This module is experimental. Please help test this, but do not use it in production.
This CQL-based Cassandra 3.9+ storage component includes a GuavaSpanStore and GuavaSpanConsumer.
GuavaSpanStore.getDependencies() returns pre-aggregated dependency links (ex via zipkin-dependencies).
The implementation uses the Datastax Java Driver 3.x.
zipkin.storage.cassandra3.Cassandra3Storage.Builder includes defaults that will operate against a local Cassandra installation.
Queries are logged to the category "com.datastax.driver.core.QueryLogger" when debug or trace is enabled via SLF4J. Trace level includes bound values.
See Logging Query Latencies for more details.
This module conditionally runs integration tests against a local Cassandra instance.
Tests are configured to automatically access Cassandra started with its defaults.
To ensure tests execute, download a Cassandra 3.9+ distribution, extract it, and run bin/cassandra.
If you run tests via Maven or otherwise when Cassandra is not running, you'll notice tests are silently skipped.
Results :
Tests run: 62, Failures: 0, Errors: 0, Skipped: 48
This behaviour is intentional: We don't want to burden developers with installing and running all storage options to test unrelated change. That said, all integration tests run on pull request via Travis.
This component is tuned to help reduce the size of indexes needed to perform query operations. The most important aspects are described below. See Cassandra3Storage for details.
Indexing in CQL is simplified by SASI, for example, reducing the number of tables from 7 down to 4. SASI also moves some write-amplification from CassandraSpanConsumer into C*.
CassandraSpanConsumer directly writes to the tables traces,
trace_by_service_span and span_name_by_service. The latter two
amplify writes by a factor of the distinct service names in a span.
Other amplification happens internally to C*, visible in the increase
write latency (although write latency remains performant at single digit
milliseconds).
- A SASI index on its 'all_annotations' column permits full-text searches against annotations.
- A SASI index on the 'duration' column.
Note: Core annotations,
ex "sr", non-string annotations, and values longer than 256 characters
are not written to the all_annotations SASI, as they aren't intended
for use in user queries.
Time-To-Live is default now at the table level. It can not be overridden in write requests.
There's a different default TTL for trace data and indexes, 7 days vs 3 days respectively. The impact is that you can retrieve a trace by ID for up to 7 days, but you can only search the last 3 days of traces (ex by service name).
Time-series data is compacted using TimeWindowCompactionStrategy, a known improved over DateTieredCompactionStrategy. Data is optimised for queries with a single day. The penalty of reading multiple days is small, a few disk seeks, compared to the otherwise overhead of reading a significantly larger amount of data.
Benchmarking the new datamodel demonstrates a significant performance improvement on reads. How much of this translates to te Zipkin UI is hard to tell due to the complexity of CassandraSpanConsumer and how searches are possible. Benchmarking stress profiles are found in traces-stress.yaml and trace_by_service_span-stress.yaml.