We suggest creating a robots.txt file in the web root of the domain to address two issues.
Control the rate at which the website is being crawled which can help prevent a bot/spider from creating a massive number of database connections at the same time.
To prevent specific bots from crawling the website.
We use the following defaults, however, you may want to add or remove the user agents denied and adjust the crawl rate.
User-agent: *Crawl-delay: 2User-agent: BaiduspiderDisallow: /User-agent: SosospiderDisallow: /
Additional Resources
The links below will provide additional information, as well as instructions for more refined usage of the robots.txt