<div dir="ltr"><div class="gmail_default" style="font-family:trebuchet ms,sans-serif">I haven't had time to properly digest this so I don't have much to say now beyond that I think Darran makes a lot of good points and we should take our time to evaluate the full picture.</div><div class="gmail_default" style="font-family:trebuchet ms,sans-serif"><br></div><div class="gmail_default" style="font-family:trebuchet ms,sans-serif">This does feel like something that needs a subsystem. I'm not sure I completely follow the <span style="color:rgb(0,0,0);font-family:Arial,Helvetica,sans-serif">JAXRSForwarderBuilder concept, but it sounds like a JAXRS-specific integration with a general server-side gRPC implementation. From a separation of concerns point of view, that integration sounds like an appropriate</span> concern of the jaxrs subsystem, but providing the general gRPC infrastructure is not a natural responsibility of the jaxrs subsystem.</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, Jul 24, 2020 at 12:56 PM Ron Sigal <<a href="mailto:rsigal@redhat.com">rsigal@redhat.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div>
<p>Recently the RESTEasy group has been looking at protobuf and gRPC
and discussing how they might fit into the JAX-RS world. We now
have a feature request
(<a href="https://github.com/wildfly/wildfly-proposals/pull/326" target="_blank">https://github.com/wildfly/wildfly-proposals/pull/326</a>) for
exposing JAX-RS resources as gRPC servers
(<a href="https://issues.redhat.com/browse/WFLY-13530" target="_blank">https://issues.redhat.com/browse/WFLY-13530</a>). Briefly, it would
work as follows. Compiling the proto file<br>
<br>
service Greeter {<br>
rpc SayHello (HelloRequest) returns (HelloReply) {}<br>
...<br>
}<br>
<br>
will create a class GreeterGrpc, and a gRPC service can be created
by subclassing an inner class. Rather than implementing a gRPC
service, we propose passing the request to the appropriate JAX-RS
resource, something like this:<br>
<br>
class GreeterImpl extends GreeterGrpc.GreeterImplBase {<br>
<br>
@Override<br>
public void sayHello(HelloRequest req,
StreamObserver<HelloReply responseObserver) {<br>
JAXRSForwarderBuilder builder = new JAXRSForwarderBuilder();<br>
builder.servlet("ResteasyServlet").pathTranslator((String s)
-> ("test/" + s)); // Configure the JAXRSForwarder<br>
JAXRSForwarder forwarder = builder.build();<br>
forwarder.forward(req, (StreamObserver) responseObserver);<br>
}<br>
}<br>
<br>
The gRPC infrasture would catch a request, dispatch it to
GreeterImpl, and the JAXRSForwarder would <br>
<br>
1. create an HttpServletRequest and an HttpServletResponse<br>
2. find and invoke the appropriate RESTEasy servlet<br>
3. pass the result to the gRPC StreamObserver<br>
<br>
The idea is to hide the complexity behind the JAXRSForwarder.<br>
<br>
Now, this proposal is limited to extending RESTEasy. However,
Darren Lofthouse has been reading it carefully and has suggested
that it could be part of a larger discussion of how WildFly could
incorporate gRPC. Some discussion points:<br>
<br>
1. Right now we're proposing to open a dedicated socket for the
gRPC infrastructure, which runs on top of Netty. When Undertow
incorporates Netty, maybe gRPC could share a socket with other
subsystems.<br>
<br>
2. Maybe there should be a separate gRPC subsystem.<br>
<br>
3. Maybe we should go beyond servers and consider supporting
gRPC clients. For example, maybe gRPC clients could be injected
into JAX-RS resources the same as MicroProfile REST Clients.<br>
<br>
4. Darren has suggested that Elytron should be involved.<br>
<br>
In fact, I'm going to quote one of Darren's recent remarks:<br>
<br>
</p>
<blockquote>
<blockquote type="cite">Starting to research gRPC myself it feels
like the kind of thing where the general support / strategy
within the application server should be defined, the individual
subsystems such as JAX-RS and EJB which want to expose their
existing deployments would then dynamically make their resources
available through this. For areas such as security this would be
provided consistently within the general support.<br>
<br>
For gRPC initially if feels like it could have a good fit with
CDI, I don't know how practical that would be and if it would
cause a lot of considerations that may make it a better fit as a
SmallRye project. On one side if that gets too complex it may be
something that makes more sense as a SmallRye project to define
how gRPC deployments are handled, on the other side unless the
exposing of JAX-RS endpoints is 100% automated including the
protobuf generation it sounds like a level of user deployment
may be necessary anyway which may mean deployment handling is
required.<br>
<br>
I think the exposed socket is possibly less of an issue compared
to the general strategy. Maybe it will be necessary to expose a
separate server socket for now, I would have thought something
like this could justify it's own subsystem which would mean it
can be defined in it's own Galleon layer but that would mean as
a subsystem it could follow a similar path the Remoting
subsystem took i.e. exposing a port and once possible adding
support to delegate through Undertow.<br>
<br>
Regarding the other comments about how this could integrate with
Undertow, the main motivation for gRPC seems to be the use of
this binary protocol we probably should be cautious that we are
not adding too many layers on our side that requests need to be
translated thought otherwise we may be negating the benefits
from the outset.<br>
<br>
Recently the tasks I have been working through have involved a
lot of DeploymentUnitProcessor refactoring to restore better
collaboration between subsystems regarding how they share
security policy information, so far it has been slow going and
considering backwards compatibility there is still quite a long
way to go. This is the reason for something like this I am
interested in the overall architecture first so we can hopefully
avoid this kind of retrospective refactoring as we need to
enhance it further.</blockquote>
</blockquote>
<p><br>
Any comments are welcome.<br>
</p>
</div>
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