Crawler Settings: Threads and Request Delay - Opensolr Drupal Docs

Crawler Settings

Two numbers decide how fast Opensolr reads your site and how gently it treats your server.

Where: Opensolr Search › Data Crawler tab › Crawler Settings (closed by default, click to open)

Setting	Range	Default	What it does
Parallel Threads	1 to 20	10	How many pages are read at the same time. More is faster. The field never goes above the maximum of your Opensolr plan, shown as Max Threads on the Settings tab.
Request Delay (seconds)	0.1 to 10	0.5	The pause between two requests. Lower is faster; raise it if your server is small or rate limits visitors.

Click Save configuration (in Content Types for Crawling, the same form). The next crawl uses the new values.

A firewall in front of your site?

More threads mean more requests per second from one address. If a firewall or rate limiter blocks the crawl, allow the crawler server IP shown in Crawl Management, or lower the threads and raise the delay.

Everything else about the crawl is set for you: Opensolr reads only the addresses in your sitemap, with the fast reader, without running the JavaScript of your pages.