Heron can use the local file system as a state manager for storing various book keeping information. Use of local file system is recommended mainly for single node server and laptop. This configuration is ideal for deploying in edge devices. Heron developers can use this setting for developing and debugging various heron components in their laptop or server.
You can make Heron aware of the ZooKeeper cluster by modifying the statemgr.yaml config file specific for the Heron cluster. You'll need to specify the following for each cluster:
heron.class.state.manager --- Indicates the class to be loaded for local file system state manager. You should set this to org.apache.heron.statemgr.localfs.LocalFileSystemStateManager
heron.statemgr.connection.string --- This should be LOCALMODE since it always localhost.
heron.statemgr.root.path --- The root path in the local file system where state information is stored. We recommend providing Heron with an exclusive directory; if you do not, make sure that the following sub-directories are unused: /tmasters, /topologies, /pplans, /executionstate, /schedulers.
heron.statemgr.localfs.is.initialize.file.tree --- Indicates whether the nodes under root /tmasters, /topologies, /pplans, /executionstate, and /schedulers need to created, if they are not found. Set it to True, if you could like Heron to create those directories. If those directories are already there, set it to False. The absence of this configuration implies True.
Below is an example configuration (in statemgr.yaml) for a local file system running in localhost:
# local state manager class for managing state in a persistent fashion heron.class.state.manager: org.apache.heron.statemgr.localfs.LocalFileSystemStateManager # local state manager connection string heron.statemgr.connection.string: LOCALMODE # path of the root address to store the state in a local file system heron.statemgr.root.path: ${HOME}/.herondata/repository/state/${CLUSTER} # create the sub directories, if needed heron.statemgr.localfs.is.initialize.file.tree: True