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Configuration
Nodes
There are two types of Crux nodes: cluster and standalone. Use a cluster node when horizontal scalability is required or when you want the guarantees that Kafka offers in terms of resiliency, availability, and retention of data.
Multiple cluster nodes participate in a cluster using Kafka as the primary store and as the central means of coordination.
The Standalone node is where a single Crux instance has everything it needs locally. This is good for experimenting with Crux and for small to medium sized deployments, where running a single instance is permissible.
| Name | Transaction Log | Java API |
|---|---|---|
Cluster Node | Uses Kafka |
|
Standalone | Uses local event log |
|
Crux nodes implement the ICruxAPI interface and are the
starting point for making use of Crux. Nodes also implement
java.io.Closeable and can therefore be lifecycle managed.
| To see an example of a Crux Node being integrated into a Clojure lifecycle management framework such as Integrant, see the example Integrant node. |
Properties
Crux Nodes will use the following properties:
| Node | Component | Property | Description |
|---|---|---|---|
Both | kv-store |
| Sets the K/V Store to use, e.g. |
Both | kv-store |
| Sets the data-directory to use, e.g. |
Standalone | tx-log |
| Kafka Servers to connect to e.g. |
Standalone | http-server |
| Port for Crux HTTP Server e.g. |
Standalone Node
Using a Crux standalone node is the best way to get started. Once you’ve started a standalone Crux instance as described below, you can then follow the getting started example.
Start the standalone node:
link:./examples.clj[role=include]For the purposes of this Hello World, we are using the simplest configuration of Crux, where all of the pluggable components are in-memory. There is no Kafka or RocksDB to worry about.
You can later stop the node if you wish:
link:./examples.clj[role=include]Cluster Nodes
When using Crux at scale it is recommended to use multiple Crux nodes connected via a Kafka cluster.
Add Crux as a project dependency:
link:./deps.edn[role=include]And Kafka Clients:
Use the API to start a cluster node, configuring it with the
bootstrap-servers property in order to connect to Kafka:
link:./examples.clj[role=include]
If you don’t specify kv-backend then by default the
cluster node will use RocksDB. You will need to add RocksDB to
your list of project dependencies.
|
You can later stop the node if you wish:
link:./examples.clj[role=include]RocksDB
Configuration
Set the following properties when configuring Crux nodes:
| Property | Value |
|---|---|
|
|
| i.e. |
| i.e. |
For example when constructing the standalone node:
link:./examples.clj[role=include]Http
Crux can be used programmatically as a library, but Crux also ships with an embedded HTTP server, that allows clients to use the API remotely via REST.
Set the server-port configuration property on a Crux node to
expose a HTTP port that will accept REST requests.
Visit the guide on using the REST api for examples of how to interact with Crux over HTTP.
Extras
Embedded Kafka
Crux is ready to work with an embedded Kafka for when you don’t have a indendepently running Kafka available to connect to (such as during development).
Add crux-kafka-embedded to your project dependencies:
See the below example code:
link:./examples.clj[role=include]You can later stop the Embedded Kafka if you wish:
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