memcachex v0.4.1 Memcache

This module provides a user friendly API to interact with the memcached server.

Example

{ :ok, pid } = Memcache.start_link()
{ :ok } = Memcache.set(pid, "hello", "world")
{ :ok, "world" } = Memcache.get(pid, "hello")

Coder

Memcache.Coder allows you to specify how the value should be encoded before sending it to the server and how it should be decoded after it is retrived. There are four built-in coders namely Memcache.Coder.Raw, Memcache.Coder.Erlang, Memcache.Coder.JSON, Memcache.Coder.ZIP. Custom coders can be created by implementing the Memcache.Coder behaviour.

CAS

CAS feature allows to atomically perform two commands on a key. Get the cas version number associated with a key during the first command and pass that value during the second command. The second command will fail if the value has changed by someone else in the mean time.

{:ok, "hello", cas} = Memcache.get(pid, "key", cas: true)
{:ok} = Memcache.set_cas(pid, "key", "world", cas)

Memcache module provides a *_cas variant for most of the functions. This function will take an additional argument named cas and returns the same value as their counterpart except in case of CAS error. In case of CAS error the returned value would be equal to { :error, "Key exists" }

Options

Most the functions in this module accept an optional Keyword list. The below list specifies the behavior of each option. The list of option accepted by a specific function will be documented in the specific funcion.

:cas - (boolean) returns the CAS value associated with the data. This value will be either in second or third position of the returned tuple depending on the command. Defaults to false.
:ttl - (integer) specifies the expiration time in seconds for the corresponding key. Can be set to 0 to disable expiration. The Default value can be configured using start_link/2.

Summary

Types

error()

fetch_integer_result()

fetch_result()

result()

store_result()

Functions

add(server, key, value, opts \\ [])

Sets the key to value if the key doesn’t exist already. Returns {:error, "Key exists"} if the given key already exists

append(server, key, value, opts \\ [])

Appends the value to the end of the current value of the key. Returns {:error, "Item not stored"} if the item is not present in the server already

append_cas(server, key, value, cas, opts \\ [])

Appends the value to the end of the current value of the key if the CAS value is equal to the provided value

cas(server, key, update, opts \\ [])

Compare and swap value using optimistic locking

decr(server, key, opts \\ [])

Decremens the current value. Only integer value can be decremented. Returns { :error, "Incr/Decr on non-numeric value"} if the value stored in the server is not numeric

decr_cas(server, key, cas, opts \\ [])

Decrements the current value if the CAS value is equal to the provided value

delete(server, key)

Removes the item with the given key value. Returns { :error, "Key not found" } if the given key is not found

delete_cas(server, key, cas)

Removes the item with the given key value if the CAS value is equal to the provided value

flush(server, opts \\ [])

Flush all the items in the server. ttl option will cause the flush to be delayed by the specified time

get(server, key, opts \\ [])

Gets the value associated with the key. Returns {:error, "Key not found"} if the given key doesn’t exist

incr(server, key, opts \\ [])

Increments the current value. Only integer value can be incremented. Returns { :error, "Incr/Decr on non-numeric value"} if the value stored in the server is not numeric

incr_cas(server, key, cas, opts \\ [])

Increments the current value if the CAS value is equal to the provided value

multi_get(server, keys, opts \\ [])

Gets the values associated with the list of keys. Returns a map. Keys that are not found in the server are filtered from the result

multi_set(server, commands, opts \\ [])

Multi version of set/4. Accepts a map or a list of {key, value}

multi_set_cas(server, commands, opts \\ [])

Multi version of set_cas/4. Accepts a list of {key, value, cas}

noop(server)

Sends a noop command

prepend(server, key, value, opts \\ [])

Prepends the value to the start of the current value of the key. Returns {:error, "Item not stored"} if the item is not present in the server already

prepend_cas(server, key, value, cas, opts \\ [])

Prepends the value to the start of the current value of the key if the CAS value is equal to the provided value

replace(server, key, value, opts \\ [])

Sets the key to value if the key already exists. Returns {:error, "Key not found"} if the given key doesn’t exist

replace_cas(server, key, value, cas, opts \\ [])

Sets the key to value if the key already exists and has CAS value equal to the provided value

set(server, key, value, opts \\ [])

Sets the key to value

set_cas(server, key, value, cas, opts \\ [])

Sets the key to value if the key exists and has CAS value equal to the provided value

start_link(connection_options \\ [], options \\ [])

Creates a connection using Memcache.Connection.start_link/2

stat(server)

Gets the default set of server statistics

stat(server, key)

Gets the specific set of server statistics

stop(server)

Closes the connection to the memcached server

version(server)

Gets the version of the server

Types

error()

error() :: {:error, binary | atom}

fetch_integer_result()

fetch_integer_result ::
  {:ok, integer} |
  {:ok, integer, integer} |
  error

fetch_result()

fetch_result() :: {:ok, any} | {:ok, any, integer} | error

result()

result ::
  {:ok} |
  {:ok, integer} |
  {:ok, any} |
  {:ok, any, integer} |
  error

store_result()

store_result() :: {:ok} | {:ok, integer} | error

Functions

add(server, key, value, opts \\ [])

add(GenServer.server, binary, binary, Keyword.t) :: store_result

Sets the key to value if the key doesn’t exist already. Returns {:error, "Key exists"} if the given key already exists.

Accepted options: :cas, :ttl

append(server, key, value, opts \\ [])

append(GenServer.server, binary, binary, Keyword.t) :: store_result

Appends the value to the end of the current value of the key. Returns {:error, "Item not stored"} if the item is not present in the server already

Accepted options: :cas

append_cas(server, key, value, cas, opts \\ [])

append_cas(GenServer.server, binary, binary, integer, Keyword.t) :: store_result

Appends the value to the end of the current value of the key if the CAS value is equal to the provided value

Accepted options: :cas

cas(server, key, update, opts \\ [])

cas(GenServer.server, binary, (binary -> binary), Keyword.t) ::
  {:ok, any} |
  error

Compare and swap value using optimistic locking.

Get the existing value for key
If it exists, call the update function with the value
Set the returned value for key

The 3rd operation will fail if someone else has updated the value for the same key in the mean time. In that case, by default, this function will go to step 1 and try again. Retry behavior can be disabled by passing [retry: false] option.

decr(server, key, opts \\ [])

decr(GenServer.server, binary, Keyword.t) :: fetch_integer_result

Decremens the current value. Only integer value can be decremented. Returns { :error, "Incr/Decr on non-numeric value"} if the value stored in the server is not numeric.

Options

:by - (integer) The amount to add to the existing value. Defaults to 1.
:default - (integer) Default value to use in case the key is not found. Defaults to 0.

other options: :cas, :ttl

decr_cas(server, key, cas, opts \\ [])

decr_cas(GenServer.server, binary, integer, Keyword.t) :: fetch_integer_result

Decrements the current value if the CAS value is equal to the provided value.

Options

:by - (integer) The amount to add to the existing value. Defaults to 1.
:default - (integer) Default value to use in case the key is not found. Defaults to 0.

other options: :cas, :ttl

delete(server, key)

delete(GenServer.server, binary) :: store_result

Removes the item with the given key value. Returns { :error, "Key not found" } if the given key is not found

delete_cas(server, key, cas)

delete_cas(GenServer.server, binary, integer) :: store_result

Removes the item with the given key value if the CAS value is equal to the provided value

flush(server, opts \\ [])

flush(GenServer.server, Keyword.t) :: store_result

Flush all the items in the server. ttl option will cause the flush to be delayed by the specified time.

Accepted options: :ttl

get(server, key, opts \\ [])

get(GenServer.server, binary, Keyword.t) :: fetch_result

Gets the value associated with the key. Returns {:error, "Key not found"} if the given key doesn’t exist.

Accepted option: :cas

incr(server, key, opts \\ [])

incr(GenServer.server, binary, Keyword.t) :: fetch_integer_result

Increments the current value. Only integer value can be incremented. Returns { :error, "Incr/Decr on non-numeric value"} if the value stored in the server is not numeric.

Options

:by - (integer) The amount to add to the existing value. Defaults to 1.
:default - (integer) Default value to use in case the key is not found. Defaults to 0.

other options: :cas, :ttl

incr_cas(server, key, cas, opts \\ [])

incr_cas(GenServer.server, binary, integer, Keyword.t) :: fetch_integer_result

Increments the current value if the CAS value is equal to the provided value.

Options

:by - (integer) The amount to add to the existing value. Defaults to 1.
:default - (integer) Default value to use in case the key is not found. Defaults to 0.

other options: :cas, :ttl

multi_get(server, keys, opts \\ [])

multi_get(GenServer.server, [binary], Keyword.t) ::
  {:ok, map} |
  error

Gets the values associated with the list of keys. Returns a map. Keys that are not found in the server are filtered from the result.

Accepted option: :cas

multi_set(server, commands, opts \\ [])

multi_set(GenServer.server, [{binary, binary}] | map, Keyword.t) ::
  {:ok, [store_result]} |
  error

Multi version of set/4. Accepts a map or a list of {key, value}.

Accepted options: :cas, :ttl

multi_set_cas(server, commands, opts \\ [])

multi_set_cas(GenServer.server, [{binary, binary, integer}], Keyword.t) ::
  {:ok, [store_result]} |
  error

Multi version of set_cas/4. Accepts a list of {key, value, cas}.

Accepted options: :cas, :ttl

noop(server)

noop(GenServer.server) :: {:ok} | error

Sends a noop command

prepend(server, key, value, opts \\ [])

prepend(GenServer.server, binary, binary, Keyword.t) :: store_result

Prepends the value to the start of the current value of the key. Returns {:error, "Item not stored"} if the item is not present in the server already

Accepted options: :cas

prepend_cas(server, key, value, cas, opts \\ [])

prepend_cas(GenServer.server, binary, binary, integer, Keyword.t) :: store_result

Prepends the value to the start of the current value of the key if the CAS value is equal to the provided value

Accepted options: :cas

replace(server, key, value, opts \\ [])

replace(GenServer.server, binary, binary, Keyword.t) :: store_result

Sets the key to value if the key already exists. Returns {:error, "Key not found"} if the given key doesn’t exist.

Accepted options: :cas, :ttl

replace_cas(server, key, value, cas, opts \\ [])

replace_cas(GenServer.server, binary, binary, integer, Keyword.t) :: store_result

Sets the key to value if the key already exists and has CAS value equal to the provided value.

Accepted options: :cas, :ttl

set(server, key, value, opts \\ [])

set(GenServer.server, binary, binary, Keyword.t) :: store_result

Sets the key to value

Accepted options: :cas, :ttl

set_cas(server, key, value, cas, opts \\ [])

set_cas(GenServer.server, binary, binary, integer, Keyword.t) :: store_result

Sets the key to value if the key exists and has CAS value equal to the provided value

Accepted options: :cas, :ttl

start_link(connection_options \\ [], options \\ [])

start_link(Keyword.t, Keyword.t) :: GenServer.on_start

Creates a connection using Memcache.Connection.start_link/2

Connection Options

This is a superset of the connection options accepted by the Memcache.Connection.start_link/2. The following list specifies the additional options.

:ttl - (integer) a default expiration time in seconds. This value will be used if the :ttl value is not specified for a operation. Defaults to 0(means forever).
:namespace - (string) prepend each key with the given value.
:coder - (module | {module, options}) Can be either a module or tuple contains the module and options. Defaults to {Memcache.Coder.Raw, []}.

Options

The second option is passed directly to the underlying GenServer.start_link/3, so it can be used to create named process.

stat(server)

stat(GenServer.server) :: {:ok, map} | error

Gets the default set of server statistics

stat(server, key)

stat(GenServer.server, String.t) :: {:ok, map} | error

Gets the specific set of server statistics

stop(server)

stop(GenServer.server) :: {:ok}

Closes the connection to the memcached server.

version(server)

version(GenServer.server) :: String.t | error

Gets the version of the server