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Golang @ Tokopedia

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Talk at Sequoia CTO Summit on programming with Go language

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Golang @ Tokopedia

  1. 1. Go @ Tokopedia Qasim Zaidi
  2. 2. About Tokopedia • Launched in 2009 • 300K Active merchants • 8 Million Products • Indonesia’s biggest online marketplace • Everyone pays shipping charges • Shipping is a function of distance • No discounting or cash-backs, neutral marketplace. • Most payments are offline
  3. 3. nginx ssl termination and proxy pass nginx-mod_perl nginx-mod_perl nginx-mod_perl The Stack postgres mongo redis proxy_pass
  4. 4. What we already use go for • Search & Discovery • Image Uploads • Analytics
  5. 5. 60% of the time, it works every time.
  6. 6. nginx ssl termination and proxy pass nginx-mod_perl nginx-mod_perl nginx-mod_perl The Stack postgres mongo redis proxy_pass mod_perl blocks nginx isolation is hard cancellation is harder
  7. 7. Challenges of scaling with mod_perl • Each request is synchronously processed in a worker • If there is one bad request, it ends up queuing everything else. • Cancellation is not easy - so even when the user moves away, the request continues to run.
  8. 8. In 2012, we bet on node.js
  9. 9. scaled well too - from 50K transactions in 2012 to over a million in 2015
  10. 10. node.js challenges • Too easy to mess up (dynamic, no type checking) • linting, code reviews • Unbounded Concurrency is hard. • async, promises • Scale issues with http client for c10k • even dns latencies can have big impact
  11. 11. Picking a new language in 2015.
  12. 12. the no QA philosophy QA is not a different role. Developers are responsible for testing their code.
  13. 13. Testing in Go • Easy to write unit tests func TestFoo(t *testing.T) { ... } • run as go test • No separate frameworks • Benchmarking is as easy as testing
  14. 14. the no Documentation philosophy Code should be self explanatory. Documentation outside of code is never updated.
  15. 15. Documentation with GoDoc • Comments in code - e.g. preceding function definition • It extracts the comments and presents them: • $ godoc strings Join
 
 func Join(a []string, sep string) string
 
 Join concatenates the elements of a to create a single string. The separator string sep is placed between elements in the resulting string. // Join concatenates the elements of a to create a single string.
 // The separator string sep is placed between elements in the resulting string.
 
 func Join(a []string, sep string) string {
 //self explanatory blah blah blah
 //more of the same }
  16. 16. godoc - examples and testing func ExampleJoin() { s := []string{"foo", "bar", "baz"} fmt.Println(strings.Join(s, ", ")) // Output: foo, bar, baz } • Also integrated with the testing framework to provide testable example functions.
  17. 17. godoc - webview
  18. 18. Concurrency should be easy And not yet forced. Too much concurrency spoils the code.
  19. 19. Code should be hard to mess with A compiler that catches bugs and is not too slow statically compiled binaries - no library mess
  20. 20. Institutional knowledge Go brings google’s institutional knowledge to you, for free - Groupcache - Expvars - Single-flights and Cancellations
  21. 21. Object Caching • In node.js - we built in an object caching solution in house, that can easily make a function called cached without changing much code. • var wrapper = cache.wrap(original); • Can chose whether to cache in memory or redis. • Can avoid thundering herds - single flighting
  22. 22. Enter group cache • In memory • distributed • single flight ELB app groupcache app app groupcachegroupcache http http
  23. 23. expvars - server metrics over http • Export variables over http • http://localhost:8123/debug/vars
 {
 "cmdline": ["/var/folders/bc/27hv15_d2zvcc3n3s9dxmfg00000gn/T/go-build421732654/command- line-arguments/_obj/exe/main","-l","debug","-s","i.sock","-c","realtest"],
 "counters": {"a": 10, "b": 10},
 "memstats": {"Alloc":1076016,"TotalAlloc":1801544,"Sys":5966072,"Lookups":209,"Mallocs": 7986,"Frees":4528,"HeapAlloc":1076016,"HeapSys":2097152,"HeapIdle":327680,"HeapInuse": 1769472,"HeapReleased":0,"HeapObjects":3458,"StackInuse":212992,"StackSys": 917504,"MSpanInuse":21504,"MSpanSys":32768,"MCacheInuse":8800,"MCacheSys": 16384,"BuckHashSys":1441160,"GCSys":1183744,"OtherSys":277360,"NextGC": 1436032,"LastGC":1418102095002592201,"PauseTotalNs":2744531,"PauseNs": [480149,171430,603839,288381,494934,522995,182803,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 ,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 ,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],"NumGC":7,"EnableGC":true,"DebugGC":false}
 }
  24. 24. Cancellations • User moves away, nginx sends 499, but queries keep running. • Not Abandoning work when user has moved away is often wasteful • Go’s has advisory cancellations - cancel across go- routines • facilitated by contexts
  25. 25. moving from ‘dynamic’ to ‘compiled’ • Deployment changes • from git clone to compile, build & deploy • have a way of knowing binary version that is automatic BUILDHASH=$(shell cd src/$(SRCDIR) && git rev-parse --verify HEAD | cut -c 1-7)
 go build —ldflags -X $BUILDHASH appname —version • config and code is separate • make sure everything you may ever need to configure is in config/flags, can’t change binary appname —port appname —configtest appname —debug • have good debugging (we have debug() statements that are turned on by —debug flag)
  26. 26. The go workflow jenkins dpkg- buildpackagetriggers build build dpkg using go get ansible srv1 srv1 srv1 elb nginx binary, run via upstart deploy dpkg restart 2 1 triggers deploy 3
  27. 27. No templates, no exceptions, weird and sometimes inconsistent. Go is an opinionated language “Instructions, registers, and assembler directives are always in UPPER CASE to remind you that assembly programming is a fraught endeavor.” - Rob Pike
  28. 28. -Dick Gabriel, from the golang FAQ Who would have guessed sophistication bought such noise?
  29. 29. Golang - missing a package manager? • go get - but its not complete • No dependency management, unlike npm, no easy hermetic builds • gopkg.in is a solution - allows versioning • if you have to change versions, edit every single import
  30. 30. Deployment Challenges • No Fork() - forking with subroutines ain’t easy • Facebook grace (https://github.com/facebookgo/grace) • PID changes - no relationship • problems with upstart / job monitor • log rotation
  31. 31. Moving from a script to binary • Deployment changes (from git clone to build, package and deploy) • Need to know which version of code is running • appname —version • Need to debug easily • appname —debug - enables debug() output • Keep configuration flexible, because in case of issues, you can’t just edit and deploy • appname —configtest • appname —port (over ride config)
  32. 32. Go @ Tokopedia • Go is a modern language, very suitable for web. • Go is Performant, unless you are doing C. • Go is mostly google still, and not 100% complete. • Go is opinionated, like Plan9, and there will be a learning curve. • Go is slower for prototyping, e.g. when compared to node.js
  33. 33. Questions?

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