Add a README section on supported runtime environments & workarounds

[saturnism]

gRPC currently don't work well in embedded Tomcat or embedded Netty envs. Document what we know works and don't work and work arounds.

Specifically, if someone uses the client lib in Spring Boot, they need to exclude tomcat starter and use jetty starter instead.

Corollary to this, in each module's README, refer to this section for supported envs.

[shinfan]

@saturnism Can you be more specific what did not work well in Tomcat or Netty?

[tswast]

I encountered this issue today with the Cloud Pub/Sub client library.

With Spring Boot, I got the error "Jetty ALPN/NPN has not been properly configured" at runtime. These were my dependencies:

    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-web</artifactId>
      <version>1.5.3.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework.security</groupId>
      <artifactId>spring-security-core</artifactId>
      <version>4.2.2.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>com.google.cloud</groupId>
      <artifactId>google-cloud-pubsub</artifactId>
      <version>0.17.2-alpha</version>
    </dependency>

The code worked without modification after I made Spring Boot use Jetty instead of Tomcat.

    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-web</artifactId>
      <version>1.5.3.RELEASE</version>
      <exclusions>
        <exclusion>
          <!-- Use Jetty instead of Tomcat
               https://www.mkyong.com/spring-boot/spring-boot-jetty-as-embedded-server/ -->
          <groupId>org.springframework.boot</groupId>
          <artifactId>spring-boot-starter-tomcat</artifactId>
        </exclusion>
      </exclusions>
    </dependency>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-jetty</artifactId>
      <version>1.5.3.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework.security</groupId>
      <artifactId>spring-security-core</artifactId>
      <version>4.2.2.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>com.google.cloud</groupId>
      <artifactId>google-cloud-pubsub</artifactId>
      <version>0.17.2-alpha</version>
    </dependency>

[jabubake]

Note has been added in the main README. We still need to add links to Supported environments on each module.

[joaoandremartins]

Yes, I just started using the PubSub API within a Spring Boot app and I'm getting this too.

After reading a bit on this, I tried importing the netty-tcnative-boringssl-static dependency, as well as org.eclipse.jetty.npn.npn-api (since the code throwing this error is checking for org.eclipse.jetty.npn.NextProtoNego in the classpath) to no avail.

[shinfan]

@jabubake Can we close the issue now since the notes has been added?

[joaoandremartins]

Ideally, we would want gRPC to work with Tomcat seamlessly too.

[joaoandremartins]

Seems like a fix for this is coming out on a next release of the grpc-java library.
grpc/grpc-java#2996

[Mistic92]

Yesterday I have encountered the same problem with spring boot and pubsub lib. Even when I'm using Jetty I'm still getting "Jetty ALPN/NPN has not been properly configured."
When can we expect fix?
I see there is new version of grpc (1.3.0) so now we are waiting for pubsub?

[garrettjonesgoogle]

We have upgraded to grpc 1.4 which removes the conflict with Tomcat. Since the underlying issue should be fixed, I'm going to close this out.