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High Performance Count Up!

High Performance Count Up!

Tatsuhiko Kubo

February 26, 2018

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  1. Tatsuhiko [email protected] Go 1.10 Release Party 2018/02/20 High Performance Count

  2. @cubicdaiya / Tatsuhiko Kubo Principal Engineer, SRE @ Mercari, Inc.

  3. None
  4. Agenda • Building High Performance count-up server with Go •

    Backend for counting page view of item at Mercari • ※ The right image is dev version’s
  5. Agenda • Building High Performance count-up server with Go •

    Backend for counting page view of item at Mercari • ※ The right image is dev version’s
  6. Difficulty in counting up page view of item in large

    web service • Large web service handles too many requests • Large web service has too many items • In general, page view of item overrepresents in all requests • Usually, page view is only read-only processing except logging • If it changes to write processing? • Write's scaling is more difficult than read's • Asynchronous processing is essential
  7. Case at Mercari • Many mercari code bases are still

    built by PHP • But, PHP is not good at asynchronous processing • We developed the service by Go to count up page view of item • The name is pvpool
  8. pvpool provides 2 HTTP APIs • POST /items/pvc • Count

    up page view of given item IDs asynchronously • POST /items/pv • Return page view of given item IDs Payload is JSON
  9. System architecture of pvpool • nginx • pvpoold • Powered

    by Go (net/http) • MySQL pvpoold pvpoold nginx MySQL pvpool.local by consul DNS : HTTP protocol : MySQL protocol The gopher was designed by Renée French
  10. Requirements and Load Characteristics of pvpool • Requirements • Reflect

    latest page view as real-time as possible (e.g. within a few seconds) • Respond as low latency as possible (e.g. within a few milli-seconds) • Load Characteristics • High throughput (Equal to page view of all items plus alpha) • Write-heavy
  11. pvpoold Internals POST /items/pvc { “item_ids": [ ... ] }

    PVCHandler Sharding Item IDs MySQL Slot Slot Slot Slot Slot Slot Pooling query Flushing periodically synchronous processing asynchronous processing
  12. pvpoold Internals • PVCHandler • HTTP Handler function • Slot

    • Processing unit to count up page view of items • Represented by goroutine
  13. pvpoold Internals • Characters in Slot • Slot -> chan

    types.ItemID • PVMap -> map[types.ItemID]int • Storer -> Fetch page view of item in Slot and store to PVMap • Flusher -> Fetch page view of item in PVMap and Issue SQL to MySQL periodically • Storer & Flusher are also represented by goroutine
  14. Slot overview Slot Storer Flusher PVMap dequeue item ID Store

    pv per item Fetch pv per item periodically MySQL Issue SQL to count up
  15. Storer behavior image func (slot *PVCSlot) storer() { for {

    itemID := <- slot.Slot slot.Lock() slot.PVMap[itemID]++ slot.Unock() } }
  16. Flusher behavior image func (slot *PVCSlot) flusher(interval time.Duration) { ticker

    := time.NewTicker(interval) for { <- ticker.C slot.Lock() if err := slot.flush(); err != nil { // transaction // error handling } slot.Unlock() } }
  17. Role of Storer & Flusher • Storer • Reduce issued

    SQLs to MySQL by aggregating page view per item • eg. UPDATE pv = pv + 5 instead of five of UPDATE pv = pv +1 • Flusher • Issue SQLs to MySQL periodically • Mitigate load of MySQL by timer control
  18. Avoid dead lock between Slots • pvpoold do not store

    some item ID to multiple Slots • Slot in which some item ID is stored is uniquely identified by its value • Because Go's map iteration order is random • So flushed item ID order in each Slot is not fixed
  19. Appendix • Fast logging • Powered by uber-go/zap • Tuning

    sql.DB • SetMaxOpenConns • SetMaxIdleConns • SetConnMaxLifetime • Great article by @methane • http://dsas.blog.klab.org/archives/2018-02/configure-sql-db.html
  20. We are hiring Go Software Engineer! https://careers.mercari.com/job/