This module handles the validation, access and modification of Partisan configuration options.

Some options will only take effect after a restart of the Partisan application, while other will take effect while the application is still running.

As per Erlang convention the options are given using the sys.config file under the partisan application section.

Example

[
 {partisan, [
     {listen_addrs, [
         #{ip => {127, 0, 0, 1}, port => 12345}
     ]},
     {channels, #{
         data => #{parallelism => 4}
     }},
     {remote_ref_format, improper_list},
     {tls, true},
     {tls_server_options, [
         {certfile, "config/_ssl/server/keycert.pem"},
         {cacertfile, "config/_ssl/server/cacerts.pem"},
         {keyfile, "config/_ssl/server/key.pem"},
         %% Authenticate peers with a cert signed by the cluster CA.
         %% verify_none would encrypt but NOT authenticate (MITM-able).
         {verify, verify_peer},
         {fail_if_no_peer_cert, true}
     ]},
     {tls_client_options, [
         {certfile, "config/_ssl/client/keycert.pem"},
         {cacertfile, "config/_ssl/client/cacerts.pem"},
         {keyfile, "config/_ssl/client/key.pem"},
         {verify, verify_peer}
     ]}
 ]}
].

Options

The following is the list of all the options you can read using get/1 and get/2, and modify using the sys.config file and set/2. Notice that most values will only take effect once you restart the Partisan application or the partisan_peer_service_manager. See Deprecated Options below.

binary_padding

A boolean value indicating whether to pad encoded messages whose external binary representation consumes less than 65 bytes.

broadcast

Enables tree-based transitive forwarding. When true, a message addressed to a peer this node has no connection to is forwarded over the broadcast tree instead of failing, provided the caller passed transitive => true in the forward options. Also starts a periodic tree refresh, whose period is the tree_refresh option (default 1000 ms). Defaults to false.

broadcast_mods

The broadcast handler modules to start, as a list of modules implementing partisan_plumtree_broadcast_handler. Defaults to [partisan_plumtree_backend], Partisan's own membership handler.

Each module listed here gets its own broadcast group: its own process, mailbox, spanning tree and outstanding-lazy table. Handlers therefore do not share a tree or block one another. Use broadcast_groups instead when you need several handlers to share one group, an explicit group name, a dedicated channel, or per-group tick periods.

channels

Defines the channels to be used by Partisan. The option takes either a channels map where keys are channel names ({@link partisan:channel()}) and values are channel options ({@link partisan:channel_opts()}), or a list of values where each value can be any of the following types:

• a channel name ({@link partisan:channel()}) e.g. the atom foo' * a channel with options:{channel(), channel_opts()}'
• a monotonic channel using the tuple {monotonic, Name :: channel()}' e.g.{monotonic, bar}'. This is a legacy representation, the same can be achieved with {bar, #{monotonic => true}}' The list can habe a mix of types and during startup they are all coerced to channels map. Coercion works by defaulting the channel'sparallelism' to the value of the global option parallelism' (which itself defaults to1'), and the channel's monotonic' tofalse'. Finally the list is transformed to a map where keys are channel names and values are channel map representation. ==== Example ==== Given the following option value: [ foo, {monotonic, bar}, {bar, #{parallelism => 4}} ] ''' The coerced representation will be the following map (which is a valid input and the final representation of this option after Partisan starts). #{ foo => #{monotonic => false, parallelism => 1}, bar => #{monotonic => true, parallelism => 1}, baz => #{monotonic => false, parallelism => 4}, } '''

connect_disterl

A configuration that is intended solely for testing of the {@link partisan_full_membership_strategy} (See membership_strategy'). It defines whether to use Distributed Erlang (disterl) in addition to Partisan channels. Defaults tofalse'. Notice that this setting does not prevent you having both disterl and Partisan enabled for your release. However, you need to have special care to avoid mixing the two, for example by calling a {@link partisan_gen_server} that uses Partisan for distribution with {@link gen_server} that uses disterl.

connection_interval

Interval of time between peer connection attempts

connection_jitter

The delay in milliseconds a node waits before opening a connection, so that a cluster forming or healing at once does not produce a simultaneous rush of connections. Defaults to 1000. With the jitter option enabled the delay is randomised between 1 and this value; otherwise it is used as a fixed sleep.

connection_ping

A map containing the following keys:

• {enabled, boolean()} - Whether pings are enabled. Default: true
• {idle_timeout, non_neg_integer()} - time in milliseconds
• {timeout, pos_integer()} - time in milliseconds
• {max_attempts, pos_integer()} - Max number of retry attempts.

disable_fast_forward

Forces outbound messages through the peer service manager instead of the direct-to-connection path. Defaults to false.

The fast path hands an encoded message straight to a connection process and does not run interposition functions, so fault injection that needs to observe, delay or drop outbound messages sets this to true. It costs throughput and exists for testing.

disable_fast_receive

Forces inbound messages through the peer service manager instead of being delivered concurrently. Defaults to false under partisan_pluggable_peer_service_manager and true under partisan_hyparview_peer_service_manager.

The receive-side counterpart of disable_fast_forward: serialising delivery lets interposition functions observe every inbound message in order, at the cost of concurrency.

distance_enabled

Enables periodic distance measurement between peers. Defaults to false. The measurement interval is the distance_interval option (default 10000 ms).

egress_delay

Milliseconds a connection process waits before writing a message to its socket. Defaults to 0.

An artificial latency injector for testing behaviour under a slow network. Leave at 0 in production.

exchange_selection

How a broadcast group picks the peer for an anti-entropy exchange. One of:

• optimized (the default) — picks from members the tree does not already reach, i.e. excluding the eager and lazy peer sets for that tree. Exchanging with a peer the tree already covers is unlikely to find a difference, so this concentrates anti-entropy where divergence can actually be.
• normal — picks from all members.

exchange_tick_period

Milliseconds between anti-entropy exchange attempts in a broadcast group. Defaults to 10000. A group may override it in its own spec via the broadcast_groups option.

gossip

If true' gossip is used to disseminate membership to peers. Default istrue'. At the moment used only by {@link partisan_full_membership_strategy}.

hyparview

The configuration for the {@link partisan_hyparview_peer_service_manager}. A list with the following properties:

• active_max_size' - Defaults to6'.
• active_min_size' - Defaults to3'.
• active_rwl' - Active View Random Walk Length. Defaults to6'.
• passive_max_size' - Defaults to30'.
• passive_rwl' - Passive View Random Walk Length. Defaults to6'.
• random_promotion' - A boolean indicating if random promotion is enabled. Defaultstrue'.
• random_promotion_interval' - Time after which the protocol attempts to promote a node in the passive view to the active view. Defaults to5000'.
• shuffle_interval' - Defaults to10000'.
• shuffle_k_active' - Number of peers to include in the shuffle exchange. Defaults to3'.
• shuffle_k_passive' - Number of peers to include in the shuffle exchange. Defaults to4'.

ingress_delay

Milliseconds a connection process waits before handing a received message to the peer service manager. Defaults to 0. The receive-side counterpart of egress_delay, and likewise for testing only.

lazy_tick_period

Milliseconds between flushes of a broadcast group's outstanding lazy pushes, each of which is sent as an i_have announcement. Defaults to 1000. A group may override it in its own spec via the broadcast_groups option.

Lazy pushes are the repair half of the epidemic broadcast: a peer that receives an i_have for a message it does not hold responds with a graft, which retrieves it. A longer period reduces announcement traffic and lengthens the window in which a missed message stays missed.

listen_addrs

A list of {@link partisan:listen_addr()} objects. This overrides listen_ip and listen_port (see below) and its the way to configure the peer listener should you want to listen on multiple IP addresses. If this option is missing, the peer_ip' property will be used, unless is also missing, in which case the nodename's host part will be used to determine the IP address. The {@link partisan:listen_addr()} object can be represented using lists, binaries, tuples or maps as shown in the following example: ``` {listen_addrs, [ "127.0.0.1:12345", <<"127.0.0.1:12345">>, {"127.0.0.1", "12345"}, {{127, 0, 0, 1}, 12345}, #{ip => "127.0.0.1", port => "12345"}, #{ip => <<"127.0.0.1">>, port => <<"12345">>}, #{ip => {127, 0, 0, 1}, port => 12345} ]} ''' Notice the above example will result in the following, as equivalent terms are deduplicated. ``` {listen_addrs, [ #{ip => {127, 0, 0, 1}, port => 12345} ]} ''' This option also accepts IP addresses without a port e.g. "127.0.0.1". In this case the port will be the value [listen_port](#listen_port) option. Notice [listen_port](#listen_port) is also used by some peer discovery strategies that cannot detect in which port the peer is listening e.g. DNS. See also [listen_ip](#listen_ip) for an alternative when using a single IP address. #### listen_ip The IP address to use for the peer connection listener when no {@link partisan:listen_addr()} have been defined via option [listen_addrs](#listen_addrs). If a value is not defined (and [listen_addrs](#listen_addrs) was not used), Partisan will attempt to resolve the IP address using the nodename's host i.e. the part to the right of the@' character in the nodename, and will default to {127,0,0,1}' if it can't. #### listen_port The port number to use for the peer connection listener when no {@link partisan:listen_addr()} have been defined via option [listen_addrs](#listen_addrs). If a value is not defined (and [listen_addrs](#listen_addrs) was not used), Partisan will use a randomly generated port. However, the random port will only work for clusters deployed within the same host i.e. used for testing. Thelisten_port' value is also used by some peer discovery strategies that cannot detect in which port the peer is listening e.g. DNS. So for production environments we recommend always setting the same value on all peers, and having at least one {@link partisan:listen_addr()} in each peer listen_addrs option (when used) having the same port value.

membership_binary_compression

A boolean value or an integer in the range from 0..9' to be used with {@link erlang:term_to_binary/2} when encoding the membership set for broadcast. A value oftrue' is equivalent to integer 6' (equivalent to optioncompressed' in {@link erlang:term_to_binary/2}). A value of false' is equivalent to0' (no compression). Default istrue'. #### membership_strategy The membership strategy to be used with {@link partisan_pluggable_peer_service_manager}. Default is {@link partisan_full_membership_strategy} #### membership_strategy_tracing Enables tracing inside the membership strategy for the trace orchestrator. Defaults tofalse. Used by the fault-injection test suites; it has no purpose in production. #### metadata A custom mapping of keys to values. #### name The nodename to be used when one was not provided via the Erlangvm.args' configuration file or via the shell flag --name'. The value should be a longname e.g.{{Name}}@{{HostOrIPAddress}}'. When neither Erlang's nodename nor this value are defined, Partisan will generate a random nodename. This is primarily used for testing and you should always set the nodename when deploying to production, either via Erlang or using this option.

orchestration_strategy

The module implementing peer discovery against an external orchestrator, for example partisan_kubernetes_orchestration_strategy. Defaults to undefined, meaning no orchestration — peers are joined explicitly through partisan_peer_service.

parallelism

The default number of connections to use per channel, when a channel hasn't been given a specific parallelism' value via thechannels' option. The default is 1'. For more information see optionchannels'.

peer_service_manager

The peer service manager to be used. An implementation of the {@link partisan_peer_service_manager} behaviour which defines the overlay network topology and the membership view maintenance strategy. Default is {@link partisan_pluggable_peer_service_manager}.

periodic_enabled

Enables the peer service manager's periodic maintenance tick, which drives connection retries and membership upkeep. Defaults to true. The interval is periodic_interval.

periodic_interval

Milliseconds between periodic maintenance ticks when periodic_enabled is set. Defaults to 10000.

pid_encoding

Whether a pid placed in a message is encoded as a partisan_remote_ref:p/0 before it goes on the wire. Defaults to true.

Encoding is what makes a pid meaningful on the receiving node: Partisan does not use Erlang distribution, so a raw pid term is not resolvable there. Disable it only when every pid in your messages is already an encoded reference, or when messages carry no pids at all.

random_seed

The seed for Partisan's randomness, as accepted by rand:seed/1. Defaults to a value generated at startup. Set it to make a test run reproducible.

ref_encoding

Whether a reference placed in a message is encoded as a partisan_remote_ref:r/0 before it goes on the wire. Defaults to true. The reference counterpart of pid_encoding.

register_pid_for_encoding

Registers a process under a generated name when its pid is encoded, so the resulting reference resolves by name rather than by pid. Defaults to false.

This exists for deployments that restart processes and need a reference to survive the restart. It adds a registration per encoded pid, so it is off by default.

remote_ref_format

Defines how partisan remote references pids, references and registered names will be encoded. See {@link partisan_remote_ref}). Accepts the following atom values:

• uri' - remote references will be encoded as binary URIs. *tuple' - remote references will be encoded as tuples (the format used by Partisan v1 to v4).
• improper_list' - remote references will be encoded as improper lists, similar to how aliases are encoded by the OTP modules. This option exists to allow the user to tradeoff between memory and latency. In terms of memoryuri' is the cheapest, followed by improper_list'. In terms of latencytuple' is the fastest followed by improper_list'. The default isimproper_list' a if offers a good balance between memory and latency. 1> partisan_config:set(remote_ref_format, uri). ok 2> partisan:self(). <<"partisan:pid:nonode@nohost:0.1062.0">> 3> partisan_config:set(remote_ref_format, tuple). 4> partisan:self(). {partisan_remote_reference, nonode@nohost, {partisan_process_reference,"<0.1062.0>"}} 5> partisan_config:set(remote_ref_format, improper_list). 6> partisan:self(). [nonode@nohost|<<"Pid#<0.1062.0>">>] ''' #### remote_ref_uri_padding If `true' and the URI encoding of a remote reference results in a binary smaller than 65 bytes, the URI will be padded. The default is `false'. 1> partisan_config:set(remote_ref_binary_padding, false). 1> partisan:self(). <"partisan:pid:nonode@nohost:0.1062.0"> 2> partisan_config:set(remote_ref_binary_padding, true). ok 3> partisan:self(). <"partisan:pid:nonode@nohost:0.1062.0:"...> '''

replaying

Set by the trace orchestrator while it replays a recorded trace. Defaults to false. Not intended to be set by hand.

reservations

Active-view slots reserved for peers carrying a given tag, as a list of tags — for example [server]. Defaults to []. Used by partisan_hyparview_peer_service_manager to guarantee that peers of a particular role keep a place in the active view even as it churns.

The list may not be longer than the HyParView active_max_size; the manager refuses to start with reservation_limit_exceeded if it is.

retransmit_interval

When option retransmission' is set totrue' in the partisan:forward_opts()' used in a call to {@link partisan:forward_message/3} and message delivery fails, the Peer Service will enqueue the message for retransmission. This option is used to control the interval of time between retransmission attempts. #### shrinking Set by the property-based test harness while it shrinks a counterexample. Defaults tofalse. Not intended to be set by hand. #### tag The role of this node when using the Client-Server topology implemented by @{link partisan_client_server_peer_manager}. ==== Options ==== *undefined' - The node acts as a normal peer in all other topologies. This the default value

• client' - The node acts as a client. To be used only in combination with{partisan_peer_manager, partisan_client_server_peer_manager}'
• server' - The node acts as a server. To be used only in combination with{partisan_peer_manager, partisan_client_server_peer_manager}'

max_message_size

Maximum size in bytes of an inbound peer message frame. Frames larger than this are rejected before they are assembled or decoded, guarding against pre-authentication memory exhaustion and decompression bombs on the peer plane. The default is 67108864' (64 MB). #### tls A boolean value indicating whether peer connections should use TLS. If enabled you must providetls_client_options' and tls_server_options'. The default isfalse'. NOTE: for authenticated (non-MITM-able) clustering set {verify, verify_peer}' with a cluster CA on BOTH sides;verify_none' only encrypts and does NOT authenticate the peer.

tls_client_options

The TLS socket options used when establishing outgoing connections to peers. The configuration applies to all Partisan channels. The default is []'. ==== Example ==== ``` {tls_client_options, [ {certfile, "config/_ssl/client/keycert.pem"}, {cacertfile, "config/_ssl/client/cacerts.pem"}, {keyfile, "config/_ssl/client/key.pem"}, {verify, verify_peer} ]} ''' #### tls_handshake_timeout Timeout in milliseconds for the server-side TLS handshake on an inbound peer connection. Bounds a stalled handshake so it cannot pin an acceptor. The default is5000'.

tls_server_options

The TLS socket options used when establishing incoming connections from peers. The configuration applies to all Partisan channels. The default is []'. ==== Example ==== ``` {tls_server_options, [ {certfile, "config/_ssl/server/keycert.pem"}, {cacertfile, "config/_ssl/server/cacerts.pem"}, {keyfile, "config/_ssl/server/key.pem"}, {verify, verify_peer}, {fail_if_no_peer_cert, true} ]} ''' #### tracing a boolean value. The default isfalse'.

xbot_interval

Milliseconds between rounds of the X-BOT active-view optimisation in partisan_hyparview_peer_service_manager, which tries to replace an active-view peer with a closer one.

Deprecated options

The following options are deprecated. Some have been renamed, or moved down a level in the configuration tree.

arwl

HyParView's Active View Random Walk Length. Defaults to 6'. Useactive_rwl' in the hyparview' option instead. #### fanout The number of nodes that are contacted at each gossip interval. #### max_active_size HyParView's Active View Random Walk Length. Defaults to6'. Use active_max_size' in thehyparview' option instead.

max_passive_size

HyParView's Active View Random Walk Length. Defaults to 30'. Usepassive_max_size' in the hyparview' option instead. #### mix_active_size HyParView's Active View Random Walk Length. Defaults to3'. Use active_min_size' in thehyparview' option instead.

passive_view_shuffle_period

Use shuffle_interval' in thehyparview' option instead.

peer_ip

Use listen_ip instead.

peer_port

Use listen_port instead.

peer_host

Use listen_addrs instead.

partisan_peer_service_manager

Use peer_service_manager' instead. #### prwl HyParView's Passive View Random Walk Length. Defaults to6'. Use passive_rwl' in thehyparview' option instead.

random_promotion

Use random_promotion' in thehyparview' option instead.

random_promotion_period

Use random_promotion_interval' in thehyparview' option instead.

remote_ref_as_uri

Use `{remote_ref_format, uri}' instead