View Source ssl_session_cache_api behaviour (ssl v11.2.5)
TLS session cache API
Defines the API for the TLS session cache (pre TLS-1.3) so that the data storage scheme can be replaced by defining a new callback module implementing this API.
Summary
Types
The opaque part of the key. Does not need to be handled by the callback.
The session data that is stored for each session.
A key to an entry in the session cache.
A term that can be used to reference the cache.
Callbacks
Deletes a cache entry.
Calls Fun(Elem, AccIn)
on successive elements of the cache, starting with
AccIn == Acc0
.
Performs possible initializations of the cache and returns a reference to it that is used as parameter to the other API functions.
Looks up a cache entry. Is to be callable from any process.
Selects sessions that can be reused, that is sessions that include PartialKey
in its key. Is to be callable from any process.
Returns the number of sessions in the cache.
Takes care of possible cleanup that is needed when the cache handling process terminates.
Caches a new session or updates an already cached one.
Types
-opaque partial_key()
The opaque part of the key. Does not need to be handled by the callback.
-opaque session()
The session data that is stored for each session.
-type session_cache_key() :: {partial_key(), ssl:session_id()}.
A key to an entry in the session cache.
-type session_cache_ref() :: any().
A term that can be used to reference the cache.
Callbacks
-callback delete(CacheRef, Key) -> DoNotCare when CacheRef :: session_cache_ref(), Key :: session_cache_key(), DoNotCare :: any().
Deletes a cache entry.
Is only called from the cache handling process.
-callback foldl(Fun, Acc0, CacheRef) -> Acc when Fun :: fun(), Acc0 :: term(), CacheRef :: session_cache_ref(), Acc :: term().
Calls Fun(Elem, AccIn)
on successive elements of the cache, starting with
AccIn == Acc0
.
Fun/2
must return a new accumulator, which is passed to the
next call. The function returns the final value of the accumulator. Acc0
is
returned if the cache is empty.
Note
Since OTP-23.3 this functions is only used on the client side and does not need to implemented for a server cache.
-callback init(InitArgs) -> CacheRef when InitArgs :: list(), CacheRef :: session_cache_ref().
Performs possible initializations of the cache and returns a reference to it that is used as parameter to the other API functions.
Is called by the cache handling processes init
function, hence
putting the same requirements on it as a normal process init
function. This function is called twice when starting the SSL
application, once with the role client and once with the role server,
as the SSL application must be prepared to take on both roles.
Includes property {role, client | server}
in init argument list.
Currently this is the only predefined property, there can also be
user-defined properties. See also application environment variable
session_cb_init_args.
-callback lookup(CacheRef, Key) -> Session when CacheRef :: session_cache_ref(), Key :: session_cache_key(), Session :: session() | undefined.
Looks up a cache entry. Is to be callable from any process.
-callback select_session(CacheRef, Server) -> Sessions when CacheRef :: session_cache_ref(), Server :: {ssl:host(), inet:port_number()} | inet:port_number(), Sessions :: [session()].
Selects sessions that can be reused, that is sessions that include PartialKey
in its key. Is to be callable from any process.
Note
Since OTP-23.3 This functions is only used on the client side and does not need to implemented for a server cache.
-callback size(CacheRef) -> Size when CacheRef :: session_cache_ref(), Size :: pos_integer().
Returns the number of sessions in the cache.
If size exceeds the maximum number of sessions, the current cache entries will be invalidated regardless of their remaining lifetime. Is to be callable from any process.
-callback terminate(CacheRef) -> DoNotCare when CacheRef :: session_cache_ref(), DoNotCare :: any().
Takes care of possible cleanup that is needed when the cache handling process terminates.
-callback update(CacheRef, Key, Session) -> DoNotCare when CacheRef :: session_cache_ref(), Key :: session_cache_key(), Session :: session() | undefined, DoNotCare :: any().
Caches a new session or updates an already cached one.
Is only called from the cache handling process.