Cassandra to Elasticsearch
real-time replication
TwinCommit replicates Apache Cassandra to Elasticsearch in real time by reading the Cassandra transaction log and applying every committed change exactly once and in commit order. Use it to keep Elasticsearch search indexes current with Cassandra, with no triggers or capture tables on the source.
Cassandra
log reader
commit-ordered · exactly-once
Elasticsearch
native writer
How capture works on Cassandra
TwinCommit tails the CDC commit-log segments on every node, deduplicates replica writes, and orders mutations by write timestamp per partition.
Prerequisites
- ✓cdc_enabled: true in cassandra.yaml
- ✓WITH cdc = true on replicated tables
- ✓Agent sidecar or shared volume access to cdc_raw on each node
How apply works on Elasticsearch
Changes are sent through the _bulk API with the document ID set to the primary key and external versioning derived from the log position, so late or replayed writes can never overwrite newer data.
Requirements
- ✓An index template or mapping per table
- ✓API key with index and write privileges
- ✓TLS endpoint
Setup
Set up Cassandra → Elasticsearch in four steps
- 1
Prepare Cassandra
Run twincommit check. It verifies cdc_enabled: true in cassandra.yaml and the other prerequisites, and prints the exact fix for anything missing.
- 2
Point at Elasticsearch
Add a target block for Elasticsearch. TwinCommit can generate target DDL with twincommit ddl -apply.
- 3
Snapshot
twincommit snapshot copies each table under a brief share lock and records the exact log position.
- 4
Stream
twincommit run streams every committed change from that position, exactly once and in commit order.
source:
type: cassandra
contact_points: [cass-1, cass-2, cass-3]
cdc_dir: /var/lib/cassandra/cdc_raw
target:
type: elasticsearch
url: https://search.internal:9200
api_key: ${ES_API_KEY}
index_template: "{schema}-{table}"
tables:
- source: sales.orders
- source: sales.customersCassandra to Elasticsearch replication FAQ
How does TwinCommit replicate Cassandra to Elasticsearch?
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TwinCommit reads changes from the Cassandra transaction log, buffers them per transaction, and applies each committed transaction to Elasticsearch in commit order. Changes are sent through the _bulk API with the document ID set to the primary key and external versioning derived from the log position, so late or replayed writes can never overwrite newer data.
Does Cassandra to Elasticsearch replication need triggers or capture tables?
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No. TwinCommit reads the Cassandra log directly and creates no objects in the source database.
Is Cassandra to Elasticsearch replication exactly-once?
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Yes. TwinCommit commits its checkpoint in the same Elasticsearch transaction as the data, so a crash or restart never loses or duplicates a transaction.
What Cassandra versions are supported?
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Apache Cassandra 4.0, 4.1, 5.0 · DataStax Enterprise 6.8+ · Astra DB (target) · ScyllaDB (target).
Stream Cassandra to Elasticsearch today.
Download the free Developer edition, or have one of our replication engineers walk you through a migration plan.