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<div class="moz-cite-prefix">On 8/5/20 3:28 AM, Darran Lofthouse
wrote:<br>
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cite="mid:CAMxVf4MbhjTBQhhS=6QSrUgTva3C82d_-9a9Pi-J1_ryXkhDHg@mail.gmail.com">
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<div dir="ltr">On Wed, Aug 5, 2020 at 2:01 AM Ron Sigal <<a
href="mailto:rsigal@redhat.com" moz-do-not-send="true">rsigal@redhat.com</a>>
wrote:<br>
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<p>Hi Brian,</p>
<p>Sorry for the late response. I've been on PTO.</p>
<p>The only reason the feature request is jaxrs specific
is just because it comes out of RESTEasy. If there's a
desire for a more general gRPC treatment, we would be
happy to contribute to it.</p>
<p>The point of the JAXRSForwarder is to massage a gRPC
request to match a JAX-RS resource. For example, gRPC
has its own way of matching HTTP paths to services. We
could either write a JAX-RS resource to match the gRPC
conventions, or modify the gRPC request in order to
dispatch it to an existing JAX-RS resource. The latter
seems like the more likely use case.</p>
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<div><br>
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<div>I think in the JAX-RS case it would need some form of
forwarding providing as JAX-RS doesn't provide a way to call
endpoints directly already.</div>
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</div>
</blockquote>
<p>Specifically, I have RESTEasy maintain a map from servlet names
to servlets, and the JAXRSForwarder is supplied with the
appropriate servlet name. Btw, I tried to extract that information
from undertow, successfully, but, as far as I could tell, it
involved some messy digging.</p>
<p>An alternative might be to automate turning a JAX-RS resource
class into a gRPC proto file, and then automating the forwarding,
but it doesn't seem feasible since JAX-RS has things like query
method parameters and matrix method parameters, which, as far as I
know, don't exist in gRPC.<br>
</p>
<blockquote type="cite"
cite="mid:CAMxVf4MbhjTBQhhS=6QSrUgTva3C82d_-9a9Pi-J1_ryXkhDHg@mail.gmail.com">
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<p>Now, I don't know anything about EJB internals, but I
can imagine doing something similar to dispatch a gRPC
request to an EJB. So, maybe we need a general purpose
Forwarder interface.</p>
</div>
</blockquote>
<div>In the EJB case however in-vm invocations from one
component to an EJB are already possible. For gRPC it feels
like it may be natural for a class to be deployed as a
service which in turn could call EJBs if it chooses. </div>
<div><br>
</div>
</div>
</div>
</blockquote>
My example of building and calling the JAXRSForwarder was meant to
be written by the application developer, with as much help as
possible from RESTEasy. If forwarding to EJBs would work
differently, then it seems reasonable for that code to look somewhat
different. I.e., my comment about a general purpose Forwarder
interface might make no sense.<br>
<blockquote type="cite"
cite="mid:CAMxVf4MbhjTBQhhS=6QSrUgTva3C82d_-9a9Pi-J1_ryXkhDHg@mail.gmail.com">
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<p>Anyway, if anyone wants to talk about it, this thread
might be a good place to start.</p>
<p>-Ron<br>
</p>
<div>On 7/28/20 8:44 AM, Brian Stansberry wrote:<br>
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<div 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 style="font-family:"trebuchet
ms",sans-serif"><br>
</div>
<div 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" target="_blank"
moz-do-not-send="true">rsigal@redhat.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px
0px 0.8ex;border-left:1px solid
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<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" moz-do-not-send="true">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"
moz-do-not-send="true">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>
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-- <br>
<div dir="ltr">
<div dir="ltr">Brian Stansberry
<div>Manager, Senior Principal Software Engineer</div>
<div>Red Hat</div>
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