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Clojureのstm実装について

The document discusses Clojure software transactional memory (STM). It explains that Clojure uses STM as an alternative to atoms, agents and vars for shared mutable state. STM provides ACID transactional guarantees and uses multi-version concurrency control. The document includes a diagram demonstrating two sample transactions operating on a shared reference with STM.

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Clojure STM @marblejenka 2011 5 24
• Clojure STM • STM STM • Clojure/Java java.util.concurrent.* 2 2011 5 24
Agenda • Clojure • STM • Clojure STM • Clojure STM API • Clojure STM • Clojure STM 3 2011 5 24
Clojure • Clojure – – • – 4 2011 5 24
Clojure • • Clojure • ref STM:Software Transactional Memory – ref atom/agent/var 5 2011 5 24
Agenda • Clojure • STM • Clojure STM • Clojure STM API • Clojure STM • Clojure STM 6 2011 5 24
STM • Software Transactional Memory • ACID ACI – Atomic • – Consistency • – Isolation • – Durabilty • STM D • DB • MVCC 7 2011 5 24
STM reference F v=42, t=0 The Joy of Clojure Figure 10.1 8 2011 5 24
Tx A STM reference F v=42, t=0 The Joy of Clojure Figure 10.1 8 2011 5 24
Tx A STM reference A F v=42, t=0 The Joy of Clojure Figure 10.1 8 2011 5 24
Tx A STM reference A F v=42, t=0 read The Joy of Clojure Figure 10.1 8 2011 5 24
Tx A STM reference A F v=42, t=0 read The Joy of Clojure Figure 10.1 8 2011 5 24
Tx A STM reference A F v=42, t=0 read F v=42, t=0 The Joy of Clojure Figure 10.1 8 2011 5 24
Tx A STM reference A F v=42, t=0 read F v=42, t=0 calc The Joy of Clojure Figure 10.1 8 2011 5 24
Tx A STM reference A F v=42, t=0 read F v=42, t=0 calc local write The Joy of Clojure Figure 10.1 8 2011 5 24
Tx A STM reference A F v=42, t=0 read F v=42, t=0 calc local write F v=9, t=0 The Joy of Clojure Figure 10.1 8 2011 5 24
Tx A STM reference A F v=42, t=0 read Tx B F v=42, t=0 calc local write F v=9, t=0 The Joy of Clojure Figure 10.1 8 2011 5 24
Tx A STM reference A F v=42, t=0 read Tx B F v=42, t=0 calc B local write F v=9, t=0 The Joy of Clojure Figure 10.1 8 2011 5 24
Tx A STM reference A F v=42, t=0 read Tx B F v=42, t=0 calc B local write read F v=9, t=0 The Joy of Clojure Figure 10.1 8 2011 5 24
Tx A STM reference A F v=42, t=0 read Tx B F v=42, t=0 calc B local write read F v=9, t=0 The Joy of Clojure Figure 10.1 8 2011 5 24
Tx A STM reference A F v=42, t=0 read Tx B F v=42, t=0 calc B local write read F v=42, t=0 F v=9, t=0 The Joy of Clojure Figure 10.1 8 2011 5 24
Tx A STM reference A F v=42, t=0 read Tx B F v=42, t=0 calc B local write read F v=42, t=0 F calc v=9, t=0 The Joy of Clojure Figure 10.1 8 2011 5 24
Tx A STM reference A F v=42, t=0 read Tx B F v=42, t=0 calc B local write read F v=42, t=0 F calc v=9, t=0 local write The Joy of Clojure Figure 10.1 8 2011 5 24
Tx A STM reference A F v=42, t=0 read Tx B F v=42, t=0 calc B local write read F v=42, t=0 F calc v=9, t=0 local write F v=27, t=0 The Joy of Clojure Figure 10.1 8 2011 5 24
Tx A STM reference A F v=42, t=0 read Tx B F v=42, t=0 calc B local write read F v=42, t=0 F calc v=9, t=0 conflict? local write F v=27, t=0 The Joy of Clojure Figure 10.1 8 2011 5 24
Tx A STM reference A F v=42, t=0 read Tx B F v=42, t=0 calc B local write read F v=42, t=0 F calc v=9, t=0 conflict? local write F v=27, t=0 The Joy of Clojure Figure 10.1 8 2011 5 24
Tx A STM reference A F v=42, t=0 read Tx B F v=42, t=0 calc B local write read F v=42, t=0 F calc v=9, t=0 conflict? NO local write F v=27, t=0 The Joy of Clojure Figure 10.1 8 2011 5 24
Tx A STM reference A F v=42, t=0 read Tx B F v=42, t=0 calc B local write read F v=42, t=0 F calc v=9, t=0 conflict? NO local write F commit v=27, t=0 The Joy of Clojure Figure 10.1 8 2011 5 24
Tx A STM reference A F v=42, t=0 read Tx B F v=42, t=0 calc B local write read F v=42, t=0 F calc v=9, t=0 conflict? NO local write F commit v=27, t=0 F v=9, t=1 The Joy of Clojure Figure 10.1 8 2011 5 24
Tx A STM reference A F v=42, t=0 read Tx B F v=42, t=0 calc B local write read F v=42, t=0 F calc v=9, t=0 conflict? NO local write F commit v=27, t=0 F v=9, t=1 conflict? The Joy of Clojure Figure 10.1 8 2011 5 24
Tx A STM reference A F v=42, t=0 read Tx B F v=42, t=0 calc B local write read F v=42, t=0 F calc v=9, t=0 conflict? NO local write F commit v=27, t=0 F v=9, t=1 conflict? The Joy of Clojure Figure 10.1 8 2011 5 24
Tx A STM reference A F v=42, t=0 read Tx B F v=42, t=0 calc B local write read F v=42, t=0 F calc v=9, t=0 conflict? NO local write F commit v=27, t=0 F v=9, t=1 conflict? YES The Joy of Clojure Figure 10.1 8 2011 5 24
Tx A STM reference A F v=42, t=0 read Tx B F v=42, t=0 calc B local write read F v=42, t=0 F calc v=9, t=0 conflict? NO local write F commit v=27, t=0 F v=9, t=1 conflict? YES retry! The Joy of Clojure Figure 10.1 8 2011 5 24
STM • STM – • – Transactional • atmic • STM – – I/O – 9 2011 5 24
Agenda • Clojure • STM • Clojure STM • Clojure STM API • Clojure STM • Clojure STM 10 2011 5 24
Clojure STM • – ref – Clojure immutable – ref • ref all-or-noting – dosync – ref all-of-nothing – 11 2011 5 24
Clojure STM • a,b • def – a,b – a b – a b – a,b • def dosync – a,b – a,b 12 2011 5 24
Clojure STM (def a 0) (def b 1) (inc a) ; a +1 (dec b) ; b -1 (println a b) ; -> 1 0 • a,b • Clojure immutable println a,b 13 2011 5 24
Clojure STM (def a (ref 0)) (def b (ref 1)) (dosync (alter a inc) (alter b dec)) (println @a @b) • a,b all-or-nothing • ref println 1,0 14 2011 5 24
Clojure STM (def a (ref 0)) (def b (ref 1)) (dosync (alter a inc) (alter b dec)) (println @a @b) • a,b all-or-nothing • ref println 1,0 14 2011 5 24
Agenda • Clojure • STM • Clojure STM • Clojure STM API • Clojure STM • Clojure STM 15 2011 5 24
Clojure STM API • API(Clojure STM ) • Java • URL – https://github.com/clojure/clojure/blob/master/src/clj/clojure/ core.clj#L1831 16 2011 5 24
API • ref – ref • deref – • ref-set – ref • alter – ref • commute – alter • ensure – in-transaction-value 17 2011 5 24
ref (defn ref {:added "1.0" :static true } ([x] (new clojure.lang.Ref x)) ([x & options] (let [r ^clojure.lang.Ref (setup-reference (ref x) options) opts (apply hash-map options)] (when (:max-history opts) (.setMaxHistory r (:max-history opts))) (when (:min-history opts) (.setMinHistory r (:min-history opts))) r))) • • ref dosync • 18 2011 5 24
deref (defn deref "Also reader macro: @ref/@agent/@var/@atom/@delay/@future/@promise. Within a transaction, returns the in-transaction-value of ref, else returns the most-recently-committed value of ref. When applied to a var, agent or atom, returns its current state. When applied to a delay, forces it if not already forced. When applied to a future, will block if computation not complete. When applied to a promise, will block until a value is delivered. The variant taking a timeout can be used for blocking references (futures and promises), and will return timeout-val if the timeout (in milliseconds) is reached before a value is available. See also - realized?." {:added "1.0" :static true} ([^clojure.lang.IDeref ref] (.deref ref)) ([^clojure.lang.IBlockingDeref ref timeout-ms timeout-val] (.deref ref timeout-ms timeout-val))) • ref – dosync dosync in- transaction-value • future 19 2011 5 24
ref-set (defn ref-set "Must be called in a transaction. Sets the value of ref. Returns val." {:added "1.0" :static true} [^clojure.lang.Ref ref val] (. ref (set val))) • ref 20 2011 5 24
alter (defn alter "Must be called in a transaction. Sets the in-transaction-value of ref to: (apply fun in-transaction-value-of-ref args) and returns the in-transaction-value of ref." {:added "1.0" :static true} [^clojure.lang.Ref ref fun & args] (. ref (alter fun args))) • ref • 21 2011 5 24
commute (defn commute "Must be called in a transaction. Sets the in-transaction-value of ref to: (apply fun in-transaction-value-of-ref args) and returns the in-transaction-value of ref. At the commit point of the transaction, sets the value of ref to be: (apply fun most-recently-committed-value-of-ref args) Thus fun should be commutative, or, failing that, you must accept last-one-in-wins behavior. commute allows for more concurrency than ref-set." {:added "1.0" :static true} [^clojure.lang.Ref ref fun & args] (. ref (commute fun args))) • ref • alter 22 2011 5 24
ensure (defn ensure "Must be called in a transaction. Protects the ref from modification by other transactions. Returns the in-transaction-value of ref. Allows for more concurrency than (ref-set ref @ref)" {:added "1.0" :static true} [^clojure.lang.Ref ref] (. ref (touch)) (. ref (deref))) • in- transaction-value • ref ref ref 23 2011 5 24
dosync (defmacro dosync "Runs the exprs (in an implicit do) in a transaction that encompasses exprs and any nested calls. Starts a transaction if none is already running on this thread. Any uncaught exception will abort the transaction and flow out of dosync. The exprs may be run more than once, but any effects on Refs will be atomic." {:added "1.0"} [& exprs] `(sync nil ~@exprs)) • 24 2011 5 24
sync (defmacro sync "transaction-flags => TBD, pass nil for now Runs the exprs (in an implicit do) in a transaction that encompasses exprs and any nested calls. Starts a transaction if none is already running on this thread. Any uncaught exception will abort the transaction and flow out of sync. The exprs may be run more than once, but any effects on Refs will be atomic." {:added "1.0"} [flags-ignored-for-now & body] `(. clojure.lang.LockingTransaction (runInTransaction (fn [] ~@body)))) • • “flags-ignored-for-now” 25 2011 5 24
io! (defmacro io! "If an io! block occurs in a transaction, throws an IllegalStateException, else runs body in an implicit do. If the first expression in body is a literal string, will use that as the exception message." {:added "1.0"} [& body] (let [message (when (string? (first body)) (first body)) body (if message (next body) body)] `(if (clojure.lang.LockingTransaction/isRunning) (throw (new IllegalStateException ~(or message "I/O in transaction"))) (do ~@body)))) • dosync io • STM I/O • I/O sync 26 2011 5 24
set/get-validator (defn set-validator! "Sets the validator-fn for a var/ref/agent/atom. validator-fn must be nil or a side-effect-free fn of one argument, which will be passed the intended new state on any state change. If the new state is unacceptable, the validator-fn should return false or throw an exception. If the current state (root value if var) is not acceptable to the new validator, an exception will be thrown and the validator will not be changed." {:added "1.0" :static true} [^clojure.lang.IRef iref validator-fn] (. iref (setValidator validator-fn))) (defn get-validator "Gets the validator-fn for a var/ref/agent/atom." {:added "1.0" :static true} [^clojure.lang.IRef iref] (. iref (getValidator))) • • 27 2011 5 24
alter/reset-meta (defn alter-meta! "Atomically sets the metadata for a namespace/var/ref/agent/atom to be: (apply f its-current-meta args) f must be free of side-effects" {:added "1.0" :static true} [^clojure.lang.IReference iref f & args] (.alterMeta iref f args)) (defn reset-meta! "Atomically resets the metadata for a namespace/var/ref/agent/atom" {:added "1.0" :static true} [^clojure.lang.IReference iref metadata-map] (.resetMeta iref metadata-map)) • • 28 2011 5 24
ref-history (defn ref-history-count "Returns the history count of a ref" • ref {:added "1.1" :static true} [^clojure.lang.Ref ref] (.getHistoryCount ref)) • (defn ref-min-history "Gets the min-history of a ref, or sets it and returns the ref" {:added "1.1" :static true} ([^clojure.lang.Ref ref] (.getMinHistory ref)) ([^clojure.lang.Ref ref n] (.setMinHistory ref n))) (defn ref-max-history "Gets the max-history of a ref, or sets it and returns the ref" {:added "1.1" :static true} ([^clojure.lang.Ref ref] (.getMaxHistory ref)) ([^clojure.lang.Ref ref n] (.setMaxHistory ref n))) 29 2011 5 24
Agenda • Clojure • STM • Clojure STM • Clojure STM API • Clojure STM • Clojure STM 30 2011 5 24
Clojure STM • STM • STM 31 2011 5 24
• 32 2011 5 24
33 2011 5 24
Ref • STM – TVal • Ref TVal 34 2011 5 24
Ref.Tval • ref • 35 2011 5 24
LockingTransaction • • – 10000000nano second kill • vals vals Ref • sets/commutes/ensures – sets ref comutes commute – alter ref-set ref-set – ensures commute 36 2011 5 24
LockingTransaction.Info • ref ref transaction ref • • running/commiting/retry/killed/ commited • 37 2011 5 24
LockingTransaction.RetryEx • • 38 2011 5 24
LockingTransaction.AbortException • 39 2011 5 24
• ref-set 40 2011 5 24
(def current-track (ref "initial state of current track")) (dosync (ref-set current-track "changed")) • ref • dosync ref-set 41 2011 5 24
ref 42 2011 5 24
transaction run 43 2011 5 24
ref-set 44 2011 5 24
ref 45 2011 5 24
Agenda • Clojure • STM • Clojure STM • Clojure STM API • Clojure STM • Clojure STM 46 2011 5 24
Clojure STM Transaction • Multiversion Concurrency Control – • Snapshot Isolation – – Oracle/PostgereSQL RDBMS SERIALIZABLE 47 2011 5 24
• Clojure – conj – • – Map Idel Hash Tree • STM – Snapshot Isolation ref 48 2011 5 24
STM I/O • No I/O in STM transactions? – http://groups.google.com/group/clojure/ browse_thread/thread/ d967171ed4b0f20c/9f55aead761f3e99? lnk=gst&q=STM#9f55aead761f3e99 • Agent 49 2011 5 24
• Extending Clojure's STM with external transactions – http://groups.google.com/group/clojure/ browse_thread/thread/ aa22a709501a64ac • RDBMS JTA – – 50 2011 5 24
• Long-running STM updates will never complete... is there a solution? – http://groups.google.com/group/clojure/ browse_thread/thread/ 7edd12e22eb120ea/207888a0d12ade38? lnk=gst&q=STM#207888a0d12ade38 • ensure – 51 2011 5 24
• LL tiger clojure – – http://www.slideshare.net/makingx/ll-tiger-clojure • The Art of Multiprocessor Programming – 18 Transactional Memory STM Java Java – http://amzn.to/kJCkyT 52 2011 5 24

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Clojureのstm実装について

  • 1.
    Clojure STM @marblejenka 2011 5 24
  • 2.
    • Clojure STM • STM STM • Clojure/Java java.util.concurrent.* 2 2011 5 24
  • 3.
    Agenda • Clojure • STM • Clojure STM • Clojure STM API • Clojure STM • Clojure STM 3 2011 5 24
  • 4.
    Clojure • Clojure – – • – 4 2011 5 24
  • 5.
    Clojure • • Clojure • ref STM:Software Transactional Memory – ref atom/agent/var 5 2011 5 24
  • 6.
    Agenda • Clojure • STM • Clojure STM • Clojure STM API • Clojure STM • Clojure STM 6 2011 5 24
  • 7.
    STM • Software Transactional Memory • ACID ACI – Atomic • – Consistency • – Isolation • – Durabilty • STM D • DB • MVCC 7 2011 5 24
  • 8.
    STM reference F v=42, t=0 The Joy of Clojure Figure 10.1 8 2011 5 24
  • 9.
    Tx A STM reference F v=42, t=0 The Joy of Clojure Figure 10.1 8 2011 5 24
  • 10.
    Tx A STM reference A F v=42, t=0 The Joy of Clojure Figure 10.1 8 2011 5 24
  • 11.
    Tx A STM reference A F v=42, t=0 read The Joy of Clojure Figure 10.1 8 2011 5 24
  • 12.
    Tx A STM reference A F v=42, t=0 read The Joy of Clojure Figure 10.1 8 2011 5 24
  • 13.
    Tx A STM reference A F v=42, t=0 read F v=42, t=0 The Joy of Clojure Figure 10.1 8 2011 5 24
  • 14.
    Tx A STM reference A F v=42, t=0 read F v=42, t=0 calc The Joy of Clojure Figure 10.1 8 2011 5 24
  • 15.
    Tx A STM reference A F v=42, t=0 read F v=42, t=0 calc local write The Joy of Clojure Figure 10.1 8 2011 5 24
  • 16.
    Tx A STM reference A F v=42, t=0 read F v=42, t=0 calc local write F v=9, t=0 The Joy of Clojure Figure 10.1 8 2011 5 24
  • 17.
    Tx A STM reference A F v=42, t=0 read Tx B F v=42, t=0 calc local write F v=9, t=0 The Joy of Clojure Figure 10.1 8 2011 5 24
  • 18.
    Tx A STM reference A F v=42, t=0 read Tx B F v=42, t=0 calc B local write F v=9, t=0 The Joy of Clojure Figure 10.1 8 2011 5 24
  • 19.
    Tx A STM reference A F v=42, t=0 read Tx B F v=42, t=0 calc B local write read F v=9, t=0 The Joy of Clojure Figure 10.1 8 2011 5 24
  • 20.
    Tx A STM reference A F v=42, t=0 read Tx B F v=42, t=0 calc B local write read F v=9, t=0 The Joy of Clojure Figure 10.1 8 2011 5 24
  • 21.
    Tx A STM reference A F v=42, t=0 read Tx B F v=42, t=0 calc B local write read F v=42, t=0 F v=9, t=0 The Joy of Clojure Figure 10.1 8 2011 5 24
  • 22.
    Tx A STM reference A F v=42, t=0 read Tx B F v=42, t=0 calc B local write read F v=42, t=0 F calc v=9, t=0 The Joy of Clojure Figure 10.1 8 2011 5 24
  • 23.
    Tx A STM reference A F v=42, t=0 read Tx B F v=42, t=0 calc B local write read F v=42, t=0 F calc v=9, t=0 local write The Joy of Clojure Figure 10.1 8 2011 5 24
  • 24.
    Tx A STM reference A F v=42, t=0 read Tx B F v=42, t=0 calc B local write read F v=42, t=0 F calc v=9, t=0 local write F v=27, t=0 The Joy of Clojure Figure 10.1 8 2011 5 24
  • 25.
    Tx A STM reference A F v=42, t=0 read Tx B F v=42, t=0 calc B local write read F v=42, t=0 F calc v=9, t=0 conflict? local write F v=27, t=0 The Joy of Clojure Figure 10.1 8 2011 5 24
  • 26.
    Tx A STM reference A F v=42, t=0 read Tx B F v=42, t=0 calc B local write read F v=42, t=0 F calc v=9, t=0 conflict? local write F v=27, t=0 The Joy of Clojure Figure 10.1 8 2011 5 24
  • 27.
    Tx A STM reference A F v=42, t=0 read Tx B F v=42, t=0 calc B local write read F v=42, t=0 F calc v=9, t=0 conflict? NO local write F v=27, t=0 The Joy of Clojure Figure 10.1 8 2011 5 24
  • 28.
    Tx A STM reference A F v=42, t=0 read Tx B F v=42, t=0 calc B local write read F v=42, t=0 F calc v=9, t=0 conflict? NO local write F commit v=27, t=0 The Joy of Clojure Figure 10.1 8 2011 5 24
  • 29.
    Tx A STM reference A F v=42, t=0 read Tx B F v=42, t=0 calc B local write read F v=42, t=0 F calc v=9, t=0 conflict? NO local write F commit v=27, t=0 F v=9, t=1 The Joy of Clojure Figure 10.1 8 2011 5 24
  • 30.
    Tx A STM reference A F v=42, t=0 read Tx B F v=42, t=0 calc B local write read F v=42, t=0 F calc v=9, t=0 conflict? NO local write F commit v=27, t=0 F v=9, t=1 conflict? The Joy of Clojure Figure 10.1 8 2011 5 24
  • 31.
    Tx A STM reference A F v=42, t=0 read Tx B F v=42, t=0 calc B local write read F v=42, t=0 F calc v=9, t=0 conflict? NO local write F commit v=27, t=0 F v=9, t=1 conflict? The Joy of Clojure Figure 10.1 8 2011 5 24
  • 32.
    Tx A STM reference A F v=42, t=0 read Tx B F v=42, t=0 calc B local write read F v=42, t=0 F calc v=9, t=0 conflict? NO local write F commit v=27, t=0 F v=9, t=1 conflict? YES The Joy of Clojure Figure 10.1 8 2011 5 24
  • 33.
    Tx A STM reference A F v=42, t=0 read Tx B F v=42, t=0 calc B local write read F v=42, t=0 F calc v=9, t=0 conflict? NO local write F commit v=27, t=0 F v=9, t=1 conflict? YES retry! The Joy of Clojure Figure 10.1 8 2011 5 24
  • 34.
    STM • STM – • – Transactional • atmic • STM – – I/O – 9 2011 5 24
  • 35.
    Agenda • Clojure • STM • Clojure STM • Clojure STM API • Clojure STM • Clojure STM 10 2011 5 24
  • 36.
    Clojure STM • – ref – Clojure immutable – ref • ref all-or-noting – dosync – ref all-of-nothing – 11 2011 5 24
  • 37.
    Clojure STM • a,b • def – a,b – a b – a b – a,b • def dosync – a,b – a,b 12 2011 5 24
  • 38.
    Clojure STM (def a 0) (def b 1) (inc a) ; a +1 (dec b) ; b -1 (println a b) ; -> 1 0 • a,b • Clojure immutable println a,b 13 2011 5 24
  • 39.
    Clojure STM (def a (ref 0)) (def b (ref 1)) (dosync (alter a inc) (alter b dec)) (println @a @b) • a,b all-or-nothing • ref println 1,0 14 2011 5 24
  • 40.
    Clojure STM (def a (ref 0)) (def b (ref 1)) (dosync (alter a inc) (alter b dec)) (println @a @b) • a,b all-or-nothing • ref println 1,0 14 2011 5 24
  • 41.
    Agenda • Clojure • STM • Clojure STM • Clojure STM API • Clojure STM • Clojure STM 15 2011 5 24
  • 42.
    Clojure STM API • API(Clojure STM ) • Java • URL – https://github.com/clojure/clojure/blob/master/src/clj/clojure/ core.clj#L1831 16 2011 5 24
  • 43.
    API • ref – ref • deref – • ref-set – ref • alter – ref • commute – alter • ensure – in-transaction-value 17 2011 5 24
  • 44.
    ref (defn ref {:added "1.0" :static true } ([x] (new clojure.lang.Ref x)) ([x & options] (let [r ^clojure.lang.Ref (setup-reference (ref x) options) opts (apply hash-map options)] (when (:max-history opts) (.setMaxHistory r (:max-history opts))) (when (:min-history opts) (.setMinHistory r (:min-history opts))) r))) • • ref dosync • 18 2011 5 24
  • 45.
    deref (defn deref "Also reader macro: @ref/@agent/@var/@atom/@delay/@future/@promise. Within a transaction, returns the in-transaction-value of ref, else returns the most-recently-committed value of ref. When applied to a var, agent or atom, returns its current state. When applied to a delay, forces it if not already forced. When applied to a future, will block if computation not complete. When applied to a promise, will block until a value is delivered. The variant taking a timeout can be used for blocking references (futures and promises), and will return timeout-val if the timeout (in milliseconds) is reached before a value is available. See also - realized?." {:added "1.0" :static true} ([^clojure.lang.IDeref ref] (.deref ref)) ([^clojure.lang.IBlockingDeref ref timeout-ms timeout-val] (.deref ref timeout-ms timeout-val))) • ref – dosync dosync in- transaction-value • future 19 2011 5 24
  • 46.
    ref-set (defn ref-set "Must be called in a transaction. Sets the value of ref. Returns val." {:added "1.0" :static true} [^clojure.lang.Ref ref val] (. ref (set val))) • ref 20 2011 5 24
  • 47.
    alter (defn alter "Must be called in a transaction. Sets the in-transaction-value of ref to: (apply fun in-transaction-value-of-ref args) and returns the in-transaction-value of ref." {:added "1.0" :static true} [^clojure.lang.Ref ref fun & args] (. ref (alter fun args))) • ref • 21 2011 5 24
  • 48.
    commute (defn commute "Must be called in a transaction. Sets the in-transaction-value of ref to: (apply fun in-transaction-value-of-ref args) and returns the in-transaction-value of ref. At the commit point of the transaction, sets the value of ref to be: (apply fun most-recently-committed-value-of-ref args) Thus fun should be commutative, or, failing that, you must accept last-one-in-wins behavior. commute allows for more concurrency than ref-set." {:added "1.0" :static true} [^clojure.lang.Ref ref fun & args] (. ref (commute fun args))) • ref • alter 22 2011 5 24
  • 49.
    ensure (defn ensure "Must be called in a transaction. Protects the ref from modification by other transactions. Returns the in-transaction-value of ref. Allows for more concurrency than (ref-set ref @ref)" {:added "1.0" :static true} [^clojure.lang.Ref ref] (. ref (touch)) (. ref (deref))) • in- transaction-value • ref ref ref 23 2011 5 24
  • 50.
    dosync (defmacro dosync "Runs the exprs (in an implicit do) in a transaction that encompasses exprs and any nested calls. Starts a transaction if none is already running on this thread. Any uncaught exception will abort the transaction and flow out of dosync. The exprs may be run more than once, but any effects on Refs will be atomic." {:added "1.0"} [& exprs] `(sync nil ~@exprs)) • 24 2011 5 24
  • 51.
    sync (defmacro sync "transaction-flags => TBD, pass nil for now Runs the exprs (in an implicit do) in a transaction that encompasses exprs and any nested calls. Starts a transaction if none is already running on this thread. Any uncaught exception will abort the transaction and flow out of sync. The exprs may be run more than once, but any effects on Refs will be atomic." {:added "1.0"} [flags-ignored-for-now & body] `(. clojure.lang.LockingTransaction (runInTransaction (fn [] ~@body)))) • • “flags-ignored-for-now” 25 2011 5 24
  • 52.
    io! (defmacro io! "If an io! block occurs in a transaction, throws an IllegalStateException, else runs body in an implicit do. If the first expression in body is a literal string, will use that as the exception message." {:added "1.0"} [& body] (let [message (when (string? (first body)) (first body)) body (if message (next body) body)] `(if (clojure.lang.LockingTransaction/isRunning) (throw (new IllegalStateException ~(or message "I/O in transaction"))) (do ~@body)))) • dosync io • STM I/O • I/O sync 26 2011 5 24
  • 53.
    set/get-validator (defn set-validator! "Sets the validator-fn for a var/ref/agent/atom. validator-fn must be nil or a side-effect-free fn of one argument, which will be passed the intended new state on any state change. If the new state is unacceptable, the validator-fn should return false or throw an exception. If the current state (root value if var) is not acceptable to the new validator, an exception will be thrown and the validator will not be changed." {:added "1.0" :static true} [^clojure.lang.IRef iref validator-fn] (. iref (setValidator validator-fn))) (defn get-validator "Gets the validator-fn for a var/ref/agent/atom." {:added "1.0" :static true} [^clojure.lang.IRef iref] (. iref (getValidator))) • • 27 2011 5 24
  • 54.
    alter/reset-meta (defn alter-meta! "Atomically sets the metadata for a namespace/var/ref/agent/atom to be: (apply f its-current-meta args) f must be free of side-effects" {:added "1.0" :static true} [^clojure.lang.IReference iref f & args] (.alterMeta iref f args)) (defn reset-meta! "Atomically resets the metadata for a namespace/var/ref/agent/atom" {:added "1.0" :static true} [^clojure.lang.IReference iref metadata-map] (.resetMeta iref metadata-map)) • • 28 2011 5 24
  • 55.
    ref-history (defn ref-history-count "Returns the history count of a ref" • ref {:added "1.1" :static true} [^clojure.lang.Ref ref] (.getHistoryCount ref)) • (defn ref-min-history "Gets the min-history of a ref, or sets it and returns the ref" {:added "1.1" :static true} ([^clojure.lang.Ref ref] (.getMinHistory ref)) ([^clojure.lang.Ref ref n] (.setMinHistory ref n))) (defn ref-max-history "Gets the max-history of a ref, or sets it and returns the ref" {:added "1.1" :static true} ([^clojure.lang.Ref ref] (.getMaxHistory ref)) ([^clojure.lang.Ref ref n] (.setMaxHistory ref n))) 29 2011 5 24
  • 56.
    Agenda • Clojure • STM • Clojure STM • Clojure STM API • Clojure STM • Clojure STM 30 2011 5 24
  • 57.
    Clojure STM • STM • STM 31 2011 5 24
  • 58.
    • 32 2011 5 24
  • 59.
  • 60.
    Ref • STM – TVal • Ref TVal 34 2011 5 24
  • 61.
    Ref.Tval • ref • 35 2011 5 24
  • 62.
    LockingTransaction • • – 10000000nano second kill • vals vals Ref • sets/commutes/ensures – sets ref comutes commute – alter ref-set ref-set – ensures commute 36 2011 5 24
  • 63.
    LockingTransaction.Info • ref ref transaction ref • • running/commiting/retry/killed/ commited • 37 2011 5 24
  • 64.
    LockingTransaction.RetryEx • • 38 2011 5 24
  • 65.
  • 66.
    • ref-set 40 2011 5 24
  • 67.
    (def current-track (ref"initial state of current track")) (dosync (ref-set current-track "changed")) • ref • dosync ref-set 41 2011 5 24
  • 68.
    ref 42 2011 5 24
  • 69.
    transaction run 43 2011 5 24
  • 70.
    ref-set 44 2011 5 24
  • 71.
    ref 45 2011 5 24
  • 72.
    Agenda • Clojure • STM • Clojure STM • Clojure STM API • Clojure STM • Clojure STM 46 2011 5 24
  • 73.
    Clojure STM Transaction • Multiversion Concurrency Control – • Snapshot Isolation – – Oracle/PostgereSQL RDBMS SERIALIZABLE 47 2011 5 24
  • 74.
    • Clojure – conj – • – Map Idel Hash Tree • STM – Snapshot Isolation ref 48 2011 5 24
  • 75.
    STM I/O • No I/O in STM transactions? – http://groups.google.com/group/clojure/ browse_thread/thread/ d967171ed4b0f20c/9f55aead761f3e99? lnk=gst&q=STM#9f55aead761f3e99 • Agent 49 2011 5 24
  • 76.
    • Extending Clojure'sSTM with external transactions – http://groups.google.com/group/clojure/ browse_thread/thread/ aa22a709501a64ac • RDBMS JTA – – 50 2011 5 24
  • 77.
    • Long-running STMupdates will never complete... is there a solution? – http://groups.google.com/group/clojure/ browse_thread/thread/ 7edd12e22eb120ea/207888a0d12ade38? lnk=gst&q=STM#207888a0d12ade38 • ensure – 51 2011 5 24
  • 78.
    • LL tiger clojure – – http://www.slideshare.net/makingx/ll-tiger-clojure • The Art of Multiprocessor Programming – 18 Transactional Memory STM Java Java – http://amzn.to/kJCkyT 52 2011 5 24