usage

README

gocrud

Go framework to simplify creating, reading, updating, and deleting arbitrary depth structured data — to make building REST services fast and easy.

• Link to blog posts
• Example Usage

Releases

Note that the master branch always refers to latest version of Gocrud, which would contain breaking changes. To use stable version of Gocrud APIs, please use the packages released via gopkg.in.

Gocrud version	Install instructions	Godoc	Source
v1 (stable)	go get -v gopkg.in/manishrjain/gocrud.v1/...	godoc	source
master (dev)	go get -v github.com/manishrjain/gocrud/...	godoc	source

Questions / Support

I hang out at the gophers.slack.com, at #gocrud channel. You can get an invitation to join Slack via this link: Gopher Slack Signup. You can also direct message me, my user id is @manishrjain.

Why?

_{Courtesy: Monish, co-founder karma.wiki}

Having built over 3 different startup backends, I think a lot of time is wasted figuring out and coding CRUD for data structures. In addition, the choice of database has to be made up front, which causes a lot of headache for startup founders. Gocrud was written with the aim to make CRUD easy, and provide the flexibility to switch out both the underlying storage and search engines at any stage of development.

Data stores

Datastore	Driver Available	Status
LevelDB	Yes	Ready
MySQL	Yes	Needs to implement Iterate func
PostgreSQL	Yes	Needs to implement Iterate func
Cassandra	Yes	Ready
MongoDB	Yes	Needs to implement Iterate func
Google Datastore	Yes	Needs to implement Iterate func
RethinkDB	Yes	Needs to implement Iterate func
Amazon DynamoDB	No	Needs work
Datastore usage shows how to use and initialize various datastores. One can add support for more by implementing this interface:

type Store interface {
  Init(args ...string)
  Commit(its []*x.Instruction) error
  IsNew(subject string) bool
  GetEntity(subject string) ([]x.Instruction, error)
  Iterate(fromId string, num int, ch chan x.Entity) (int, error)
}

Search engines

Search Engine	Drive Available
Elastic Search	Yes
Solr	No

Can be added by implementing these interfaces:

type Engine interface {
	Init(args ...string)
	Update(x.Doc) error
	NewQuery(kind string) Query
}

type Query interface {
	Limit(num int) Query
	Order(field string) Query
	Run() ([]x.Doc, error)
  // and few others
}

Framework

This framework is built to follow these principles:

1. Versioning: Keep track of all edits to the data, including deletion operations.
2. Authorship: Be able to track who edited (/deleted) what.
3. Retention: On deletion, only mark it as deleted. Never actually delete any data.

The framework makes it easy to have Parent-Child relationships, quite common in today’s CRUD operations. For e.g.

- Posts created by User (User -> Post)
- Comments on Posts (Post -> Comment)
- Likes on Posts (Post -> Like)
- Likes on Comments (Comment -> Like)

And be able to traverse these relationships and retrieve all of the children, grandchildren etc. For e.g. (User -> Post -> [(Comment -> Like), Like])

The framework does this by utilizing Graph operations, but without using a Graph database. This means the framework can be used to quickly build a Go backend to serve arbitrarily complex data, while still using your database of choice. See example usage

Dependency management

Users who import Gocrud into their packages are responsible to organize and maintain all of their dependencies to ensure code compatibility and build reproducibility. Gocrud makes no direct use of dependency management tools like Godep.

Performance considerations

For the example, this is what gets stored in the database:

mysql> select * from instructions;
+------------+--------------+-----------+--------------------------------------+-----------+---------------------+---------+----+
| subject_id | subject_type | predicate | object                               | object_id | nano_ts             | source  | id |
+------------+--------------+-----------+--------------------------------------+-----------+---------------------+---------+----+
| uid_oNM    | User         | Post      | NULL                                 | wClGp     | 1435408916326573229 | uid_oNM |  1 |
| wClGp      | Post         | body      | "You can search for cat videos here" |           | 1435408916326573229 | uid_oNM |  2 |
| wClGp      | Post         | tags      | ["search","cat","videos"]            |           | 1435408916326573229 | uid_oNM |  3 |
| wClGp      | Post         | url       | "www.google.com"                     |           | 1435408916326573229 | uid_oNM |  4 |
| wClGp      | Post         | Like      | NULL                                 | kStx9     | 1435408916341828408 | uid_qB3 |  5 |
| kStx9      | Like         | thumb     | 1                                    |           | 1435408916341828408 | uid_qB3 |  6 |
| wClGp      | Post         | Comment   | NULL                                 | 8f78r     | 1435408916341828408 | uid_qB3 |  7 |
| 8f78r      | Comment      | body      | "Comment by on the post"             |           | 1435408916341828408 | uid_qB3 |  8 |
| wClGp      | Post         | Like      | NULL                                 | Gyd7G     | 1435408916352622582 | uid_a30 |  9 |
| Gyd7G      | Like         | thumb     | 1                                    |           | 1435408916352622582 | uid_a30 | 10 |
| 8f78r      | Comment      | Like      | NULL                                 | q2IKK     | 1435408916357443075 | uid_I5u | 11 |
| q2IKK      | Like         | thumb     | 1                                    |           | 1435408916357443075 | uid_I5u | 12 |
| 8f78r      | Comment      | Comment   | NULL                                 | g8llL     | 1435408916357443075 | uid_I5u | 13 |
| g8llL      | Comment      | body      | "Comment xv on comment"              |           | 1435408916357443075 | uid_I5u | 14 |
| q2IKK      | Like         | Comment   | NULL                                 | oaztb     | 1435408916368908590 | uid_SPX | 15 |
| oaztb      | Comment      | body      | "Comment kL on Like"                 |           | 1435408916368908590 | uid_SPX | 16 |
| 8f78r      | Comment      | censored  | true                                 |           | 1435408916377065650 | uid_D2g | 17 |
| kStx9      | Like         | _delete_  | true                                 |           | 1435408916384422689 | uid_2a5 | 18 |
+------------+--------------+-----------+--------------------------------------+-----------+---------------------+---------+----+
18 rows in set (0.00 sec)

The writes are in constant time, where each (entity,predicate) constitutes one row. As the properties per entity grow, more rows need to be read (1 row = 1 edge/predicate) to get the entity, it's predicates and it's children. This however, shouldn't be much of a concern for any standard data, which has limited number of predicates/properties per entity. Gocrud in addition, retrieves all children in parallel via goroutines, instead of retrieving them one by one.

Property value filtering, sorting, full and partial text matching are now being made available via various search engines. Gocrud provides a search interface, which provides the most common search functionality right out of the box. Thus, there's a clear distinction between data store and search right from the beginning.

Reserved keywords

The following predicates are reserved by the framework, and shouldn't be used by the caller. Currently, this guideline isn't being hardly enforced by the framework.

Predicate	Meaning
_parent_	Stores an edge from child -> parent entity.
_delete_	Marks a particular entity as deleted.

Contact

Feel free to contact me at my Twitter handle @manishrjain for any discussions related to this framework. Also, feel free to send pull requests, they're welcome!

Documentation

Overview

Usage is a dummy package to showcase how to use gocrud with various examples.

Index

• func Search()
• func Store()

Examples

• Search
• Store

Functions

func Search

func Search()

Example

package main

import (
	"fmt"
	"io/ioutil"
	"time"

	_ "gopkg.in/manishrjain/gocrud.v1/drivers/leveldb"
	_ "gopkg.in/manishrjain/gocrud.v1/drivers/memsearch"
	"gopkg.in/manishrjain/gocrud.v1/indexer"
	"gopkg.in/manishrjain/gocrud.v1/req"
	"gopkg.in/manishrjain/gocrud.v1/search"
	"gopkg.in/manishrjain/gocrud.v1/store"
	"gopkg.in/manishrjain/gocrud.v1/x"
)

var log = x.Log("usage")

type SimpleIndexer struct {
}

func (si SimpleIndexer) OnUpdate(e x.Entity) (result []x.Entity) {
	result = append(result, e)
	return
}

func (si SimpleIndexer) Regenerate(e x.Entity) (rdoc x.Doc) {
	rdoc.Id = e.Id
	rdoc.Kind = e.Kind
	rdoc.NanoTs = time.Now().UnixNano()

	result, err := store.NewQuery(e.Id).Run()
	if err != nil {
		x.LogErr(log, err).Fatal("While querying store")
		return
	}
	data := result.ToMap()
	rdoc.Data = data
	return
}

var particles = [...]string{
	"up", "charm", "top", "gluon", "down", "strange",
	"bottom", "photon", "boson", "higgs boson",
}

func main() {
	path, err := ioutil.TempDir("", "gocrudldb_")
	if err != nil {
		x.LogErr(log, err).Fatal("Opening file")
		return
	}
	store.Get().Init(path) // leveldb
	search.Get().Init()    // memsearch

	// Run indexer to update entities in search engine in real time.
	c := req.NewContextWithUpdates(10, 100)
	indexer.Register("Child", SimpleIndexer{})
	indexer.Run(c, 2)

	u := store.NewUpdate("Root", "bigbang").SetSource("author")
	for i := 0; i < 10; i++ {
		child := u.AddChild("Child").Set("pos", i).Set("particle", particles[i])
		if i == 5 {
			child.MarkDeleted() // This shouldn't be retrieved anymore.
		}
	}
	if err = u.Execute(c); err != nil {
		x.LogErr(log, err).Fatal("While updating")
		return
	}

	indexer.WaitForDone(c) // Block until indexing is done.

	docs, err := search.Get().NewQuery("Child").Order("-data.pos").Run()
	if err != nil {
		x.LogErr(log, err).Fatal("While searching")
		return
	}
	fmt.Println("docs:", len(docs))
	for _, doc := range docs {
		m := doc.Data.(map[string]interface{})
		fmt.Println(m["pos"], m["particle"])
	}

}

Output:

docs: 9
9 higgs boson
8 boson
7 photon
6 bottom
4 down
3 gluon
2 top
1 charm
0 up

func Store

func Store()

Example

package main

import (
	"fmt"
	"io/ioutil"

	_ "gopkg.in/manishrjain/gocrud.v1/drivers/leveldb"
	_ "gopkg.in/manishrjain/gocrud.v1/drivers/memsearch"
	"gopkg.in/manishrjain/gocrud.v1/req"
	"gopkg.in/manishrjain/gocrud.v1/store"
	"gopkg.in/manishrjain/gocrud.v1/x"
)

var log = x.Log("usage")

func main() {
	path, err := ioutil.TempDir("", "gocrudldb_")
	if err != nil {
		x.LogErr(log, err).Fatal("Opening file")
		return
	}
	store.Get().Init(path) // leveldb

	// Update some data.
	c := req.NewContext(10) // 62^10 permutations
	err = store.NewUpdate("Root", "bigbang").SetSource("author").
		Set("when", "13.8 billion years ago").Set("explosive", true).Execute(c)
	if err != nil {
		x.LogErr(log, err).Fatal("Commiting update")
		return
	}

	// Retrieve that data
	result, err := store.NewQuery("bigbang").Run()
	if err != nil {
		x.LogErr(log, err).Fatal("While querying store")
		return
	}
	fmt.Println(result.Kind) // Root
	fmt.Println(result.Id)   // bigbang

	data := result.ToMap()
	{
		val, ok := data["explosive"]
		if !ok {
			log.Fatal("creator should be set")
			return
		}
		fmt.Println(val) // true
	}
	{
		val, ok := data["when"]
		if !ok {
			log.Fatal("creator should be set")
			return
		}
		fmt.Println(val)
	}
}

Output:

Root
bigbang
true
13.8 billion years ago