https://bz.apache.org/bugzilla/show_bug.cgi?id=68901
Bug ID: 68901
Summary: Coyote is hardcoded to drop connections on
400|408|411|414|500|503|501 which should be
configurable for application level errors to prevent
expensive TLS handshake/resumption on reconnect
Product: Tomcat 10
Version: unspecified
Hardware: All
OS: Linux
Status: NEW
Severity: enhancement
Priority: P2
Component: Connectors
Assignee: dev@tomcat.apache.org
Reporter: alessandro.vermeu...@ing.com
Target Milestone: ------
Overview:
Currently Coyote is hardcoded to drop connections when a request generates a
response with one of the following status codes: 400|408|411|414|500|503|501.
This behaviour has been around for at least 15 years and has been copied from
Apache HTTPd[1]. It makes sense in case the server itself is the origin of the
error responses.
However, in our case we have plenty of scenarios we have applications returning
generic 500 responses on generic errors, causing connections to drop and
subsequent reconnects. Status codes 503 and 501 also seem to cases which should
be handled just fine without needing to reset the connection.
We terminate TLS in the application where even session resumption is expensive
and a full TLS handshake is even more expensive.
Together with Tomcat dropping the connections on 500 errors this leads to
cascade failures where spurious load-related errors cause a spike in CPU usage
which can trigger further errors, further consuming CPU until most CPU is used
to handle TLS connections instead of actual value.
We suggest to make the the behaviour to drop connections is configurable.
Either to completely disable it, or to make the status codes configurable.
[1]:
https://github.com/apache/tomcat/blame/bc900e0100de9879604b93af4722c272ab3d1a24/java/org/apache/coyote/http11/Http11Processor.java#L604-L617
```
/**
* Determine if we must drop the connection because of the HTTP status
code. Use the same list of codes as
* Apache/httpd.
*/
private static boolean statusDropsConnection(int status) {
return status == 400 /* SC_BAD_REQUEST */ || status == 408 /*
SC_REQUEST_TIMEOUT */ ||
status == 411 /* SC_LENGTH_REQUIRED */ || status == 413 /*
SC_REQUEST_ENTITY_TOO_LARGE */ ||
status == 414 /* SC_REQUEST_URI_TOO_LONG */ || status == 500 /*
SC_INTERNAL_SERVER_ERROR */ ||
status == 503 /* SC_SERVICE_UNAVAILABLE */ || status == 501 /*
SC_NOT_IMPLEMENTED */;
}
```
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