corda/docs/source/running-a-node.rst

Running nodes locally

Note

You should already have generated your node(s) with their CorDapps installed by following the instructions in generating-a-node.

There are several ways to run a Corda node locally for testing purposes.

Starting a Corda node using DemoBench

See the instructions in demobench.

Starting a Corda node from the command line

Run a node by opening a terminal window in the node's folder and running:

java -jar corda.jar

By default, the node will look for a configuration file called node.conf and a CorDapps folder called cordapps in the current working directory. You can override the configuration file and workspace paths on the command line (e.g. ./corda.jar --config-file=test.conf --base-directory=/opt/corda/nodes/test).

Optionally run the node's webserver as well by opening a terminal window in the node's folder and running:

java -jar corda-webserver.jar

Warning

The node webserver is for testing purposes only and will be removed soon.

Setting JVM arguments

There are several ways of setting JVM arguments for the node process (particularly the garbage collector and the memory settings). They are listed here in order of increasing priority, i.e. if the same flag is set in a way later in this list, it will override anything set earlier.

Default arguments in capsule

The capsuled Corda node has default flags set to -Xmx512m -XX:+UseG1GC - this gives the node (a relatively low) 512 MB of heap space and turns on the G1 garbage collector, ensuring low pause times for garbage collection.

Node configuration

The node configuration file can specify custom default JVM arguments by adding a section like:

custom = {
   jvmArgs: [ '-Xmx1G', '-XX:+UseG1GC' ]
}

Note that this will completely replace any defaults set by capsule above, not just the flags that are set here, so if you use this to set e.g. the memory, you also need to set the garbage collector, or it will revert to whatever default your JVM is using.

Capsule specific system property

You can use a special system property that Capsule understands to set JVM arguments only for the Corda process, not the launcher that actually starts it:

java -Dcapsule.jvm.args="-Xmx:1G" corda.jar

Setting a property like this will override any value for this property, but not interfere with any other JVM arguments that are configured in any way mentioned above. In this example, it would reset the maximum heap memory to -Xmx1G but not touch the garbage collector settings. This is particarly useful for either setting large memory allowances that you don't want to give to the launcher or for setting values that can only be set on one process at a time, e.g. a debug port.

Command line flag

You can set JVM args on the command line that apply to the launcher process and the node process as in the example above. This will override any value for the same flag set any other way, but will leave any other JVM arguments alone.

OutOfMemoryError handling

In addition to the JVM arguments listed above, the capsuled Corda node has two flags that cause the node to stop on out-of-memory error and generate the corresponding diagnostic files:

-XX:+HeapDumpOnOutOfMemoryError -XX:+CrashOnOutOfMemoryError

With CrashOnOutOfMemoryError the node which is running out of memory is expected to stop immediately (fail-fast) to preserve ledger consistency and avoid flaws in operations.

Unlike for arguments related to memory and GC, to completely replace the default out-of-memory error args, you must explicitly add at least one out-of-memory error related argument into the custom.jvmArgs section. For example, the following config turns off HeapDumpOnOutOfMemoryError and doesn't invoke CrashOnOutOfMemoryError option:

custom = {
   jvmArgs: [ '-Xmx1G', '-XX:+UseG1GC', '-XX:-HeapDumpOnOutOfMemoryError' ]
}

Starting all nodes at once on a local machine from the command line

Native

If you created your nodes using deployNodes, a runnodes shell script (or batch file on Windows) will have been generated to allow you to quickly start up all nodes and their webservers. runnodes should only be used for testing purposes.

Start the nodes with runnodes by running the following command from the root of the project:

• Linux/macOS: build/nodes/runnodes
• Windows: call build\nodes\runnodes.bat

Warning

On macOS, do not click/change focus until all the node terminal windows have opened, or some processes may fail to start.

If you receive an OutOfMemoryError exception when interacting with the nodes, you need to increase the amount of Java heap memory available to them, which you can do when running them individually. See starting-an-individual-corda-node.

docker-compose

If you created your nodes using Dockerform, the docker-compose.yml file and corresponding Dockerfile for nodes has been created and configured appropriately. Navigate to build/nodes directory and run docker-compose up command. This will startup nodes inside new, internal network. After the nodes are started up, you can use docker ps command to see how the ports are mapped.

Warning

You need both Docker and docker-compose installed and enabled to use this method. Docker CE (Community Edition) is enough. Please refer to Docker CE documentation and Docker Compose documentation for installation instructions for all major operating systems.

Starting all nodes at once on a remote machine from the command line

By default, Cordform expects the nodes it generates to be run on the same machine where they were generated. In order to run the nodes remotely, the nodes can be deployed locally and then copied to a remote server. If after copying the nodes to the remote machine you encounter errors related to localhost resolution, you will additionally need to follow the steps below.

To create nodes locally and run on a remote machine perform the following steps:

1. Configure Cordform task and deploy the nodes locally as described in generating-a-node.

2. Copy the generated directory structure to a remote machine using e.g. Secure Copy.

3. Optionally, bootstrap the network on the remote machine.

   This is optional step when a remote machine doesn't accept localhost addresses, or the generated nodes are configured to run on another host's IP address.

   If required change host addresses in top level configuration files [NODE NAME]_node.conf for entries p2pAddress , rpcSettings.address and rpcSettings.adminAddress.

   Run the network bootstrapper tool to regenerate the nodes network map (see for more explanation network-bootstrapper):

   java -jar corda-tools-network-bootstrapper-Master.jar --dir <nodes-root-dir>

4. Run nodes on the remote machine using runnodes command <starting-all-nodes-at-once>.

The above steps create a test deployment as deployNodes Gradle task would do on a local machine.

Stability of the Corda Node

There are a number of critical resources necessary for Corda Node to operate to ensure transactional consistency of the ledger. These critical resources include:

1. Connection to a database;
2. Connection to Artemis Broker for P2P communication;
3. Connection to Artemis Broker for RPC communication.

Should any of those critical resources become not available, Corda Node will be getting into an unstable state and as a safety precaution it will shut itself down reporting the cause as an error message to the Node's log file.

Note

On some operating systems when PC is going to sleep whilst Corda Node is running, imbedded into Node Artemis message broker reports the loss of heartbeat event which in turn causes loss of connectivity to Artemis. In such circumstances Corda Node will exit reporting broker connectivity problem in the log.

Once critical resources node relies upon are available again, it is safe for Node operator to re-start the node for normal operation.