ArangoDB GO Driver - Getting Started

Supported versions

  • ArangoDB versions 3.1 and up.
    • Single server & cluster setups
    • With or without authentication
  • Go 1.7 and up.

Go dependencies

  • None (Additional error libraries are supported).

Configuration

To use the driver, first fetch the sources into your GOPATH.

go get github.com/arangodb/go-driver

Using the driver, you always need to create a Client. The following example shows how to create a Client for a single server running on localhost.

import (
	"fmt"

	driver "github.com/arangodb/go-driver"
	"github.com/arangodb/go-driver/http"
)

...

conn, err := http.NewConnection(http.ConnectionConfig{
    Endpoints: []string{"http://localhost:8529"},
})
if err != nil {
    // Handle error
}
c, err := driver.NewClient(driver.ClientConfig{
    Connection: conn,
})
if err != nil {
    // Handle error
}

Once you have a Client you can access/create databases on the server, access/create collections, graphs, documents and so on.

The following example shows how to open an existing collection in an existing database and create a new document in that collection.

// Open "examples_books" database
db, err := c.Database(nil, "examples_books")
if err != nil {
    // Handle error
}

// Open "books" collection
col, err := db.Collection(nil, "books")
if err != nil {
    // Handle error
}

// Create document
book := Book{
    Title:   "ArangoDB Cookbook",
    NoPages: 257,
}
meta, err := col.CreateDocument(nil, book)
if err != nil {
    // Handle error
}
fmt.Printf("Created document in collection '%s' in database '%s'\n", col.Name(), db.Name())

API design

Concurrency

All functions of the driver are stricly synchronous. They operate and only return a value (or error) when they’re done.

If you want to run operations concurrently, use a go routine. All objects in the driver are designed to be used from multiple concurrent go routines, except Cursor.

All database objects (except Cursor) are considered static. After their creation they won’t change. E.g. after creating a Collection instance you can remove the collection, but the (Go) instance will still be there. Calling functions on such a removed collection will of course fail.

Structured error handling & wrapping

All functions of the driver that can fail return an error value. If that value is not nil, the function call is considered to be failed. In that case all other return values are set to their zero values.

All errors are structured using error checking functions named Is<SomeErrorCategory>. E.g. IsNotFound(error) return true if the given error is of the category “not found”. There can be multiple internal error codes that all map onto the same category.

All errors returned from any function of the driver (either internal or exposed) wrap errors using the WithStack function. This can be used to provide detail stack trackes in case of an error. All error checking functions use the Cause function to get the cause of an error instead of the error wrapper.

Note that WithStack and Cause are actually variables to you can implement it using your own error wrapper library.

If you for example use github.com/pkg/errors, you want to initialize to go driver like this:

import (
    driver "github.com/arangodb/go-driver"
    "github.com/pkg/errors"
)

func init() {
    driver.WithStack = errors.WithStack 
    driver.Cause = errors.Cause
}

Context aware

All functions of the driver that involve some kind of long running operation or support additional options not given as function arguments, have a context.Context argument. This enables you cancel running requests, pass timeouts/deadlines and pass additional options.

In all methods that take a context.Context argument you can pass nil as value. This is equivalent to passing context.Background().

Many functions support 1 or more optional (and infrequently used) additional options. These can be used with a With<OptionName> function. E.g. to force a create document call to wait until the data is synchronized to disk, use a prepared context like this:

ctx := driver.WithWaitForSync(parentContext)
collection.CreateDocument(ctx, yourDocument)