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metadata.go
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metadata.go
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// Copyright 2014 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package metadata provides access to Google Compute Engine (GCE)
// metadata and API service accounts.
//
// This package is a wrapper around the GCE metadata service,
// as documented at https://cloud.google.com/compute/docs/metadata/overview.
package metadata // import "cloud.google.com/go/compute/metadata"
import (
"context"
"encoding/json"
"fmt"
"io"
"net"
"net/http"
"net/url"
"os"
"strings"
"sync"
"time"
)
const (
// metadataIP is the documented metadata server IP address.
metadataIP = "169.254.169.254"
// metadataHostEnv is the environment variable specifying the
// GCE metadata hostname. If empty, the default value of
// metadataIP ("169.254.169.254") is used instead.
// This is variable name is not defined by any spec, as far as
// I know; it was made up for the Go package.
metadataHostEnv = "GCE_METADATA_HOST"
userAgent = "gcloud-golang/0.1"
)
type cachedValue struct {
k string
trim bool
mu sync.Mutex
v string
}
var (
projID = &cachedValue{k: "project/project-id", trim: true}
projNum = &cachedValue{k: "project/numeric-project-id", trim: true}
instID = &cachedValue{k: "instance/id", trim: true}
)
var defaultClient = &Client{hc: newDefaultHTTPClient()}
func newDefaultHTTPClient() *http.Client {
return &http.Client{
Transport: &http.Transport{
Dial: (&net.Dialer{
Timeout: 2 * time.Second,
KeepAlive: 30 * time.Second,
}).Dial,
IdleConnTimeout: 60 * time.Second,
},
Timeout: 5 * time.Second,
}
}
// NotDefinedError is returned when requested metadata is not defined.
//
// The underlying string is the suffix after "/computeMetadata/v1/".
//
// This error is not returned if the value is defined to be the empty
// string.
type NotDefinedError string
func (suffix NotDefinedError) Error() string {
return fmt.Sprintf("metadata: GCE metadata %q not defined", string(suffix))
}
func (c *cachedValue) get(ctx context.Context, cl *Client) (v string, err error) {
defer c.mu.Unlock()
c.mu.Lock()
if c.v != "" {
return c.v, nil
}
if c.trim {
v, err = cl.getTrimmed(ctx, c.k)
} else {
v, err = cl.GetWithContext(ctx, c.k)
}
if err == nil {
c.v = v
}
return
}
var (
onGCEOnce sync.Once
onGCE bool
)
// OnGCE reports whether this process is running on Google Compute Platforms.
// NOTE: True returned from `OnGCE` does not guarantee that the metadata server
// is accessible from this process and have all the metadata defined.
func OnGCE() bool {
onGCEOnce.Do(initOnGCE)
return onGCE
}
func initOnGCE() {
onGCE = testOnGCE()
}
func testOnGCE() bool {
// The user explicitly said they're on GCE, so trust them.
if os.Getenv(metadataHostEnv) != "" {
return true
}
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
resc := make(chan bool, 2)
// Try two strategies in parallel.
// See https://github.com/googleapis/google-cloud-go/issues/194
go func() {
req, _ := http.NewRequest("GET", "http://"+metadataIP, nil)
req.Header.Set("User-Agent", userAgent)
res, err := newDefaultHTTPClient().Do(req.WithContext(ctx))
if err != nil {
resc <- false
return
}
defer res.Body.Close()
resc <- res.Header.Get("Metadata-Flavor") == "Google"
}()
go func() {
resolver := &net.Resolver{}
addrs, err := resolver.LookupHost(ctx, "metadata.google.internal.")
if err != nil || len(addrs) == 0 {
resc <- false
return
}
resc <- strsContains(addrs, metadataIP)
}()
tryHarder := systemInfoSuggestsGCE()
if tryHarder {
res := <-resc
if res {
// The first strategy succeeded, so let's use it.
return true
}
// Wait for either the DNS or metadata server probe to
// contradict the other one and say we are running on
// GCE. Give it a lot of time to do so, since the system
// info already suggests we're running on a GCE BIOS.
timer := time.NewTimer(5 * time.Second)
defer timer.Stop()
select {
case res = <-resc:
return res
case <-timer.C:
// Too slow. Who knows what this system is.
return false
}
}
// There's no hint from the system info that we're running on
// GCE, so use the first probe's result as truth, whether it's
// true or false. The goal here is to optimize for speed for
// users who are NOT running on GCE. We can't assume that
// either a DNS lookup or an HTTP request to a blackholed IP
// address is fast. Worst case this should return when the
// metaClient's Transport.ResponseHeaderTimeout or
// Transport.Dial.Timeout fires (in two seconds).
return <-resc
}
// Subscribe calls Client.SubscribeWithContext on the default client.
//
// Deprecated: Please use the context aware variant [SubscribeWithContext].
func Subscribe(suffix string, fn func(v string, ok bool) error) error {
return defaultClient.SubscribeWithContext(context.Background(), suffix, func(ctx context.Context, v string, ok bool) error { return fn(v, ok) })
}
// SubscribeWithContext calls Client.SubscribeWithContext on the default client.
func SubscribeWithContext(ctx context.Context, suffix string, fn func(ctx context.Context, v string, ok bool) error) error {
return defaultClient.SubscribeWithContext(ctx, suffix, fn)
}
// Get calls Client.GetWithContext on the default client.
//
// Deprecated: Please use the context aware variant [GetWithContext].
func Get(suffix string) (string, error) {
return defaultClient.GetWithContext(context.Background(), suffix)
}
// GetWithContext calls Client.GetWithContext on the default client.
func GetWithContext(ctx context.Context, suffix string) (string, error) {
return defaultClient.GetWithContext(ctx, suffix)
}
// ProjectID returns the current instance's project ID string.
//
// Deprecated: Please use the context aware variant [ProjectIDWithContext].
func ProjectID() (string, error) {
return defaultClient.ProjectIDWithContext(context.Background())
}
// ProjectIDWithContext returns the current instance's project ID string.
func ProjectIDWithContext(ctx context.Context) (string, error) {
return defaultClient.ProjectIDWithContext(ctx)
}
// NumericProjectID returns the current instance's numeric project ID.
//
// Deprecated: Please use the context aware variant [NumericProjectIDWithContext].
func NumericProjectID() (string, error) {
return defaultClient.NumericProjectIDWithContext(context.Background())
}
// NumericProjectIDWithContext returns the current instance's numeric project ID.
func NumericProjectIDWithContext(ctx context.Context) (string, error) {
return defaultClient.NumericProjectIDWithContext(ctx)
}
// InternalIP returns the instance's primary internal IP address.
//
// Deprecated: Please use the context aware variant [InternalIPWithContext].
func InternalIP() (string, error) {
return defaultClient.InternalIPWithContext(context.Background())
}
// InternalIPWithContext returns the instance's primary internal IP address.
func InternalIPWithContext(ctx context.Context) (string, error) {
return defaultClient.InternalIPWithContext(ctx)
}
// ExternalIP returns the instance's primary external (public) IP address.
//
// Deprecated: Please use the context aware variant [ExternalIPWithContext].
func ExternalIP() (string, error) {
return defaultClient.ExternalIPWithContext(context.Background())
}
// ExternalIPWithContext returns the instance's primary external (public) IP address.
func ExternalIPWithContext(ctx context.Context) (string, error) {
return defaultClient.ExternalIPWithContext(ctx)
}
// Email calls Client.EmailWithContext on the default client.
//
// Deprecated: Please use the context aware variant [EmailWithContext].
func Email(serviceAccount string) (string, error) {
return defaultClient.EmailWithContext(context.Background(), serviceAccount)
}
// EmailWithContext calls Client.EmailWithContext on the default client.
func EmailWithContext(ctx context.Context, serviceAccount string) (string, error) {
return defaultClient.EmailWithContext(ctx, serviceAccount)
}
// Hostname returns the instance's hostname. This will be of the form
// "<instanceID>.c.<projID>.internal".
//
// Deprecated: Please use the context aware variant [HostnameWithContext].
func Hostname() (string, error) {
return defaultClient.HostnameWithContext(context.Background())
}
// HostnameWithContext returns the instance's hostname. This will be of the form
// "<instanceID>.c.<projID>.internal".
func HostnameWithContext(ctx context.Context) (string, error) {
return defaultClient.HostnameWithContext(ctx)
}
// InstanceTags returns the list of user-defined instance tags,
// assigned when initially creating a GCE instance.
//
// Deprecated: Please use the context aware variant [InstanceTagsWithContext].
func InstanceTags() ([]string, error) {
return defaultClient.InstanceTagsWithContext(context.Background())
}
// InstanceTagsWithContext returns the list of user-defined instance tags,
// assigned when initially creating a GCE instance.
func InstanceTagsWithContext(ctx context.Context) ([]string, error) {
return defaultClient.InstanceTagsWithContext(ctx)
}
// InstanceID returns the current VM's numeric instance ID.
//
// Deprecated: Please use the context aware variant [InstanceIDWithContext].
func InstanceID() (string, error) {
return defaultClient.InstanceIDWithContext(context.Background())
}
// InstanceIDWithContext returns the current VM's numeric instance ID.
func InstanceIDWithContext(ctx context.Context) (string, error) {
return defaultClient.InstanceIDWithContext(ctx)
}
// InstanceName returns the current VM's instance ID string.
//
// Deprecated: Please use the context aware variant [InstanceNameWithContext].
func InstanceName() (string, error) {
return defaultClient.InstanceNameWithContext(context.Background())
}
// InstanceNameWithContext returns the current VM's instance ID string.
func InstanceNameWithContext(ctx context.Context) (string, error) {
return defaultClient.InstanceNameWithContext(ctx)
}
// Zone returns the current VM's zone, such as "us-central1-b".
//
// Deprecated: Please use the context aware variant [ZoneWithContext].
func Zone() (string, error) {
return defaultClient.ZoneWithContext(context.Background())
}
// ZoneWithContext returns the current VM's zone, such as "us-central1-b".
func ZoneWithContext(ctx context.Context) (string, error) {
return defaultClient.ZoneWithContext(ctx)
}
// InstanceAttributes calls Client.InstanceAttributesWithContext on the default client.
//
// Deprecated: Please use the context aware variant [InstanceAttributesWithContext.
func InstanceAttributes() ([]string, error) {
return defaultClient.InstanceAttributesWithContext(context.Background())
}
// InstanceAttributesWithContext calls Client.ProjectAttributesWithContext on the default client.
func InstanceAttributesWithContext(ctx context.Context) ([]string, error) {
return defaultClient.InstanceAttributesWithContext(ctx)
}
// ProjectAttributes calls Client.ProjectAttributesWithContext on the default client.
//
// Deprecated: Please use the context aware variant [ProjectAttributesWithContext].
func ProjectAttributes() ([]string, error) {
return defaultClient.ProjectAttributesWithContext(context.Background())
}
// ProjectAttributesWithContext calls Client.ProjectAttributesWithContext on the default client.
func ProjectAttributesWithContext(ctx context.Context) ([]string, error) {
return defaultClient.ProjectAttributesWithContext(ctx)
}
// InstanceAttributeValue calls Client.InstanceAttributeValueWithContext on the default client.
//
// Deprecated: Please use the context aware variant [InstanceAttributeValueWithContext].
func InstanceAttributeValue(attr string) (string, error) {
return defaultClient.InstanceAttributeValueWithContext(context.Background(), attr)
}
// InstanceAttributeValueWithContext calls Client.InstanceAttributeValueWithContext on the default client.
func InstanceAttributeValueWithContext(ctx context.Context, attr string) (string, error) {
return defaultClient.InstanceAttributeValueWithContext(ctx, attr)
}
// ProjectAttributeValue calls Client.ProjectAttributeValueWithContext on the default client.
//
// Deprecated: Please use the context aware variant [ProjectAttributeValueWithContext].
func ProjectAttributeValue(attr string) (string, error) {
return defaultClient.ProjectAttributeValueWithContext(context.Background(), attr)
}
// ProjectAttributeValueWithContext calls Client.ProjectAttributeValueWithContext on the default client.
func ProjectAttributeValueWithContext(ctx context.Context, attr string) (string, error) {
return defaultClient.ProjectAttributeValueWithContext(ctx, attr)
}
// Scopes calls Client.ScopesWithContext on the default client.
//
// Deprecated: Please use the context aware variant [ScopesWithContext].
func Scopes(serviceAccount string) ([]string, error) {
return defaultClient.ScopesWithContext(context.Background(), serviceAccount)
}
// ScopesWithContext calls Client.ScopesWithContext on the default client.
func ScopesWithContext(ctx context.Context, serviceAccount string) ([]string, error) {
return defaultClient.ScopesWithContext(ctx, serviceAccount)
}
func strsContains(ss []string, s string) bool {
for _, v := range ss {
if v == s {
return true
}
}
return false
}
// A Client provides metadata.
type Client struct {
hc *http.Client
}
// NewClient returns a Client that can be used to fetch metadata.
// Returns the client that uses the specified http.Client for HTTP requests.
// If nil is specified, returns the default client.
func NewClient(c *http.Client) *Client {
if c == nil {
return defaultClient
}
return &Client{hc: c}
}
// getETag returns a value from the metadata service as well as the associated ETag.
// This func is otherwise equivalent to Get.
func (c *Client) getETag(ctx context.Context, suffix string) (value, etag string, err error) {
// Using a fixed IP makes it very difficult to spoof the metadata service in
// a container, which is an important use-case for local testing of cloud
// deployments. To enable spoofing of the metadata service, the environment
// variable GCE_METADATA_HOST is first inspected to decide where metadata
// requests shall go.
host := os.Getenv(metadataHostEnv)
if host == "" {
// Using 169.254.169.254 instead of "metadata" here because Go
// binaries built with the "netgo" tag and without cgo won't
// know the search suffix for "metadata" is
// ".google.internal", and this IP address is documented as
// being stable anyway.
host = metadataIP
}
suffix = strings.TrimLeft(suffix, "/")
u := "http://" + host + "/computeMetadata/v1/" + suffix
req, err := http.NewRequestWithContext(ctx, "GET", u, nil)
if err != nil {
return "", "", err
}
req.Header.Set("Metadata-Flavor", "Google")
req.Header.Set("User-Agent", userAgent)
var res *http.Response
var reqErr error
retryer := newRetryer()
for {
res, reqErr = c.hc.Do(req)
var code int
if res != nil {
code = res.StatusCode
}
if delay, shouldRetry := retryer.Retry(code, reqErr); shouldRetry {
if res != nil && res.Body != nil {
res.Body.Close()
}
if err := sleep(ctx, delay); err != nil {
return "", "", err
}
continue
}
break
}
if reqErr != nil {
return "", "", reqErr
}
defer res.Body.Close()
if res.StatusCode == http.StatusNotFound {
return "", "", NotDefinedError(suffix)
}
all, err := io.ReadAll(res.Body)
if err != nil {
return "", "", err
}
if res.StatusCode != 200 {
return "", "", &Error{Code: res.StatusCode, Message: string(all)}
}
return string(all), res.Header.Get("Etag"), nil
}
// Get returns a value from the metadata service.
// The suffix is appended to "http://${GCE_METADATA_HOST}/computeMetadata/v1/".
//
// If the GCE_METADATA_HOST environment variable is not defined, a default of
// 169.254.169.254 will be used instead.
//
// If the requested metadata is not defined, the returned error will
// be of type NotDefinedError.
//
// Deprecated: Please use the context aware variant [Client.GetWithContext].
func (c *Client) Get(suffix string) (string, error) {
return c.GetWithContext(context.Background(), suffix)
}
// GetWithContext returns a value from the metadata service.
// The suffix is appended to "http://${GCE_METADATA_HOST}/computeMetadata/v1/".
//
// If the GCE_METADATA_HOST environment variable is not defined, a default of
// 169.254.169.254 will be used instead.
//
// If the requested metadata is not defined, the returned error will
// be of type NotDefinedError.
//
// NOTE: Without an extra deadline in the context this call can take in the
// worst case, with internal backoff retries, up to 15 seconds (e.g. when server
// is responding slowly). Pass context with additional timeouts when needed.
func (c *Client) GetWithContext(ctx context.Context, suffix string) (string, error) {
val, _, err := c.getETag(ctx, suffix)
return val, err
}
func (c *Client) getTrimmed(ctx context.Context, suffix string) (s string, err error) {
s, err = c.GetWithContext(ctx, suffix)
s = strings.TrimSpace(s)
return
}
func (c *Client) lines(ctx context.Context, suffix string) ([]string, error) {
j, err := c.GetWithContext(ctx, suffix)
if err != nil {
return nil, err
}
s := strings.Split(strings.TrimSpace(j), "\n")
for i := range s {
s[i] = strings.TrimSpace(s[i])
}
return s, nil
}
// ProjectID returns the current instance's project ID string.
//
// Deprecated: Please use the context aware variant [Client.ProjectIDWithContext].
func (c *Client) ProjectID() (string, error) { return c.ProjectIDWithContext(context.Background()) }
// ProjectIDWithContext returns the current instance's project ID string.
func (c *Client) ProjectIDWithContext(ctx context.Context) (string, error) { return projID.get(ctx, c) }
// NumericProjectID returns the current instance's numeric project ID.
//
// Deprecated: Please use the context aware variant [Client.NumericProjectIDWithContext].
func (c *Client) NumericProjectID() (string, error) {
return c.NumericProjectIDWithContext(context.Background())
}
// NumericProjectIDWithContext returns the current instance's numeric project ID.
func (c *Client) NumericProjectIDWithContext(ctx context.Context) (string, error) {
return projNum.get(ctx, c)
}
// InstanceID returns the current VM's numeric instance ID.
//
// Deprecated: Please use the context aware variant [Client.InstanceIDWithContext].
func (c *Client) InstanceID() (string, error) {
return c.InstanceIDWithContext(context.Background())
}
// InstanceIDWithContext returns the current VM's numeric instance ID.
func (c *Client) InstanceIDWithContext(ctx context.Context) (string, error) {
return instID.get(ctx, c)
}
// InternalIP returns the instance's primary internal IP address.
//
// Deprecated: Please use the context aware variant [Client.InternalIPWithContext].
func (c *Client) InternalIP() (string, error) {
return c.InternalIPWithContext(context.Background())
}
// InternalIPWithContext returns the instance's primary internal IP address.
func (c *Client) InternalIPWithContext(ctx context.Context) (string, error) {
return c.getTrimmed(ctx, "instance/network-interfaces/0/ip")
}
// Email returns the email address associated with the service account.
//
// Deprecated: Please use the context aware variant [Client.EmailWithContext].
func (c *Client) Email(serviceAccount string) (string, error) {
return c.EmailWithContext(context.Background(), serviceAccount)
}
// EmailWithContext returns the email address associated with the service account.
// The serviceAccount parameter default value (empty string or "default" value)
// will use the instance's main account.
func (c *Client) EmailWithContext(ctx context.Context, serviceAccount string) (string, error) {
if serviceAccount == "" {
serviceAccount = "default"
}
return c.getTrimmed(ctx, "instance/service-accounts/"+serviceAccount+"/email")
}
// ExternalIP returns the instance's primary external (public) IP address.
//
// Deprecated: Please use the context aware variant [Client.ExternalIPWithContext].
func (c *Client) ExternalIP() (string, error) {
return c.ExternalIPWithContext(context.Background())
}
// ExternalIPWithContext returns the instance's primary external (public) IP address.
func (c *Client) ExternalIPWithContext(ctx context.Context) (string, error) {
return c.getTrimmed(ctx, "instance/network-interfaces/0/access-configs/0/external-ip")
}
// Hostname returns the instance's hostname. This will be of the form
// "<instanceID>.c.<projID>.internal".
//
// Deprecated: Please use the context aware variant [Client.HostnameWithContext].
func (c *Client) Hostname() (string, error) {
return c.HostnameWithContext(context.Background())
}
// HostnameWithContext returns the instance's hostname. This will be of the form
// "<instanceID>.c.<projID>.internal".
func (c *Client) HostnameWithContext(ctx context.Context) (string, error) {
return c.getTrimmed(ctx, "instance/hostname")
}
// InstanceTags returns the list of user-defined instance tags.
//
// Deprecated: Please use the context aware variant [Client.InstanceTagsWithContext].
func (c *Client) InstanceTags() ([]string, error) {
return c.InstanceTagsWithContext(context.Background())
}
// InstanceTagsWithContext returns the list of user-defined instance tags,
// assigned when initially creating a GCE instance.
func (c *Client) InstanceTagsWithContext(ctx context.Context) ([]string, error) {
var s []string
j, err := c.GetWithContext(ctx, "instance/tags")
if err != nil {
return nil, err
}
if err := json.NewDecoder(strings.NewReader(j)).Decode(&s); err != nil {
return nil, err
}
return s, nil
}
// InstanceName returns the current VM's instance ID string.
//
// Deprecated: Please use the context aware variant [Client.InstanceNameWithContext].
func (c *Client) InstanceName() (string, error) {
return c.InstanceNameWithContext(context.Background())
}
// InstanceNameWithContext returns the current VM's instance ID string.
func (c *Client) InstanceNameWithContext(ctx context.Context) (string, error) {
return c.getTrimmed(ctx, "instance/name")
}
// Zone returns the current VM's zone, such as "us-central1-b".
//
// Deprecated: Please use the context aware variant [Client.ZoneWithContext].
func (c *Client) Zone() (string, error) {
return c.ZoneWithContext(context.Background())
}
// ZoneWithContext returns the current VM's zone, such as "us-central1-b".
func (c *Client) ZoneWithContext(ctx context.Context) (string, error) {
zone, err := c.getTrimmed(ctx, "instance/zone")
// zone is of the form "projects/<projNum>/zones/<zoneName>".
if err != nil {
return "", err
}
return zone[strings.LastIndex(zone, "/")+1:], nil
}
// InstanceAttributes returns the list of user-defined attributes,
// assigned when initially creating a GCE VM instance. The value of an
// attribute can be obtained with InstanceAttributeValue.
//
// Deprecated: Please use the context aware variant [Client.InstanceAttributesWithContext].
func (c *Client) InstanceAttributes() ([]string, error) {
return c.InstanceAttributesWithContext(context.Background())
}
// InstanceAttributesWithContext returns the list of user-defined attributes,
// assigned when initially creating a GCE VM instance. The value of an
// attribute can be obtained with InstanceAttributeValue.
func (c *Client) InstanceAttributesWithContext(ctx context.Context) ([]string, error) {
return c.lines(ctx, "instance/attributes/")
}
// ProjectAttributes returns the list of user-defined attributes
// applying to the project as a whole, not just this VM. The value of
// an attribute can be obtained with ProjectAttributeValue.
//
// Deprecated: Please use the context aware variant [Client.ProjectAttributesWithContext].
func (c *Client) ProjectAttributes() ([]string, error) {
return c.ProjectAttributesWithContext(context.Background())
}
// ProjectAttributesWithContext returns the list of user-defined attributes
// applying to the project as a whole, not just this VM. The value of
// an attribute can be obtained with ProjectAttributeValue.
func (c *Client) ProjectAttributesWithContext(ctx context.Context) ([]string, error) {
return c.lines(ctx, "project/attributes/")
}
// InstanceAttributeValue returns the value of the provided VM
// instance attribute.
//
// If the requested attribute is not defined, the returned error will
// be of type NotDefinedError.
//
// InstanceAttributeValue may return ("", nil) if the attribute was
// defined to be the empty string.
//
// Deprecated: Please use the context aware variant [Client.InstanceAttributeValueWithContext].
func (c *Client) InstanceAttributeValue(attr string) (string, error) {
return c.InstanceAttributeValueWithContext(context.Background(), attr)
}
// InstanceAttributeValueWithContext returns the value of the provided VM
// instance attribute.
//
// If the requested attribute is not defined, the returned error will
// be of type NotDefinedError.
//
// InstanceAttributeValue may return ("", nil) if the attribute was
// defined to be the empty string.
func (c *Client) InstanceAttributeValueWithContext(ctx context.Context, attr string) (string, error) {
return c.GetWithContext(ctx, "instance/attributes/"+attr)
}
// ProjectAttributeValue returns the value of the provided
// project attribute.
//
// If the requested attribute is not defined, the returned error will
// be of type NotDefinedError.
//
// ProjectAttributeValue may return ("", nil) if the attribute was
// defined to be the empty string.
//
// Deprecated: Please use the context aware variant [Client.ProjectAttributeValueWithContext].
func (c *Client) ProjectAttributeValue(attr string) (string, error) {
return c.ProjectAttributeValueWithContext(context.Background(), attr)
}
// ProjectAttributeValueWithContext returns the value of the provided
// project attribute.
//
// If the requested attribute is not defined, the returned error will
// be of type NotDefinedError.
//
// ProjectAttributeValue may return ("", nil) if the attribute was
// defined to be the empty string.
func (c *Client) ProjectAttributeValueWithContext(ctx context.Context, attr string) (string, error) {
return c.GetWithContext(ctx, "project/attributes/"+attr)
}
// Scopes returns the service account scopes for the given account.
// The account may be empty or the string "default" to use the instance's
// main account.
//
// Deprecated: Please use the context aware variant [Client.ScopesWithContext].
func (c *Client) Scopes(serviceAccount string) ([]string, error) {
return c.ScopesWithContext(context.Background(), serviceAccount)
}
// ScopesWithContext returns the service account scopes for the given account.
// The account may be empty or the string "default" to use the instance's
// main account.
func (c *Client) ScopesWithContext(ctx context.Context, serviceAccount string) ([]string, error) {
if serviceAccount == "" {
serviceAccount = "default"
}
return c.lines(ctx, "instance/service-accounts/"+serviceAccount+"/scopes")
}
// Subscribe subscribes to a value from the metadata service.
// The suffix is appended to "http://${GCE_METADATA_HOST}/computeMetadata/v1/".
// The suffix may contain query parameters.
//
// Deprecated: Please use the context aware variant [Client.SubscribeWithContext].
func (c *Client) Subscribe(suffix string, fn func(v string, ok bool) error) error {
return c.SubscribeWithContext(context.Background(), suffix, func(ctx context.Context, v string, ok bool) error { return fn(v, ok) })
}
// SubscribeWithContext subscribes to a value from the metadata service.
// The suffix is appended to "http://${GCE_METADATA_HOST}/computeMetadata/v1/".
// The suffix may contain query parameters.
//
// SubscribeWithContext calls fn with the latest metadata value indicated by the
// provided suffix. If the metadata value is deleted, fn is called with the
// empty string and ok false. Subscribe blocks until fn returns a non-nil error
// or the value is deleted. Subscribe returns the error value returned from the
// last call to fn, which may be nil when ok == false.
func (c *Client) SubscribeWithContext(ctx context.Context, suffix string, fn func(ctx context.Context, v string, ok bool) error) error {
const failedSubscribeSleep = time.Second * 5
// First check to see if the metadata value exists at all.
val, lastETag, err := c.getETag(ctx, suffix)
if err != nil {
return err
}
if err := fn(ctx, val, true); err != nil {
return err
}
ok := true
if strings.ContainsRune(suffix, '?') {
suffix += "&wait_for_change=true&last_etag="
} else {
suffix += "?wait_for_change=true&last_etag="
}
for {
val, etag, err := c.getETag(ctx, suffix+url.QueryEscape(lastETag))
if err != nil {
if _, deleted := err.(NotDefinedError); !deleted {
time.Sleep(failedSubscribeSleep)
continue // Retry on other errors.
}
ok = false
}
lastETag = etag
if err := fn(ctx, val, ok); err != nil || !ok {
return err
}
}
}
// Error contains an error response from the server.
type Error struct {
// Code is the HTTP response status code.
Code int
// Message is the server response message.
Message string
}
func (e *Error) Error() string {
return fmt.Sprintf("compute: Received %d `%s`", e.Code, e.Message)
}