github.com/cloudbase/juju-core@v0.0.0-20140504232958-a7271ac7912f/environs/simplestreams/datasource.go (about)

     1  // Copyright 2013 Canonical Ltd.
     2  // Licensed under the AGPLv3, see LICENCE file for details.
     3  
     4  package simplestreams
     5  
     6  import (
     7  	"fmt"
     8  	"io"
     9  	"net/http"
    10  	"strings"
    11  
    12  	"launchpad.net/juju-core/errors"
    13  	"launchpad.net/juju-core/utils"
    14  )
    15  
    16  // A DataSource retrieves simplestreams metadata.
    17  type DataSource interface {
    18  	// Description describes the origin of this datasource.
    19  	// eg tools-metadata-url, cloud storage, keystone catalog etc.
    20  	Description() string
    21  	// Fetch loads the data at the specified relative path. It returns a reader from which
    22  	// the data can be retrieved as well as the full URL of the file. The full URL is typically
    23  	// used in log messages to help diagnose issues accessing the data.
    24  	Fetch(path string) (io.ReadCloser, string, error)
    25  	// URL returns the full URL of the path, as applicable to this datasource.
    26  	// This method is used primarily for logging purposes.
    27  	URL(path string) (string, error)
    28  	// SetAllowRetry sets the flag which determines if the datasource will retry fetching the metadata
    29  	// if it is not immediately available.
    30  	SetAllowRetry(allow bool)
    31  }
    32  
    33  // SSLHostnameVerification is used as a switch for when a given provider might
    34  // use self-signed credentials and we should not try to verify the hostname on
    35  // the TLS/SSL certificates
    36  type SSLHostnameVerification bool
    37  
    38  const (
    39  	// VerifySSLHostnames ensures we verify the hostname on the certificate
    40  	// matches the host we are connecting and is signed
    41  	VerifySSLHostnames = SSLHostnameVerification(true)
    42  	// NoVerifySSLHostnames informs us to skip verifying the hostname
    43  	// matches a valid certificate
    44  	NoVerifySSLHostnames = SSLHostnameVerification(false)
    45  )
    46  
    47  // A urlDataSource retrieves data from an HTTP URL.
    48  type urlDataSource struct {
    49  	description          string
    50  	baseURL              string
    51  	hostnameVerification SSLHostnameVerification
    52  }
    53  
    54  // NewURLDataSource returns a new datasource reading from the specified baseURL.
    55  func NewURLDataSource(description, baseURL string, verify SSLHostnameVerification) DataSource {
    56  	return &urlDataSource{
    57  		description:          description,
    58  		baseURL:              baseURL,
    59  		hostnameVerification: verify,
    60  	}
    61  }
    62  
    63  // Description is defined in simplestreams.DataSource.
    64  func (u *urlDataSource) Description() string {
    65  	return u.description
    66  }
    67  
    68  func (u *urlDataSource) GoString() string {
    69  	return fmt.Sprintf("%v: urlDataSource(%q)", u.description, u.baseURL)
    70  }
    71  
    72  // urlJoin returns baseURL + relpath making sure to have a '/' inbetween them
    73  // This doesn't try to do anything fancy with URL query or parameter bits
    74  // It also doesn't use path.Join because that normalizes slashes, and you need
    75  // to keep both slashes in 'http://'.
    76  func urlJoin(baseURL, relpath string) string {
    77  	if strings.HasSuffix(baseURL, "/") {
    78  		return baseURL + relpath
    79  	}
    80  	return baseURL + "/" + relpath
    81  }
    82  
    83  // Fetch is defined in simplestreams.DataSource.
    84  func (h *urlDataSource) Fetch(path string) (io.ReadCloser, string, error) {
    85  	dataURL := urlJoin(h.baseURL, path)
    86  	// dataURL can be http:// or file://
    87  	client := http.DefaultClient
    88  	if !h.hostnameVerification {
    89  		client = utils.GetNonValidatingHTTPClient()
    90  	}
    91  	resp, err := client.Get(dataURL)
    92  	if err != nil {
    93  		logger.Debugf("Got error requesting %q: %v", dataURL, err)
    94  		return nil, dataURL, errors.NotFoundf("invalid URL %q", dataURL)
    95  	}
    96  	if resp.StatusCode == http.StatusNotFound {
    97  		return nil, dataURL, errors.NotFoundf("cannot find URL %q", dataURL)
    98  	}
    99  	if resp.StatusCode == http.StatusUnauthorized {
   100  		return nil, dataURL, errors.Unauthorizedf("unauthorised access to URL %q", dataURL)
   101  	}
   102  	if resp.StatusCode != http.StatusOK {
   103  		return nil, dataURL, fmt.Errorf("cannot access URL %q, %q", dataURL, resp.Status)
   104  	}
   105  	return resp.Body, dataURL, nil
   106  }
   107  
   108  // URL is defined in simplestreams.DataSource.
   109  func (h *urlDataSource) URL(path string) (string, error) {
   110  	return urlJoin(h.baseURL, path), nil
   111  }
   112  
   113  // SetAllowRetry is defined in simplestreams.DataSource.
   114  func (h *urlDataSource) SetAllowRetry(allow bool) {
   115  	// This is a NOOP for url datasources.
   116  }