Mohammad Sadeq Dousti created HTTPCORE-473:
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Summary: ElementalReverseProxy does not properly handle POST
requests
Key: HTTPCORE-473
URL: https://issues.apache.org/jira/browse/HTTPCORE-473
Project: HttpComponents HttpCore
Issue Type: Bug
Components: Examples
Affects Versions: 4.4.6
Environment: Windows 7, Java 8
Reporter: Mohammad Sadeq Dousti
Priority: Minor
Dear Oleg et al.,
I understand that {{ElementalReverseProxy}} is provided just as an example, but
it will be great if this example works properly, as it shows how the underlying
API must be used.
Here's a simple setup that shows why {{ElementalReverseProxy}} fails to work
with POST request (and in fact, any requests including {{Content-Length}} or
{{Transfer-Content}} headers):
# Let {{http://127.0.0.1:80}} denote the back-end server which we want to proxy
against, and assume the server hosts the file {{/index.html}}.
# Run {{ElementalReverseProxy}} with default config against the back-end server.
Test the back-end server using {{wget}}:
{{wget http://127.0.0.1:80 --post-data="some data"
--2017-06-24 11:52:30-- http://127.0.0.1/
Connecting to 127.0.0.1:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 343 [text/html]
Saving to: 'index.html'
index.html
100%[====================================================>] 343 --.-KB/s
in 0s
2017-06-24 11:52:30 (9.78 MB/s) - 'index.html' saved [343/343]}}
As you can see, it works just fine. Now try it with {{ElementalReverseProxy}}:
{{wget http://127.0.0.1:8888 --post-data="some data"
--2017-06-24 11:53:31-- http://127.0.0.1:8888/
Connecting to 127.0.0.1:8888... connected.
HTTP request sent, awaiting response... 400 Bad Request
2017-06-24 11:53:31 ERROR 400: Bad Request.}}
h3. Resolution
{{ProxyThread}} executes {{httpservice.handleRequest}}, which in turn calls
{{processor.process(request, context)}}. This causes
{{RequestContent.process()}} to be executed, which throws an exception as it
finds that the request already contains the {{Content-Length}} header.
One way to rectify this is to initialize {{inhttpproc}} with
{{RequestContent(true)}}, which overwrites the {{Content-Length}} header even
if it is present, without throwing an exception.
Running {{wget}} again will now result in no error, but with one catch: Notice
the response misses the {{Content-Length}} header (this is evident from
{{Length: unspecified}} below):
{{wget http://127.0.0.1:8888 --post-data="some data"
--2017-06-24 12:09:25-- http://127.0.0.1:8888/
Connecting to 127.0.0.1:8888... connected.
HTTP request sent, awaiting response... 200 OK
Length: unspecified [text/html]
Saving to: 'index.html'
index.html [ <=>
] 343 --.-KB/s in 0s
2017-06-24 12:09:25 (8.82 MB/s) - 'index.html' saved [343]}}
This is due to the line {{targetResponse.removeHeaders(HTTP.CONTENT_LEN)}} in
{{ProxyHandler#handle()}} method. Commenting this line will resolve the issue.
In general, I don't get the {{ProxyHandler#handle()}} method: It is called by
{{HttpService#doService()}}, which in turn gets called just after the following
line:
{{this.processor.process(request, context);}}
So, it means that just after the above line applied mandatory HTTP headers,
{{ProxyHandler#handle()}} removes them all! Next, it tries to re-apply them:
{{this.httpexecutor.preProcess(request, this.httpproc, context);}}
But here, {{this.httpproc}} refers to {{outhttpproc}}, for which the
{{requestInterceptors}} instance is {{null}} effectively doing nothing.
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