Deployment

This section covers basic operational aspects of deploying Hermes. For more on configuring Hermes read:

• how to connect to Kafka and Zookeeper
• how to fine tune Frontend
• how to fine tune Consumers
• how to configure Console
• how to publish metrics

Dependencies

As the architecture overview states, there are two systems that are required to run Hermes:

• Kafka
• Zookeeper

In our opinion it is best practice, to run them on separate hosts, so Hermes does not affect them.

Scalability

Each module is a stateless application. There can be as many of them running in parallel as it is required. For best performance and easy maintenance, each Hermes module should also be deployed on separate host.

Requirements

All Hermes Java modules require Java 8 to work. Hermes Console has no external dependencies.

Passing environment variables

All Java modules share the same bundling strategy: Gradle distZips. In order to pass any command line options to executables use:

• HERMES_<module name>_OPTS for application options
• JAVA_OPTS for Java specific options

for example:

export HERMES_FRONTEND_OPTS="-Dfrontend.port=8090"
export JAVA_OPTS="-Xmx2g"

Frontend and Consumers

External configuration

Hermes Frontend and Consumers modules use Netflix Archaius to manage configuration.

To read external configuration from any URL (local file or remote HTTP source), specify its location in system property:

export HERMES_FRONTEND_OPTS="-Darchaius.configurationSource.additionalUrls=file:///opt/hermes/conf/frontend.properties"
export HERMES_CONSUMERS_OPTS="-Darchaius.configurationSource.additionalUrls=file:///opt/hermes/conf/consumers.properties"

Configuration is stored in Java properties format.

Overwriting configuration using ENV

It is possible to overwrite any configuration variable using environment variable:

export HERMES_FRONTEND_OPTS="-D<configuration-option>=<value>"

for example:

export HERMES_FRONTEND_OPTS="-Dfrontend.port=8090 -Dfrontend.idle.timeout=30"

Java options

It is advised to run Hermes Frontend and Consumers with G1 garbage collector and at least 1GB heap:

-XX:+UseG1GC -Xms1g

Management

External configuration

Management being Spring Boot application, shares the same options to provide additional configuration. The most basic way to provide external configuration file is to export an environment variable:

SPRING_CONFIG_LOCATION="file:///opt/hermes/conf/management.properties"

Overwriting configuration using ENV

export HERMES_MANAGEMENT_OPTS="-D<configuration-option>=<value>"

export HERMES_MANAGEMENT_OPTS="-Dserver.port=8070"

Console

Hermes Console is a simple Single Page Application served using NodeJS. It accepts two arguments:

• -p or HERMES_CONSOLE_PORT env variable to specify port (default: 8000)
• -c or HERMES_CONSOLE_CONFIG env variable to specify configuration file (default: ./config.json)

The config.json file is mandatory, Hermes Console will crash when unable to read it. See configuring Hermes Console section for more information.

Hermes Console has no dependencies and will run out of box on Linux machines. To run it, use provided script:

./run.sh -p 8000 -c /etc/hermes-console/config.json