The Endeca MDEX Engine is the indexing and query engine that provides the backbone for all Endeca solutions.
The MDEX Engine uses proprietary data structures and algorithms that allow it to provide real-time responses to client requests. The MDEX Engine stores the indices that were created by the Endeca Information Transformation Layer (ITL). After the indices are stored, the MDEX Engine receives client requests via the application tier, queries the indices, and then returns the results.
The MDEX Engine is designed to be stateless. This design requires that a complete query be sent to the MDEX Engine for each request. The stateless design of the MDEX Engine facilitates the addition of MDEX Engine servers for load balancing and redundancy. Because the MDEX Engine is stateless, any replica of an MDEX Engine on one server can reply to queries independently of a replica on other MDEX Engine servers.
Consequently, adding replicas of MDEX Engines on additional servers provides redundancy and improved query response time. That is, if any one particular server goes down, a replica of an MDEX Engine provides redundancy by allowing other servers in the implementation to continue to reply to queries. In addition, total response time is improved by using load balancers to distribute queries to a replica MDEX Engine on any of the additional servers.
| MDEX Engine Component | Description |
|---|---|
| Dgraph |
The Dgraph is the name of the process for the MDEX Engine. A typical Endeca implementation includes one or more Dgraphs. Optionally, it can include an Agraph that manages a number of Dgraphs.
|
| Agraph |
The Agraph is the name of the program that runs in a distributed configuration in addition to the Dgraph. The Agraph typically resides on a separate machine. The Agraph program is responsible for receiving requests from clients, forwarding the requests to the distributed Dgraphs, and coordinating the results. From the perspective of the Endeca Presentation API, the Agraph program behaves similarly to the Dgraph program. Agraph-based implementations allow parallelization of query processing. The implementation of this parallelization results from partitioning the set of records into two or more disjoint subsets of records and then assigning each subset to its own Dgraph. Note: Starting with the MDEX Engine version 6.0, (namely, with
installations on the 64-bit platforms) a more powerful Dgraph can accommodate
much larger data sets without the need to implement an Agraph.
|
| Dgidx |
Dgidx is the indexing program that reads the tagged Endeca records that were prepared by Forge and creates the proprietary indices for the Endeca MDEX Engine.
|
| Agidx |
Agidx is the program that creates a set of Agidx indices which support the Agraph program in a distributed environment.
|
| dgwordlist | The dgwordlist utility is used to manually compile the text-based worddat dictionary into the binary spelldat dictionary. This enables use of the Aspell dictionary module in the MDEX Engine. |
| enecerts |
The Endeca enecerts utility creates the SSL certificates. |
