Remote references are Partisan's representation for remote process identifiers (pid()), registered names and references (reference()).

Distributed Erlang (disterl) will transform the representation of process identifiers, registered names and references when they are sent to a remote node. This is done to disambiguate between remote and local instances. Because Partisan doesn't use disterl it needs to implement this same disambiguation mechanism somehow. As disterl's implementation is done by the BEAM internally and not API is exposed, this module is required to achieve a similar result.

Representation

In cases where lots of references are stored in process state, ets and specially where those are uses as keys, a binary format is preferable to the tuple format in order to save memory and avoid copying the term every time a message is send between processes (by leveraging off-heap binary storage).

For this reason, this module implements two alternative representations:

• references as binary URIs
• references as tuples

The representation to use is controlled by the configuration option remote_ref_as_uri`. If `true this module will generate references as binary URIs. Otherwise it will generate them as tuples.r

URI Representation

  1> partisan_remote_ref:from_term(self()).
  <<"partisan:pid:nonode@nohost:0.1062.0">>

URI Padding

For those cases where the resulting references are smaller than 64 bytes ( and thus will be stored on the process heap) this module can pad the generated binary URIs to 65 bytes, thus forcing them to be stored off-heap. This is controlled with the configuration option remote_ref_binary_padding.

  1> partisan_config:set(remote_ref_binary_padding, false).
  2> partisan_remote_ref:from_term(self()).
  <<"partisan:pid:nonode@nohost:0.1062.0">>
  3> partisan_config:set(remote_ref_binary_padding, true).
  ok
  4> partisan_remote_ref:from_term(self()).
  <<"partisan:pid:nonode@nohost:0.1062.0:"...>>

Tuple Representation

  1> partisan_remote_ref:from_term(self()).
  {partisan_remote_reference,
     nonode@nohost,
     {partisan_process_reference,"<0.1062.0>"}}

Issues and TODOs

As opposed to erlang pid encodintg (NEW_PID_EXT`) our current representation cannot distinguished between identifiers from old (crashed) nodes from a new one. So maybe we need to adopt the `NEW_PID_EXTCreation attribute.