terraform/svchost/disco/host.go

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package disco
import (
"encoding/json"
"fmt"
"log"
"net/http"
"net/url"
"os"
"strconv"
"strings"
"time"
"github.com/hashicorp/go-version"
"github.com/hashicorp/terraform/httpclient"
)
const versionServiceID = "versions.v1"
// Host represents a service discovered host.
type Host struct {
discoURL *url.URL
hostname string
services map[string]interface{}
transport http.RoundTripper
}
// Constraints represents the version constraints of a service.
type Constraints struct {
Service string `json:"service"`
Product string `json:"product"`
Minimum string `json:"minimum"`
Maximum string `json:"maximum"`
Excluding []string `json:"excluding"`
}
// ErrServiceNotProvided is returned when the service is not provided.
type ErrServiceNotProvided struct {
hostname string
service string
}
// Error returns a customized error message.
func (e *ErrServiceNotProvided) Error() string {
if e.hostname == "" {
return fmt.Sprintf("host does not provide a %s service", e.service)
}
return fmt.Sprintf("host %s does not provide a %s service", e.hostname, e.service)
}
// ErrVersionNotSupported is returned when the version is not supported.
type ErrVersionNotSupported struct {
hostname string
service string
version string
}
// Error returns a customized error message.
func (e *ErrVersionNotSupported) Error() string {
if e.hostname == "" {
return fmt.Sprintf("host does not support %s version %s", e.service, e.version)
}
return fmt.Sprintf("host %s does not support %s version %s", e.hostname, e.service, e.version)
}
// ErrNoVersionConstraints is returned when checkpoint was disabled
// or the endpoint to query for version constraints was unavailable.
type ErrNoVersionConstraints struct {
disabled bool
}
// Error returns a customized error message.
func (e *ErrNoVersionConstraints) Error() string {
if e.disabled {
return "checkpoint disabled"
}
return "unable to contact versions service"
}
// ServiceURL returns the URL associated with the given service identifier,
// which should be of the form "servicename.vN".
//
// A non-nil result is always an absolute URL with a scheme of either HTTPS
// or HTTP.
func (h *Host) ServiceURL(id string) (*url.URL, error) {
svc, ver, err := parseServiceID(id)
if err != nil {
return nil, err
}
// No services supported for an empty Host.
if h == nil || h.services == nil {
return nil, &ErrServiceNotProvided{service: svc}
}
urlStr, ok := h.services[id].(string)
if !ok {
// See if we have a matching service as that would indicate
// the service is supported, but not the requested version.
for serviceID := range h.services {
if strings.HasPrefix(serviceID, svc+".") {
return nil, &ErrVersionNotSupported{
hostname: h.hostname,
service: svc,
version: ver.Original(),
}
}
}
// No discovered services match the requested service.
return nil, &ErrServiceNotProvided{hostname: h.hostname, service: svc}
}
u, err := url.Parse(urlStr)
if err != nil {
return nil, fmt.Errorf("Failed to parse service URL: %v", err)
}
// Make relative URLs absolute using our discovery URL.
if !u.IsAbs() {
u = h.discoURL.ResolveReference(u)
}
if u.Scheme != "https" && u.Scheme != "http" {
return nil, fmt.Errorf("Service URL is using an unsupported scheme: %s", u.Scheme)
}
if u.User != nil {
return nil, fmt.Errorf("Embedded username/password information is not permitted")
}
// Fragment part is irrelevant, since we're not a browser.
u.Fragment = ""
return h.discoURL.ResolveReference(u), nil
}
// VersionConstraints returns the contraints for a given service identifier
// (which should be of the form "servicename.vN") and product.
//
// When an exact (service and version) match is found, the constraints for
// that service are returned.
//
// When the requested version is not provided but the service is, we will
// search for all alternative versions. If mutliple alternative versions
// are found, the contrains of the latest available version are returned.
//
// When a service is not provided at all an error will be returned instead.
//
// When checkpoint is disabled or when a 404 is returned after making the
// HTTP call, an ErrNoVersionConstraints error will be returned.
func (h *Host) VersionConstraints(id, product string) (*Constraints, error) {
svc, _, err := parseServiceID(id)
if err != nil {
return nil, err
}
// Return early if checkpoint is disabled.
if disabled := os.Getenv("CHECKPOINT_DISABLE"); disabled != "" {
return nil, &ErrNoVersionConstraints{disabled: true}
}
// No services supported for an empty Host.
if h == nil || h.services == nil {
return nil, &ErrServiceNotProvided{service: svc}
}
// Try to get the service URL for the version service and
// return early if the service isn't provided by the host.
u, err := h.ServiceURL(versionServiceID)
if err != nil {
return nil, err
}
// Check if we have an exact (service and version) match.
if _, ok := h.services[id].(string); !ok {
// If we don't have an exact match, we search for all matching
// services and then use the service ID of the latest version.
var services []string
for serviceID := range h.services {
if strings.HasPrefix(serviceID, svc+".") {
services = append(services, serviceID)
}
}
if len(services) == 0 {
// No discovered services match the requested service.
return nil, &ErrServiceNotProvided{hostname: h.hostname, service: svc}
}
// Set id to the latest service ID we found.
var latest *version.Version
for _, serviceID := range services {
if _, ver, err := parseServiceID(serviceID); err == nil {
if latest == nil || latest.LessThan(ver) {
id = serviceID
latest = ver
}
}
}
}
// Set a default timeout of 1 sec for the versions request (in milliseconds)
timeout := 1000
if _, err := strconv.Atoi(os.Getenv("CHECKPOINT_TIMEOUT")); err == nil {
timeout, _ = strconv.Atoi(os.Getenv("CHECKPOINT_TIMEOUT"))
}
client := &http.Client{
Transport: h.transport,
Timeout: time.Duration(timeout) * time.Millisecond,
}
// Prepare the service URL by setting the service and product.
v := u.Query()
v.Set("product", product)
u.Path += id
u.RawQuery = v.Encode()
// Create a new request.
req, err := http.NewRequest("GET", u.String(), nil)
if err != nil {
return nil, fmt.Errorf("Failed to create version constraints request: %v", err)
}
req.Header.Set("Accept", "application/json")
req.Header.Set("User-Agent", httpclient.UserAgentString())
log.Printf("[DEBUG] Retrieve version constraints for service %s and product %s", id, product)
resp, err := client.Do(req)
if err != nil {
return nil, fmt.Errorf("Failed to request version constraints: %v", err)
}
defer resp.Body.Close()
if resp.StatusCode == 404 {
return nil, &ErrNoVersionConstraints{disabled: false}
}
if resp.StatusCode != 200 {
return nil, fmt.Errorf("Failed to request version constraints: %s", resp.Status)
}
// Parse the constraints from the response body.
result := &Constraints{}
if err := json.NewDecoder(resp.Body).Decode(result); err != nil {
return nil, fmt.Errorf("Error parsing version constraints: %v", err)
}
return result, nil
}
func parseServiceID(id string) (string, *version.Version, error) {
parts := strings.SplitN(id, ".", 2)
if len(parts) != 2 {
return "", nil, fmt.Errorf("Invalid service ID format (i.e. service.vN): %s", id)
}
version, err := version.NewVersion(parts[1])
if err != nil {
return "", nil, fmt.Errorf("Invalid service version: %v", err)
}
return parts[0], version, nil
}