httpvar

Documentation

Overview

Package httpvar provides a runtimevar implementation with variables backed by http endpoint. Use OpenVariable to construct a *runtimevar.Variable.

URLs

For runtimevar.OpenVariable, httpvar registers for the schemes "http" and "https". The default URL opener will use http.DefaultClient. To customize the URL opener, or for more details on the URL format, see URLOpener. See https://gocloud.dev/concepts/urls/ for background information.

As

httpvar exposes the following types for As:

• Snapshot: *http.Response
• Error: httpvar.RequestError, url.Error

Example (OpenVariableFromURL)

package main

import (
	"context"
	"log"

	"gocloud.dev/runtimevar"
)

func main() {
	// PRAGMA: This example is used on gocloud.dev; PRAGMA comments adjust how it is shown and can be ignored.
	// PRAGMA: On gocloud.dev, add a blank import: _ "gocloud.dev/runtimevar/httpvar"
	// PRAGMA: On gocloud.dev, hide lines until the next blank line.
	ctx := context.Background()

	// runtimevar.OpenVariable creates a *runtimevar.Variable from a URL.
	// The default opener connects to an etcd server based on the environment
	// variable ETCD_SERVER_URL.

	v, err := runtimevar.OpenVariable(ctx, "http://myserver.com/foo.txt?decoder=string")
	if err != nil {
		log.Fatal(err)
	}
	defer v.Close()
}

Index

• Variables
• func OpenVariable(client *http.Client, urlStr string, decoder *runtimevar.Decoder, opts *Options) (*runtimevar.Variable, error)
• type Options
• type RequestError
  • func (e *RequestError) Error() string
• type URLOpener
  • func (o *URLOpener) OpenVariableURL(ctx context.Context, u *url.URL) (*runtimevar.Variable, error)

Examples

• Package (OpenVariableFromURL)
• OpenVariable

Variables

var Schemes = []string{"http", "https"}

Schemes are the URL schemes httpvar registers its URLOpener under on runtimevar.DefaultMux.

Functions

func OpenVariable

func OpenVariable(client *http.Client, urlStr string, decoder *runtimevar.Decoder, opts *Options) (*runtimevar.Variable, error)

OpenVariable constructs a *runtimevar.Variable that uses client to retrieve the variable contents from the URL urlStr.

Example

package main

import (
	"log"
	"net/http"

	"gocloud.dev/runtimevar"
	"gocloud.dev/runtimevar/httpvar"
)

func main() {
	// PRAGMA: This example is used on gocloud.dev; PRAGMA comments adjust how it is shown and can be ignored.

	// Create an HTTP.Client
	httpClient := http.DefaultClient

	// Construct a *runtimevar.Variable that watches the page.
	v, err := httpvar.OpenVariable(httpClient, "http://example.com", runtimevar.StringDecoder, nil)
	if err != nil {
		log.Fatal(err)
	}
	defer v.Close()
}

Types

type Options

type Options struct {
	// WaitDuration controls the rate at which the HTTP endpoint is called to check for changes.
	// Defaults to 30 seconds.
	WaitDuration time.Duration
}

Options sets options.

type RequestError

type RequestError struct {
	Response *http.Response
}

RequestError represents an HTTP error that occurred during endpoint call.

func (*RequestError) Error

func (e *RequestError) Error() string

type URLOpener

type URLOpener struct {
	// The Client to use; required.
	Client *http.Client

	// Decoder specifies the decoder to use if one is not specified in the URL.
	// Defaults to runtimevar.BytesDecoder.
	Decoder *runtimevar.Decoder

	// Options specifies the options to pass to OpenVariable.
	Options Options
}

URLOpener opens HTTP URLs like "http://myserver.com/foo.txt".

The full URL, including scheme, is used as the endpoint, except that the the following URL parameters are removed if present:

• decoder: The decoder to use. Defaults to runtimevar.BytesDecoder. See runtimevar.DecoderByName for supported values.

func (*URLOpener) OpenVariableURL

func (o *URLOpener) OpenVariableURL(ctx context.Context, u *url.URL) (*runtimevar.Variable, error)

OpenVariableURL opens a httpvar Variable for u.