{"id":109,"date":"2006-03-29T15:55:57","date_gmt":"2006-03-29T22:55:57","guid":{"rendered":"http:\/\/kennyw.com\/indigo\/109"},"modified":"2006-03-29T15:55:57","modified_gmt":"2006-03-29T22:55:57","slug":"demystifying-hostnamecomparisonmode-wildcards-and-uri-matching","status":"publish","type":"post","link":"https:\/\/kennyw.com\/?p=109","title":{"rendered":"Demystifying HostNameComparisonMode: Wildcards, and URI Matching"},"content":{"rendered":"

Today I was asked “what is StrongWildcard and WeakWildcard, and which one should I use?”. The piece of object model that my co-worker is asking about is:<\/p>\n

\npublic enum<\/code> HostNameComparisonMode
\n{<\/p>\n
StrongWildcard = 0,
\nExact = 1,
\nWeakWildcard = 2,<\/div>\n

}<\/p><\/div>\n

Most bindings have a HostNameComparisonMode property on them. This property is used for service-side endpoints (IChannelListener), in conjunction with the ListenUri of that endpoint. The values are semantics similar to + and * for http.sys registrations<\/a>. “Wildcard” vs. “Exact” refers to how we match the authority (hostname+port) piece of an incoming Uri. For “Wildcard”, anything matches. For “Exact”, we perform a case-insensitive string comparison to determine equality.<\/p>\n

“Strong” vs. “Weak” has to do with the relative priorities of endpoints. We use three longest-prefix-match tables, one each for StrongWildcard, Exact, and WeakWildcard. When a Message comes into the system, we first try to match the Uri against our Strong table (which uses a wildcard comparison on hostname+port). If nothing matches, we try the Exact table (using a case-insensitive exact comparison on hostname+port). Lastly, if there was no match on Strong or Exact, we check the Weak table (again using a wildcard match for hostname+port).<\/p>\n

For example, let’s say you have the following endpoints registered on your machine:<\/p>\n

    \n
  1. (http:\/\/foo.com\/a\/b\/c\/, StrongWildcard)<\/li>\n
  2. (http:\/\/foo.com\/a\/b\/, Exact)<\/li>\n
  3. (http:\/\/bar.com\/, Exact)<\/li>\n
  4. (http:\/\/foo.com\/a\/, WeakWildcard)<\/li>\n<\/ol>\n

    A request coming in for http:\/\/foo.com\/a\/b\/c\/d\/<\/code> will match (1).<\/p>\n

    A request for http:\/\/foo.com\/a\/b\/<\/code> will match (2) since the strong comparison fails (\/a\/b\/c\/ is not a prefix of \/a\/b\/).<\/p>\n

    A request for http:\/\/foo.com\/a\/d\/<\/code> will match (4). Even though “\/” is a prefix match of “\/a\/d\/” for (3), the hostnames differ and so the Exact match will fail.<\/p>\n

    Lastly, a request for http:\/\/bar.com\/a\/b\/<\/code> will match (3). (2) is a prefix match but the hostnames differ, and (3) takes precedence over (4) in priority order.<\/p>\n

    Hopfully this helps demystify our endpoint URI matching process!<\/p>\n","protected":false},"excerpt":{"rendered":"

    Today I was asked “what is StrongWildcard and WeakWildcard, and which one should I use?”. The piece of object model that my co-worker is asking about is: public enum HostNameComparisonMode { StrongWildcard = 0, Exact = 1, WeakWildcard = 2, } Most bindings have a HostNameComparisonMode property on them. This property is used for service-side […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[11],"tags":[],"class_list":["post-109","post","type-post","status-publish","format-standard","hentry","category-indigo"],"_links":{"self":[{"href":"https:\/\/kennyw.com\/index.php?rest_route=\/wp\/v2\/posts\/109","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/kennyw.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/kennyw.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/kennyw.com\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/kennyw.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=109"}],"version-history":[{"count":0,"href":"https:\/\/kennyw.com\/index.php?rest_route=\/wp\/v2\/posts\/109\/revisions"}],"wp:attachment":[{"href":"https:\/\/kennyw.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=109"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/kennyw.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=109"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/kennyw.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=109"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}