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Use AWS SDK to fetch metadata #9227

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May 31, 2020
Merged

Use AWS SDK to fetch metadata #9227

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27 changes: 24 additions & 3 deletions util/pkg/vfs/context.go
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,8 @@ import (
"sync"
"time"

"github.com/aws/aws-sdk-go/aws/ec2metadata"
"github.com/aws/aws-sdk-go/aws/session"
"github.com/denverdino/aliyungo/oss"
"github.com/gophercloud/gophercloud"
"google.golang.org/api/option"
Expand Down Expand Up @@ -69,11 +71,13 @@ func WithBackoff(backoff wait.Backoff) VFSOption {
}
}

// ReadLocation reads a file from a vfs URL
// ReadFile reads a file from a vfs URL
// It supports additional schemes which don't (yet) have full VFS implementations:
// metadata: reads from instance metadata on GCE/AWS
// http / https: reads from HTTP
func (c *VFSContext) ReadFile(location string, options ...VFSOption) ([]byte, error) {
ctx := context.TODO()

var opts vfsOptions
// Exponential backoff, starting with 500 milliseconds, doubling each time, 5 steps
opts.backoff = wait.Backoff{
Expand Down Expand Up @@ -102,8 +106,7 @@ func (c *VFSContext) ReadFile(location string, options ...VFSOption) ([]byte, er
httpHeaders["Metadata-Flavor"] = "Google"
return c.readHTTPLocation(httpURL, httpHeaders, opts)
case "aws":
httpURL := "http://169.254.169.254/latest/" + u.Path
return c.readHTTPLocation(httpURL, nil, opts)
return c.readAWSMetadata(ctx, u.Path)
case "digitalocean":
httpURL := "http://169.254.169.254/metadata/v1" + u.Path
return c.readHTTPLocation(httpURL, nil, opts)
Expand Down Expand Up @@ -169,6 +172,24 @@ func (c *VFSContext) BuildVfsPath(p string) (Path, error) {
return nil, fmt.Errorf("unknown / unhandled path type: %q", p)
}

// readAWSMetadata reads the specified path from the AWS EC2 metadata service
func (c *VFSContext) readAWSMetadata(ctx context.Context, path string) ([]byte, error) {
awsSession, err := session.NewSession()
if err != nil {
return nil, fmt.Errorf("error building AWS session: %v", err)
}
client := ec2metadata.New(awsSession)
if strings.HasPrefix(path, "/meta-data/") {
s, err := client.GetMetadataWithContext(ctx, strings.TrimPrefix(path, "/meta-data/"))
if err != nil {
return nil, fmt.Errorf("error reading from AWS metadata service: %v", err)
}
return []byte(s), nil
}
// There are others (e.g. user-data), but as we don't use them yet let's not expose them
return nil, fmt.Errorf("unhandled aws metadata path %q", path)
}

// readHTTPLocation reads an http (or https) url.
// It returns the contents, or an error on any non-200 response. On a 404, it will return os.ErrNotExist
// It will retry a few times on a 500 class error
Expand Down