HaHelper

Need your data highly available but don't want the overheard of deploying and managing a third party database? Attach your data directly to your app! HaHelper is a client library that turns your server into a highly available data store for itself!

HaHelper stores your data and provides many configuration options to help facilitate how your data is made available.

• Easily replicate your data to tolerate node failures
• Cross Language support! Link two servers in any language!
• Listen for data changes and act on updates!
• Choose between disk-based or memory-based storage
• Configurable service discovery methods

Getting Started

To being using HaHelper, simply download the HaHelper client library for the language of your choice. Read the documentation for your language for more details about implementation.

Starting a Server

Making your server HA is as simple as starting the HAHelper server/client library.

HaHelper(HaHelperServerConfig.load()).start()

Configuration

Configuration can be provided to HaHelper in a number of ways. Using HaHelperServerConfig.load() will search the following default locations in order of priority:

• File defined at by the environment variable: HA_HELPER_CONFIG_PATH
• ./ha_helper_config.yaml
• ./config/ha_helper_config.yaml

If multiple configuration files exist, the first file found will be used. You must provide a configuration, no defaults exist.

The following configuration options are available:

Config Value	Description	DataType
local.serverPort	The port to start the server on	Int
cluster.clusterSize	The number of services your cluster contains. Used to determine quorum.	Int
cluster.multiMaster	If the cluster should have evnetualConsistency instead of using leaderElection.	Boolean
cluster.discoveryMethod	How the server should detect other servers in the cluster. Either one of knownHosts or domainDiscoverey should be used.	Object
cluster.discoveryMethod.knownHosts	A list of known IP addresses and ports that are in the cluster. Example: cluster.discoveryMethod.knownHosts: - hostname: localhost port: 9998 List may or may not include itself.	List
cluster.discoveryMethod.domainDiscovery	A list of domain names to search	List
persistence.enabled	If data should be written to disk	Boolean
persistence.replicas	The number of locations where the data should be written.	Int
persistence.storageLocation	The file path of where files should be written	String
persistence.compactionIntervalSeconds	If compaction should occur. Compaction will minimize stored files to only include the most recently committed key-value pairs. Otherwise, all deltas are kept. Set to zero to disable compaction.	Long

Storing Data

TODO

Fetching Data

TODO

Listening for Changes

TODO