mediaapi: Add support for downloading of remote files

This commit is contained in:
Robert Swain 2017-05-31 17:56:11 +02:00
parent 07c821daec
commit 923013aa55
3 changed files with 329 additions and 8 deletions

View File

@ -16,7 +16,6 @@ package routing
import (
"net/http"
"sync"
"github.com/gorilla/mux"
"github.com/matrix-org/dendrite/common"
@ -42,7 +41,7 @@ func Setup(servMux *http.ServeMux, httpClient *http.Client, cfg *config.MediaAPI
}))
activeRemoteRequests := &types.ActiveRemoteRequests{
MXCToCond: map[string]*sync.Cond{},
MXCToResult: map[string]*types.RemoteRequestResult{},
}
r0mux.Handle("/download/{serverName}/{mediaId}",
prometheus.InstrumentHandler("download", http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {

View File

@ -59,10 +59,18 @@ type MediaMetadata struct {
UserID MatrixUserID
}
// RemoteRequestResult is used for broadcasting the result of a request for a remote file to routines waiting on the condition
type RemoteRequestResult struct {
// Condition used for the requester to signal the result to all other routines waiting on this condition
Cond *sync.Cond
// Resulting HTTP status code from the request
Result int
}
// ActiveRemoteRequests is a lockable map of media URIs requested from remote homeservers
// It is used for ensuring multiple requests for the same file do not clobber each other.
type ActiveRemoteRequests struct {
sync.Mutex
// The string key is an mxc:// URL
MXCToCond map[string]*sync.Cond
MXCToResult map[string]*RemoteRequestResult
}

View File

@ -18,10 +18,15 @@ import (
"encoding/json"
"fmt"
"io"
"net"
"net/http"
"net/url"
"os"
"path/filepath"
"regexp"
"strconv"
"strings"
"sync"
log "github.com/Sirupsen/logrus"
"github.com/matrix-org/dendrite/clientapi/jsonerror"
@ -47,6 +52,10 @@ type downloadRequest struct {
// Download implements /download
// Files from this server (i.e. origin == cfg.ServerName) are served directly
// Files from remote servers (i.e. origin != cfg.ServerName) are cached locally.
// If they are present in the cache, they are served directly.
// If they are not present in the cache, they are obtained from the remote server and
// simultaneously served back to the client and written into the cache.
func Download(w http.ResponseWriter, req *http.Request, origin gomatrixserverlib.ServerName, mediaID types.MediaID, cfg *config.MediaAPI, db *storage.Database, activeRemoteRequests *types.ActiveRemoteRequests) {
r := &downloadRequest{
MediaMetadata: &types.MediaMetadata{
@ -130,11 +139,8 @@ func (r *downloadRequest) doDownload(w http.ResponseWriter, cfg *config.MediaAPI
JSON: jsonerror.NotFound(fmt.Sprintf("File with media ID %q does not exist", r.MediaMetadata.MediaID)),
}
}
// TODO: If we do not have a record and the origin is remote, we need to fetch it and respond with that file
return &util.JSONResponse{
Code: 404,
JSON: jsonerror.NotFound(fmt.Sprintf("File with media ID %q does not exist", r.MediaMetadata.MediaID)),
}
// If we do not have a record and the origin is remote, we need to fetch it and respond with that file
return r.respondFromRemoteFile(w, cfg, db, activeRemoteRequests)
}
// If we have a record, we can respond from the local file
r.MediaMetadata = mediaMetadata
@ -200,3 +206,311 @@ func (r *downloadRequest) respondFromLocalFile(w http.ResponseWriter, absBasePat
}
return nil
}
// respondFromRemoteFile fetches the remote file, caches it locally and responds from that local file
// A hash map of active remote requests to a struct containing a sync.Cond is used to only download remote files once,
// regardless of how many download requests are received.
// Returns a util.JSONResponse error in case of error
func (r *downloadRequest) respondFromRemoteFile(w http.ResponseWriter, cfg *config.MediaAPI, db *storage.Database, activeRemoteRequests *types.ActiveRemoteRequests) *util.JSONResponse {
// Note: getMediaMetadataForRemoteFile uses mutexes and conditions from activeRemoteRequests
mediaMetadata, resErr := r.getMediaMetadataForRemoteFile(db, activeRemoteRequests)
if resErr != nil {
return resErr
} else if mediaMetadata != nil {
// If we have a record, we can respond from the local file
r.MediaMetadata = mediaMetadata
} else {
// If we do not have a record, we need to fetch the remote file first and then respond from the local file
// Note: getRemoteFile uses mutexes and conditions from activeRemoteRequests
if resErr := r.getRemoteFile(cfg.AbsBasePath, cfg.MaxFileSizeBytes, db, activeRemoteRequests); resErr != nil {
return resErr
}
}
return r.respondFromLocalFile(w, cfg.AbsBasePath)
}
func (r *downloadRequest) getMediaMetadataForRemoteFile(db *storage.Database, activeRemoteRequests *types.ActiveRemoteRequests) (*types.MediaMetadata, *util.JSONResponse) {
activeRemoteRequests.Lock()
defer activeRemoteRequests.Unlock()
// check if we have a record of the media in our database
mediaMetadata, err := db.GetMediaMetadata(r.MediaMetadata.MediaID, r.MediaMetadata.Origin)
if err != nil {
r.Logger.WithError(err).Error("Error querying the database.")
resErr := jsonerror.InternalServerError()
return nil, &resErr
}
if mediaMetadata != nil {
// If we have a record, we can respond from the local file
return mediaMetadata, nil
}
// No record was found
// Check if there is an active remote request for the file
mxcURL := "mxc://" + string(r.MediaMetadata.Origin) + "/" + string(r.MediaMetadata.MediaID)
if activeRemoteRequestResult, ok := activeRemoteRequests.MXCToResult[mxcURL]; ok {
r.Logger.Info("Waiting for another goroutine to fetch the remote file.")
activeRemoteRequestResult.Cond.Wait()
activeRemoteRequests.Unlock()
// NOTE: there is still a deferred Unlock() that will unlock this
activeRemoteRequests.Lock()
// check if we have a record of the media in our database
mediaMetadata, err := db.GetMediaMetadata(r.MediaMetadata.MediaID, r.MediaMetadata.Origin)
if err != nil {
r.Logger.WithError(err).Error("Error querying the database.")
resErr := jsonerror.InternalServerError()
return nil, &resErr
}
if mediaMetadata != nil {
// If we have a record, we can respond from the local file
return mediaMetadata, nil
}
// Note: if the result was 200, we shouldn't get here
switch activeRemoteRequestResult.Result {
case 404:
return nil, &util.JSONResponse{
Code: 404,
JSON: jsonerror.NotFound("File not found."),
}
case 500:
r.Logger.Error("Other goroutine failed to fetch the remote file.")
resErr := jsonerror.InternalServerError()
return nil, &resErr
default:
r.Logger.Error("Other goroutine failed to fetch the remote file.")
return nil, &util.JSONResponse{
Code: activeRemoteRequestResult.Result,
JSON: jsonerror.Unknown("Failed to fetch file from remote server."),
}
}
}
// No active remote request so create one
activeRemoteRequests.MXCToResult[mxcURL] = &types.RemoteRequestResult{
Cond: &sync.Cond{L: activeRemoteRequests},
}
return nil, nil
}
// getRemoteFile fetches the file from the remote server and stores its metadata in the database
// Only the owner of the activeRemoteRequestResult for this origin and media ID should call this function.
func (r *downloadRequest) getRemoteFile(absBasePath types.Path, maxFileSizeBytes types.FileSizeBytes, db *storage.Database, activeRemoteRequests *types.ActiveRemoteRequests) *util.JSONResponse {
// Wake up other goroutines after this function returns.
isError := true
var result int
defer func() {
if isError {
// If an error happens, the lock MUST NOT have been taken, isError MUST be true and so the lock is taken here.
activeRemoteRequests.Lock()
}
defer activeRemoteRequests.Unlock()
mxcURL := "mxc://" + string(r.MediaMetadata.Origin) + "/" + string(r.MediaMetadata.MediaID)
if activeRemoteRequestResult, ok := activeRemoteRequests.MXCToResult[mxcURL]; ok {
r.Logger.Info("Signalling other goroutines waiting for this goroutine to fetch the file.")
if result == 0 {
r.Logger.Error("Invalid result, treating as InternalServerError")
result = 500
}
activeRemoteRequestResult.Result = result
activeRemoteRequestResult.Cond.Broadcast()
}
delete(activeRemoteRequests.MXCToResult, mxcURL)
}()
finalPath, duplicate, resErr := r.fetchRemoteFile(absBasePath, maxFileSizeBytes)
if resErr != nil {
result = resErr.Code
return resErr
}
// NOTE: Writing the metadata to the media repository database and removing the mxcURL from activeRemoteRequests needs to be atomic.
// If it were not atomic, a new request for the same file could come in in routine A and check the database before the INSERT.
// Routine B which was fetching could then have its INSERT complete and remove the mxcURL from the activeRemoteRequests.
// If routine A then checked the activeRemoteRequests it would think it needed to fetch the file when it's already in the database.
// The locking below mitigates this situation.
// NOTE: The following two lines MUST remain together!
// isError == true causes the lock to be taken in a deferred function!
activeRemoteRequests.Lock()
isError = false
r.Logger.WithFields(log.Fields{
"Base64Hash": r.MediaMetadata.Base64Hash,
"UploadName": r.MediaMetadata.UploadName,
"FileSizeBytes": r.MediaMetadata.FileSizeBytes,
"Content-Type": r.MediaMetadata.ContentType,
}).Info("Storing file metadata to media repository database")
// FIXME: timeout db request
if err := db.StoreMediaMetadata(r.MediaMetadata); err != nil {
// If the file is a duplicate (has the same hash as an existing file) then
// there is valid metadata in the database for that file. As such we only
// remove the file if it is not a duplicate.
if duplicate == false {
finalDir := filepath.Dir(string(finalPath))
fileutils.RemoveDir(types.Path(finalDir), r.Logger)
}
// NOTE: It should really not be possible to fail the uniqueness test here so
// there is no need to handle that separately
resErr := jsonerror.InternalServerError()
result = resErr.Code
return &resErr
}
// TODO: generate thumbnails
r.Logger.WithFields(log.Fields{
"UploadName": r.MediaMetadata.UploadName,
"Base64Hash": r.MediaMetadata.Base64Hash,
"FileSizeBytes": r.MediaMetadata.FileSizeBytes,
"Content-Type": r.MediaMetadata.ContentType,
}).Infof("Remote file cached")
result = 200
return nil
}
func (r *downloadRequest) fetchRemoteFile(absBasePath types.Path, maxFileSizeBytes types.FileSizeBytes) (types.Path, bool, *util.JSONResponse) {
r.Logger.Info("Fetching remote file")
// create request for remote file
resp, resErr := r.createRemoteRequest()
if resErr != nil {
return "", false, resErr
}
defer resp.Body.Close()
// get metadata from request and set metadata on response
contentLength, err := strconv.ParseInt(resp.Header.Get("Content-Length"), 10, 64)
if err != nil {
r.Logger.WithError(err).Warn("Failed to parse content length")
return "", false, &util.JSONResponse{
Code: 502,
JSON: jsonerror.Unknown("Invalid response from remote server"),
}
}
if contentLength > int64(maxFileSizeBytes) {
return "", false, &util.JSONResponse{
Code: 413,
JSON: jsonerror.Unknown(fmt.Sprintf("Remote file is too large (%v > %v bytes)", contentLength, maxFileSizeBytes)),
}
}
r.MediaMetadata.FileSizeBytes = types.FileSizeBytes(contentLength)
r.MediaMetadata.ContentType = types.ContentType(resp.Header.Get("Content-Type"))
r.MediaMetadata.UploadName = types.Filename(contentDispositionToFilename(resp.Header.Get("Content-Disposition")))
r.Logger.Info("Transferring remote file")
// The file data is hashed but is NOT used as the MediaID, unlike in Upload. The hash is useful as a
// method of deduplicating files to save storage, as well as a way to conduct
// integrity checks on the file data in the repository.
// Data is truncated to maxFileSizeBytes. Content-Length was reported as 0 < Content-Length <= maxFileSizeBytes so this is OK.
hash, bytesWritten, tmpDir, err := fileutils.WriteTempFile(resp.Body, maxFileSizeBytes, absBasePath)
if err != nil {
r.Logger.WithError(err).WithFields(log.Fields{
"MaxFileSizeBytes": maxFileSizeBytes,
}).Warn("Error while downloading file from remote server")
fileutils.RemoveDir(tmpDir, r.Logger)
return "", false, &util.JSONResponse{
Code: 502,
JSON: jsonerror.Unknown("File could not be downloaded from remote server"),
}
}
r.Logger.Info("Remote file transferred")
// It's possible the bytesWritten to the temporary file is different to the reported Content-Length from the remote
// request's response. bytesWritten is therefore used as it is what would be sent to clients when reading from the local
// file.
r.MediaMetadata.FileSizeBytes = types.FileSizeBytes(bytesWritten)
r.MediaMetadata.Base64Hash = hash
// The database is the source of truth so we need to have moved the file first
finalPath, duplicate, err := fileutils.MoveFileWithHashCheck(tmpDir, r.MediaMetadata, absBasePath, r.Logger)
if err != nil {
r.Logger.WithError(err).Error("Failed to move file.")
resErr := jsonerror.InternalServerError()
return "", false, &resErr
}
if duplicate {
r.Logger.WithField("dst", finalPath).Info("File was stored previously - discarding duplicate")
// Continue on to store the metadata in the database
}
return types.Path(finalPath), duplicate, nil
}
func (r *downloadRequest) createRemoteRequest() (*http.Response, *util.JSONResponse) {
dnsResult, err := gomatrixserverlib.LookupServer(r.MediaMetadata.Origin)
if err != nil {
if dnsErr, ok := err.(*net.DNSError); ok && dnsErr.Timeout() {
return nil, &util.JSONResponse{
Code: 504,
JSON: jsonerror.Unknown(fmt.Sprintf("DNS look up for homeserver at %v timed out", r.MediaMetadata.Origin)),
}
}
resErr := jsonerror.InternalServerError()
return nil, &resErr
}
url := "https://" + strings.Trim(dnsResult.SRVRecords[0].Target, ".") + ":" + strconv.Itoa(int(dnsResult.SRVRecords[0].Port))
r.Logger.WithField("URL", url).Info("Connecting to remote")
remoteReqAddr := url + "/_matrix/media/v1/download/" + string(r.MediaMetadata.Origin) + "/" + string(r.MediaMetadata.MediaID)
remoteReq, err := http.NewRequest("GET", remoteReqAddr, nil)
if err != nil {
resErr := jsonerror.InternalServerError()
return nil, &resErr
}
remoteReq.Header.Set("Host", string(r.MediaMetadata.Origin))
client := http.Client{}
resp, err := client.Do(remoteReq)
if err != nil {
r.Logger.Warn("Failed to execute request for remote file")
return nil, &util.JSONResponse{
Code: 502,
JSON: jsonerror.Unknown(fmt.Sprintf("File with media ID %q could not be downloaded from %q", r.MediaMetadata.MediaID, r.MediaMetadata.Origin)),
}
}
if resp.StatusCode != 200 {
if resp.StatusCode == 404 {
return nil, &util.JSONResponse{
Code: 404,
JSON: jsonerror.NotFound(fmt.Sprintf("File with media ID %q does not exist", r.MediaMetadata.MediaID)),
}
}
r.Logger.WithFields(log.Fields{
"StatusCode": resp.StatusCode,
}).Warn("Received error response")
return nil, &util.JSONResponse{
Code: 502,
JSON: jsonerror.Unknown(fmt.Sprintf("File with media ID %q could not be downloaded from %q", r.MediaMetadata.MediaID, r.MediaMetadata.Origin)),
}
}
return resp, nil
}
var contentDispositionRegex = regexp.MustCompile("filename([*])?=(utf-8'')?([A-Za-z0-9._-]+)")
func contentDispositionToFilename(contentDisposition string) types.Filename {
filename := ""
if matches := contentDispositionRegex.FindStringSubmatch(contentDisposition); len(matches) == 4 {
// Note: the filename should already be escaped. If not, unescape should be close to a no-op. This way filename is sure to be safe.
unescaped, err := url.PathUnescape(matches[3])
if err != nil {
unescaped = matches[3]
}
filename = url.PathEscape(unescaped)
}
return types.Filename(filename)
}