@Override
    public void initialize() {
        InetSocketAddress address = new InetSocketAddress(host, port);
        nettyServerBuilder = NettyServerBuilder.forAddress(address);

        if (maxConcurrentCallsPerConnection > 0) {
            nettyServerBuilder.maxConcurrentCallsPerConnection(maxConcurrentCallsPerConnection);
        }
        if (maxMessageSize > 0) {
            nettyServerBuilder.maxInboundMessageSize(maxMessageSize);
        }
        if (threadPoolSize > 0) {
            ExecutorService executor = new ThreadPoolExecutor(
                threadPoolSize, threadPoolSize, 60, TimeUnit.SECONDS, new SynchronousQueue<>(),
                new CustomThreadFactory("grpcServerPool"), new CustomRejectedExecutionHandler()
            );
            nettyServerBuilder.executor(executor);
        }

        if (!Strings.isNullOrEmpty(privateKeyFile) && !Strings.isNullOrEmpty(certChainFile)) {
            sslContext = DynamicSslContext.forServer(privateKeyFile, certChainFile, trustedCAsFile);
            nettyServerBuilder.sslContext(sslContext);
        }
        log.info(SERVER_START_MARKER, "Server started, host {} listening on {}", host, port);
    }
Require for `server.crt` and `server.pem` for open ssl at server side.

@param certChainFile  `server.crt` file
@param privateKeyFile `server.pem` file
oap-server/server-library/library-server/src/main/java/org/apache/skywalking/oap/server/library/server/grpc/GRPCServer.java