gRPC version upgrade

[jabubake]

Looks like certain version of Maven (2.2.1, 3.2.2 and 3.2.3) run into issues with com.google.code.gson:gson:2.3: google/gson#588
The issue is resolved in gson : 2.3.1.
The older version(2.3) is linked in google-cloud-core from grpc 1.0.3.
grpc 1.1+ support gson:2.7. Is there a reason not to be on atleast 1.1.x of grpc ?

[INFO] | | +- io.grpc:grpc-protobuf:jar:1.0.3:compile
[INFO] | | | +- (com.google.guava:guava:jar:19.0:compile - omitted for duplicate)
[INFO] | | | +- com.google.protobuf:protobuf-java-util:jar:3.0.2:compile
[INFO] | | | | +- (com.google.protobuf:protobuf-java:jar:3.0.2:compile - omitted for conflict with 3.0.0)
[INFO] | | | | +- (com.google.guava:guava:jar:18.0:compile - omitted for conflict with 20.0)
[INFO] | | | | - com.google.code.gson:gson:jar:2.3:compile

[buchgr]

tl;dr;
Yes to upgrading! :-)

There is another problem due to no fault of Google Cloud Java. gRPC 1.1.x and 1.0x aren't API compatible. This commit [1] changed the return type of NettyChannelBuilder.build() from ManagedChannelImpl (1.0.x) to ManagedChannel (1.1.0). By coincidence google-cloud-spanner uses ManagedChannel [2] and so the code still compiles with newer gRPC versions, but doesn't run. Here is the byte code version of SpannerOptions$NettyRpcChannelFactory#newChannel(String, int) with the class file taken from maven central version 0.10.0-beta. Notice, how it calls a method with a ManagedChannelImpl return type.

[1] grpc/grpc-java@d17a7b5#diff-34c34e0485cd6a3ebabb1f46de341a1aL269
[2] https://github.com/GoogleCloudPlatform/google-cloud-java/blob/master/google-cloud-spanner/src/main/java/com/google/cloud/spanner/SpannerOptions.java#L272

[garrettjonesgoogle]

We already have this issue for upgrading grpc: #1691 ; work hasn't started yet.

We have also already pulled in a change in gax-java (googleapis/gax-java#208) to switch from NettyChannelBuilder to ManagedChannelBuilder. This is in master but hasn't been released yet.

[garrettjonesgoogle]

Resolving this issue in favor of #1691 .