A drop-in, non-distributed, replacement for Storm in Kotlin aimed for low latency requirements
Clone or download
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Failed to load latest commit information.


Build Status


A drop-in, non-distributed, replacement for Storm in Kotlin aimed for a sparse processing stream with low latency requirements.

In comparison to Storm, Kumulus is optimized for low end-to-end latency rather then high throughput.

As opposed to Storm that creates at least a single thread per bolt, Kumulus uses a constant size thread pool.

Possible scenarios to use Kumulus:

  • You think you would need to use Storm in the future, but don't have a way to justify the kind of cluster it takes to use Storm today.
  • You have huge topologies that can't be run on developer machines and are looking for a way to achieve that
  • You have low latency requirements and don't imagine needing to shard your topology across multiple machines

Include via maven


Use by initializing a regular Storm topology via org.apache.storm.topology.TopologyBuilder and produce a StormTopology object. Use it to transform the topology into a KumulusTopology, and run it in-process.

val builder = org.apache.storm.topology.TopologyBuilder()

val config: MutableMap<String, Any> = mutableMapOf()

builder.setSpout("spout", Spout())
builder.setBolt("bolt", Bolt())

val kumulusTopology = KumulusStormTransformer.initializeTopology(
        builder.createTopology(), config, "topology_name")

Or from Java:

TopologyBuilder builder = new TopologyBuilder();

Map<String, Object> config = new HashMap<String, Object>();

builder.setSpout("spout", new Spout());
builder.setBolt("bolt", new Bolt())

KumulusTopology kumulusTopology =
            builder.createTopology(), config, "topology_name");

Latency histograms produced by passing 100,000 (10% warm-up) tiny tuples into the fairly simple topology defined in KumulusStormTransformerTest:

Storm 1.0.4

5.0 (4512): 0.081ms
25.0 (22515): 0.126ms
50.0 (45501): 0.172ms
75.0 (67549): 0.211ms
90.0 (81003): 0.246ms
95.0 (85555): 0.269ms
98.0 (88203): 0.297ms
99.0 (89114): 0.321ms
99.9 (89910): 0.721ms
99.99 (89991): 5.035ms

Processed 100000 end-to-end messages in 109097ms


5.0 (16148): 0.01ms
25.0 (28869): 0.011ms
50.0 (53048): 0.014ms
75.0 (68302): 0.018ms
90.0 (81416): 0.029ms
95.0 (85758): 0.037ms
98.0 (88673): 0.04ms
99.0 (89207): 0.043ms
99.9 (89913): 0.064ms
99.99 (89991): 0.281ms

Processed 100000 end-to-end messages in 2813ms

Startup time was not included in the test results. Naturally, Storm's startup times are significantly higher in local-cluster mode.

Licensed under Apache 2.0