Migrating from DataClient to DataConnection

In this document we describe how to migrate existing code that uses DataClient to use DataConnection .

All examples use the following aliases:

 namespace gc = ::google::cloud;
namespace cbt = ::google::cloud::bigtable;

Simple case

 cbt::Table OldCode() {
  auto data_client = cbt::MakeDataClient("project-id", "instance-id");
  return cbt::Table(data_client, "table-id");
}

cbt::Table UpdatedCode() {
  auto connection = cbt::MakeDataConnection();
  return cbt::Table(
      connection, cbt::TableResource("project-id", "instance-id", "table-id"));
}

Note that the DataConnection is not associated with any resource ids. They are instead packaged as a TableResource and passed as a single object to Table .

Optional configuration

Note that there is only one Table constructor that accepts a DataConnection . All configuration is done via the Options parameter.

Set an application profile id

 cbt::Table OldCode() {
  auto data_client = cbt::MakeDataClient("project-id", "instance-id");
  return cbt::Table(data_client, "app-profile-id", "table-id");
}

cbt::Table UpdatedCode() {
  auto connection = cbt::MakeDataConnection();
  return cbt::Table(
      connection, cbt::TableResource("project-id", "instance-id", "table-id"),
      gc::Options{}.set<cbt::AppProfileIdOption>("app-profile-id"));
}

Set a custom retry policy

 cbt::Table OldCode() {
  auto data_client = cbt::MakeDataClient("project-id", "instance-id");
  return cbt::Table(data_client, "table-id",
                    cbt::LimitedErrorCountRetryPolicy(7));
}

cbt::Table UpdatedCode() {
  auto connection = cbt::MakeDataConnection();
  return cbt::Table(connection,
                    cbt::TableResource("project-id", "instance-id", "table-id"),
                    gc::Options{}.set<cbt::DataRetryPolicyOption>(
                        cbt::DataLimitedErrorCountRetryPolicy(7).clone()));
}

The retry, backoff, and idempotency policies are packaged in Options as shared_ptr s, instead of passed by value as variadic parameters to Table(..., Policies&&) .

Also note that the retry and backoff policy types have changed. If you defined your own policy, extending RPCRetryPolicy or RPCBackoffPolicy , it will not be compatible with the new types. The new policies do not have a Setup(grpc::ClientContext&) function. This function has not been included because we believe that setting up the grpc::ClientContext ...

Should not be tied to the retry policies.
Is unlikely to be needed by external customers.

If you do need a Setup() feature, please open a feature request explaining your use case, and we will be happy to accommodate you.