About the Dgraph

The Dgraph uses data structures and algorithms to issue real-time responses to queries.

The Dgraph stores the ingested data in the indexes. The Dgraph receives client requests from Studio, queries the indexes, and returns the results. The Dgraph is stateless. This design requires that a complete query is sent to it for each request. The stateless design facilitates the addition of Dgraph instances for load balancing and redundancy. Any instance of a Dgraph can reply to queries independently of other instances.

A Big Data Discovery cluster can include two or more Dgraph instances. They handle end-user query requests and store indexes on shared storage. One of the Dgraphs is the leader. It handles all write operations, such as updates and configuration changes. The remaining Dgraphs serve as read-only followers. The Dgraph Gateway performs the routing of requests to the Dgraph nodes. It handles query caching, business logic, and cluster services for the Dgraph nodes.

The Dgraph instances do not need a Hadoop environment to run. They are often hosted on standalone and powerful hardware servers. The Dgraph Gateway is a Java-based application hosted in WebLogic Server, together with Studio. The deployment of Dgraphs occurs at the installation time. For information, see the Installation and Deployment Guide.

The Dgraph Tracing Utility

The Dgraph Tracing Utility is a Dgraph diagnostic program used by Oracle Support. It stores the Dgraph trace data, which are useful in troubleshooting the Dgraph. It starts when the Dgraph starts and keeps track of all Dgraph operations. It stops when the Dgraph shuts down. You can save and download trace data to share it with Oracle Support.

The BDD administration tools

Two tools for administering Big Data Discovery exist: the Enterprise Manager plug-in and the bdd-admin script. For information on the Dgraph and the administrative tools, see the Administrator's Guide.

The Dgraph HDFS Agent

The Dgraph HDFS Agent loads data into the Dgraph. It reads the Avro files from the data processing workflow and formats them for data loading. It then sends them to the Dgraph. For information on the Dgraph HDFS Agent, see the Data Processing Guide.