Exceptions

Follow a record from routing through processing and delivery. Whatever stops a record on the way is an exception, and you choose each exception's answer.

Find the right answer

What happened?	Exception	Where to answer it	Default
A pipeline lost a value	a parse, math, limits or encoding kind	Routes → Exceptions	tag, or ignore for encoding
No route or delivery condition took it	`Unmatched`	Routes → Exceptions	block
A batch could not be processed	`Unprocessable`	Routes → Exceptions	block
A destination refused a record	`Refused`	Routes → Exceptions	block
A destination could not be reached	none	Repair its connection or service	Retry; pause input when buffers fill

Answer exceptions

Each exception has a kind, and each kind belongs to a category: parse, math, limits, encoding or delivery. The Exceptions on the Routes page give every kind in the group one of five answers:

ignore: the record goes on unmarked. Smeltr still counts the exception.
tag: the record goes on with its exceptions written to the tag field.
drop: Smeltr counts the record and discards it.
deliver: the record goes to the destinations you pick, with its exceptions in the tag field, each in its own format.
block: the source stops. Processing waits for a new deployment; Smeltr sends a refused record again until the destination takes it. Status → Issues shows it as Source blocked, or Blocked by destination refusals; capture it to see the records.

An answer for a category covers every kind in it, and a kind's own answer beats its category's. A record with several exceptions takes the strongest answer: block, then deliver, then drop, then tag, then ignore. The delivery kinds have no record on a route to tag, so you cannot ignore or tag them.

The Exceptions on the Routes page: math is dropped, limits block the source, and Overflow, a math kind, is tagged. — The group's Exceptions on the Routes page. Overflow's answer beats its category's, so Overflow is tagged while the rest of math is dropped.

A route or a destination can answer differently from the group, under Exceptions in its card. A destination answers only the records it refuses.

Tag and route

A tagged record carries its exceptions in smeltr.exception. Delivery conditions read that field to choose a destination. Use smeltr.exception != null to send tagged records to an investigation destination, and smeltr.exception == null to send only clean records to the normal one.

The Tag field, under Exceptions → Advanced, names another field for the group or for one route. If you rename it, update both conditions. See unparsable records for examples you can test.

When no route matches

A record that matches none of its source's routes is Unmatched. Blocking holds the records and pauses the source until a new deployment: add or correct a route, or change the answer, then review and deploy. Delivering keeps them in another destination for investigation or later processing.

Use route conditions to decide what belongs in each pipeline. An unconditional route matches all records from its source, so no record of that source is left without a route.

Every record a pipeline finishes goes to a destination, is dropped by your pipeline, or is Unmatched: if no delivery condition takes it, it gets the Unmatched answer, delivered as the pipeline left it.

When processing cannot finish

A batch Smeltr cannot process, including a record that exceeds its memory budget, is Unprocessable. Blocking waits for a new deployment. No pipeline finished the record, so a destination that writes the record writes {"_raw": …}.