Avoid using Regex for matching URL paths when possible as doing so causes more of the request time to be spent in regex then doing the API call itself.

Affects: I don’t know of a version this does not affect.

Hi, profiling reveals that a bunch of time is spent in in this stack trace:

    at java.base@11.0.3/java.util.regex.Matcher.<init>(Matcher.java:248)
    at java.base@11.0.3/java.util.regex.Pattern.matcher(Pattern.java:1133)
    at org.springframework.util.AntPathMatcher$AntPathStringMatcher.matchStrings(AntPathMatcher.java:686)
    at org.springframework.util.AntPathMatcher.matchStrings(AntPathMatcher.java:421)
    at org.springframework.util.AntPathMatcher.doMatch(AntPathMatcher.java:218)
    at org.springframework.util.AntPathMatcher.match(AntPathMatcher.java:177)
    at org.springframework.web.servlet.mvc.condition.PatternsRequestCondition.getMatchingPattern(PatternsRequestCondition.java:258)
    at org.springframework.web.servlet.mvc.condition.PatternsRequestCondition.getMatchingPatterns(PatternsRequestCondition.java:223)
    at org.springframework.web.servlet.mvc.condition.PatternsRequestCondition.getMatchingCondition(PatternsRequestCondition.java:205)
    at org.springframework.web.servlet.mvc.method.RequestMappingInfo.getMatchingCondition(RequestMappingInfo.java:229)
    at org.springframework.web.servlet.mvc.method.RequestMappingInfoHandlerMapping.getMatchingMapping(RequestMappingInfoHandlerMapping.java:93)
    at org.springframework.web.servlet.mvc.method.RequestMappingInfoHandlerMapping.getMatchingMapping(RequestMappingInfoHandlerMapping.java:57)
    at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.addMatchingMappings(AbstractHandlerMethodMapping.java:428)
    at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.lookupHandlerMethod(AbstractHandlerMethodMapping.java:394)
    at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.getHandlerInternal(AbstractHandlerMethodMapping.java:368)
    at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.getHandlerInternal(AbstractHandlerMethodMapping.java:65)
    at org.springframework.web.servlet.handler.AbstractHandlerMapping.getHandler(AbstractHandlerMapping.java:401)
    at org.springframework.web.servlet.DispatcherServlet.getHandler(DispatcherServlet.java:1231)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1014)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:942)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1005)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:897)

I think this is trying to work out which API method to call and to do that it is matching the URL path against a regex. Regex is extremely slow, by using regex here it makes the APIs spend most of their time in this rather than doing the actual work. This is not good especially when we want to use spring to slice up an application served over many APIs e.g. micro services. I think a case in which this gets especially bad is when many APIs exist, I think this does a linear search 😦.

One step towards not having all time spent in this regex matching would be to create simple matchers for some of the more trivial and common cases like those where the API method is not presenting a complex regex. I think some thought might need to go into this, you may want to collection the value of a bunch of @RequestMappings to find out what common styles of request mappings are in use.

I think this is looking at all @RequestMapping trying to find which ones match, perhaps what might also work is having the matcher defined as two sections a quick match which is fast to exclude (e.g. path length, starts with X etc) and if that matches then go on to the slow regex matching.

[encircled]

Sure, I will prepare the PR later

[rstoyanchev]

As a side note, I’d like to point out that we’re aware that AntPathMatcher is not optimized for matching request path patterns (memory allocation, CPU). We’ve introduced PathPattern and PathPatternParser in Spring WebFlux since.

This implementation is not currently the default in Spring MVC as it’s a breaking change - but it’s a change we’re considering for future versions.

There is an issue for that now #24945.