Open and close channel in the gRPC client with every request - grpc

Question

I have a gRPC client in a kafka application. This means the client will constantly open and close channels.
public class UserAgentClient {
protected final Logger logger = LoggerFactory.getLogger(getClass());
private static final Config uaparserConfig = ConfigFactory.load().getConfig(ua);
private final ManagedChannel channel;
private final UserAgentServiceGrpc.UserAgentServiceBlockingStub userAgentBlockingStub;
public UserAgentParserClient() {
this(ManagedChannelBuilder.forAddress(uaConfig.getString("host"), uaConfig.getInt("port")).usePlaintext());
}
public UserAgentClient(ManagedChannelBuilder<?> usePlaintext) {
channel = usePlaintext.build();
userAgentBlockingStub = UserAgentServiceGrpc.newBlockingStub(channel);
}
public UserAgentParseResponse getUserAgent(String userAgent ) {
UserAgentRequest request = UserAgentRequest.newBuilder().setUserAgent(userAgent).build();
UserAgentParseResponse response = null;
try {
response = userAgentBlockingStub.parseUserAgent(request);
} catch(Exception e) {
logger.warn("An exception has occurred during gRPC call to the user agent.", e.getMessage());
}
shutdown();
return response;
}
public void shutdown() {
try {
channel.shutdown();
} catch (InterruptedException ie) {
logger.warn("Interrupted exception during gRPC channel close", ie);
}
}
}
I was wondering if I can keep the channel open the whole time? Or do I have to open a channel every time I make a new call? I was wondering because I was testing the performance and it seems to improve drastically if I just keep the channel open. On the other hand is there something that I'm missing?

Answer 1

creating a new channel has huge overhead, you should keep the channel open as long as possible.

Answer 2

Since the opening and closing of channel is expensive I removed the channel = usePlaintext.build(); completely from my client
Instead I'm opening and closing it in my kafka Transformer. In my class UserAgentDataEnricher that implements Transformer.
public class UserAgentDataEnricher implements Transformer<byte[], EnrichedData, KeyValue<byte[], EnrichedData>> {
private UserAgentParserClient userAgentParserClient;
#Override
public void init(ProcessorContext context) {
this.context = context;
open();
// schedule a punctuate() method every 15 minutes
this.context.schedule(900000, PunctuationType.WALL_CLOCK_TIME, (timestamp) -> {
close();
open();
logger.info("Re-opening of user agent channel is initialized");
});
}
#Override
public void close() {
userAgentParserClient.shutdown();
}
private void open() {
channel = ManagedChannelBuilder.forAddress("localhost", 50051).usePlaintext().build();
userAgentClient = new UserAgentClient(channel);
}
...
}
and now I initialize my client like that:
public UserAgentClient(ManagedChannel channel) {
this.channel = channel;
userAgentBlockingStub = UserAgentServiceGrpc.newBlockingStub(channel);
}