Apache Solr Architecture - Apache Solr

Explain the architecture of Apache Solr

The block diagram of the architecture of Apache Solr is:

Solr Architecture

What are the building blocks of Apache Solr Architecture?

The major building blocks or the components of Apache Solr are:

Request Handler

The request handlers process the request (query request or the index update request) sent to Apache Solr. The request handler is selected based on the search requirement. The handler is mapped to a URL end-point to pass a request to Solr and the request will be served by it.

Search Component

A feature or a type of the search provided in Apache Solr is a search component. It can be spell checking, query, faceting, hit highlighting, etc. They are registered as Search handlers. A search handler can register multiple components.

Query Parser

The query that is passed to Solr is parsed by Apache Solr query parser and the query is verified for syntactical errors. The quesry which is aprsed is translated to a format understood by Lucene.

Response Writer

For the user queries, the component that generates formatted output is Apache Solr response writer. The response formats like XML, JSON, CSV, etc are supported by Solr. Each type of response has a different response writer.


The data is recognized by Lucene in the form of tokens. The content is analyzed by Apache Solr, divided into tokens and then these tokens are passed to Lucene. The text of the fields is examined by the analyzer in Apache Solr and a token stream is generated. The tokenstream prepared by the analyzer is broken into tokens by tokenizer.

Update Request Processor

When a update request is sent to Apache Solr, the request runs through a set of plugins (signature, logging, indexing), which are collectively known as update request processor. Some of the modifications like dropping a field, adding a field, etc. Are done by the processor.

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