fix: grpc issue (UNAUTHENTICATED errors against Cloud Spanner emulator in v1.45.0)

[HannahShiSFB]

fix of grpc/grpc#29233, which is caused by grpc/grpc#25586 which removed insecure channel.

Regardless whether Spanner connects to emulator or production server, gax-php always create a CredentialsWrapper (https://github.com/googleapis/gax-php/blob/v1.12.0/src/GapicClientTrait.php#L434) and add it to callstack (https://github.com/googleapis/gax-php/blob/v1.12.0/src/GapicClientTrait.php#L610).
When creating gRPC calls, GrpcTransport calls CredentialsWrapper (https://github.com/googleapis/gax-php/blob/v1.12.0/src/Transport/GrpcTransport.php#L258-L259) to setup a callback for auth token, which requires secure level to be equal or higher than GRPC_PRIVACY_AND_INTEGRITY which doesn’t work on an insecure channel.

[saranshdhingra]

Hi @HannahShiSFB
I went ahead and fixed some linting issues, to speed the process.
(Just an FYI)

[fqqdk]

There is this part, where the array union operator is replaced with array_merge(), in Spanner/src/Connection/Grpc.php ie:

$grpcConfig = array_merge(
    $grpcConfig,
    $this->emulatorGapicConfig($config['emulatorHost'])
);

A similar change is also needed in vendor/google/cloud-pubsub/src/Connection/Grpc.php (line 118) (and maybe in other Grpc Connection classes)

[bshaffer]

That's a good catch, otherwise behavior could change for some implementations!

[HannahShiSFB]

There is this part, where the array union operator is replaced with array_merge(), in Spanner/src/Connection/Grpc.php ie:

$grpcConfig = array_merge(
    $grpcConfig,
    $this->emulatorGapicConfig($config['emulatorHost'])
);

A similar change is also needed in vendor/google/cloud-pubsub/src/Connection/Grpc.php (line 118) (and maybe in other Grpc Connection classes)

There are 5 emulators in google cloud: Spanner, Firestore, PubSub, Datastore, BigTable. They all have the same issue.
Spanner and BigTable have been fixed by this PR. After testing, I'll fix the other 3.

[jmleroux]

Hello guys,
Is there any update about this PR? We are looking at it because it is blocking us from using the Firestore emulator.
We would be glad to help if needed. 😉

[bshaffer]

Hi @jmleroux !

The changes here only effect Spanner. We will need to make additional changes for them to be added to Firestore, PubSub, Datastore, and BigTable. However, this can be done at any time (the changes here will not effect existing behavior).

EDIT: I've added the changes for the other relevant packages in #5250