Handing off Maintenance of Partisan

13 Jun 2022

I’m happy to announce that I am handing off maintenance of Partisan, the distributed runtime system I built as part of my Ph.D. (and my first paper published at CMU!), to Alejandro Ramallo at Leapsight.

Alejandro has done tremendous work on Partisan over the last two years: from fixing bugs, feature enhancement to performance improvements.

Alejandro has also brought Partisan to places that, as a PhD student who works mostly in a lab, never imagined: LO/JACK LATAM, the lost vehicle recovery service, since 2019, has been using Partisan as part of its Magenta Platform, tracking 300k vehicles, 10k devices, receiving over 30M GPS transmissions each day!

At LO/JACK LATAM, Leapsight uses Partisan as a foundational component for:

  • Magenta Twin Service: an IoT twins implementation using a modified version of Erleans, an implementation of the Microsoft Orlean’s virtual actor model for Erlang, modified to use PlumDB for metadata and state storage and Partisan for transport.
  • Magenta Agent Service: an IoT Rule-based system built using PlumDB and Partisan.

You can learn more about how it’s used here:

Industrial Usage

Leapsight has used Partisan as the backbone of two of their products:

  • Bondy, an open source, always-on and scalable application networking platform for modern architectures. Bondy is an all-in-one event and service mesh that offers both Publish-Subscribe (PubSub) and routed Remote Procedure Calls (RPC). Bondy implements the open Web Application Messaging Protocol (WAMP) and is written in Erlang.
  • PlumDB, a database globally replicated via Epidemic Broadcast Trees and lasp-lang’s Partisan. An offspring of Plumtree and Partisan, a descendant of Riak Core Metadata Store.

Future Plans

Alejandro has a lot in store for Partisan:

  • API usage
    • Add remote monitoring support of the local node using partisan.
    • Allowing the parallelism setting to apply in a per-channel, not global, setting.
    • Normalize all APIs to use the URI encoded remote pids, references, and node names.
  • Feature: Casual delivery
  • Maintenance: Overlay Tree Construction
    • One partisan_plumtree_broadcast server per channel to increase throughput
    • Explore allowing concurrent access to broadcast members by making partisan_plumtree_broadcast server use ets
    • Implement Thicket
  • General improvements
    • OTP 25 support
    • QUIC Transport


Since Alejandro is hard at work on getting 5.0.0 release of Partisan prepared, I include the incredibly long list of changes, bug fixes, and improvements planned for the next week that him and his team completed over the last two years.

Thanks Alejandro and LeapSight!


v5.0.0 (beta)


In general, the API was redesigned to concentrate all functions around two modules: partisan and partisan_peer_service.


  • partisan module was repurposed as a replacement for the erlang module for use cases related to distribution e.g. erlang:nodes/0 -> partisan:nodes/0.
    • Several functions previously found in partisan_peer_service, partisan_monitor and partisan_util are now in this module:
      • partisan:broadcast/2
      • partisan:cast_message/3
      • partisan:cast_message/4
      • partisan:cast_message/5
      • partisan:default_channel/0
      • partisan:demonitor/1
      • partisan:demonitor/2
      • partisan:forward_message/2
      • partisan:forward_message/3
      • partisan:forward_message/4
      • partisan:forward_message/5
      • partisan:is_connected/1
      • partisan:is_connected/2
      • partisan:is_fully_connected/1
      • partisan:is_local/1
      • partisan:is_pid/1
      • partisan:is_process_alive/1
      • partisan:is_reference/1
      • partisan:make_ref/0
      • partisan:monitor/1
      • partisan:monitor/2
      • partisan:monitor/3
      • partisan:monitor_node/2
      • partisan:monitor_nodes/1
      • partisan:monitor_nodes/2
      • partisan:node/0
      • partisan:nodestring/0
      • partisan:node/1
      • partisan:node_spec/0
      • partisan:node_spec/1
      • partisan:node_spec/2
      • partisan:nodes/0
      • partisan:nodes/1
      • partisan:self/0
      • partisan:send_message/2
  • Added the following functions:
    • partisan_peer_service:broadcast_members/0
    • partisan_peer_service:broadcast_members/1
    • partisan_peer_service:cancel_exchanges/1
    • partisan_peer_service:exchanges/0
    • partisan_peer_service:exchanges/1
    • partisan_peer_service:get_local_state/0
    • partisan_peer_service:inject_partition/2
    • partisan_peer_service:leave/1
    • partisan_peer_service:member/1
    • partisan_peer_service:members_for_orchestration/0
    • partisan_peer_service:on_down/2
    • partisan_peer_service:on_up/2
    • partisan_peer_service:partitions/0
    • partisan_peer_service:reserve/1
    • partisan_peer_service:resolve_partition/1
    • partisan_peer_service:update_members/1
  • Use of partisan_peer_service:mynode/0 has been replaced by partisan:node/0 to follow Erlang convention
  • Use of partisan_peer_service:myself/0 has been replaced by partisan:node_spec/0 to disambiguate from partisan:node/0.
  • Use of Node variable name for node() type (as opposed to Name) and NodeSpec for node_spec() (as opposed to Node) to disambiguate.
  • Adde new module partisan_rpc that will provide and API that mirrors Erlangs rpc and erpc modules
  • Added partisan_remote_ref to encapsulate the creation of reference and added an optional/alternative representation for encoded pids, references and registered names. The module offers all the functions to convert pids, references and names to/from Partisan encoded references.
    • Alternative 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 usage and avoid copying the term every time a message is send between processes. partisan_remote_ref represents an encoded reference as binary URI. This is controlled by the config option remote_ref_as_uri and remote_ref_binary_padding in case the resulting URIs are smaller than 65 bytes.

        1> partisan_remote_ref:from_term(self()).
        2> partisan_config:set(remote_ref_as_uri, true).
        3> partisan_remote_ref:from_term(self()).
        <<"partisan:pid:[email protected]:0.1062.0">>
        4> partisan_config:set(remote_ref_binary_padding, true).
        5> partisan_remote_ref:from_term(self()).
        <<"partisan:pid:[email protected]:0.1062.0:"...>>

Peer Membership


  • Replaced the use of state_orset CRDT with state_awmap to avoid an issue where a node will crash and restart with a different IP address e.g. when deploying in K8s. As the membership set contains node_spec() objects which contain the IP address we ended up with duplicate entries for the node. The state_awmap tries to solve that by mapping a node() => state_mvregister(node_spec())
  • Fixes several bugs related to the leave operation in partisan_pluggable_peer_service_manager:
    • Added a missing call to update the membership set during leave
    • Fixed a concurrency issue whereby on self leave the peer service server will restart before being able to sending the new state with the cluster peers and thus the node would remain as a member in all other nodes.
  • Resolves an issue partisan_plumtree_broadcast where the all_members set was not updated when a member is removed.
  • Resolves the issue where the partisan_plumtree_broadcast was not removing the local node from the broadcast member set.
  • Gen Behaviours take new option channel if defined.
  • Fixed implementation of on_up and on_down callback functions in partisan_pluggable_peer_service_manager


  • Added function partisan_peer_service_manager:member/1
  • Replaced the use of in-process sets in plumtree_broadcast_backend with an ets table for outstanding messages keeping the gen_server stack lean and avoiding garbage collection

Peer Connection management


  • Fixes a bug where connections where not properly kill during a leave
  • Split TLS options for client and server roles
    • Removed tls_options
    • Added tls_client_options and tls_server_options


  • New module peer_service_connections replaces the former process state data structure and the partisan_connection_cache module. It offers an ets-based solution with use of counters for quick node connection status check
  • partisan_peer_connections has been re-implemented to use ets to increase perfomance and remove the need for an additional caching feature.
    • As a result, the partisan_connection_cache module has been was removed.
    • Checking connection status is now a fast ets lookup operation and leverages ets:update_counter/4, ets:lookup_element/3 and ets:select_count/2 to handle concurreny and minimise copying data into the caller’s process heap.

Process and Peer Monitoring


  • A more complete/safe implementation of process monitoring in partisan_monitor.
  • More robust implementation of monitors using the new subscription capabilities provided by peer_service on_up and on_down callback functions.
    • monitor a node or all nodes
    • use node monitors to signal a process monitor when the remote node is disconnected
    • avoid leaking monitors
    • new supervisor to ensure that partisan_monitor is restarted every time the configured partisan_peer_service_manager is restarted.


  • New api in partisan module following the same name, signature and semantics of their erlang and net_kernel modules counterparts:
    • partisan:monitor/1
    • partisan:monitor/2
    • partisan:monitor/3
    • partisan:monitor_node/2
    • partisan:monitor_nodes/1
    • partisan:monitor_nodes/2

OTP compatibility



  • Partisan now requires OTP24 or later.
  • Upgraded partisan_gen and partisan_gen_server to match their OTP24 counterparts implementation
  • Added partisan_gen_statem
  • partisan_gen_fsm deprecated as it was not complete and focus was given to the implementation of partisan_gen_statem instead
  • Module partisan_mochiglobal has been removed and replaced by persistent_term



  • Most existing INFO level logs have been reclassified as DEBUG
  • Fixed types specifications in various modules


  • lager dependency has been removed and all logging is done using the new Erlang logger
  • Most uses of the orddict module have been replaced by maps for extra performance and better usability
  • Most API options using proplists module have been replaced by maps for extra performance and better usability
  • In several functions the computation of options (merging user provided with defaults, validation, etc.) has been posponed until (and only if) it is needed for extra performance e.g. partisan_pluggable_peer_servie_manager:forward_message
  • More utils in partisan_util
  • Added ex_doc (Elixir documentation) rebar plugin
  • Upgraded the following dependencies:
    • uuid
    • types
    • rebar plugins