gocloud.devgocloud.dev/runtimevar/blobvar Index | Examples | Files

package blobvar

import "gocloud.dev/runtimevar/blobvar"

Package blobvar provides a runtimevar implementation with variables read from a blob.Bucket. Use NewVariable to construct a *runtimevar.Variable.

As

blobvar exposes the following types for As:

Index

Examples

Functions

func NewVariable

func NewVariable(bucket *blob.Bucket, key string, decoder *runtimevar.Decoder, opts *Options) (*runtimevar.Variable, error)

NewVariable constructs a *runtimevar.Variable backed by the referenced blob. Reads of the blob return raw bytes; provide a decoder to decode the raw bytes into the appropriate type for runtimevar.Snapshot.Value. See the runtimevar package documentation for examples of decoders.

Example

Code:play 

package main

import (
	"context"
	"fmt"
	"log"

	"gocloud.dev/blob/memblob"
	"gocloud.dev/runtimevar"
	"gocloud.dev/runtimevar/blobvar"
)

// MyConfig is a sample configuration struct.
type MyConfig struct {
	Server string
	Port   int
}

// jsonCreds is a fake GCP JSON credentials file.
const jsonCreds = `
{
  "type": "service_account",
  "project_id": "my-project-id"
}
`

func main() {
	ctx := context.Background()

	// Create a *blob.Bucket.
	// Here, we use an in-memory implementation.
	bucket := memblob.OpenBucket(nil)

	// Create a decoder for decoding JSON strings into MyConfig.
	decoder := runtimevar.NewDecoder(MyConfig{}, runtimevar.JSONDecode)

	// Construct a *runtimevar.Variable that watches the blob.
	v, err := blobvar.NewVariable(bucket, "blob name", decoder, nil)
	if err != nil {
		log.Fatal(err)
	}
	defer v.Close()

	// You can now read the current value of the variable from v.
	snapshot, err := v.Watch(ctx)
	if err != nil {
		// This is expected due to the fake credentials we used above.
		fmt.Println("Watch failed due to blob not existing")
		return
	}
	// We'll never get here when running this sample, but the resulting
	// runtimevar.Snapshot.Value would be of type MyConfig.
	log.Printf("Snapshot.Value: %#v", snapshot.Value.(MyConfig))

}

Output:

Watch failed due to blob not existing

Types

type Options

type Options struct {
	// WaitDuration controls the rate at which the blob is polled.
	// Defaults to 30 seconds.
	WaitDuration time.Duration
}

Options sets options.

Source Files

blobvar.go

Version
v0.9.0
Published
Jan 15, 2019
Platform
js/wasm
Imports
6 packages
Last checked
3 hours ago

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