terraform/backend/atlas/state_client.go

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package atlas
import (
"bytes"
"context"
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"crypto/md5"
"crypto/tls"
"crypto/x509"
"encoding/base64"
"fmt"
"io"
"log"
"net/http"
"net/url"
"os"
"path"
"github.com/hashicorp/go-cleanhttp"
"github.com/hashicorp/go-retryablehttp"
"github.com/hashicorp/go-rootcerts"
"github.com/hashicorp/terraform/state/remote"
"github.com/hashicorp/terraform/terraform"
)
const (
// defaultAtlasServer is used when no address is given
defaultAtlasServer = "https://atlas.hashicorp.com/"
atlasTokenHeader = "X-Atlas-Token"
)
// AtlasClient implements the Client interface for an Atlas compatible server.
type stateClient struct {
Server string
ServerURL *url.URL
User string
Name string
AccessToken string
RunId string
HTTPClient *retryablehttp.Client
conflictHandlingAttempted bool
}
func (c *stateClient) Get() (*remote.Payload, error) {
// Make the HTTP request
req, err := retryablehttp.NewRequest("GET", c.url().String(), nil)
if err != nil {
return nil, fmt.Errorf("Failed to make HTTP request: %v", err)
}
req.Header.Set(atlasTokenHeader, c.AccessToken)
// Request the url
client, err := c.http()
if err != nil {
return nil, err
}
resp, err := client.Do(req)
if err != nil {
return nil, err
}
defer resp.Body.Close()
// Handle the common status codes
switch resp.StatusCode {
case http.StatusOK:
// Handled after
case http.StatusNoContent:
return nil, nil
case http.StatusNotFound:
return nil, nil
case http.StatusUnauthorized:
return nil, fmt.Errorf("HTTP remote state endpoint requires auth")
case http.StatusForbidden:
return nil, fmt.Errorf("HTTP remote state endpoint invalid auth")
case http.StatusInternalServerError:
return nil, fmt.Errorf("HTTP remote state internal server error")
default:
return nil, fmt.Errorf(
"Unexpected HTTP response code: %d\n\nBody: %s",
resp.StatusCode, c.readBody(resp.Body))
}
// Read in the body
buf := bytes.NewBuffer(nil)
if _, err := io.Copy(buf, resp.Body); err != nil {
return nil, fmt.Errorf("Failed to read remote state: %v", err)
}
// Create the payload
payload := &remote.Payload{
Data: buf.Bytes(),
}
if len(payload.Data) == 0 {
return nil, nil
}
// Check for the MD5
if raw := resp.Header.Get("Content-MD5"); raw != "" {
md5, err := base64.StdEncoding.DecodeString(raw)
if err != nil {
return nil, fmt.Errorf("Failed to decode Content-MD5 '%s': %v", raw, err)
}
payload.MD5 = md5
} else {
// Generate the MD5
hash := md5.Sum(payload.Data)
payload.MD5 = hash[:]
}
return payload, nil
}
func (c *stateClient) Put(state []byte) error {
// Get the target URL
base := c.url()
// Generate the MD5
hash := md5.Sum(state)
b64 := base64.StdEncoding.EncodeToString(hash[:])
// Make the HTTP client and request
req, err := retryablehttp.NewRequest("PUT", base.String(), bytes.NewReader(state))
if err != nil {
return fmt.Errorf("Failed to make HTTP request: %v", err)
}
// Prepare the request
req.Header.Set(atlasTokenHeader, c.AccessToken)
req.Header.Set("Content-MD5", b64)
req.Header.Set("Content-Type", "application/json")
req.ContentLength = int64(len(state))
// Make the request
client, err := c.http()
if err != nil {
return err
}
resp, err := client.Do(req)
if err != nil {
return fmt.Errorf("Failed to upload state: %v", err)
}
defer resp.Body.Close()
// Handle the error codes
switch resp.StatusCode {
case http.StatusOK:
return nil
case http.StatusConflict:
return c.handleConflict(c.readBody(resp.Body), state)
default:
return fmt.Errorf(
"HTTP error: %d\n\nBody: %s",
resp.StatusCode, c.readBody(resp.Body))
}
}
func (c *stateClient) Delete() error {
// Make the HTTP request
req, err := retryablehttp.NewRequest("DELETE", c.url().String(), nil)
if err != nil {
return fmt.Errorf("Failed to make HTTP request: %v", err)
}
req.Header.Set(atlasTokenHeader, c.AccessToken)
// Make the request
client, err := c.http()
if err != nil {
return err
}
resp, err := client.Do(req)
if err != nil {
return fmt.Errorf("Failed to delete state: %v", err)
}
defer resp.Body.Close()
// Handle the error codes
switch resp.StatusCode {
case http.StatusOK:
return nil
case http.StatusNoContent:
return nil
case http.StatusNotFound:
return nil
default:
return fmt.Errorf(
"HTTP error: %d\n\nBody: %s",
resp.StatusCode, c.readBody(resp.Body))
}
}
func (c *stateClient) readBody(b io.Reader) string {
var buf bytes.Buffer
if _, err := io.Copy(&buf, b); err != nil {
return fmt.Sprintf("Error reading body: %s", err)
}
result := buf.String()
if result == "" {
result = "<empty>"
}
return result
}
func (c *stateClient) url() *url.URL {
values := url.Values{}
values.Add("atlas_run_id", c.RunId)
return &url.URL{
Scheme: c.ServerURL.Scheme,
Host: c.ServerURL.Host,
Path: path.Join("api/v1/terraform/state", c.User, c.Name),
RawQuery: values.Encode(),
}
}
func (c *stateClient) http() (*retryablehttp.Client, error) {
if c.HTTPClient != nil {
return c.HTTPClient, nil
}
tlsConfig := &tls.Config{}
err := rootcerts.ConfigureTLS(tlsConfig, &rootcerts.Config{
CAFile: os.Getenv("ATLAS_CAFILE"),
CAPath: os.Getenv("ATLAS_CAPATH"),
})
if err != nil {
return nil, err
}
rc := retryablehttp.NewClient()
rc.CheckRetry = func(ctx context.Context, resp *http.Response, err error) (bool, error) {
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if err != nil {
// don't bother retrying if the certs don't match
if err, ok := err.(*url.Error); ok {
if _, ok := err.Err.(x509.UnknownAuthorityError); ok {
return false, nil
}
}
}
return retryablehttp.DefaultRetryPolicy(ctx, resp, err)
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}
t := cleanhttp.DefaultTransport()
t.TLSClientConfig = tlsConfig
rc.HTTPClient.Transport = t
c.HTTPClient = rc
return rc, nil
}
// Atlas returns an HTTP 409 - Conflict if the pushed state reports the same
// Serial number but the checksum of the raw content differs. This can
// sometimes happen when Terraform changes state representation internally
// between versions in a way that's semantically neutral but affects the JSON
// output and therefore the checksum.
//
// Here we detect and handle this situation by ticking the serial and retrying
// iff for the previous state and the proposed state:
//
// * the serials match
// * the parsed states are Equal (semantically equivalent)
//
// In other words, in this situation Terraform can override Atlas's detected
// conflict by asserting that the state it is pushing is indeed correct.
func (c *stateClient) handleConflict(msg string, state []byte) error {
log.Printf("[DEBUG] Handling Atlas conflict response: %s", msg)
if c.conflictHandlingAttempted {
log.Printf("[DEBUG] Already attempted conflict resolution; returning conflict.")
} else {
c.conflictHandlingAttempted = true
log.Printf("[DEBUG] Atlas reported conflict, checking for equivalent states.")
payload, err := c.Get()
if err != nil {
return conflictHandlingError(err)
}
currentState, err := terraform.ReadState(bytes.NewReader(payload.Data))
if err != nil {
return conflictHandlingError(err)
}
proposedState, err := terraform.ReadState(bytes.NewReader(state))
if err != nil {
return conflictHandlingError(err)
}
if statesAreEquivalent(currentState, proposedState) {
log.Printf("[DEBUG] States are equivalent, incrementing serial and retrying.")
proposedState.Serial++
var buf bytes.Buffer
if err := terraform.WriteState(proposedState, &buf); err != nil {
return conflictHandlingError(err)
}
return c.Put(buf.Bytes())
} else {
log.Printf("[DEBUG] States are not equivalent, returning conflict.")
}
}
return fmt.Errorf(
"Atlas detected a remote state conflict.\n\nMessage: %s", msg)
}
func conflictHandlingError(err error) error {
return fmt.Errorf(
"Error while handling a conflict response from Atlas: %s", err)
}
func statesAreEquivalent(current, proposed *terraform.State) bool {
return current.Serial == proposed.Serial && current.Equal(proposed)
}