Painless Data Storage with

MongoDB & Go

• Author of Hugo, Cobra, Viper & More

• Chief Developer Advocate for MongoDB

• Gopher

@spf13

Why Go?

Why Another Language?

• Software is slow • Sofware is hard to write • Software doesn’t scale well

Go is Fast• Go execution speed is close to C • Go compile time rivals dynamic

interpretation

Go is Friendly• Feels like a dynamic language in many ways

• Very small core language, easy to remember all of it

• Single binary installation, no dependencies

• Extensive Tooling & StdLib

Go is Concurrent• Concurrency is part of the language

• Any function can become a goroutine

• Goroutines run concurrently, communicate through channels

• Select waits for communication on any of a set of channels

MongoDB

Why Another Database?• Databases are slow • Relational structures don’t fit well

with modern programming (ORMs)

• Databases don’t scale well

MongoDB is Fast• Written in C++

• Extensive use of memory-mapped files i.e. read-through write-through memory caching.

• Runs nearly everywhere

• Data serialized as BSON (fast parsing)

• Full support for primary & secondary indexes

• Document model = less work

MongoDB is Friendly• Ad Hoc queries

• Real time aggregation

• Rich query capabilities

• Traditionally consistent

• Geospatial features

• Support for most programming languages

• Flexible schema

MongoDB is “Web Scale”• Built in sharding support distributes data

across many nodes

• MongoS intelligently routes to the correct nodes

• Aggregation done in parallel across nodes

Document Database• Not for .PDF & .DOC files

• A document is essentially an associative array

• Document == JSON object

• Document == PHP Array

• Document == Python Dict

• Document == Ruby Hash

• etc

Data Serialization• Applications need persistant data

• The process of translating data structures into a format that can be stored

• Ideal format accessible from many languages

BSON• Inspired by JSON

• Cross language binary serialization format

• Optimized for scanning

• Support for richer types

MongoDB & Go

Go’s Data Types• Go uses strict & static typing

• 2 Types are similar to a BSON document

• Struct

• Map

bob := &Person{ Name: "Bob", Birthday: time.Now(), } !data, err := bson.Marshal(bob) if err != nil { return err } fmt.Printf("Data: %q\n", data)

!var person Person err = bson.Unmarshal(data, &person) if err != nil { return err } fmt.Printf("Person: %v\n", person)

Serializing with BSON

bob := &Person{ Name: "Bob", Birthday: time.Now(), } !data, err := bson.Marshal(bob) if err != nil { return err } fmt.Printf("Data: %q\n", data)

!var person Person err = bson.Unmarshal(data, &person) if err != nil { return err } fmt.Printf("Person: %v\n", person)

Serializing with BSON

bob := &Person{ Name: "Bob", Birthday: time.Now(), } !data, err := bson.Marshal(bob) if err != nil { return err } fmt.Printf("Data: %q\n", data)

!var person Person err = bson.Unmarshal(data, &person) if err != nil { return err } fmt.Printf("Person: %v\n", person)

Serializing with BSON

bob := &Person{ Name: "Bob", Birthday: time.Now(), } !data, err := bson.Marshal(bob) if err != nil { return err } fmt.Printf("Data: %q\n", data)

!var person Person err = bson.Unmarshal(data, &person) if err != nil { return err } fmt.Printf("Person: %v\n", person)

Serializing with BSON

bob := &Person{ Name: "Bob", Birthday: time.Now(), } !data, err := bson.Marshal(bob) if err != nil { return err } fmt.Printf("Data: %q\n", data)

!var person Person err = bson.Unmarshal(data, &person) if err != nil { return err } fmt.Printf("Person: %v\n", person)

Serializing with BSON

bob := &Person{ Name: "Bob", Birthday: time.Now(), } !data, err := bson.Marshal(bob) if err != nil { return err } fmt.Printf("Data: %q\n", data)

!var person Person err = bson.Unmarshal(data, &person) if err != nil { return err } fmt.Printf("Person: %v\n", person)

Serializing with BSONData: "%\x00\x00\x00\x02name\x00\x04\x00\x00\x00Bob\x00\tbirthday\x00\x80\r\x97|^\x00\x00\x00\x00"!

Person: {Bob 2014-07-21 18:00:00 -0500 EST}

! type Project struct { Name string `bson:"name"` ImportPath string `bson:"importPath"` } project := Project{name, path} !!! project := map[string]string{"name": name, "importPath": path} !!! project := bson.D{{"name", name}, {"importPath", path}}

Equal After MarshalingStruct

Custom Map

Document Slice

mgo (mango)• Pure Go

• Created in late 2010 ("Where do I put my Go data?")

• Adopted by Canonical and MongoDB Inc. itself

• Sponsored by MongoDB Inc. from late 2011

Connecting

• Same interface for server, replica set, or shard

• Driver discovers and maintains topology

• Server added/removed, failovers, response times, etc

Connectingsession, err := mgo.Dial("localhost") if err != nil { return err }

• Sessions are lightweight

• Sessions are copied (settings preserved)

• Single management goroutine for all copied sessions

Sessionsfunc (s *Server) handle(w http.ResponseWriter, r *http.Request) { session := s.session.Copy() defer session.Close() // ... handle request ... }

• Saves typing

• Uses the same session over and over

Convenient Accessprojects := session.DB("OSCON").C("projects")

Writing

type Project struct { Name string `bson:"name,omitempty"` ImportPath string `bson:"importPath,omitempty"` }

Defining Our Own Type

var projectList = []Project{ {"gocheck", "gopkg.in/check.v1"}, {"qml", "gopkg.in/qml.v0"}, {"pipe", "gopkg.in/pipe.v2"}, {"yaml", "gopkg.in/yaml.v1"}, } !for _, project := range projectList { err := projects.Insert(project) if err != nil { return err } } fmt.Println("Okay!")

Insert

Okay!

type M map[string]interface{} !change := M{"$set": Project{ImportPath: "gopkg.in/qml.v1"}} !err = projects.Update(Project{Name: "qml"}, change) if err != nil { return err } !fmt.Println("Done!")

Update

Done!

Querying

var project Project !err = projects.Find(Project{Name: "qml"}).One(&project) if err != nil { return err } !fmt.Printf("Project: %v\n", project)

Find

Project: {qml gopkg.in/qml.v0}

iter := projects.Find(nil).Iter() !

var project Project for iter.Next(&project) { fmt.Printf("Project: %v\n", project) } !

return iter.Err()

Iterate

Project: {gocheck gopkg.in/check.v1} Project: {qml gopkg.in/qml.v0} Project: {pipe gopkg.in/pipe.v2} Project: {yaml gopkg.in/yaml.v1}

m := map[string]interface{}{ "name": "godep", "tags": []string{"tool", "dependency"}, "contact": bson.M{ "name": "Keith Rarick", "email": "kr@nospam.com", }, } !err = projects.Insert(m) if err != nil { return err } fmt.Println("Okay!")

Nesting

Okay!

type Contact struct { Name string Email string } !type Project struct { Name string Tags []string `bson:",omitempty"` Contact Contact `bson:",omitempty"` } !err = projects.Find(Project{Name: "godep"}).One(&project) if err != nil { return err } !pretty.Println("Project:", project)

Nesting IIProject: main.Project{ Name: "godep", Tags: {"tool", "dependency"}, Contact: {Name:"Keith Rarick", Email:"kr@XZY.com"}, }

• Compound

• List indexing (think tag lists)

• Geospatial

• Dense or sparse

• Full-text searching

Indexing// Root field err = projects.EnsureIndexKey("name") ... !// Nested field err = projects.EnsureIndexKey("author.email") ...

Concurrency

func f(projects *mgo.Collection, name string, done chan error) { var project Project err := projects.Find(Project{Name: name}).One(&project) if err == nil { fmt.Printf("Project: %v\n", project) } done <- err } !done := make(chan error) !go f(projects, "qml", done) go f(projects, "gocheck", done) !if err = firstError(2, done); err != nil { return err }

Concurrent

func f(projects *mgo.Collection, name string, done chan error) { var project Project err := projects.Find(Project{Name: name}).One(&project) if err == nil { fmt.Printf("Project: %v\n", project) } done <- err } !done := make(chan error) !go f(projects, "qml", done) go f(projects, "gocheck", done) !if err = firstError(2, done); err != nil { return err }

Concurrent

func f(projects *mgo.Collection, name string, done chan error) { var project Project err := projects.Find(Project{Name: name}).One(&project) if err == nil { fmt.Printf("Project: %v\n", project) } done <- err } !done := make(chan error) !go f(projects, "qml", done) go f(projects, "gocheck", done) !if err = firstError(2, done); err != nil { return err }

Concurrent

func f(projects *mgo.Collection, name string, done chan error) { var project Project err := projects.Find(Project{Name: name}).One(&project) if err == nil { fmt.Printf("Project: %v\n", project) } done <- err } !done := make(chan error) !go f(projects, "qml", done) go f(projects, "gocheck", done) !if err = firstError(2, done); err != nil { return err }

Concurrent

func f(projects *mgo.Collection, name string, done chan error) { var project Project err := projects.Find(Project{Name: name}).One(&project) if err == nil { fmt.Printf("Project: %v\n", project) } done <- err } !done := make(chan error) !go f(projects, "qml", done) go f(projects, "gocheck", done) !if err = firstError(2, done); err != nil { return err }

Concurrent

func f(projects *mgo.Collection, name string, done chan error) { var project Project err := projects.Find(Project{Name: name}).One(&project) if err == nil { fmt.Printf("Project: %v\n", project) } done <- err } !done := make(chan error) !go f(projects, "qml", done) go f(projects, "gocheck", done) !if err = firstError(2, done); err != nil { return err }

Concurrent

func f(projects *mgo.Collection, name string, done chan error) { var project Project err := projects.Find(Project{Name: name}).One(&project) if err == nil { fmt.Printf("Project: %v\n", project) } done <- err } !done := make(chan error) !go f(projects, "qml", done) go f(projects, "gocheck", done) !if err = firstError(2, done); err != nil { return err }

Concurrent

func f(projects *mgo.Collection, name string, done chan error) { var project Project err := projects.Find(Project{Name: name}).One(&project) if err == nil { fmt.Printf("Project: %v\n", project) } done <- err } !done := make(chan error) !go f(projects, "qml", done) go f(projects, "gocheck", done) !if err = firstError(2, done); err != nil { return err }

Concurrent

Project: {qml gopkg.in/qml.v1} Project: {gocheck gopkg.in/check.v1}

• Find 1 issued

• Doc 1 returned • Find 2 issued

• Doc 2 returned

A Common ApproachFind 1 Find 2 DB

}}

• Find 1 issued • Find 2 issued

• Doc 1 returned • Doc 2 returned

Concurrent QueriesFind 1 Find 2 DB

}}

• Loads 200 results at a time

• Loads next batch with (0.25 * 200) results left to process

Concurrent Loadingsession.SetBatch(200) session.SetPrefetch(0.25) !for iter.Next(&result) { ... }

• Each Copy uses a different connection

• Closing session returns socket to the pool

• defer runs at end of function

Handler With Session Copyfunc (s *Server) handle(w http.ResponseWriter, r *http.Request) { session := s.session.Copy() defer session.Close() ! // ... handle request ... }

• Shares a single connection

• Still quite efficient thanks to concurrent capabilities of go + mgo

Handler With Single Sessionfunc (s *Server) handle(w http.ResponseWriter, r *http.Request) { session := s.session ! // ... handle request ... }

GridFS

GridFS• Not quite a file system

• Really useful for local file storage

• A convention, not a feature

• Supported by all drivers

• Fully replicated, sharded file storage

gridfs := session.DB("OSCON").GridFS("fs") !file, err := gridfs.Create("cd.iso") if err != nil { return err } defer file.Close() !started := time.Now() !_, err = io.Copy(file, iso) if err != nil { return err } !fmt.Printf("Wrote %d bytes in %s\n", file.Size(), time.Since(started))

GridFS

gridfs := session.DB("OSCON").GridFS("fs") !file, err := gridfs.Create("cd.iso") if err != nil { return err } defer file.Close() !started := time.Now() !_, err = io.Copy(file, iso) if err != nil { return err } !fmt.Printf("Wrote %d bytes in %s\n", file.Size(), time.Since(started))

GridFS

gridfs := session.DB("OSCON").GridFS("fs") !file, err := gridfs.Create("cd.iso") if err != nil { return err } defer file.Close() !started := time.Now() !_, err = io.Copy(file, iso) if err != nil { return err } !fmt.Printf("Wrote %d bytes in %s\n", file.Size(), time.Since(started))

GridFS

gridfs := session.DB("OSCON").GridFS("fs") !file, err := gridfs.Create("cd.iso") if err != nil { return err } defer file.Close() !started := time.Now() !_, err = io.Copy(file, iso) if err != nil { return err } !fmt.Printf("Wrote %d bytes in %s\n", file.Size(), time.Since(started))

GridFS

gridfs := session.DB("OSCON").GridFS("fs") !file, err := gridfs.Create("cd.iso") if err != nil { return err } defer file.Close() !started := time.Now() !_, err = io.Copy(file, iso) if err != nil { return err } !fmt.Printf("Wrote %d bytes in %s\n", file.Size(), time.Since(started))

GridFS

gridfs := session.DB("OSCON").GridFS("fs") !file, err := gridfs.Create("cd.iso") if err != nil { return err } defer file.Close() !started := time.Now() !_, err = io.Copy(file, iso) if err != nil { return err } !fmt.Printf("Wrote %d bytes in %s\n", file.Size(), time.Since(started))

GridFS

gridfs := session.DB("OSCON").GridFS("fs") !file, err := gridfs.Create("cd.iso") if err != nil { return err } defer file.Close() !started := time.Now() !_, err = io.Copy(file, iso) if err != nil { return err } !fmt.Printf("Wrote %d bytes in %s\n", file.Size(), time.Since(started))

GridFS

!

Wrote 470386961 bytes in 7.0s

Full Featured

Features• Transactions (mgo/txn experiment)

• Aggregation pipelines

• Full-text search

• Geospatial support

• Hadoop

In Conclusion

Getting Started• 1. Install MongoDB

• 2. go get gopkg.in/mgo.v2

• 3. Start small

• 4. Build something great

Learning More• MongoDB Manual

• Effective Go

• labix.org/mgo

Workshop Using mgo on spf13.com

on spf13.com

• @spf13

• Author of Hugo, Cobra, Viper & More

• Chief Developer Advocate for MongoDB

• Gopher

Thank You