C# hello world

Este exemplo de código é uma aplicação "hello world" escrita em C#. O exemplo ilustra como concluir as seguintes tarefas:

• Configure a autenticação
• Associe-se a uma instância do Bigtable
• Criar uma nova tabela.
• Escreva dados na tabela.
• Ler os dados novamente.
• Eliminar a tabela.

Configure a autenticação

Para usar os .NET exemplos nesta página num ambiente de desenvolvimento local, instale e inicialize a CLI gcloud e, em seguida, configure as Credenciais predefinidas da aplicação com as suas credenciais de utilizador.

Instale a CLI Google Cloud.

Se estiver a usar um fornecedor de identidade (IdP) externo, primeiro tem de iniciar sessão na CLI gcloud com a sua identidade federada.

If you're using a local shell, then create local authentication credentials for your user account:

gcloud auth application-default login

You don't need to do this if you're using Cloud Shell.

If an authentication error is returned, and you are using an external identity provider (IdP), confirm that you have signed in to the gcloud CLI with your federated identity.

Para mais informações, consulte Set up authentication for a local development environment.

Executar o exemplo

Este código comunica com o Bigtable através das bibliotecas da API C# Admin e da API C# Data nas bibliotecas cliente do Google Cloud para .NET.

Para executar este programa de exemplo, siga as instruções dos exemplos do.NET Bigtable no GitHub. Conclua os passos Criar e executar e Início rápido para criar recursos que pode usar na sua aplicação Hello World. Certifique-se de que edita o ficheiro HelloWorld.cs para adicionar os nomes dos recursos que cria.

Usar as bibliotecas cliente da Google Cloud com o Bigtable

A aplicação de exemplo liga-se ao Bigtable e demonstra algumas operações simples.

Associar ao Bigtable

Para começar, crie dois objetos de cliente que pode usar para se ligar ao Bigtable. As APIs de administrador C# BigtableTableAdminClient ajudam a criar e eliminar instâncias e tabelas. As APIs Data C# BigtableClient ajudam a ler e escrever dados de tabelas.

// BigtableTableAdminClient API lets us create, manage and delete tables.
BigtableTableAdminClient bigtableTableAdminClient = BigtableTableAdminClient.Create();

// BigtableClient API lets us read and write to a table.
BigtableClient bigtableClient = BigtableClient.Create();

Criar uma tabela

Chame o método CreateTable() na classe BigtableTableAdminClient para gerar um objeto Table que armazena as saudações "Olá, mundo". A tabela tem uma única família de colunas que retém uma versão de cada valor.

Nota: as colunas relacionadas entre si são normalmente agrupadas numa família de colunas. Para mais informações sobre famílias de colunas, consulte o modelo de armazenamento do Bigtable.

// Create a table with a single column family.
Console.WriteLine($"Create new table: {tableId} with column family: {columnFamily}, instance: {instanceId}");

// Check whether a table with given TableName already exists.
if (!TableExist(bigtableTableAdminClient))
{
    bigtableTableAdminClient.CreateTable(
        new InstanceName(projectId, instanceId),
        tableId,
        new Table
        {
            Granularity = Table.Types.TimestampGranularity.Millis,
            ColumnFamilies =
            {
                {
                    columnFamily, new ColumnFamily
                    {
                        GcRule = new GcRule
                        {
                            MaxNumVersions = 1
                        }
                    }
                }
            }
        });
    // Confirm that table was created successfully.
    Console.WriteLine(TableExist(bigtableTableAdminClient)
        ? $"Table {tableId} created successfully\n"
        : $"There was a problem creating a table {tableId}");
}
else
{
    Console.WriteLine($"Table: {tableId} already exists");
}

Escrever linhas numa tabela

Use a matriz de strings s_greetings[], que contém três saudações simples, como uma origem de dados para escrever na tabela. Primeiro, escreva uma única linha na tabela usando MutateRow(). Em seguida, percorra o resto da matriz para criar um objeto MutateRowsRequest que contenha uma entrada para cada saudação. Faça o pedido para escrever todas as entradas de uma só vez com MutateRows(). Em seguida, percorra a resposta devolvida para verificar o código de estado de cada entrada para se certificar de que foi escrita com êxito.

// Initialize Google.Cloud.Bigtable.V2.TableName object.
Google.Cloud.Bigtable.Common.V2.TableName tableName = new Google.Cloud.Bigtable.Common.V2.TableName(projectId, instanceId, tableId);

// Write some rows
/* Each row has a unique row key.

       Note: This example uses sequential numeric IDs for simplicity, but
       this can result in poor performance in a production application.
       Since rows are stored in sorted order by key, sequential keys can
       result in poor distribution of operations across nodes.

       For more information about how to design a Bigtable schema for the
       best performance, see the documentation:

       https://cloud.google.com/bigtable/docs/schema-design */

Console.WriteLine($"Write some greetings to the table {tableId}");

// Insert 1 row using MutateRow()
s_greetingIndex = 0;
try
{
    bigtableClient.MutateRow(tableName, rowKeyPrefix + s_greetingIndex, MutationBuilder());
    Console.WriteLine($"\tGreeting:   -- {s_greetings[s_greetingIndex],-18}-- written successfully");
}
catch (Exception ex)
{
    Console.WriteLine($"\tFailed to write greeting: --{s_greetings[s_greetingIndex]}");
    Console.WriteLine(ex.Message);
    throw;
}

// Insert multiple rows using MutateRows()
// Build a MutateRowsRequest (contains table name and a collection of entries).
MutateRowsRequest request = new MutateRowsRequest
{
    TableNameAsTableName = tableName
};

s_mapToOriginalGreetingIndex = new List<int>();
while (++s_greetingIndex < s_greetings.Length)
{
    s_mapToOriginalGreetingIndex.Add(s_greetingIndex);
    // Build an entry for every greeting (consists of rowkey and a collection of mutations).
    string rowKey = rowKeyPrefix + s_greetingIndex;
    request.Entries.Add(Mutations.CreateEntry(rowKey, MutationBuilder()));
}

// Make the request to write multiple rows.
MutateRowsResponse response = bigtableClient.MutateRows(request);

// Check the status code of each entry to ensure that it was written successfully.
foreach (MutateRowsResponse.Types.Entry entry in response.Entries)
{
    s_greetingIndex = s_mapToOriginalGreetingIndex[(int)entry.Index];
    if (entry.Status.Code == 0)
    {
        Console.WriteLine($"\tGreeting:   -- {s_greetings[s_greetingIndex],-18}-- written successfully");
    }
    else
    {
        Console.WriteLine($"\tFailed to write greeting: --{s_greetings[s_greetingIndex]}");
        Console.WriteLine(entry.Status.Message);
    }
}

Mutation MutationBuilder() =>
    Mutations.SetCell(columnFamily, columnName, s_greetings[s_greetingIndex], new BigtableVersion(DateTime.UtcNow));

Criar um filtro

Antes de ler os dados que escreveu, crie um filtro para limitar os dados que o Bigtable devolve. Este filtro indica ao Bigtable que deve devolver apenas a versão mais recente de cada valor, mesmo que a tabela contenha células mais antigas elegíveis para a recolha de lixo, mas que ainda não foram eliminadas.

RowFilter filter = RowFilters.CellsPerRowLimit(1);

Ler uma linha pela respetiva chave de linha

Use o método ReadRow(), transmitindo o filtro que acabou de criar, para obter uma versão de cada valor nessa linha.

// Read from the table.
Console.WriteLine("Read the first row");

int rowIndex = 0;

// Read a specific row. Apply a filter to return latest only cell value accross entire row.
Row rowRead = bigtableClient.ReadRow(
    tableName, rowKey: rowKeyPrefix + rowIndex, filter: filter);
Console.WriteLine(
    $"\tRow key: {rowRead.Key.ToStringUtf8()} " +
    $"  -- Value: {rowRead.Families[0].Columns[0].Cells[0].Value.ToStringUtf8(),-16} " +
    $"  -- Time Stamp: {rowRead.Families[0].Columns[0].Cells[0].TimestampMicros}");

Analisar todas as linhas da tabela

Chame o método ReadRows(), transmitindo o filtro, para obter todas as linhas na tabela. Como transmitiu o filtro, o Bigtable devolve apenas uma versão de cada valor.

Console.WriteLine("Read all rows using streaming");
// stream the content of the whole table. Apply a filter to return latest only cell values accross all rows.
ReadRowsStream responseRead = bigtableClient.ReadRows(tableName, filter: filter);

Task printRead = PrintReadRowsAsync();
printRead.Wait();

async Task PrintReadRowsAsync()
{
    var responseEnumerator = responseRead.GetAsyncEnumerator(default);
    while (await responseEnumerator.MoveNextAsync())
    {
        Row row = responseEnumerator.Current;
        Console.WriteLine(
            $"\tRow key: {row.Key.ToStringUtf8()} " +
            $"  -- Value: {row.Families[0].Columns[0].Cells[0].Value.ToStringUtf8(),-16} " +
            $"  -- Time Stamp: {row.Families[0].Columns[0].Cells[0].TimestampMicros}");
    }
}

Eliminar uma tabela

Elimine a tabela com o método DeleteTable().

// Clean up. Delete the table.
Console.WriteLine($"Delete table: {tableId}");

bigtableTableAdminClient.DeleteTable(name: tableName);
if (!TableExist(bigtableTableAdminClient))
{
    Console.WriteLine($"Table: {tableId} deleted successfully");
}

A reunir tudo

Segue-se o exemplo de código completo sem comentários.

using Google.Cloud.Bigtable.Admin.V2;
using Google.Cloud.Bigtable.Common.V2;
using Google.Cloud.Bigtable.V2;
using Grpc.Core;
using System;
using System.Collections.Generic;
using System.Threading.Tasks;

namespace GoogleCloudSamples.Bigtable
{
    public class HelloWorld
    {
        private const string projectId = "YOUR-PROJECT-ID";

        private const string instanceId = "YOUR-INSTANCE-ID";

        private const string tableId = "Hello-Bigtable";
        private const string columnFamily = "cf";
        private const string columnName = "greeting";
        private static readonly string[] s_greetings = { "Hello World!", "Hello Bigtable!", "Hello C#!" };
        private static List<int> s_mapToOriginalGreetingIndex;
        private const string rowKeyPrefix = "greeting";
        private static int s_greetingIndex;

        private static void DoHelloWorld()
        {
            try
            {
                BigtableTableAdminClient bigtableTableAdminClient = BigtableTableAdminClient.Create();

                BigtableClient bigtableClient = BigtableClient.Create();

                Console.WriteLine($"Create new table: {tableId} with column family: {columnFamily}, instance: {instanceId}");

                if (!TableExist(bigtableTableAdminClient))
                {
                    bigtableTableAdminClient.CreateTable(
                        new InstanceName(projectId, instanceId),
                        tableId,
                        new Table
                        {
                            Granularity = Table.Types.TimestampGranularity.Millis,
                            ColumnFamilies =
                            {
                                {
                                    columnFamily, new ColumnFamily
                                    {
                                        GcRule = new GcRule
                                        {
                                            MaxNumVersions = 1
                                        }
                                    }
                                }
                            }
                        });
                    Console.WriteLine(TableExist(bigtableTableAdminClient)
                        ? $"Table {tableId} created successfully\n"
                        : $"There was a problem creating a table {tableId}");
                }
                else
                {
                    Console.WriteLine($"Table: {tableId} already exists");
                }

                Google.Cloud.Bigtable.Common.V2.TableName tableName = new Google.Cloud.Bigtable.Common.V2.TableName(projectId, instanceId, tableId);


                       Note: This example uses sequential numeric IDs for simplicity, but
                       this can result in poor performance in a production application.
                       Since rows are stored in sorted order by key, sequential keys can
                       result in poor distribution of operations across nodes.

                       For more information about how to design a Bigtable schema for the
                       best performance, see the documentation:

                       https://cloud.google.com/bigtable/docs/schema-design */

                Console.WriteLine($"Write some greetings to the table {tableId}");

                s_greetingIndex = 0;
                try
                {
                    bigtableClient.MutateRow(tableName, rowKeyPrefix + s_greetingIndex, MutationBuilder());
                    Console.WriteLine($"\tGreeting:   -- {s_greetings[s_greetingIndex],-18}-- written successfully");
                }
                catch (Exception ex)
                {
                    Console.WriteLine($"\tFailed to write greeting: --{s_greetings[s_greetingIndex]}");
                    Console.WriteLine(ex.Message);
                    throw;
                }

                MutateRowsRequest request = new MutateRowsRequest
                {
                    TableNameAsTableName = tableName
                };

                s_mapToOriginalGreetingIndex = new List<int>();
                while (++s_greetingIndex < s_greetings.Length)
                {
                    s_mapToOriginalGreetingIndex.Add(s_greetingIndex);
                    string rowKey = rowKeyPrefix + s_greetingIndex;
                    request.Entries.Add(Mutations.CreateEntry(rowKey, MutationBuilder()));
                }

                MutateRowsResponse response = bigtableClient.MutateRows(request);

                foreach (MutateRowsResponse.Types.Entry entry in response.Entries)
                {
                    s_greetingIndex = s_mapToOriginalGreetingIndex[(int)entry.Index];
                    if (entry.Status.Code == 0)
                    {
                        Console.WriteLine($"\tGreeting:   -- {s_greetings[s_greetingIndex],-18}-- written successfully");
                    }
                    else
                    {
                        Console.WriteLine($"\tFailed to write greeting: --{s_greetings[s_greetingIndex]}");
                        Console.WriteLine(entry.Status.Message);
                    }
                }

                Mutation MutationBuilder() =>
                    Mutations.SetCell(columnFamily, columnName, s_greetings[s_greetingIndex], new BigtableVersion(DateTime.UtcNow));

                RowFilter filter = RowFilters.CellsPerRowLimit(1);

                Console.WriteLine("Read the first row");

                int rowIndex = 0;

                Row rowRead = bigtableClient.ReadRow(
                    tableName, rowKey: rowKeyPrefix + rowIndex, filter: filter);
                Console.WriteLine(
                    $"\tRow key: {rowRead.Key.ToStringUtf8()} " +
                    $"  -- Value: {rowRead.Families[0].Columns[0].Cells[0].Value.ToStringUtf8(),-16} " +
                    $"  -- Time Stamp: {rowRead.Families[0].Columns[0].Cells[0].TimestampMicros}");

                Console.WriteLine("Read all rows using streaming");
                ReadRowsStream responseRead = bigtableClient.ReadRows(tableName, filter: filter);

                Task printRead = PrintReadRowsAsync();
                printRead.Wait();

                async Task PrintReadRowsAsync()
                {
                    var responseEnumerator = responseRead.GetAsyncEnumerator(default);
                    while (await responseEnumerator.MoveNextAsync())
                    {
                        Row row = responseEnumerator.Current;
                        Console.WriteLine(
                            $"\tRow key: {row.Key.ToStringUtf8()} " +
                            $"  -- Value: {row.Families[0].Columns[0].Cells[0].Value.ToStringUtf8(),-16} " +
                            $"  -- Time Stamp: {row.Families[0].Columns[0].Cells[0].TimestampMicros}");
                    }
                }

                Console.WriteLine($"Delete table: {tableId}");

                bigtableTableAdminClient.DeleteTable(name: tableName);
                if (!TableExist(bigtableTableAdminClient))
                {
                    Console.WriteLine($"Table: {tableId} deleted successfully");
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine($"Exception while running HelloWorld: {ex.Message}");
            }
        }

        private static bool TableExist(BigtableTableAdminClient bigtableTableAdminClient)
        {
            GetTableRequest request = new GetTableRequest
            {
                TableName = new Google.Cloud.Bigtable.Common.V2.TableName(projectId, instanceId, tableId),
                View = Table.Types.View.NameOnly
            };
            try
            {
                var tables = bigtableTableAdminClient.GetTable(request);
                return true;
            }
            catch (RpcException ex)
            {
                if (ex.StatusCode == StatusCode.NotFound)
                {
                    return false;
                }

                throw;
            }
        }

        public static int Main(string[] args)
        {
            if (projectId == "YOUR-PROJECT" + "-ID")
            {
                Console.WriteLine("Edit HelloWorld.cs and replace YOUR-PROJECT-ID with your project ID.");
                return -1;
            }
            if (instanceId == "YOUR-INSTANCE" + "-ID")
            {
                Console.WriteLine("Edit HelloWorld.cs and replace YOUR-INSTANCE-ID with your instance ID.");
                return -1;
            }

            DoHelloWorld();
            return 0;
        }
    }
}