ͭ·Βͳ͍γεςϜ(1) - FutureͱExecutionContext - mashi

૝ఆͯ͠Δಡऀ •  ৽ଔͷΈͳ͞Μ •  Scalaॻ͘ͷָ͕͘͠ͳ͖ͬͯͨ •  Future͍͢͝ʂָ͍͠ʂ

Future[T] ͱ͸ •  ͍͔ͭT͕ฦͬͯ͘Δ •  ͍ͭʁ – Θ͔Μͳ͍

Future ͷ࡞Γํ •  Future.apply Λ࢖͏ def apply(f: => T)(implicit ec: ExecutionContext): T •  f Ͱ౉ͨؔ͠਺͸ec: ExecutionContext ʹ Α࣮ͬͯߦ͞ΕΔ – ͜ͷ f Λࠓ͔Β Runnable ͱݺͼ·͢ •  ͍࣮ͭߦ͞ΕΔͷ͔ – Θ͔Μͳ͍ (ExecutionContext ͕ܾΊΔ) ৄ͘͠͸http://mashi.hatenablog.com/entry/2014/11/24/010417 Scala ExecutionContextͬͯԿ/ Future͸εϨου্ཱͪ͛͡Όͳ͍Α

ExecutionContext ͷҰൠతͳ࣮૷ Thread 1 Thread 2 Thread 3 Thread 4 •  ༩͑ͨ Runnable Λۭ͍ͯΔεϨουͰ͍ ͍ײ͡ʹ࣮ߦ͢Δ Runnable 1 Runnable 2 Runnable 3 Runnable n ۭ͖࣍ୈ࣮ߦ͢Δ

ৗʹొ৔͢ΔExecutionContext •  Future Λ͍͘͡Δʹ͸ৗʹ ExecutionContext ΛٻΊΒΕΔ •  ීஈॻ͍͍ͯΔίʔυ val dbData: Future[A] = getFromDB() val result: Future[B] = dbData.map({ e => convertToB(e) })

ৗʹొ৔͢ΔExecutionContext •  ීஈԿؾͳ͘ॻ͍͍ͯΔίʔυ΋࣮͸ implicit ͰExecutionContextΛ౉͍ͯ͠Δ •  mapʹ౉ͨؔ͠਺Λ࣮ߦ͢Δ ExecutionContext Λ҉໧తʹࢦఆ͍ͯ͠Δ val dbData: Future[A] = getFromDB() val result: Future[B] = dbData.map({ e => convertToB(e) })(ec: ExecutionContext)

ExecutionContext ͸༻్ผʹఆٛ͢΂͠ •  ྫ) memcached ͱ MySQL Ͱ෼͚Δ •  ྫ) MySQL ͷσʔλϕʔε1 ͱ 2 Ͱ෼͚Δ •  ྫ) MySQL ͷ master ͱ slaveͰ෼͚Δ •  ͳ͔ͥʁ

ExecutionContext ͸٧·Δ •  ϒϩοΩϯά͢Δ΋ͷΛ࢖͏ͱ٧·Δ – ྫ͑͹ MySQL ͷૢ࡞͸٧·Δ ˞͜͜Ͱ͸লུ͢Δ͕ɺscala-redis-nb ͷΑ͏ͳϊϯϒϩοΩϯάͳ࣮૷ Λ࢖͏ͱجຊతʹ٧·Βͳ͍

1つのExecutionContextΛ࢖͍·Θͨ͠৔߹ •  ྫ͑͹MySQL ͱmemcached͕৐͍ͬͯΔγεςϜ •  MySQLͷԠ౴͕஗͘ͳΔͱશ෦ॏ͘ͳΔ Thread 1 Thread 2 Thread 3 Thread 4 MySQLૢ࡞ MySQLૢ࡞ MySQLૢ࡞ 1ͭͷExecutionContext Λྲྀ༻ memcached ૢ࡞ MySQL ૢ࡞ MySQL ૢ࡞ MySQL ૢ࡞ MySQL ૢ࡞ ͦͷଞͷ ૢ࡞ ؔ܎ͳ͍ૢ࡞·Ͱಉ͡Ωϡʔʹ٧·ΕΔͷͰ memcached ͷૢ࡞΋ॏ͘ͳΔ MySQL͔Β ͷԠ౴଴ͪ…

ExecutionContextΛ༻్ผʹ෼͚ͨ৔߹ •  ͋ΔՕॴ͕٧·ͬͯ΋ଞʹӨڹ͠ͳ͘ͳΔ Thread 1 Thread 2 MySQLૢ࡞ MySQLૢ࡞ MySQLૢ࡞ memcached ૢ࡞ MySQL ૢ࡞ MySQL ૢ࡞ ͦͷଞͷ ૢ࡞ Thread 1 Thread 2 Thread 1 Thread 2 ͬͪ͜ʹ͸Өڹ͠ͳ͍ MySQL͚͕ͩ٧·Δ

·ͱΊ •  ීஈؾʹ͍ͯ͠ͳͯ͘΋implicitͰ҉໧తʹ ExecutionContextΛ౉͍ͯ͠Δ͜ͱ͕͋Δ –  'VUVSFͷNBQ΍qBU.BQΛ͢Δͱඞͣ౉ͯ͠ ͍Δ •  map ΍flatMap Λ͢Δͱ͖ʹࠓ͜͜Ͱ౉͍ͯ͠ ΔExecutionContextΛ٧·ΒͤΔڪΕ͕ͳ͍͔Λ ৗʹҙࣝ͢΂͠ –  ࣮૷ɾϨϏϡʔ࣌ʹΑ͘ݟ·͠ΐ͏ •  ͪΌΜͱ࣮૷͢Ε͹ྫ͑͹ʮmemcached ͕յ Εͯ΋memcached ʹ͸ؔ܎ͳ͍ͱ͜Ζʹ͸Ұ ੾Өڹ͕Ͱͳ͍ʯΑ͏ͳϑΣʔϧιϑτͳγε ςϜΛ࡞Γ্͛ΒΕΔ