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[#259] Allow client to detect sudden abnormal disconnects (e.g. airpl…
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…ane mode)

Situation before #230:
  Clients maintain keep-alive, sending pings to server.
  On sudden conn break (e.g. airplane mode), clients would know about
  the break but the server wouldn't

Situation after #230:
  Server maintains keep-alive, sending pings to clients.
  On sudden conn break (e.g. airplane mode), server would know about
  the break but clients wouldn't.

As of this commit:
  Server and clients each maintain a keep-alive[1]. I.e. each side will
  attempt to ping if it hasn't heard from the other side in a
  prescribed window.

  On sudden conn break, each side will be made aware of the break when
  its own scheduled window fires and fails to successfully send a ping.

[1] Timeouts should be different. In particular, the client may like to
choose a much more aggressive window (e.g. 5s) to provide a rapid
indicator to users.
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@ptaoussanis
ptaoussanis committed Aug 31, 2016
1 parent defc610 commit 0312cfe
Showing 1 changed file with 60 additions and 33 deletions.
93 changes: 60 additions & 33 deletions src/taoensso/sente.cljc
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Original file line number Diff line number Diff line change
Expand Up @@ -32,12 +32,14 @@
[:chsk/handshake [<?uid> <?csrf-token> <?handshake-data> <first-handshake?>]]
[:chsk/state [<old-state-map> <new-state-map>]]
[:chsk/recv <ev-as-pushed-from-server>] ; Server>user push
[:chsk/ws-ping]
* Server-side events:
[:chsk/bad-package <packed-str>]
[:chsk/bad-event <event>]
[:chsk/uidport-open <uid>]
[:chsk/uidport-close <uid>]
[:chsk/ws-ping]
Channel socket state map:
:type - e/o #{:auto :ws :ajax}
Expand Down Expand Up @@ -272,7 +274,7 @@
:csrf-token-fn ; (fn [ring-req]) -> CSRF token for Ajax POSTs.
: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.
; 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]
Expand Down Expand Up @@ -593,10 +595,11 @@
(when (interfaces/sch-open? server-ch)
;; (assert (= _sch server-ch))
(when (= udt-t1 udt-t0)
;; Ref. issue #230:
;; We've seen no send/recv activity on this
;; conn w/in our kalive window so send a ping
;; ->client (should auto-close conn if it's
;; gone dead)
;; gone dead).
(interfaces/sch-send! server-ch websocket?
(pack packer nil :chsk/ws-ping)))
(recur udt-t1))))))
Expand Down Expand Up @@ -927,16 +930,17 @@
;; WebSocket-only IChSocket implementation
;; Handles (re)connections, cbs, etc.

[client-id chs params packer url
[client-id chs params packer url ws-kalive-ms
state_ ; {:type _ :open? _ :uid _ :csrf-token _ ...}
retry-handle_ retry-count_ ever-opened?_
instance-handle_ retry-count_ ever-opened?_
backoff-ms-fn ; (fn [nattempt]) -> msecs
cbs-waiting_ ; {<cb-uuid> <fn> ...}
socket_]
socket_
udt-last-comms_]

IChSocket
(-chsk-disconnect! [chsk reason]
(reset! retry-handle_ "_disable-auto-retry")
(reset! instance-handle_ nil) ; Disable auto retry
(swap-chsk-state! chsk #(chsk-state->closed % reason))
(when-let [s @socket_] (.close s 1000 "CLOSE_NORMAL")))

Expand Down Expand Up @@ -965,6 +969,7 @@

(try
(.send @socket_ ppstr)
(reset! udt-last-comms_ (enc/now-udt))
:apparent-success
(catch :default e
(errorf e "Chsk send error")
Expand All @@ -981,8 +986,8 @@
(enc/oget goog/global "MozWebSocket")
(enc/oget @?node-npm-websocket_ "w3cwebsocket"))]

(let [retry-handle (enc/uuid-str)
have-handle? (fn [] (= @retry-handle_ retry-handle))
(let [instance-handle (reset! instance-handle_ (enc/uuid-str))
have-handle? (fn [] (= @instance-handle_ instance-handle))
connect-fn
(fn connect-fn []
(when (have-handle?)
Expand Down Expand Up @@ -1033,14 +1038,15 @@
;; whether they're wrapped or not
[clj ?cb-uuid] (unpack packer ppstr)]

(reset! udt-last-comms_ (enc/now-udt))

(or
(when (handshake? clj)
(receive-handshake! :ws chsk clj)
(reset! retry-count_ 0))

(when (= clj :chsk/ws-ping)
(when @debug-mode?_
(receive-buffered-evs! chs [[:debug/ws-ping]]))
(put! (:<server chs) [:chsk/ws-ping])
:noop)

(if-let [cb-uuid ?cb-uuid]
Expand Down Expand Up @@ -1078,7 +1084,24 @@
:last-ws-close last-ws-close))
(retry-fn))))))))))))]

(reset! retry-handle_ retry-handle)
(when-let [ms ws-kalive-ms]
(go-loop []
(let [udt-t0 @udt-last-comms_]
(<! (async/timeout ms))
(when (have-handle?)
(let [udt-t1 @udt-last-comms_]
(when (= udt-t0 udt-t1)
;; Ref. issue #259:
;; We've seen no send/recv activity on this
;; conn w/in our kalive window so send a ping
;; ->server (should auto-close conn if it's
;; gone dead). The server generally sends pings so
;; this should be rare. Mostly here to help clients
;; identify conns that were suddenly dropped.

(-chsk-send! chsk [:chsk/ws-ping] {:flush? true})))
(recur)))))

(reset! retry-count_ 0)
(connect-fn)
chsk)))))
Expand All @@ -1087,12 +1110,13 @@
(defn- new-ChWebSocket [opts]
(map->ChWebSocket
(merge
{:state_ (atom {:type :ws :open? false :ever-opened? false})
:retry-handle_ (atom "_pending")
:retry-count_ (atom 0)
:ever-opened?_ (atom false)
:cbs-waiting_ (atom {})
:socket_ (atom nil)}
{:state_ (atom {:type :ws :open? false :ever-opened? false})
:instance-handle_ (atom nil)
:retry-count_ (atom 0)
:ever-opened?_ (atom false)
:cbs-waiting_ (atom {})
:socket_ (atom nil)
:udt-last-comms_ (atom nil)}
opts))))

(def ^:private default-client-side-ajax-timeout-ms
Expand All @@ -1107,13 +1131,13 @@
;; Handles (re)polling, etc.

[client-id chs params packer url state_
retry-handle_ ever-opened?_
instance-handle_ ever-opened?_
backoff-ms-fn
ajax-opts curr-xhr_]

IChSocket
(-chsk-disconnect! [chsk reason]
(reset! retry-handle_ "_disable-auto-retry")
(reset! instance-handle_ nil) ; Disable auto retry
(swap-chsk-state! chsk #(chsk-state->closed % reason))
(when-let [x @curr-xhr_] (.abort x)))

Expand Down Expand Up @@ -1177,8 +1201,8 @@
:apparent-success))))

(-chsk-connect! [chsk]
(let [retry-handle (enc/uuid-str)
have-handle? (fn [] (= @retry-handle_ retry-handle))
(let [instance-handle (reset! instance-handle_ (enc/uuid-str))
have-handle? (fn [] (= @instance-handle_ instance-handle))
poll-fn ; async-poll-for-update-fn
(fn poll-fn [retry-count]
(tracef "async-poll-for-update!")
Expand Down Expand Up @@ -1250,18 +1274,17 @@
(let [buffered-evs clj] ; An application reply
(receive-buffered-evs! chs buffered-evs))))))))))))]

(reset! retry-handle_ retry-handle)
(poll-fn 0)
chsk))))

#?(:cljs
(defn- new-ChAjaxSocket [opts]
(map->ChAjaxSocket
(merge
{:state_ (atom {:type :ajax :open? false :ever-opened? false})
:retry-handle_ (atom "_pending")
:ever-opened?_ (atom false)
:curr-xhr_ (atom nil)}
{:state_ (atom {:type :ajax :open? false :ever-opened? false})
:instance-handle_ (atom nil)
:ever-opened?_ (atom false)
:curr-xhr_ (atom nil)}
opts))))

#?(:cljs
Expand Down Expand Up @@ -1357,10 +1380,12 @@
; for application-level auth, etc.).
:packer ; :edn (default), or an IPacker implementation.
:ajax-opts ; Base opts map provided to `taoensso.encore/ajax-lite`.
:wrap-recv-evs? ; Should events from server be wrapped in [:chsk/recv _]?"
:wrap-recv-evs? ; Should events from server be wrapped in [:chsk/recv _]?
: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."

[path &
[{:keys [type protocol host params recv-buf-or-n packer
[{:keys [type protocol host params recv-buf-or-n packer ws-kalive-ms
client-id ajax-opts wrap-recv-evs? backoff-ms-fn]
:as opts
:or {type :auto
Expand All @@ -1369,7 +1394,8 @@
client-id (or (:client-uuid opts) ; Backwards compatibility
(enc/uuid-str))
wrap-recv-evs? true
backoff-ms-fn enc/exp-backoff}}
backoff-ms-fn enc/exp-backoff
ws-kalive-ms (enc/ms :secs 20)}}

_deprecated-more-opts]]

Expand Down Expand Up @@ -1406,10 +1432,11 @@
(chan buf)))}

common-chsk-opts
{:client-id client-id
:chs private-chs
:params params
:packer packer}
{:client-id client-id
:chs private-chs
:params params
:packer packer
:ws-kalive-ms ws-kalive-ms}

ws-chsk-opts
(merge common-chsk-opts
Expand Down

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