taoensso.sente — com.taoensso/sente 1.21.0-alpha4

Channel sockets for Clojure/Script.

Protocol  | client>server | client>server ?+ ack/reply | server>user push

• WebSockets: ✓ [1] ✓
• Ajax: [2] ✓ [3]

[1] Emulate with cb-uuid wrapping [2] Emulate with dummy-cb wrapping [3] Emulate with long-polling

Abbreviations:

• chsk - Channel socket (Sente's own pseudo "socket")
• server-ch - Underlying web server's async channel that implement Sente's server channel interface
• sch - server-ch alias
• uid - User-id. An application-level user identifier used for async push. May have semantic meaning (e.g. username, email address), may not (e.g. client/random id) - app's discretion.
• cb - Callback
• tout - Timeout
• ws - WebSocket/s
• pstr - Packed string. Arbitrary Clojure data serialized as a string (e.g. edn) for client<->server comms
• udt - Unix timestamp (datetime long)

Special messages:

• Callback wrapping: [<clj> <?cb-uuid>] for [1], [2]

• Callback replies: :chsk/closed, :chsk/timeout, :chsk/error

• Client-side events: [:chsk/ws-ping] ; ws-ping from server [:chsk/handshake [<?uid> nil[4] <?handshake-data> <first-handshake?>]] [:chsk/state [<old-state-map> <new-state-map> <open-change?>]] [:chsk/recv <ev-as-pushed-from-server>] ; Server>user push

• Server-side events: [:chsk/ws-ping] ; ws-ping from client [:chsk/ws-pong] ; ws-pong from client [:chsk/uidport-open <uid>] [:chsk/uidport-close <uid>] [:chsk/bad-package <packed-str>] [:chsk/bad-event <event>]

Channel socket state map: :type - e/o #{:auto :ws :ajax} :open? - Truthy iff chsk appears to be open (connected) now :ever-opened? - Truthy iff chsk handshake has ever completed successfully :first-open? - Truthy iff chsk just completed first successful handshake :uid - User id provided by server on handshake, or nil :handshake-data - Arb user data provided by server on handshake :last-ws-error - ?{:udt _ :ev <WebSocket-on-error-event>} :last-ws-close - ?{:udt _ :ev <WebSocket-on-close-event> :clean? _ :code _ :reason _} :last-close - ?{:udt _ :reason _}, with reason e/o #{nil :clean :unexpected :requested-disconnect :requested-reconnect :downgrading-ws-to-ajax :ws-ping-timeout :ws-error} :udt-next-reconnect - Approximate udt of next scheduled auto-reconnect attempt

Notable implementation details:

• core.async is used liberally where brute-force core.async allows for significant implementation simplifications. We lean on core.async's efficiency here.
• For WebSocket fallback we use long-polling rather than HTTP 1.1 streaming (chunked transfer encoding). Http-kit does support chunked transfer encoding but a small minority of browsers &/or proxies do not. Instead of implementing all 3 modes (WebSockets, streaming, long-polling) - it seemed reasonable to focus on the two extremes (performance + compatibility). In any case client support for WebSockets is growing rapidly so fallback modes will become increasingly irrelevant while the extra simplicity will continue to pay dividends.

General-use notes:

• Single HTTP req+session persists over entire chsk session but cannot modify sessions! Use standard a/sync HTTP Ring req/resp for logins, etc.
• Easy to wrap standard HTTP Ring resps for transport over chsks. Prefer this approach to modifying handlers (better portability).

[4] Used to be a csrf-token. Was removed in v1.14 for security reasons. A nil remains for limited backwards-compatibility with pre-v1.14 clients.

*simulated-bad-conn-rate* clj/s

Debugging tool. Proportion ∈ℝ[0,1] of connection activities to sabotage.

*write-legacy-pack-format?* clj/s

Advanced option, most users can ignore this var. Only necessary for those that want to use Sente < v1.18 with a non-standard IPacker that deals with non-string payloads.

Details: Sente uses a private message format as an implementation detail for client<->server comms.

As part of [#398], this format is being updated to support non-string (e.g. binary) payloads.

Unfortunately updating the format is non-trivial because: 1. Both the client & server need to support the same format. 2. Clients are often served as cached cl/js.

To help ease migration, the new pack format is being rolled out in stages:

Sente <= v1.16: reads  v1 format only
                writes v1 format only

Sente    v1.17: reads  v1 and v2 formats
                writes v1 and v2 formats (v1 default)

Sente    v1.18: reads  v1 and v2 formats
                writes v1 and v2 formats (v2 default)  <- Currently here

Sente >= v1.19: reads  v2 format only
                writes v2 format only

This var controls which format to use for writing. Override default with alter-var-root or binding.

ajax-call cljs

Alias of taoensso.encore/ajax-call

allow-origin? clj/s

(allow-origin? allowed-origins ring-req)

Alpha, subject to change. Returns true iff given Ring request is allowed by allowed-origins. allowed-origins may be :all or #{<origin> ...}.

as-event clj/s

(as-event x)

assert-event clj/s

(assert-event x)

Returns given argument if it is a valid [ev-id ?ev-data] form. Otherwise throws a validation exception.

cb-error? clj/s

(cb-error? cb-reply-clj)

cb-success? clj/s

(cb-success? cb-reply-clj)

chsk-break-connection! clj/s

(chsk-break-connection! chsk)

(chsk-break-connection! chsk {:keys [close-ws?] :as opts :or {close-ws? true}})

Breaks channel socket's underlying connection without doing a clean disconnect as in chsk-disconnect!. Useful for simulating broken connections in testing, etc.

Options:

:close-ws? - (Default: true) Allow WebSocket's on-close event to fire? Set to falsey to ~simulate a broken socket that doesn't realise it's broken.

chsk-connect! clj/s

(chsk-connect! chsk)

chsk-disconnect! clj/s

(chsk-disconnect! chsk)

chsk-reconnect! clj/s

(chsk-reconnect! chsk)

Cycles connection, useful for reauthenticating after login/logout, etc.

chsk-send! clj/s

(chsk-send! chsk ev)

(chsk-send! chsk ev opts)

(chsk-send! chsk ev ?timeout-ms ?cb)

Sends [ev-id ev-?data :as event], returns true on apparent success.

client-event-msg? clj/s

(client-event-msg? x)

client-unloading?_ clj/s

event-msg? clj/s

Alias for: Cljs: client-event-msg?. Clj: server-event-msg?.

If you're using a Clj client or Cljs server, use the above utils directly instead.

event? clj/s

(event? x)

Valid [ev-id ?ev-data] form?

IChSocket clj/s protocol

-chsk-break-connection! clj/s

(-chsk-break-connection! chsk opts)

-chsk-connect! clj/s

(-chsk-connect! chsk)

-chsk-disconnect! clj/s

(-chsk-disconnect! chsk reason)

-chsk-reconnect! clj/s

(-chsk-reconnect! chsk reason)

-chsk-send! clj/s

(-chsk-send! chsk ev opts)

make-channel-socket! clj/s

Alias for: Cljs: make-channel-socket-client!. Clj: make-channel-socket-server!.

If you're using a Clj client or Cljs server, use the above utils directly instead. See above docstrings for details.

make-channel-socket-client! clj/s

(make-channel-socket-client!
  path
  ?csrf-token-or-fn
  &
  [{:as opts
    :keys [type protocol host port params headers recv-buf-or-n packer
           ws-constructor ws-kalive-ms ws-ping-timeout-ms ws-opts client-id
           ajax-opts wrap-recv-evs? backoff-ms-fn]
    :or {ws-ping-timeout-ms 5000
         ws-kalive-ms 20000
         ws-constructor default-client-ws-constructor
         client-id (or (:client-uuid opts) (enc/uuid-str))
         packer :edn
         type :auto
         recv-buf-or-n (async/sliding-buffer 2048)
         backoff-ms-fn enc/exp-backoff
         wrap-recv-evs? false}} _deprecated-more-opts])

Returns nil on failure, or a map with keys: :ch-recv ; core.async channel to receive event-msgs (internal or from ; clients). May put! (inject) arbitrary events to this channel. :send-fn ; (fn [event & [?timeout-ms ?cb-fn]]) for client>server send. :state ; Watchable, read-only (atom {:type _ :open? _ :uid _ :csrf-token _}). :chsk ; IChSocket implementer. You can usu. ignore this.

Required arguments: path ; Channel socket server route/path (typically /chsk) ?csrf-token-or-fn ; CSRF string or (fn [])->string to match token expected by server. ; nil => server not expecting any CSRF token.

Common options: :type ; e/o #{:auto :ws :ajax}. You'll usually want the default (:auto). :protocol ; Server protocol, e/o #{:http :https}. :host ; Server host (defaults to current page's host). :port ; Server port (defaults to current page's port). :params ; Map of any params to incl. in chsk Ring requests (handy ; for application-level auth, etc.). :headers ; Map of additional headers to include in the initiating request ; (currently only for Java clients). :packer ; :edn (default), or an IPacker implementation. :ajax-opts ; Base opts map provided to taoensso.encore/ajax-call, see ; relevant docstring for more info. :wrap-recv-evs? ; Should events from server be wrapped in [:chsk/recv _]? ; Default false for Sente >= v1.18, true otherwise.

:ws-kalive-ms ; Ping to keep a WebSocket conn alive if no activity ; w/in given msecs. Should be different to server's :ws-kalive-ms. :ws-ping-timeout-ms ; When pinging to test WebSocket connections, msecs to ; await reply before regarding the connection as broken

:ws-constructor ; Advanced, (fn [{:keys [uri-str headers on-message on-error on-close]}] ; => nil, or delay that can be dereffed to get a connected WebSocket. ; See default-client-ws-constructor code for details.

make-channel-socket-server! clj/s

(make-channel-socket-server!
  web-server-ch-adapter
  &
  [{:keys [recv-buf-or-n ws-kalive-ms lp-timeout-ms ws-ping-timeout-ms
           send-buf-ms-ajax send-buf-ms-ws user-id-fn bad-csrf-fn bad-origin-fn
           csrf-token-fn handshake-data-fn packer allowed-origins authorized?-fn
           unauthorized-fn ?unauthorized-fn ms-allow-reconnect-before-close-ws
           ms-allow-reconnect-before-close-ajax]
    :or {ws-ping-timeout-ms nil
         ws-kalive-ms (enc/ms :secs 25)
         send-buf-ms-ws 30
         allowed-origins :all
         lp-timeout-ms (enc/ms :secs 20)
         ms-allow-reconnect-before-close-ws 2500
         csrf-token-fn
           (fn [ring-req]
               (or (:anti-forgery-token ring-req)
                   (get-in ring-req [:session :csrf-token])
                   (get-in ring-req
                           [:session
                            :ring.middleware.anti-forgery/anti-forgery-token])
                   (get-in ring-req [:session "__anti-forgery-token"])))
         packer :edn
         ms-allow-reconnect-before-close-ajax 5000
         unauthorized-fn (fn [_ring-req]
                             {:status 401 :body "Unauthorized request"})
         send-buf-ms-ajax 100
         bad-origin-fn (fn [_ring-req]
                           {:status 403 :body "Unauthorized origin"})
         handshake-data-fn (fn [ring-req] nil)
         user-id-fn (fn [ring-req] (get-in ring-req [:session :uid]))
         recv-buf-or-n (async/sliding-buffer 1000)
         bad-csrf-fn (fn [_ring-req] {:status 403 :body "Bad CSRF token"})}}])

Takes a web server adapter[1] and returns a map with keys:

:ch-recv ; core.async channel to receive event-msgs (internal or from clients). :send-fn ; (fn [user-id ev] for server>user push. :ajax-post-fn ; Ring handler for CSRF-POST + chsk URL. :ajax-get-or-ws-handshake-fn ; Ring handler for Ring GET + chsk URL. :connected-uids ; Watchable, read-only (atom {:ws #{} :ajax #{} :any #{_}}).

Security options:

:allowed-origins ; e.g. #{"http://site.com" ...}, defaults to :all. ; Alpha

:csrf-token-fn ; ?(fn [ring-req]) -> CSRF-token for Ajax POSTs and WS handshake. ; nil fn or :sente/skip-CSRF-check return val => CSRF check will be ; SKIPPED (can pose a CSRF SECURITY RISK for website use cases, so ; please ONLY do this check if you're very sure you understand the ; security implications!).

:authorized?-fn ; ?(fn [ring-req]) -> When non-nil, (authorized?-fn <ring-req>) ; must return truthy, otherwise connection requests will be ; rejected with (unauthorized-fn <ring-req>) response. ; ; May check Authroization HTTP header, etc.

:?unauthorized-fn ; An alternative API to authorized?-fn+unauthorized-fn pair. ; ?(fn [ring-req)) -> <?rejection-resp>. I.e. when return value ; is non-nil, connection requests will be rejected with that ; non-nil value.

Other common options:

:user-id-fn ; (fn [ring-req]) -> unique user-id for server>user push. :handshake-data-fn ; (fn [ring-req]) -> arb user data to append to handshake evs. :ws-kalive-ms ; Ping to keep a WebSocket conn alive if no activity ; w/in given msecs. Should be different to client's :ws-kalive-ms. :lp-timeout-ms ; Timeout (repoll) long-polling Ajax conns after given msecs. :send-buf-ms-ajax ; [2] :send-buf-ms-ws ; [2] :packer ; :edn (default), or an IPacker implementation.

:ws-ping-timeout-ms ; When pinging to test WebSocket connections, msecs to ; await reply before regarding the connection as broken

;; When a connection is closed, Sente waits a little for possible reconnection before ;; actually marking the connection as closed. This facilitates Ajax long-polling, ;; server->client buffering, and helps to reduce event noise from spotty connections. :ms-allow-reconnect-before-close-ws ; Msecs to wait for WebSocket conns (default: 2500) :ms-allow-reconnect-before-close-ajax ; Msecs to wait for Ajax conns (default: 5000)

[1] e.g. (taoensso.sente.server-adapters.http-kit/get-sch-adapter) or (taoensso.sente.server-adapters.immutant/get-sch-adapter). You must have the necessary web-server dependency in your project.clj and the necessary entry in your namespace's ns form.

[2] Optimization to allow transparent batching of rapidly-triggered server>user pushes. This is esp. important for Ajax clients which use a (slow) reconnecting poller. Actual event dispatch may occur <= given ms after send call (larger values => larger batch windows).

sente-version clj/s

Useful for identifying client/server mismatch

server-event-msg? clj/s

(server-event-msg? x)

set-min-log-level! clj/s

(set-min-log-level! level)

Sets Timbre's minimum log level for internal Sente namespaces. Possible levels: #{:trace :debug :info :warn :error :fatal :report}. Default level: :warn.

start-chsk-router! clj/s

Alias for: Cljs: start-client-chsk-router!. Clj: start-server-chsk-router!.

If you're using a Clj client or Cljs server, use the above utils directly instead. See above docstrings for details.

start-client-chsk-router! clj/s

(start-client-chsk-router! ch-recv
                           event-msg-handler
                           &
                           [{:as opts :keys [trace-evs? error-handler]}])

Creates a simple go-loop to call (event-msg-handler <server-event-msg>) and log any errors. Returns a (fn stop! []). Note that advanced users may prefer to just write their own loop against ch-recv.

Nb performance note: since your event-msg-handler fn will be executed within a simple go block, you'll want this fn to be ~non-blocking (you'll especially want to avoid blocking IO) to avoid starving the core.async thread pool under load. To avoid blocking, you can use futures, agents, core.async, etc. as appropriate.

start-server-chsk-router! clj/s

(start-server-chsk-router!
  ch-recv
  event-msg-handler
  &
  [{:as opts :keys [trace-evs? error-handler simple-auto-threading?]}])

Creates a simple go-loop to call (event-msg-handler <server-event-msg>) and log any errors. Returns a (fn stop! []). Note that advanced users may prefer to just write their own loop against ch-recv.

Nb performance note: since your event-msg-handler fn will be executed within a simple go block, you'll want this fn to be ~non-blocking (you'll especially want to avoid blocking IO) to avoid starving the core.async thread pool under load. To avoid blocking, you can use futures, agents, core.async, etc. as appropriate.

Or for simple automatic future-based threading of every request, enable the :simple-auto-threading? opt (disabled by default).

validate-event clj/s

(validate-event x)

Returns nil if given argument is a valid [ev-id ?ev-data] form. Otherwise returns a map of validation errors like {:wrong-type {:expected _ :actual _}}.