The State of Go
Where we are in February 2017

Francesc Campoy
Google Developer Advocate
@francesc
campoy@golang.org

* Time flies

Go 1.6 is one year old (happy birthday!)

Go 1.7 is already 6 months old!

Go 1.8 to be released sometime in February.

Go 1.8 Candidate Release 3 was released on January 26th.

.image state-of-go/img/flying.png

* Notes

The slides are available on [[https://talks.golang.org/2017/state-of-go.slide]]

Most of the code examples won't run except locally and using Go 1.8.

The playground still runs Go 1.7.

* Agenda

Changes since Go 1.7:

- The Language
- The Standard Library
- The Runtime
- The Tooling
- The Community

* Changes to the language

* Conversion rules

How many times have you found yourself with two types that were *almost* equal?

Let's say you define `Person`:

.code state-of-go/stdlib/json_old.go /type Person/,/^}/

And that for some reason, like JSON you also have:

.code state-of-go/stdlib/json_old.go /var aux/,/}/

* Conversion rules

In order to convert `aux` to type `Person` you needed to do:

.code state-of-go/stdlib/json_old.go /type Person/,/}/

    return Person{
        Name:     aux.Name,
        AgeYears: aux.AgeYears,
        SSN:      aux.SSN
    }

* Conversion rules

Since Go 1.8 you can simply do:

    return Person(aux)

Both types still need to have:

- same *sequence* of fields (the order matters)
- corresponding fields with same type.

* Conversion rules

A non-constant value x can be converted to type T in any of these cases:

- x is assignable to T.
- x's type and T have identical underlying types.
- x's type and T are unnamed pointer types and their pointer base types have identical underlying types.
- ...

* Conversion rules

A non-constant value x can be converted to type T in any of these cases:

- x is assignable to T.
- *ignoring*struct*tags*, x's type and T have identical underlying types.
- *ignoring*struct*tags*, x's type and T are unnamed pointer types and their pointer base types have identical underlying types.
- ...

* Ports to other platforms

* Ports to other platforms

32-bit MIPS

- big-endian (`linux/mips`)
- little-endian (`linux/mipsle`) - requires Floating Point Unit

Go on DragonFly BSD now requires DragonFly 4.4.4+.

Go on OpenBSD now requires OpenBSD 5.9+.

Plan 9 is now better!

* Ports to other platforms

Go 1.8 supports OS X 10.8+. Likely last time we support 10.8.

ARM:

- Go 1.8 is the last version to support ARMv5E and ARMv6 processors.

- Go 1.9 will require ARMv6K. Will it work on my platform?

    go tool dist -check-armv6k

* Tools

* Fix

Fixes the import path `"golang.org/x/net/context"` to `"context"`.

.code state-of-go/tools/gofix.go

Simply run the command below:

.play state-of-go/tools/gofix.sh /go tool/

Drop the `-diff` flag to rewrite the files.

* Vet

"Vet is stricter in some ways and looser where it previously caused false positives."

Example of extra check:

.play -edit state-of-go/tools/govet.go /func main/,

`govet` detects the problem statically:

.play state-of-go/tools/govet.sh /go vet/

* SSA everywhere!

The SSA backend:

- generates more compact and efficient code
- is a better platform for optimizations

For 32-bit ARM systems this means 20-30% speed up!

For others (where SSA was used already) gains are 0-10%.

* SSA everywhere

.image state-of-go/img/benchmark.png _ 800

* Default GOPATH

Yay!

When `GOPATH` is not defined, the tool will use:

- `$HOME/go` on Unix
- `%USERPROFILE%\go` on Windows

* go bug

Easier way to create bugs including all relevant information.

Example:

.play state-of-go/tools/gobug.sh /go bug/

* Runtime

* Detection of concurrent map accesses

Improvement on Go 1.6.

.play state-of-go/runtime/mapcrash.go /const/,/Wait\(\)/

Outputs:

	fatal error: concurrent map read and map write
	fatal error: concurrent map writes

* Mutext Contention Profiling

Profile your benchmarks and the contention on your mutexes.

    go test bench=. -mutexprofile=mutex.out


Alternatively, activate contention profiling with this new method.

    runtime.SetMutexProfileFraction

_Note_: For now `sync.RWMutex` is not profiled.

* Mutex Contention Profiling

Let's write a program to count how many times each factor appears from 2 to N.

Example N = 10:

    Factorizations:

        2:  2
        3:  3
        4:  2 2
        5:  5
        6:  2 3
        7:  7
        8:  2 2 2
        9:  3 3
        10: 2 5

    Count:

        2: 8
        3: 4
        5: 2
        7: 1

* Mutex Contention Profiling

Which option is better?

Wide protected region:

.play state-of-go/runtime/mutex/main.go /WIDE/,/Unlock/

Narrow protected region:

.play state-of-go/runtime/mutex/main.go /NARROW/,/}/

* Benchmark

    $ go test -bench=.

#    BenchmarkNarrowSection/10-8         	  300000	      5085 ns/op
#    BenchmarkNarrowSection/100-8        	   20000	     77458 ns/op
#    BenchmarkNarrowSection/1000-8       	    2000	    909658 ns/op
#    BenchmarkNarrowSection/10000-8      	     100	  21230633 ns/op
#
#    BenchmarkWideSection/10-8           	  200000	      5323 ns/op
#    BenchmarkWideSection/100-8          	   10000	    103228 ns/op
#    BenchmarkWideSection/1000-8         	    1000	   2131861 ns/op
#    BenchmarkWideSection/10000-8        	      10	 103575793 ns/op

.image state-of-go/img/mutex_noprofile.png _ 1000

* Benchmarking with Mutex Contention

    $ go test -bench=. -mutexprofile=mutex.out

#    BenchmarkNarrowSection/10-8         	  300000	      5464 ns/op
#    BenchmarkNarrowSection/100-8        	   10000	    108583 ns/op
#    BenchmarkNarrowSection/1000-8       	    1000	   1378379 ns/op
#    BenchmarkNarrowSection/10000-8      	     100	  32828827 ns/op
#
#    BenchmarkWideSection/10-8           	  200000	      7155 ns/op
#    BenchmarkWideSection/100-8          	   10000	    197001 ns/op
#    BenchmarkWideSection/1000-8         	     300	   4339571 ns/op
#    BenchmarkWideSection/10000-8        	       5	 303559562 ns/op

.image state-of-go/img/mutex_profile.png _ 1000

* Analyzing the Mutex Contention Profile

    $ go tool pprof runtime.test mutex.out
    Entering interactive mode (type "help" for commands)
    (pprof) list

    0      5.38s (flat, cum) 43.97% of Total
    .          .     34:				mu.Lock()
    .          .     35:				m[f]++
    .      5.38s     36:				mu.Unlock()

    0      6.86s (flat, cum) 56.03% of Total
    .          .     53:			mu.Lock()
    .          .     54:			for _, f := range factors(i) {
    .          .     55:				m[f]++
    .          .     56:			}
    .      6.86s     57:			mu.Unlock()

* So much contention ...

* Contention by CPU

.image state-of-go/img/mutex_procs.png _ 1000

* Comparing it to sequential algorithm

.image state-of-go/img/mutex_all.png _ 1000

* Comparing it to sequential algorithm (zoom)

.image state-of-go/img/mutex_all_zoom.png _ 1000

* Performance

* GC history in tweets

* go 1.5

.image state-of-go/img/gct1.png _ 900

* go 1.6

.image state-of-go/img/gct2.png _ 900

* go 1.7

.image state-of-go/img/gct4.png _ 900

* go 1.8 (beta 1)

.image state-of-go/img/gct5.png _ 700

* go 1.8 (beta 1) CPU

.image state-of-go/img/gctcpu.png _ 800

* defer is faster

    name         old time/op  new time/op  delta
    Defer-4       101ns ± 1%    66ns ± 0%  -34.73%  (p=0.000 n=20+20)
    Defer10-4    93.2ns ± 1%  62.5ns ± 8%  -33.02%  (p=0.000 n=20+20)
    DeferMany-4   148ns ± 3%   131ns ± 3%  -11.42%  (p=0.000 n=19+19)

.image state-of-go/img/defer.png _ 500

* cgo is also faster!

    name       old time/op  new time/op  delta
    CgoNoop-8  93.5ns ± 0%  51.1ns ± 1%  -45.34%  (p=0.016 n=4+5)

.image state-of-go/img/cgo.png _ 500

Source: [[https://dave.cheney.net/2016/11/19/go-1-8-toolchain-improvements][dave.cheney.net]]

* Changes to the standard library

* Sorting

Exercise:

Given a slice of `Person`

    var p []Person

Print the slice sorted by name, age, and SSN.

.code state-of-go/stdlib/sort/sort_test.go /sort.Sort/,/bySSN/

Easy, right?

* Sorting

Well, you forgot about this part.

.code state-of-go/stdlib/sort/sort_test.go /byName/,/bySSN\) Swap/

* sort.Slice

Since Go 1.8 you can simply write this:

.code state-of-go/stdlib/sort/sort_test.go /sort\.Slice/,/SSN/

Also new `SliceStable` and `SliceIsSorted`.

* Benchmark

    N=1 go test -bench=.
        BenchmarkSortSort-8     10000000               145 ns/op
        BenchmarkSortSlice-8    10000000               190 ns/op
    N=10 go test -bench=.
        BenchmarkSortSort-8      2000000               918 ns/op
        BenchmarkSortSlice-8     1000000              1776 ns/op
    N=100 go test -bench=.
        BenchmarkSortSort-8       100000             16588 ns/op
        BenchmarkSortSlice-8       50000             39035 ns/op
    N=1000 go test -bench=.
        BenchmarkSortSort-8         5000            320951 ns/op
        BenchmarkSortSlice-8        3000            446677 ns/op
    N=10000 go test -bench=.
        BenchmarkSortSort-8          500           3644480 ns/op
        BenchmarkSortSlice-8         300           4962263 ns/op
    N=100000 go test -bench=.
        BenchmarkSortSort-8           30          43573572 ns/op
        BenchmarkSortSlice-8          20          60861706 ns/op

.caption Benchmark ran on my MacBook Pro (8 cores), simply indicative.

* Benchmark

.image state-of-go/img/bench.png _ 800

* Benchmark (log/log)

.image state-of-go/img/bench_log.png _ 800


* Plugins

Define a plugin:

.code state-of-go/stdlib/plugin/plugin.go

Then build it:

    go build -buildmode=plugin

* Plugins

.code state-of-go/stdlib/plugin/main.go /plugin.Open/,/Hello/

* Plugins demo

Demo video: [[https://twitter.com/francesc/status/827851085943566336][twitter.com/francesc]]

Source code: [[https://github.com/campoy/golang-plugins][github.com/campoy/golang-plugins]]

* HTTP shutdown

Added `Shutdown` method to `http.Server`.

Example:

Call `Shutdown` when a signal is received:

.code state-of-go/stdlib/shutdown.go /subscribe/,/}\(\)/

* HTTP shutdown

Check why the server stopped.

.code state-of-go/stdlib/shutdown.go /HandleFunc/,/gracefully/


* HTTP/2

`http.Response` now satisfies the `http.Pusher` interface.

    type Pusher interface {
        Push(target string, opts *PushOptions) error
    }

A simple example:

.code state-of-go/stdlib/http2/http2.go /func rootHandler/,/^}/

* HTTP/2

.play state-of-go/stdlib/http2/http2.go /func main/,/^}/

HTTP: [[http://localhost:8080]]
HTTP/2: [[https://localhost:8081]]

* HTTP/2

HTTP

.image state-of-go/img/http.png _ 800

HTTP/2

.image state-of-go/img/http2.png _ 800

* More context support

Since Go 1.7:

- net
- net/http
- os/exec

Since Go 1.8:

- http.Server.Shutdown
- database/sql
- net.Resolver

* A couple more changes too

.image state-of-go/img/more.png _ 1000
.caption [[https://beta.golang.org/doc/go1.8][Go 1.8 release notes]]

* The community

* Women Who Go

.image state-of-go/img/wwg.png _ 800
.caption 16 chapters already! [[http://www.womenwhogo.org]]

* Go meetups

.image state-of-go/img/meetups.png _ 900
.caption Gophers all around the world! [[http://go-meetups.appspot.com]]

* Conferences:

- [[https://fosdem.org/2017/][FOSDEM]], right here right now!
- [[http://www.gophercon.in/][GopherCon India]], Feb 25-25th
- [[https://gophercon.com/][Gophercon Denver]], Jul 12-15th
- [[http://golanguk.com/][Golang UK]], August 16th-18th
- [[http://2017.dotgo.eu/][dotGo]], Nov 6th

* Go 1.8 release party, February 16th

Go 1.8 ships soon!

Go meetups are organising to hold a [[https://github.com/golang/go/wiki/Go-1.8-release-party][release party]] on the 16th of February.

.image state-of-go/img/party-gopher.png _ 300
.caption Join the party!!!