Hello Joakim,
Is there any documentation or a basic example of how to set up the
AsyncProxyServlet? I am thinking of using it as a reverse proxy for
implementing a load balancer. Basically all it would need to do is
determine the target server (based on some request properties) and then
act as a reverse proxy between the client and that server.
Thanks,
Silvio
On 27-09-17 02:05, Joakim Erdfelt wrote:
modifying the request or response during proxy is also supported out
of the box by the ...
org.eclipse.jetty.proxy.AsyncMiddleManServlet
https://github.com/eclipse/jetty.project/blob/jetty-9.4.x/jetty-proxy/src/main/java/org/eclipse/jetty/proxy/AsyncMiddleManServlet.java
Joakim Erdfelt / [email protected] <mailto:[email protected]>
On Tue, Sep 26, 2017 at 5:03 PM, Steven Schlansker
<[email protected] <mailto:[email protected]>> wrote:
> On Sep 26, 2017, at 4:51 PM, Joakim Erdfelt <[email protected]
<mailto:[email protected]>> wrote:
>
> This is what our org.eclipse.jetty.proxy.AsyncProxyServlet
already does.
>
>
https://github.com/eclipse/jetty.project/blob/jetty-9.4.x/jetty-proxy/src/main/java/org/eclipse/jetty/proxy/AsyncProxyServlet.java
<https://github.com/eclipse/jetty.project/blob/jetty-9.4.x/jetty-proxy/src/main/java/org/eclipse/jetty/proxy/AsyncProxyServlet.java>
>
> Why write your own?
Because I did not know this existed :)
Also, I do nontrivial rewriting of the request (this is not at all
a transparent proxy,
it is quite invasive) so I will probably not be able to use the
code as is.
But it probably answers my questions and just needs adaptation, so
thank you very much
for the pointer.
(This is a lot of complex code! Asynchronous programming is hard...)
>
>
> Joakim Erdfelt / [email protected] <mailto:[email protected]>
>
> On Tue, Sep 26, 2017 at 4:47 PM, Steven Schlansker
<[email protected] <mailto:[email protected]>>
wrote:
> Hi jetty-users,
>
> Still working on my http proxy :)
> Now I'm trying to make sure I've got the content proxying
working correctly
> using both asynchronous servlet as well as NIO nonblocking writing.
>
> Because both the server and client are pushing notifications at
me, I believe
> I need to implement some sort of transfer queue. I was hoping
that I'd end up
> in a push-pull situation but ServletOutputStream calls you via a
WriteListener
> and Jetty-Client calls you via a Response.ContentListener.
>
> Unfortunately, this leaves me in a position where I don't know
how to get flow
> control working. The client pushes data at me and I don't have
a way to push back.
>
> My current pesudocoded approach:
>
> Deque<Runnable> writes;
> volatile boolean complete = false;
>
> asyncCtx = httpResponse.startAsync();
> out = (HttpOutput) httpResponse.getOutputStream();
>
> writeListener = new WriteListener() {
> synchronized void onWritePossible() { // avoid re-entrance
with 'synchronized'
> while(out.isReady()) {
> pending = writes.removeFirst();
> if (pending != null) {
> pending.run();
> } else if (complete && writes.isEmpty()) {
> asyncCtx.complete();
> } else {
> return;
> }
> }
> }
> };
>
> out.setWriteListener(writeListener);
>
> proxyClientRequest.send(new Response.ContentListener() {
> void onContent(ByteBuffer buf, Callback complete) {
> writes.push(() -> {
> out.write(buf);
> complete.succeeded();
> };
> writeListener.onWritePossible(); // See if we can write
it immediately
> }
>
> void onComplete() {
> complete = true;
> writeListener.onWritePossible();
> }
> });
>
> This has the nice property where I don't copy buffers, just keep
them in a queue
> of pending writes -- but I worry that in the case of a slow
reader, Jetty Client
> will continue onContent-pushing buffers at me until I run out of
memory.
>
> I could instead use the OutputStreamContentProvider and just
read from it in the
> WriteListener, which might fix the flow control, but that seems
likely to involve
> a number of byte[] copies that I was hoping to avoid.
>
> What's the right approach to wire up Jetty server to Jetty
client with full NIO + Async
> content proxying, without introducing an intermediate transfer
buffer that might grow
> without bound? Am I on the right path or am I missing
something? Thanks for any guidance!
>
>
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