kit

kit

EyeCueLab's kit is a repository of open-source golang libraries developed by EyeCueLab for use in our various projects.

philosophy / notes

EyeCueLab tries to follow the philosphy of the twelve-factor app. All non-business logic should be open & accessible to the public, and configuration details should be in the environment.

Accordingly, EyeCueLab uses the cobra command-line interface and the viper configuration library. Many parts of kit either rely on these libraries for configuration or hook into them during init() so that cobra/viper can access them.

Testing

Navigate to the root of the source directory for kit

go test ./... -cover

address

address contains tools for storing and comparing street addreses.

assets

(TODO)

brake

brake contains tools for setting up and working with the airbrake error monitoring software.

branch

(TODO)

cmd

cmd contains helper fucntions for the cobra command-line interface

coerce

coerce contains functions which use reflection to coerce various numeric types using c-style numeric promotion. This is mostly for testing.

config

config contains helper functions to help set up viper configuration library

counter

counter implements various counter types, similar to python's collections.counter

db

db contains tools for various databases. See db/mongo or db/psql.

db/mongo

db/mongo helps connect to our mongoDB instances and provides various helper functions

db/psql

db/psql helps connect to psql instances and provides various helper functions

dockerfiles

(TODO)

env

env contains tools for accessing and manipulating environment variables

errorlib

errorlib contains tools to deal with errors, including the heavily-used ErrorString type (for errors that are compile-time constants) and LoggedChannel function (to report non-fatal errors during concurrent execution)

flect

flect is meant to work alongside go's reflect library, containing additional runtime reflection tools

geojson

geojson contains an interface and various structs for 2d and 3d geometry that correspond to the geojson format.

goenv

(TODO)

imath

imath is contains tools for signed integer math. it largely corresponds with go's built in math library for float64s

imath/operator

imath/operator contains functions which represent all of golang's built in operators,as well as bitwise operators

log

log is an extension of the logrus package. It contains various tools for logging information and errors during runtime.

mailman

(TODO)

maputil

maputil contains various helper functions for maps with string keys.

the maputil package itself covers map[string]interface{}

maputil/string

maputil contains helper functions for the type map[string]string

oauth

(TODO)

pretty

pretty provides pretty-printing for go values. It is a fork of the kr/pretty package, obtained under the MIT license.

random

random provides tools for generating cryptographically secure random elements. it uses golang's built in crypto/rand for it's RNG.

random/shuffle

random/shuffle provides tools for creating shuffled copies of various golang slice types using the fisher-yates shuffle. It uses crypto/rand for it's RNG.

retry

(TODO)

runeset

runeset implements a set of runes and various methods for dealing with strings accordingly. it should probably be folded into the set package.

s3

s3 contains helper functions for dealing with amazon's aws/s3 and integrating it with the cobra CLI.

set

set implements various set types and associated methods; union, intersection, containment, etc. see runeset for a set of runes (this will be folded into set.)

str

str contains various tools for manipulation of strings beyond those available in golang's strings library. it also contains a wide variety of string constants.

stringslice

stringslice contains various functions to work with slices of strings and the strings contained within.

set/int

set/int implements a set type for int

set/string

set/string implements a set type for string

sortlib

sortlib contains tools for producing sorted copies of various golang types

tickertape

tickertape provides an implenetation of a concurrency-safe 'ticker tape' of current information during a running program - that is, repeatedly updating the same line with new information.

tsv

tsv contains tools for dealing with tab-separated values.

umath

umath contains various math functions for unsigned integers, roughly corresponding with imath and golang's built in math package.

web

web is the bones of our web framework, built on top of google's jsonapi framework and labstack's echo framework.

web/middleware

(TODO)

web/server

(TODO)

web/testing

(TODO)

web/webtest

(TODO)

jsonapi

A serializer/deserializer for JSON payloads that comply to the JSON API - jsonapi.org spec in go.

Installation

go get -u github.com/google/jsonapi

Or, see Alternative Installation.

Background

You are working in your Go web application and you have a struct that is organized similarly to your database schema. You need to send and receive json payloads that adhere to the JSON API spec. Once you realize that your json needed to take on this special form, you go down the path of creating more structs to be able to serialize and deserialize JSON API payloads. Then there are more models required with this additional structure. Ugh! With JSON API, you can keep your model structs as is and use StructTags to indicate to JSON API how you want your response built or your request deserialized. What about your relationships? JSON API supports relationships out of the box and will even put them in your response into an included side-loaded slice--that contains associated records.

Introduction

JSON API uses StructField tags to annotate the structs fields that you already have and use in your app and then reads and writes JSON API output based on the instructions you give the library in your JSON API tags. Let's take an example. In your app, you most likely have structs that look similar to these:

type Blog struct {
	ID            int       `json:"id"`
	Title         string    `json:"title"`
	Posts         []*Post   `json:"posts"`
	CurrentPost   *Post     `json:"current_post"`
	CurrentPostId int       `json:"current_post_id"`
	CreatedAt     time.Time `json:"created_at"`
	ViewCount     int       `json:"view_count"`
}

type Post struct {
	ID       int        `json:"id"`
	BlogID   int        `json:"blog_id"`
	Title    string     `json:"title"`
	Body     string     `json:"body"`
	Comments []*Comment `json:"comments"`
}

type Comment struct {
	Id     int    `json:"id"`
	PostID int    `json:"post_id"`
	Body   string `json:"body"`
	Likes  uint   `json:"likes_count,omitempty"`
}

These structs may or may not resemble the layout of your database. But these are the ones that you want to use right? You wouldn't want to use structs like those that JSON API sends because it is difficult to get at all of your data easily.

Example App

examples/app.go

This program demonstrates the implementation of a create, a show, and a list http.Handler. It outputs some example requests and responses as well as serialized examples of the source/target structs to json. That is to say, I show you that the library has successfully taken your JSON API request and turned it into your struct types.

To run,

• Make sure you have Go installed
• Create the following directories or similar: ~/go
• Set GOPATH to PWD in your shell session, export GOPATH=$PWD
• go get github.com/google/jsonapi. (Append -u after get if you are updating.)
• cd $GOPATH/src/github.com/google/jsonapi/examples
• go build && ./examples

jsonapi Tag Reference

Example

The jsonapi StructTags tells this library how to marshal and unmarshal your structs into JSON API payloads and your JSON API payloads to structs, respectively. Then Use JSON API's Marshal and Unmarshal methods to construct and read your responses and replies. Here's an example of the structs above using JSON API tags:

type Blog struct {
	ID            int       `jsonapi:"primary,blogs"`
	Title         string    `jsonapi:"attr,title"`
	Posts         []*Post   `jsonapi:"relation,posts"`
	CurrentPost   *Post     `jsonapi:"relation,current_post"`
	CurrentPostID int       `jsonapi:"attr,current_post_id"`
	CreatedAt     time.Time `jsonapi:"attr,created_at"`
	ViewCount     int       `jsonapi:"attr,view_count"`
}

type Post struct {
	ID       int        `jsonapi:"primary,posts"`
	BlogID   int        `jsonapi:"attr,blog_id"`
	Title    string     `jsonapi:"attr,title"`
	Body     string     `jsonapi:"attr,body"`
	Comments []*Comment `jsonapi:"relation,comments"`
}

type Comment struct {
	ID     int    `jsonapi:"primary,comments"`
	PostID int    `jsonapi:"attr,post_id"`
	Body   string `jsonapi:"attr,body"`
	Likes  uint   `jsonapi:"attr,likes-count,omitempty"`
}

Permitted Tag Values

primary

`jsonapi:"primary,<type field output>"`

This indicates this is the primary key field for this struct type. Tag value arguments are comma separated. The first argument must be, primary, and the second must be the name that should appear in the type* field for all data objects that represent this type of model.

* According the JSON API spec, the plural record types are shown in the examples, but not required.

attr

`jsonapi:"attr,<key name in attributes hash>,<optional: omitempty>"`

These fields' values will end up in the attributeshash for a record. The first argument must be, attr, and the second should be the name for the key to display in the attributes hash for that record. The optional third argument is omitempty - if it is present the field will not be present in the "attributes" if the field's value is equivalent to the field types empty value (ie if the count field is of type int, omitempty will omit the field when count has a value of 0). Lastly, the spec indicates that attributes key names should be dasherized for multiple word field names.

relation

`jsonapi:"relation,<key name in relationships hash>,<optional: omitempty>"`

Relations are struct fields that represent a one-to-one or one-to-many relationship with other structs. JSON API will traverse the graph of relationships and marshal or unmarshal records. The first argument must be, relation, and the second should be the name of the relationship, used as the key in the relationships hash for the record. The optional third argument is omitempty - if present will prevent non existent to-one and to-many from being serialized.

Methods Reference

All Marshal and Unmarshal methods expect pointers to struct instance or slices of the same contained with the interface{}s

Now you have your structs prepared to be seralized or materialized, What about the rest?

Create Record Example

You can Unmarshal a JSON API payload using jsonapi.UnmarshalPayload. It reads from an io.Reader containing a JSON API payload for one record (but can have related records). Then, it materializes a struct that you created and passed in (using new or &). Again, the method supports single records only, at the top level, in request payloads at the moment. Bulk creates and updates are not supported yet.

After saving your record, you can use, MarshalOnePayload, to write the JSON API response to an io.Writer.

UnmarshalPayload

UnmarshalPayload(in io.Reader, model interface{})

Visit godoc

MarshalPayload

MarshalPayload(w io.Writer, models interface{}) error

Visit godoc

Writes a JSON API response, with related records sideloaded, into an included array. This method encodes a response for either a single record or many records.

func CreateBlog(w http.ResponseWriter, r *http.Request) {
	blog := new(Blog)

	if err := jsonapi.UnmarshalPayload(r.Body, blog); err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	// ...save your blog...

	w.Header().Set("Content-Type", jsonapi.MediaType)
	w.WriteHeader(http.StatusCreated)

	if err := jsonapi.MarshalPayload(w, blog); err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
	}
}

Create Records Example

UnmarshalManyPayload

UnmarshalManyPayload(in io.Reader, t reflect.Type) ([]interface{}, error)

Visit godoc

Takes an io.Reader and a reflect.Type representing the uniform type contained within the "data" JSON API member.

func CreateBlogs(w http.ResponseWriter, r *http.Request) {
	// ...create many blogs at once

	blogs, err := UnmarshalManyPayload(r.Body, reflect.TypeOf(new(Blog)))
	if err != nil {
		t.Fatal(err)
	}

	for _, blog := range blogs {
		b, ok := blog.(*Blog)
		// ...save each of your blogs
	}

	w.Header().Set("Content-Type", jsonapi.MediaType)
	w.WriteHeader(http.StatusCreated)

	if err := jsonapi.MarshalPayload(w, blogs); err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
	}
}

Links

If you need to include link objects along with response data, implement the Linkable interface for document-links, and RelationshipLinkable for relationship links:

func (post Post) JSONAPILinks() *Links {
	return &Links{
		"self": "href": fmt.Sprintf("https://example.com/posts/%d", post.ID),
		"comments": Link{
			Href: fmt.Sprintf("https://example.com/api/blogs/%d/comments", post.ID),
			Meta: map[string]interface{}{
				"counts": map[string]uint{
					"likes":    4,
				},
			},
		},
	}
}

// Invoked for each relationship defined on the Post struct when marshaled
func (post Post) JSONAPIRelationshipLinks(relation string) *Links {
	if relation == "comments" {
		return &Links{
			"related": fmt.Sprintf("https://example.com/posts/%d/comments", post.ID),
		}
	}
	return nil
}

Meta

If you need to include meta objects along with response data, implement the Metable interface for document-meta, and RelationshipMetable for relationship meta:

func (post Post) JSONAPIMeta() *Meta {
   return &Meta{
   	"details": "sample details here",
   }
}

// Invoked for each relationship defined on the Post struct when marshaled
func (post Post) JSONAPIRelationshipMeta(relation string) *Meta {
   if relation == "comments" {
   	return &Meta{
   		"this": map[string]interface{}{
   			"can": map[string]interface{}{
   				"go": []interface{}{
   					"as",
   					"deep",
   					map[string]interface{}{
   						"as": "required",
   					},
   				},
   			},
   		},
   	}
   }
   return nil
}

Errors

This package also implements support for JSON API compatible errors payloads using the following types.

MarshalErrors

MarshalErrors(w io.Writer, errs []*ErrorObject) error

Writes a JSON API response using the given []error.

ErrorsPayload

type ErrorsPayload struct {
	Errors []*ErrorObject `json:"errors"`
}

ErrorsPayload is a serializer struct for representing a valid JSON API errors payload.

ErrorObject

type ErrorObject struct { ... }

// Error implements the `Error` interface.
func (e *ErrorObject) Error() string {
	return fmt.Sprintf("Error: %s %s\n", e.Title, e.Detail)
}

ErrorObject is an Error implementation as well as an implementation of the JSON API error object.

The main idea behind this struct is that you can use it directly in your code as an error type and pass it directly to MarshalErrors to get a valid JSON API errors payload.

// An error has come up in your code, so set an appropriate status, and serialize the error.
if err := validate(&myStructToValidate); err != nil {
	context.SetStatusCode(http.StatusBadRequest) // Or however you need to set a status.
	jsonapi.MarshalErrors(w, []*ErrorObject{{
		Title: "Validation Error",
		Detail: "Given request body was invalid.",
		Status: "400",
		Meta: map[string]interface{}{"field": "some_field", "error": "bad type", "expected": "string", "received": "float64"},
	}})
	return
}

Testing

MarshalOnePayloadEmbedded

MarshalOnePayloadEmbedded(w io.Writer, model interface{}) error

Visit godoc

This method is not strictly meant to for use in implementation code, although feel free. It was mainly created for use in tests; in most cases, your request payloads for create will be embedded rather than sideloaded for related records. This method will serialize a single struct pointer into an embedded json response. In other words, there will be no, included, array in the json; all relationships will be serialized inline with the data.

However, in tests, you may want to construct payloads to post to create methods that are embedded to most closely model the payloads that will be produced by the client. This method aims to enable that.

Example

out := bytes.NewBuffer(nil)

// testModel returns a pointer to a Blog
jsonapi.MarshalOnePayloadEmbedded(out, testModel())

h := new(BlogsHandler)

w := httptest.NewRecorder()
r, _ := http.NewRequest(http.MethodPost, "/blogs", out)

h.CreateBlog(w, r)

blog := new(Blog)
jsonapi.UnmarshalPayload(w.Body, blog)

// ... assert stuff about blog here ...

Alternative Installation

I use git subtrees to manage dependencies rather than go get so that the src is committed to my repo.

git subtree add --squash --prefix=src/github.com/google/jsonapi https://github.com/google/jsonapi.git master

To update,

git subtree pull --squash --prefix=src/github.com/google/jsonapi https://github.com/google/jsonapi.git master

This assumes that I have my repo structured with a src dir containing a collection of packages and GOPATH is set to the root folder--containing src.

Contributing

Fork, Change, Pull Request with tests.