Blob writer

Uploads text or a file stream to a blob in Azure Storage, or appends records to an append blob, and passes the input on. Sets content type, metadata and access tier, and can create the container.

Pins

Pin	Kind	Types	Description
Input	input	Viaducta.Plugins.TextPlugin.Types.TextRecord, Viaducta.Plugins.Files.Types.ViaFileStream	Content to store: TextRecord.Value (UTF-8) or the stream.
Output	output	same as input	Called with the input record after a successful write.

Configuration

Field	Type	Default	Description
Authentication	dropdown: 0 ConnectionString, 1 EntraId, 2 ServicePrincipal, 3 SasToken	0	How to sign in to the storage account.
ConnectionString	string		Storage connection string. Required when Authentication is 0.
AccountUrl	string		Blob endpoint, for example https://myaccount.blob.core.windows.net, no query. Required when Authentication is 1, 2 or 3.
TenantId	string		Entra ID tenant id. Required for 2, optional for 1.
ClientId	string		2: client id of the app registration (required). 1: client id of a user-assigned managed identity (optional).
ClientSecret	password		Client secret of the app registration. Required for 2.
SasToken	password		Account or container SAS token with write permission (a leading ? is ignored). Required for 3.
ContainerName	string		Target container.
CreateContainer	boolean	false	true creates the container (private) when it does not exist.
BlobName	string		Target blob name including virtual folders, for example exports/daily.csv. Ending with / it is a folder and the record's name is appended (see Behaviour).
WriteMode	dropdown: 0 Block, 1 Append	0	0: one block blob upload per record. 1: append blob, every record is appended.
Overwrite	boolean	true	Block: true replaces an existing blob; false fails the upload (HTTP 409) when the blob exists.
AppendNewLine	boolean	true	Append: add a line break (\n) after each TextRecord.
ContentType	string		Content type of the blob, for example text/csv. Empty: the ContentType of the TextRecord, otherwise from the extension of the blob name (.csv, .json, .jsonl, .xml, .txt, .pdf, .zip, .gz, .parquet, images, ...), otherwise application/octet-stream.
AccessTier	dropdown: 0 Default, 1 Hot, 2 Cool, 3 Cold, 4 Archive	0	Block: tier of the uploaded blob; 0 uses the account's default tier.
Metadata	dictionary		Name/value pairs stored as blob metadata (names must be valid C# identifiers).

Behaviour

• The storage client is created at flow start; missing sign-in fields fail the start. 1 EntraId uses the default Azure credential (managed identity of the host, workload identity, environment variables or Azure CLI); the identity needs the Storage Blob Data Contributor role (it covers CreateContainer). With 3 SasToken, CreateContainer needs an account SAS that allows the container resource type.
• Blob name: for a TextRecord, its Name replaces BlobName, or is appended when BlobName ends with /; without a Name, BlobName is used. For a ViaFileStream, BlobName is used; when it is empty the stream's Name is used, and when it ends with / the stream's Name is appended. An empty result fails the record.
• With CreateContainer the container is created on the first write of the run if it is missing.
• 0 Block: the content is uploaded with content type, metadata and tier. 1 Append: the append blob is created when missing (with content type and metadata), then the content is appended in blocks of up to 4 MB; following records and later runs append to the same blob.
• Then Output is called with the input record. Other input types fail with a "not supported" error. Storage errors (missing container, authentication, existing blob with Overwrite false, append to an existing block blob) raise an error.

Notes

• ViaFileStream input: the content of Stream is uploaded from its current position; the stream stays open (it belongs to the component that opened it).
• Append blobs suit logs and JSON lines (.jsonl); appends of parallel writers interleave per record. An append blob holds at most 50,000 appends.
• Archive blobs can't be read until they are rehydrated (set the tier back with Blob operation).
• Store secrets as expression settings (=Secrets.AzureStorage).

Example

{ "Authentication": 1, "AccountUrl": "https://myaccount.blob.core.windows.net", "ContainerName": "exports", "CreateContainer": true, "BlobName": "daily/", "Metadata": { "source": "erp" } }

Timer → Sql query → Json serializer → Blob writer → Log (the TextRecord.Name of the serializer becomes the file in daily/)