internal async Task ValidateHostIdUsageAsync(string hostId)
{
try
{
if (!_azureBlobStorageProvider.TryCreateHostingBlobContainerClient(out var blobContainerClient))
{
return;
}
HostIdInfo hostIdInfo = await ReadHostIdInfoAsync(hostId, blobContainerClient);
if (hostIdInfo != null)
{
// an existing record exists for this host ID
CheckForCollision(hostId, hostIdInfo);
}
else
{
// no existing record, so write one, claiming this host ID for this host name
// in this storage account
hostIdInfo = new HostIdInfo
{
Hostname = _hostNameProvider.Value
};
await WriteHostIdAsync(hostId, hostIdInfo, blobContainerClient);
}
}
catch (Exception ex)
{
// best effort - log error and continue
_logger.LogError(ex, "Error validating host ID usage.");
}
}
internal async Task WriteHostIdAsync(string hostId, HostIdInfo hostIdInfo, BlobContainerClient blobContainerClient)
{
try
{
string blobPath = string.Format(BlobPathFormat, hostId);
BlobClient blobClient = blobContainerClient.GetBlobClient(blobPath);
BinaryData data = BinaryData.FromObjectAsJson(hostIdInfo);
await blobClient.UploadAsync(data);
_logger.LogDebug($"Host ID record written (ID:{hostId}, HostName:{hostIdInfo.Hostname})");
}
catch (RequestFailedException rfex) when(rfex.Status == 409)
{
// Another instance wrote the blob between the time when we initially
// checked and when we attempted to write. Read the blob and validate it.
hostIdInfo = await ReadHostIdInfoAsync(hostId, blobContainerClient);
if (hostIdInfo != null)
{
CheckForCollision(hostId, hostIdInfo);
}
}
catch (Exception ex)
{
// best effort
_logger.LogError(ex, "Error writing host ID info");
}
}
internal async Task <HostIdInfo> ReadHostIdInfoAsync(string hostId, BlobContainerClient blobContainerClient)
{
HostIdInfo hostIdInfo = null;
try
{
// check storage to see if a record already exists for this host ID
string blobPath = string.Format(BlobPathFormat, hostId);
BlobClient blobClient = blobContainerClient.GetBlobClient(blobPath);
var downloadResponse = await blobClient.DownloadAsync();
string content;
using (StreamReader reader = new StreamReader(downloadResponse.Value.Content))
{
content = reader.ReadToEnd();
}
if (!string.IsNullOrEmpty(content))
{
hostIdInfo = JsonConvert.DeserializeObject <HostIdInfo>(content);
}
}
catch (RequestFailedException exception) when(exception.Status == 404)
{
// no record stored for this host ID
}
catch (Exception ex)
{
// best effort
_logger.LogError(ex, "Error reading host ID info");
}
return(hostIdInfo);
}
private void CheckForCollision(string hostId, HostIdInfo hostIdInfo)
{
// verify the host name is the same as our host name
if (!string.Equals(_hostNameProvider.Value, hostIdInfo.Hostname, StringComparison.OrdinalIgnoreCase))
{
HandleCollision(hostId);
}
}
