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new d21863011 docs(connectors): align MongoDB sink duplicate-key semantics
(#2941)
d21863011 is described below
commit d218630116ae9dfa1b6c2a62b56a605a3823a89a
Author: Aviraj Khare <[email protected]>
AuthorDate: Tue Mar 17 16:34:39 2026 +0530
docs(connectors): align MongoDB sink duplicate-key semantics (#2941)
---
core/connectors/sinks/mongodb_sink/README.md | 9 +++++----
core/integration/tests/connectors/mongodb/mongodb_sink.rs | 2 +-
2 files changed, 6 insertions(+), 5 deletions(-)
diff --git a/core/connectors/sinks/mongodb_sink/README.md
b/core/connectors/sinks/mongodb_sink/README.md
index 550612cc3..5e0dd4cfa 100644
--- a/core/connectors/sinks/mongodb_sink/README.md
+++ b/core/connectors/sinks/mongodb_sink/README.md
@@ -137,10 +137,11 @@ This connector provides **at-least-once** delivery
semantics.
### Behavior
- Messages may be delivered more than once on retry or restart
-- Uses Iggy message ID as MongoDB `_id` for document identity
-- **Insert-only mode**: duplicate key error is a hard failure (not upsert)
+- Uses a deterministic composite MongoDB `_id`:
`stream:topic:partition:message_id`
+- Duplicate key collisions are treated as idempotent replay of already-written
messages
+- The sink remains insert-only; it does not upsert existing documents
### Known Limitations
-- On network timeout during insert, retry may cause duplicate key error
-- Sink does not upsert on duplicate (future improvement)
+- On network timeout during insert, MongoDB may partially commit a batch
before returning an error
+- The sink does not upsert on duplicate; replay safety relies on deterministic
`_id` values and duplicate-key tolerance
diff --git a/core/integration/tests/connectors/mongodb/mongodb_sink.rs
b/core/integration/tests/connectors/mongodb/mongodb_sink.rs
index 37c522e34..474b809ed 100644
--- a/core/integration/tests/connectors/mongodb/mongodb_sink.rs
+++ b/core/integration/tests/connectors/mongodb/mongodb_sink.rs
@@ -261,7 +261,7 @@ async fn large_batch_processed_correctly(harness:
&TestHarness, fixture: MongoDb
server(connectors_runtime(config_path =
"tests/connectors/mongodb/sink.toml")),
seed = seeds::connector_stream
)]
-async fn duplicate_key_is_explicit_failure_and_not_silent_success(
+async fn duplicate_key_is_idempotent_replay_not_sink_error(
harness: &TestHarness,
fixture: MongoDbSinkFixture,
) {
