php小编西瓜在介绍Go语言开发中的一个重要细节时指出，使用http.Request.Context()代替context.Background()时，上传文件不会被自动提交到谷歌云存储。这个小细节对于开发者来说非常重要，因为它可能会导致文件上传失败或数据丢失。了解并正确使用这个方法可以避免不必要的问题，确保文件的安全上传和存储。
问题内容
我是新手，我编写了一个简单的宠物项目来将加密文件上传到谷歌云存储。
问题：
在我调用 addentry 函数的http处理程序中，当我传递 r.context() 而不是 context.background() 时，文件不会上传到谷歌存储。在谷歌的控制台中，我可以看到收到的字节，而且我根本没有收到任何错误，但文件本身不存在。
处理程序代码：
//imports, structs skipped
func processaddentryrequest(w http.responsewriter, r *http.request) {
//validation, getting params from jwt skipped
reader, err := r.multipartreader()
if err != nil {
http.error(w, "multipart/form-data expected, not found", http.statusbadrequest)
log.println("could not init multipartreader from request: %w", err)
return
}
gsservice, err := googlestorageservice.new()
if err != nil {
http.error(w, "internal server error", http.statusinternalservererror)
log.println(err)
return
}
bservice, err := backupservice.new(
backupservice.withcipher(aes.new()),
backupservice.withstorageservice(gsservice))
if err != nil {
http.error(w, "internal server error", http.statusinternalservererror)
log.println(err)
return
}
var entry *entryrepo.backupentry
for {
part, err := reader.nextpart()
if err == io.eof {
break
}
if err != nil {
err = fmt.errorf("error reading: %w", err)
log.println(err)
http.error(w, "internal server error", http.statusinternalservererror)
return
}
formname := part.formname()
if formname == "file" {
entry, err = bservice.addentry(r.context(), backupid, part.filename(), part.header.get("content-type"), part)
if err != nil {
errclose := part.close()
err = fmt.errorf("failed to add entry for backup %s: %w; error while closing multipart.part: %w", backupid, err, errclose)
log.println(err)
http.error(w, "internal server error", http.statusinternalservererror)
return
}
}
err = part.close()
if err != nil {
err = fmt.errorf("failed to close part for backup %s: %w", backupid, err)
log.println(err)
http.error(w, "internal server error", http.statusinternalservererror)
return
}
}
response.entry = *entry
jsondata, err := json.marshal(response)
if err != nil {
http.error(w, "internal server error", http.statusinternalservererror)
log.println("failed to marshal json: %w
", err)
return
}
w.writeheader(http.statusok)
w.header().set("content-type", "application/json")
w.write(jsondata)
}
addentry函数代码：
func (backupservice *backupservice) addentry(ctx context.context, backupid string, entryfullname string,
entrymimetype string, in io.reader) (*ber.backupentry, error) {
// validation skipped for readability
entryid := uuid.new()
outpath := backupid + "/" + entryid.string()
entrychan := make(chan *ber.backupentry)
errchan := make(chan error)
go func() {
gstorageclient, err := backupservice.storageservice.getclient(ctx)
if err != nil {
errchan <- fmt.errorf("could not add entry: %w", err)
}
defer gstorageclient.close()
out := gstorageclient.bucket(config.gcbucketname()).object(outpath).newwriter(ctx)
defer out.close()
mac, size, err := backupservice.cipher.encrypt(ctx, in, out,
[]byte(config.encryptionkey()), []byte(config.hmackey()))
if err != nil {
errchan <- fmt.errorf("could not upload encrypted backupentry with id=%s: %w", entryid.string(), err)
}
//db operation skipped
entrychan <- entry
}()
select {
case <-ctx.done():
dbcleanuperr, storagecleanuperr := backupservice.cleanupentry(entryid.string(), outpath)
return nil,
fmt.errorf("could not add entry %s to backup %s: context was cancelled; db cleanup err: %w; gstorage cleanup err: %w",
entryid.string(), backupid, dbcleanuperr, storagecleanuperr)
case err := <-errchan:
dbcleanuperr, storagecleanuperr := backupservice.cleanupentry(entryid.string(), outpath)
return nil,
fmt.errorf("could not add entry %s to backup %s: %w; db cleanup err: %w; gstorage cleanup err: %w",
entryid.string(), backupid, err, dbcleanuperr, storagecleanuperr)
case entry := <-entrychan:
return entry, nil
}
}
我尝试过的：
- 启用
godebug：http2debug=1检查调试 http 日志。日志不同，我将它们放在下面。 - 检查上下文是否在所有级别上都关闭：在http处理程序本身中，在
addentry函数中添加encrypt函数。上下文没有关闭，一切似乎都工作正常。 - 从
r.context()创建派生上下文，结果与r.context()相同 - 显然，将
context.background()而不是r.context()传递给addentry函数，就可以解决问题
当 r.context() 作为参数传递时的调试日志：
ft-api | 2023/08/02 19:23:46 stdout: 2023/08/02 19:23:46 [2606f10843ab/yuha6i98ak-000004] "post http://0.0.0.0:8080/backup http/1.1" from 172.18.0.1:36052 - 200 570b in 193.850041ms ft-api | 2023/08/02 19:23:47 stdout: 2023/08/02 19:23:47 [2606f10843ab/yuha6i98ak-000005] "post http://0.0.0.0:8080/entry http/1.1" from 172.18.0.1:36052 - 200 127b in 171.975584ms ft-api | 2023/08/02 19:23:47 stderr: 2023/08/02 19:23:47 h2_bundle.go:9019: http2: transport encoding header ":authority" = "oauth2.googleapis.com" ft-api | 2023/08/02 19:23:47 stderr: 2023/08/02 19:23:47 h2_bundle.go:9019: http2: transport encoding header ":method" = "post" ft-api | 2023/08/02 19:23:47 stderr: 2023/08/02 19:23:47 h2_bundle.go:9019: http2: transport encoding header ":path" = "/token" ft-api | 2023/08/02 19:23:47 stderr: 2023/08/02 19:23:47 h2_bundle.go:9019: http2: transport encoding header ":scheme" = "https" ft-api | 2023/08/02 19:23:47 stderr: 2023/08/02 19:23:47 h2_bundle.go:9019: http2: transport encoding header "content-type" = "application/x-www-form-urlencoded" ft-api | 2023/08/02 19:23:47 stderr: 2023/08/02 19:23:47 h2_bundle.go:9019: http2: transport encoding header "content-length" = "861" ft-api | 2023/08/02 19:23:47 stderr: 2023/08/02 19:23:47 h2_bundle.go:9019: http2: transport encoding header "accept-encoding" = "gzip" ft-api | 2023/08/02 19:23:47 stderr: 2023/08/02 19:23:47 h2_bundle.go:9019: http2: transport encoding header "user-agent" = "go-http-client/2.0" ft-api | 2023/08/02 19:23:47 stderr: 2023/08/02 19:23:47 h2_bundle.go:9968: http2: transport received headers flags=end_headers stream=3 len=42 ft-api | 2023/08/02 19:23:47 stderr: 2023/08/02 19:23:47 h2_bundle.go:9968: http2: transport received data flags=padded stream=3 len=974 data=" Ɏh ia&܌]*l.%dxs ).q)&$z.g uf13dƸ8= 3fѶϪn-]|!ha^[:1u~2 tν9з!ȡӝybn*|ڗ}pd" l'g=oc?fk^!81g6njpzwjͯn[۰xbp--" (613 bytes omitted) ft-api | 2023/08/02 19:23:47 stderr: 2023/08/02 19:23:47 h2_bundle.go:9968: http2: transport received data flags=end_stream|padded stream=3 len=136 data="" ft-api | 2023/08/02 19:23:47 stderr: 2023/08/02 19:23:47 h2_bundle.go:9968: http2: transport received ping len=8 ping=" " ft-api | 2023/08/02 19:23:47 stderr: 2023/08/02 19:23:47 transport.go:3015: http2: transport failed to get client conn for storage.googleapis.com:443: http2: no cached connection was available
当 context.background() 作为参数传递时的调试日志（我从日志中删除了 jwt 令牌值，但它在那里）
ft-api | 2023/08/02 19:24:51 stdout: 2023/08/02 19:24:51 [2606f10843ab/ukd5p0sXox-000001] "POST http://0.0.0.0:8080/backup HTTP/1.1" from 172.18.0.1:38934 - 200 570B in 465.2635ms
ft-api | 2023/08/02 19:24:52 stdout: 2023/08/02 19:24:52 [2606f10843ab/ukd5p0sXox-000002] "POST http://0.0.0.0:8080/entry HTTP/1.1" from 172.18.0.1:38934 - 200 127B in 172.084834ms
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 h2_bundle.go:9968: http2: Transport failed to get client conn for oauth2.googleapis.com:443: http2: no cached connection was available
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 h2_bundle.go:9968: http2: Transport creating client conn 0x40003cc780 to 142.250.186.74:443
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 h2_bundle.go:9019: http2: Transport encoding header ":authority" = "oauth2.googleapis.com"
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 h2_bundle.go:9019: http2: Transport encoding header ":method" = "POST"
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 h2_bundle.go:9019: http2: Transport encoding header ":path" = "/token"
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 h2_bundle.go:9019: http2: Transport encoding header ":scheme" = "https"
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 h2_bundle.go:9019: http2: Transport encoding header "content-type" = "application/x-www-form-urlencoded"
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 h2_bundle.go:9019: http2: Transport encoding header "content-length" = "861"
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 h2_bundle.go:9019: http2: Transport encoding header "accept-encoding" = "gzip"
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 h2_bundle.go:9019: http2: Transport encoding header "user-agent" = "Go-http-client/2.0"
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 h2_bundle.go:9968: http2: Transport received SETTINGS len=18, settings: MAX_CONCURRENT_STREAMS=100, INITIAL_WINDOW_SIZE=1048576, MAX_HEADER_LIST_SIZE=65536
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 h2_bundle.go:9968: http2: Transport received WINDOW_UPDATE len=4 (conn) incr=983041
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 h2_bundle.go:9968: http2: Transport received SETTINGS flags=ACK len=0
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 h2_bundle.go:9968: http2: Transport received HEADERS flags=END_HEADERS stream=1 len=220
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 h2_bundle.go:9968: http2: Transport received DATA flags=PADDED stream=1 len=1030 data=" Ir: лxt1z9&`#3n(!F3 ̠;zO|eht`&S
M'|' ]78,fr+ņl<\#8Op#|}&M E-<ЕXy<HL5& {?yT:ȿ X9K[4ԟa9 h0hk ) 5vT*4|P̍(l=dcqŖQ|w" (611 bytes omitted)
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 h2_bundle.go:9968: http2: Transport received DATA flags=END_STREAM|PADDED stream=1 len=208 data=""
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 h2_bundle.go:9968: http2: Transport received PING len=8 ping=" "
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 transport.go:3015: http2: Transport failed to get client conn for storage.googleapis.com:443: http2: no cached connection was available
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 transport.go:3015: http2: Transport creating client conn 0x400029e000 to 216.58.212.144:443
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 transport.go:2076: http2: Transport encoding header ":authority" = "storage.googleapis.com"
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 transport.go:2076: http2: Transport encoding header ":method" = "POST"
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 transport.go:2076: http2: Transport encoding header ":path" = "/upload/storage/v1/b/bucketname/o?alt=json&name=a934c415-07bd-4686-8ad0-90ff5ef68c7e%2F6e6b9563-c9d9-484e-a24f-cd2f8bd1fcd8&prettyPrint=false&projection=full&uploadType=multipart"
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 transport.go:2076: http2: Transport encoding header ":scheme" = "https"
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 transport.go:2076: http2: Transport encoding header "content-type" = "multipart/related; boundary=976d8006696028fea8c40fc53fe0a817a80f334ae41925d1e08c3bb3c917"
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 transport.go:2076: http2: Transport encoding header "x-cloud-trace-context" = "cb5a9d07f5007be3d8dfe277e1fb6beb/9294889295348469653;o=0"
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 transport.go:2076: http2: Transport encoding header "authorization" = "Bearer <<token value removed>>"
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 transport.go:2076: http2: Transport encoding header "x-goog-api-client" = "gl-go/1.20.6 gccl/1.30.1"
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 transport.go:2076: http2: Transport encoding header "user-agent" = "gcloud-golang-storage/1.30.1"
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 transport.go:2076: http2: Transport encoding header "accept-encoding" = "gzip"
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 transport.go:3015: http2: Transport received SETTINGS len=18, settings: MAX_CONCURRENT_STREAMS=100, INITIAL_WINDOW_SIZE=1048576, MAX_HEADER_LIST_SIZE=65536
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 transport.go:3015: http2: Transport received WINDOW_UPDATE len=4 (conn) incr=983041
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 transport.go:3015: http2: Transport received SETTINGS flags=ACK len=0
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 transport.go:3015: http2: Transport received HEADERS flags=END_HEADERS stream=1 len=314
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 transport.go:3015: http2: Transport received DATA stream=1 len=944 data="{"kind":"storage#object","id":"bucketname/a934c415-07bd-4686-8ad0-90ff5ef68c7e/6e6b9563-c9d9-484e-a24f-cd2f8bd1fcd8/1691004292747760","selfLink":"https://www.googleapis.com/storage/v1/b/bucketname/o/a934c415-07bd-4686-8ad0-90ff5ef68c7e%2F6e6b9563" (688 bytes omitted)
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 transport.go:3015: http2: Transport received DATA flags=END_STREAM stream=1 len=0 data=""
ft-api | 2023/08/02 19:24:52 stderr: 2023/08/02 19:24:52 transport.go:3015: http2: Transport received PING len=8 ping=" "解决方法
通过在 gstorage 对象编写器上显式调用 Close() 方法而不是推迟它来解决该问题。我仍然不完全确定此行为的原因（我知道除非编写器关闭，否则文件不会提交到 gstorage，但不涉及上下文取消，因此它应该已关闭）。
编辑：在我看来，问题可能出在 go 执行 goroutine 内部声明的延迟函数的顺序上。如果有人对此有解释，我们将非常欢迎。
