/// <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="requestUnitsPerSecond">(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="CosmosDatabaseSettings"/> 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?requestUnitsPerSecond = 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
CosmosDatabase database = this.GetDatabase(id);
DatabaseResponse cosmosDatabaseResponse = await database.ReadAsync(cancellationToken : cancellationToken);
if (cosmosDatabaseResponse.StatusCode != HttpStatusCode.NotFound)
{
return(cosmosDatabaseResponse);
}
cosmosDatabaseResponse = await this.CreateDatabaseAsync(id, requestUnitsPerSecond, 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));
}
public override async Task <CosmosDatabaseResponse> CreateDatabaseIfNotExistsAsync(
string id,
int?throughput = null,
CosmosRequestOptions requestOptions = null,
CancellationToken cancellationToken = default(CancellationToken))
{
// Doing a Read before Create will give us better latency for existing databases
CosmosDatabase database = this[id];
CosmosDatabaseResponse 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));
}
