Ktor: Apache HTTP Client does not send Content-Length header if body is empty content

[SIY1121]

Ktor Version and Engine Used (client or server and name)
io.ktor:ktor-client-core:1.2.4
io.ktor:ktor-client-core-jvm:1.2.4
io.ktor:ktor-client-apache:1.2.4

Describe the bug
Apache HTTP Client does not send Content-Length header if body is empty content.
CIO send the header correctly.

To Reproduce
Steps to reproduce the behavior:

1. Write the following

val apacheClient = HttpClient(Apache)
apacheClient.put<HttpResponseData>("http://example.com/") 
apacheClient.post<HttpResponseData>("http://example.com/")
apacheClient.patch<HttpResponseData>("http://example.com/")

1. Run on jvm
2. The sent header does not contain Content-Length

{
  "accept-charset": "UTF-8",
  "accept": "*/*",
  "user-agent": "Ktor client",
  "host": "example.com",
  "connection": "Keep-Alive" 
}

Some endpoints that do not require body return 411 Length Required.

Expected behavior
Content-Length: 0 Should be sent.

Apache seems not to send Content-Length if entity is null.
Following code sent the header correctly.

apacheClient.put<HttpResponseData>("http://example.com/"){
    body = ""
}

The relevant part of the code in ktor:
https://github.com/ktorio/ktor/blob/f3858b2bd95dcb35aa7755451403e7cab1dd678c/ktor-client/ktor-client-apache/jvm/src/io/ktor/client/engine/apache/ApacheRequestProducer.kt#L122-L155

and org.apache.http.client.methods.RequestBuilder 's build() method.

[cy6erGn0m]

The question is: how can a post request with no content-length, no transfer-encoding and keep-alive connection work at all❓

[SIY1121]

No. It's a client issue, not a server issue.
I tried to send a empty put request to a third-party api server.

val apacheClient = HttpClient(Apache)
apacheClient.put<HttpResponseData>("http://example.com/") 

However, the server returns 411 Length Required.
The cause is Ktor client with Apache engine didn't send content-length header.

content-length or transfer-encoding headers should be present.

RFC 7230, section 3.3.2: Content-Length

For example, a Content-Length header
field is normally sent in a POST request even when the value is 0
(indicating an empty payload body).

[christophpickl]

hi guys, i've encountered this bug in one of our production systems. we temporarily added the solution (hack?) of simply setting the body to "". in order to fix it properly i've created a PR which should do the job: https://github.com/ktorio/ktor/pull/1644

any feedback on this would be highly appreciated.

[oleg-larshin]

Please check the following ticket on YouTrack for follow-ups to this issue. GitHub issues will be closed in the coming weeks.

[KirillAmurskiy]

Had the same problem. Have solved it with the following workaround:

val client = HttpClient(Apache) {
    engine {
        customizeClient {
            setDefaultHeaders(mutableListOf(BasicHeader("Content-Length", "0")))
        }
    }
}

client.post<MyResponse>(ENDPOINT_URL) { ... }

One should use this configuration only for requests where you invoke PUT/POST methods with empty body.
It isn't the perfect solution, but if one can't use another engine for the client it will help.

[e5l]

The fix is merged in 1.3.0