachex.ttl(:my_cache, "key")
{ :ok, 5000 }
Link to this function

refresh(cache, key, options \\ [])

View Source

Specs

refresh(cache(), any(), Keyword.t()) :: {status(), boolean()}

Refreshes an expiration for an entry in a cache.

Refreshing an expiration will reset the existing expiration with an offset from the current time - i.e. if you set an expiration of 5 minutes and wait 3 minutes before refreshing, the entry will expire 8 minutes after the initial insertion.

Examples

iex> Cachex.put(:my_cache, "my_key", "my_value", ttl: :timer.seconds(5))
iex> Process.sleep(4)
iex> Cachex.ttl(:my_cache, "my_key")
{ :ok, 1000 }

iex> Cachex.refresh(:my_cache, "my_key")
iex> Cachex.ttl(:my_cache, "my_key")
{ :ok, 5000 }

iex> Cachex.refresh(:my_cache, "missing_key")
{ :ok, false }
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reset(cache, options \\ [])

View Source

Specs

reset(cache(), Keyword.t()) :: {status(), true}

Resets a cache by clearing the keyspace and restarting any hooks.

Options

  • :hooks

    A whitelist of hooks to reset on the cache instance (call the initialization phase of a hook again). This will default to resetting all hooks associated with a cache, which is usually the desired behaviour.

  • :only

    A whitelist of components to reset, which can currently contain either the :cache or :hooks tag to determine what to reset. This will default to [ :cache, :hooks ].

Examples

iex> Cachex.put(:my_cache, "my_key", "my_value")
iex> Cachex.reset(:my_cache)
iex> Cachex.size(:my_cache)
{ :ok, 0 }

iex> Cachex.reset(:my_cache, [ only: :hooks ])
{ :ok, true }

iex> Cachex.reset(:my_cache, [ only: :hooks, hooks: [ MyHook ] ])
{ :ok, true }

iex> Cachex.reset(:my_cache, [ only: :cache ])
{ :ok, true }
Link to this function

set(cache, key, value, options \\ [])

View Source
This function is deprecated. Please migrate to using put/4 instead..

Deprecated implementation delegate of put/4.

Link to this function

set_many(cache, pairs, options \\ [])

View Source
This function is deprecated. Please migrate to using put_many/3 instead..

Deprecated implementation delegate of put_many/3.

Link to this function

size(cache, options \\ [])

View Source

Specs

size(cache(), Keyword.t()) :: {status(), number()}

Retrieves the total size of a cache.

This does not take into account the expiration time of any entries inside the cache. Due to this, this call is O(1) rather than the more expensive O(n) algorithm used by count/3. Which you use depends on exactly what you want the returned number to represent.

Examples

iex> Cachex.put(:my_cache, "key1", "value1")
iex> Cachex.put(:my_cache, "key2", "value2")
iex> Cachex.put(:my_cache, "key3", "value3")
iex> Cachex.size(:my_cache)
{ :ok, 3 }
Link to this function

start(name, options \\ [])

View Source

Specs

start(atom(), Keyword.t()) :: {atom(), pid()}

Creates a new Cachex cache service tree.

This will not link the cache to the current process, so if your process dies the cache will continue to live. If you don't want this behaviour, please use the provided start_link/2.

This function is otherwise identical to start_link/2 so please see that documentation for further information and configuration.

Specs

start_link(atom() | Keyword.t()) :: {atom(), pid()}

Creates a new Cachex cache service tree, linked to the current process.

This will link the cache to the current process, so if your process dies the cache will also die. If you don't want this behaviour, please use start/2.

The first argument should be a unique atom, used as the name of the cache service for future calls through to Cachex. For all options requiring a record argument, please import Cachex.Spec in advance.

Options

  • :commands

    This option allows you to attach a set of custom commands to a cache in order to provide shorthand execution. A cache command must be constructed using the :command record provided by Cachex.Spec. A cache command will adhere to these basic rules:

    • If you define a :read command, the return value of your command will be passed through as the result of your call to invoke/4.
    • If you define a :write command, your command must return a two-element Tuple. The first element represents the value being returned from your invoke/4 call, and the second represents the value to write back into the cache (as an update). If your command does not fit this, errors will happen (intentionally). Commands are set on a per-cache basis, but can be reused across caches. They're set only on cache startup and cannot be modified after the cache tree is created. iex> import Cachex.Spec ...> ...> Cachex.start_link(:my_cache, [ ...> commands: [ ...> last: command(type: :read, execute: &List.last/1), ...> trim: command(type: :write, execute: &String.trim/1) ...> ] ...> ]) { :ok, _pid } Either a Keyword or a Map can be provided against the :commands option as we only use Enum to verify them before attaching them internally. Please see the Cachex.Spec.command/1 documentation for further customization options.
  • :compressed

    This option will specify whether this cache should have enable ETS compression, which is likely to reduce memory overhead. Please note that there is a potential for this option to slow your cache due to compression overhead, so benchmark as appropriate when using this option. This option defaults to false.

    iex> Cachex.start_link(:my_cache, [ compressed: true ])
    { :ok, _pid }
  • :expiration

    The expiration option provides the ability to customize record expiration at a global cache level. The value provided here must be a valid :expiration record provided by Cachex.Spec.

    iex> import Cachex.Spec
    ...>
    ...> Cachex.start_link(:my_cache, [
    ...>   expiration: expiration(
    ...>     # default record expiration
    ...>     default: :timer.seconds(60),
    ...>
    ...>     # how often cleanup should occur
    ...>     interval: :timer.seconds(30),
    ...>
    ...>     # whether to enable lazy checking
    ...>     lazy: true
    ...>   )
    ...> ])
    { :ok, _pid }

    Please see the Cachex.Spec.expiration/1 documentation for further customization options.

  • :fallback

    The fallback option allows global settings related to the fetch/4 command on a cache. The value provided here can either be a valid :fallback record provided by Cachex.Spec, or a single function (which is turned into a record internally).

    iex> import Cachex.Spec
    ...>
    ...> Cachex.start_link(:my_cache, [
    ...>   fallback: fallback(
    ...>     # default func to use with fetch/4
    ...>     default: &String.reverse/1,
    ...>
    ...>     # anything to pass to fallbacks
    ...>     provide: { }
    ...>   )
    ...> ])
    { :ok, _pid }

    The :default function provided will be used if fetch/2 is called, rather than explicitly passing one at call time. The :provide function contains state which can be passed to a fallback function if the arity is 2 rather than 1. Please see the documentation for fetch/4, and the Cachex.Spec.fallback/1 documentation for further information.

  • :hooks

    The :hooks option allow the user to attach a list of notification hooks to enable listening on cache actions (either before or after they happen). These hooks should be valid :hook records provided by Cachex.Spec. Example hook implementations can be found in Cachex.Stats and Cachex.Policy.LRW.

    iex> import Cachex.Spec
    ...>
    ...> Cachex.start_link(:my_cache, [
    ...>   hooks: [
    ...>     hook(module: MyHook, name: :my_hook, state: { })
    ...>   ]
    ...> ])
    { :ok, _pid }

    Please see the Cachex.Spec.hook/1 documentation for further customization options.

  • :limit

    A cache limit provides a maximum size to cap the cache keyspace at. This should be either a positive integer, or a valid :limit record provided by Cachex.Spec. Internally a provided interger will just be coerced to a :limit record with some default values set.

    iex> import Cachex.Spec
    ...>
    ...> Cachex.start_link(:my_cache, [
    ...>   # simple limit
    ...>   limit: 500,
    ...>
    ...>   # complex limit
    ...>   limit: limit(
    ...>     size: 500,
    ...>     policy: Cachex.Policy.LRW,
    ...>     reclaim: 0.5,
    ...>     options: []
    ...>   )
    ...> ])
    { :ok, _pid }

    Please see the Cachex.Spec.limit/1 documentation for further customization options.

  • :nodes

    A list of nodes this cache will live on, to provide distributed behaviour across physical nodes. This should be a list of node names, in the long form.

    iex> Cachex.start_link(:my_cache, [
    ...>   nodes: [
    ...>     :foo@localhost,
    ...>     :bar@localhost
    ...>   ]
    ...> ])
    { :ok, _pid }
  • :stats

    This option can be used to toggle statistics gathering for a cache. This is a shorthand option to avoid attaching the Cachex.Stats hook manually. Statistics gathering has very minor overhead due to being implemented as a hook, Stats can be retrieve from a running cache by using Cachex.stats/2.

    iex> Cachex.start_link(:my_cache, [ stats: true ])
    { :ok, _pid }
  • :transactional

    This option will specify whether this cache should have transactions and row locking enabled from cache startup. Please note that even if this is false, it will be enabled the moment a transaction is executed. It's recommended to leave this as default as it will handle most use cases in the most performant way possible.

    iex> Cachex.start_link(:my_cache, [ transactions: true ])
    { :ok, _pid }
Link to this function

stats(cache, options \\ [])

View Source

Specs

stats(cache(), Keyword.t()) :: {status(), %{}}

Retrieves statistics about a cache.

This will only provide statistics if the :stats option was provided on cache startup in start_link/2.

Options

  • :for

    Allows customization of exactly which statistics to retrieve.

Examples

iex> Cachex.stats(:my_cache)
{:ok, %{meta: %{creation_date: 1518984857331}}}

iex> Cachex.stats(:cache_with_no_stats)
{ :error, :stats_disabled }
Link to this function

stream(cache, query \\ Query.create(true), options \\ [])

View Source

Specs

stream(cache(), any(), Keyword.t()) :: {status(), Enumerable.t()}

Creates a Stream of entries in a cache.

This will stream all entries matching the match specification provided as the second argument. If none is provided, it will default to all entries which are yet to expire (in no particular order).

Consider using Cachex.Query to generate match specifications used when querying the contents of a cache table.

Options

  • :batch_size

    Allows customization of the internal batching when paginating the QLC cursor coming back from ETS. It's unlikely this will ever need changing.

Examples

iex> Cachex.put(:my_cache, "a", 1)
iex> Cachex.put(:my_cache, "b", 2)
iex> Cachex.put(:my_cache, "c", 3)
{:ok, true}

iex> :my_cache |> Cachex.stream! |> Enum.to_list
[{:entry, "b", 1519015801794, nil, 2},
  {:entry, "c", 1519015805679, nil, 3},
  {:entry, "a", 1519015794445, nil, 1}]

iex> query = Cachex.Query.create(true, :key)
iex> :my_cache |> Cachex.stream!(query) |> Enum.to_list
["b", "c", "a"]

iex> query = Cachex.Query.create(true, :value)
iex> :my_cache |> Cachex.stream!(query) |> Enum.to_list
[2, 3, 1]

iex> query = Cachex.Query.create(true, { :key, :value })
iex> :my_cache |> Cachex.stream!(query) |> Enum.to_list
[{"b", 2}, {"c", 3}, {"a", 1}]
Link to this function

take(cache, key, options \\ [])

View Source

Specs

take(cache(), any(), Keyword.t()) :: {status(), any()}

Takes an entry from a cache.

This is conceptually equivalent to running get/3 followed by an atomic del/3 call.

Examples

iex> Cachex.put(:my_cache, "key", "value")
iex> Cachex.take(:my_cache, "key")
{ :ok, "value" }

iex> Cachex.get(:my_cache, "key")
{ :ok, nil }

iex> Cachex.take(:my_cache, "missing_key")
{ :ok, nil }
Link to this function

touch(cache, key, options \\ [])

View Source

Specs

touch(cache(), any(), Keyword.t()) :: {status(), boolean()}

Updates the last write time on a cache entry.

This is very similar to refresh/3 except that the expiration time is maintained inside the record (using a calculated offset).

Link to this function

transaction(cache, keys, operation, options \\ [])

View Source

Specs

transaction(cache(), [any()], function(), Keyword.t()) :: {status(), any()}

Executes multiple functions in the context of a transaction.

This will operate in the same way as execute/3, except that writes to the specified keys will be blocked on the execution of this transaction.

The keys parameter should be a list of keys you wish to lock whilst your transaction is executed. Any keys not in this list can still be written even during your transaction.

Examples

iex> Cachex.put(:my_cache, "key1", "value1")
iex> Cachex.put(:my_cache, "key2", "value2")
iex> Cachex.transaction(:my_cache, [ "key1", "key2" ], fn(worker) ->
...>   val1 = Cachex.get(worker, "key1")
...>   val2 = Cachex.get(worker, "key2")
...>   [val1, val2]
...> end)
{ :ok, [ "value1", "value2" ] }
Link to this function

ttl(cache, key, options \\ [])

View Source

Specs

ttl(cache(), any(), Keyword.t()) :: {status(), integer() | nil}

Retrieves the expiration for an entry in a cache.

This is a millisecond value (if set) representing the time a cache entry has left to live in a cache. It can return nil if the entry does not have a set expiration.

Examples

iex> Cachex.ttl(:my_cache, "my_key")
{ :ok, 13985 }

iex> Cachex.ttl(:my_cache, "my_key_with_no_ttl")
{ :ok, nil }

iex> Cachex.ttl(:my_cache, "missing_key")
{ :ok, nil }
Link to this function

update(cache, key, value, options \\ [])

View Source

Specs

update(cache(), any(), any(), Keyword.t()) :: {status(), any()}

Updates an entry in a cache.

Unlike get_and_update/4, this does a blind overwrite of a value.

This operation can be seen as an internal mutation, meaning that any previously set expiration time is kept as-is.

Examples

iex> Cachex.put(:my_cache, "key", "value")
iex> Cachex.get(:my_cache, "key")
{ :ok, "value" }

iex> Cachex.update(:my_cache, "key", "new_value")
iex> Cachex.get(:my_cache, "key")
{ :ok, "new_value" }

iex> Cachex.update(:my_cache, "missing_key", "new_value")
{ :ok, false }