/// <summary>
/// Check if a database exists, and if it doesn't, create it.
/// This will make a read operation, and if the database is not found it will do a create operation.
///
/// A database manages users, permissions and a set of containers.
/// Each Azure Cosmos DB Database Account is able to support multiple independent named databases,
/// with the database being the logical container for data.
///
/// Each Database consists of one or more containers, each of which in turn contain one or more
/// documents. Since databases are an administrative resource, the Service Master Key will be
/// required in order to access and successfully complete any action using the User APIs.
/// </summary>
/// <param name="id">The database id.</param>
/// <param name="throughput">(Optional) The throughput provisioned for a database in measurement of Request Units per second in the Azure Cosmos DB service.</param>
/// <param name="requestOptions">(Optional) A set of additional options that can be set.</param>
/// <param name="cancellationToken">(Optional) <see cref="CancellationToken"/> representing request cancellation.</param>
/// <returns>A <see cref="Task"/> containing a <see cref="DatabaseResponse"/> which wraps a <see cref="DatabaseProperties"/> containing the resource record.</returns>
/// <remarks>
/// <seealso href="https://docs.microsoft.com/azure/cosmos-db/request-units"/> for details on provision throughput.
/// </remarks>
public virtual async Task <DatabaseResponse> CreateDatabaseIfNotExistsAsync(
string id,
int?throughput = null,
RequestOptions requestOptions = null,
CancellationToken cancellationToken = default(CancellationToken))
{
if (string.IsNullOrEmpty(id))
{
throw new ArgumentNullException(nameof(id));
}
// Doing a Read before Create will give us better latency for existing databases
Database database = this.GetDatabase(id);
DatabaseResponse cosmosDatabaseResponse = await database.ReadAsync(cancellationToken : cancellationToken);
if (cosmosDatabaseResponse.StatusCode != HttpStatusCode.NotFound)
{
return(cosmosDatabaseResponse);
}
cosmosDatabaseResponse = await this.CreateDatabaseAsync(id, throughput, requestOptions, cancellationToken : cancellationToken);
if (cosmosDatabaseResponse.StatusCode != HttpStatusCode.Conflict)
{
return(cosmosDatabaseResponse);
}
// This second Read is to handle the race condition when 2 or more threads have Read the database and only one succeeds with Create
// so for the remaining ones we should do a Read instead of throwing Conflict exception
return(await database.ReadAsync(cancellationToken : cancellationToken));
}
/// <summary>
/// <para>Check if a database exists, and if it doesn't, create it.
/// Only the database id is used to verify if there is an existing database. Other database properties
/// such as throughput are not validated and can be different then the passed properties.</para>
///
/// <para>A database manages users, permissions and a set of containers.
/// Each Azure Cosmos DB Database Account is able to support multiple independent named databases,
/// with the database being the logical container for data.</para>
///
/// <para>Each Database consists of one or more containers, each of which in turn contain one or more
/// documents. Since databases are an administrative resource, the Service Master Key will be
/// required in order to access and successfully complete any action using the User APIs.</para>
/// </summary>
/// <param name="id">The database id.</param>
/// <param name="throughput">(Optional) The throughput provisioned for a database in measurement of Request Units per second in the Azure Cosmos DB service.</param>
/// <param name="requestOptions">(Optional) A set of additional options that can be set.</param>
/// <param name="cancellationToken">(Optional) <see cref="CancellationToken"/> representing request cancellation.</param>
/// <returns>A <see cref="Task"/> containing a <see cref="DatabaseResponse"/> which wraps a <see cref="DatabaseProperties"/> containing the resource record.
/// <list type="table">
/// <listheader>
/// <term>StatusCode</term><description>Common success StatusCodes for the CreateDatabaseIfNotExistsAsync operation</description>
/// </listheader>
/// <item>
/// <term>201</term><description>Created - New database is created.</description>
/// </item>
/// <item>
/// <term>200</term><description>Accepted - This means the database already exists.</description>
/// </item>
/// </list>
/// </returns>
/// <seealso href="https://docs.microsoft.com/azure/cosmos-db/request-units">Request Units</seealso>
public virtual Task <DatabaseResponse> CreateDatabaseIfNotExistsAsync(
string id,
int?throughput = null,
RequestOptions requestOptions = null,
CancellationToken cancellationToken = default(CancellationToken))
{
if (string.IsNullOrEmpty(id))
{
throw new ArgumentNullException(nameof(id));
}
return(TaskHelper.RunInlineIfNeededAsync(async() =>
{
// Doing a Read before Create will give us better latency for existing databases
DatabaseProperties databaseProperties = this.PrepareDatabaseProperties(id);
Database database = this.GetDatabase(id);
ResponseMessage response = await database.ReadStreamAsync(requestOptions: requestOptions, cancellationToken: cancellationToken);
if (response.StatusCode != HttpStatusCode.NotFound)
{
return await this.ClientContext.ResponseFactory.CreateDatabaseResponseAsync(database, Task.FromResult(response));
}
response = await this.CreateDatabaseStreamAsync(databaseProperties, throughput, requestOptions, cancellationToken);
if (response.StatusCode != HttpStatusCode.Conflict)
{
return await this.ClientContext.ResponseFactory.CreateDatabaseResponseAsync(this.GetDatabase(databaseProperties.Id), Task.FromResult(response));
}
// This second Read is to handle the race condition when 2 or more threads have Read the database and only one succeeds with Create
// so for the remaining ones we should do a Read instead of throwing Conflict exception
return await database.ReadAsync(cancellationToken: cancellationToken);
}));
}
