Running behind a reverse proxy

[dkirrane]

I get the below error when I run behind a reverse proxy /kafdrop (Istio in my case).

I tried set servlet.contextPath: /kafdrop in values.yml. But I get:

2019-11-08 17:01:04.349 �[32m INFO�[m �[35m15�[m [  XNIO-1 task-1] �[36mo.s.w.s.FrameworkServlet                �[m : Completed initialization in 8 ms
errorAtts: {timestamp=Fri Nov 08 17:01:27 GMT 2019, status=404, error=Not Found, message=Not Found, path=/kafdrop}
17:01:27/0     ERROR [XNIO-1 task-11]: Error executing FreeMarker template
FreeMarker template error:
The following has evaluated to null or missing:
==> error.trace  [in template "error.ftl" at line 10, column 3]

----
Tip: It's the step after the last dot that caused this error, not those before it.
----
Tip: If the failing expression is known to legally refer to something that's sometimes null or missing, either specify a default value like myOptionalVar!myDefault, or use <#if myOptionalVar??>when-present<#else>when-missing</#if>. (These only cover the last step of the expression; to cover the whole expression, use parenthesis: (myOptionalVar.foo)!myDefault, (myOptionalVar.foo)??
----

----
FTL stack trace ("~" means nesting-related):
	- Failed at: ${error.trace}  [in template "error.ftl" at line 10, column 1]
----

Java stack trace (for programmers):
----
freemarker.core.InvalidReferenceException: [... Exception message was already printed; see it above ...]
	at freemarker.core.InvalidReferenceException.getInstance(InvalidReferenceException.java:134)
	at freemarker.core.EvalUtil.coerceModelToTextualCommon(EvalUtil.java:467)
	at freemarker.core.EvalUtil.coerceModelToStringOrMarkup(EvalUtil.java:389)
	at freemarker.core.EvalUtil.coerceModelToStringOrMarkup(EvalUtil.java:358)
	at freemarker.core.DollarVariable.calculateInterpolatedStringOrMarkup(DollarVariable.java:100)
	at freemarker.core.DollarVariable.accept(DollarVariable.java:63)
	at freemarker.core.Environment.visit(Environment.java:330)
	at freemarker.core.Environment.visit(Environment.java:336)
	at freemarker.core.Environment.process(Environment.java:309)
	at freemarker.template.Template.process(Template.java:384)
	at org.springframework.web.servlet.view.freemarker.FreeMarkerView.processTemplate(FreeMarkerView.java:389)
	at org.springframework.web.servlet.view.freemarker.FreeMarkerView.doRender(FreeMarkerView.java:302)
	at org.springframework.web.servlet.view.freemarker.FreeMarkerView.renderMergedTemplateModel(FreeMarkerView.java:253)
	at org.springframework.web.servlet.view.AbstractTemplateView.renderMergedOutputModel(AbstractTemplateView.java:178)
	at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:316)
	at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1371)
	at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1117)
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1056)
	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)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:645)
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:882)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:750)
	at io.undertow.servlet.handlers.ServletHandler.handleRequest(ServletHandler.java:74)
	at io.undertow.servlet.handlers.FilterHandler.handleRequest(FilterHandler.java:81)
	at io.undertow.servlet.handlers.security.ServletSecurityRoleHandler.handleRequest(ServletSecurityRoleHandler.java:62)
	at io.undertow.servlet.handlers.ServletChain$1.handleRequest(ServletChain.java:68)
	at io.undertow.servlet.handlers.ServletDispatchingHandler.handleRequest(ServletDispatchingHandler.java:36)
	at io.undertow.servlet.handlers.RedirectDirHandler.handleRequest(RedirectDirHandler.java:68)
	at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
	at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
	at io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:251)
	at io.undertow.servlet.handlers.ServletInitialHandler.dispatchToPath(ServletInitialHandler.java:186)
	at io.undertow.servlet.spec.RequestDispatcherImpl.error(RequestDispatcherImpl.java:501)
	at io.undertow.servlet.spec.RequestDispatcherImpl.error(RequestDispatcherImpl.java:419)
	at io.undertow.servlet.spec.HttpServletResponseImpl.doErrorDispatch(HttpServletResponseImpl.java:196)
	at io.undertow.servlet.handlers.ServletInitialHandler.handleFirstRequest(ServletInitialHandler.java:276)
	at io.undertow.servlet.handlers.ServletInitialHandler.access$100(ServletInitialHandler.java:78)
	at io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:133)
	at io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:130)
	at io.undertow.servlet.core.ServletRequestContextThreadSetupAction$1.call(ServletRequestContextThreadSetupAction.java:48)
	at io.undertow.servlet.core.ContextClassLoaderSetupAction$1.call(ContextClassLoaderSetupAction.java:43)
	at io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:249)
	at io.undertow.servlet.handlers.ServletInitialHandler.access$000(ServletInitialHandler.java:78)
	at io.undertow.servlet.handlers.ServletInitialHandler$1.handleRequest(ServletInitialHandler.java:99)
	at io.undertow.server.Connectors.executeRootHandler(Connectors.java:376)
	at io.undertow.server.HttpServerExchange$1.run(HttpServerExchange.java:830)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
	at java.base/java.lang.Thread.run(Thread.java:835)
2019-11-08 17:01:27.631 �[31mERROR�[m �[35m15�[m [ XNIO-1 task-11] �[36mi.u.s.a.LoggingExceptionHandler         �[m : UT005023: Exception handling request to /error

java.lang.RuntimeException: org.springframework.web.util.NestedServletException: Request processing failed; nested exception is freemarker.core.InvalidReferenceException: The following has evaluated to null or missing:
==> error.trace  [in template "error.ftl" at line 10, column 3]

----
Tip: It's the step after the last dot that caused this error, not those before it.
----
Tip: If the failing expression is known to legally refer to something that's sometimes null or missing, either specify a default value like myOptionalVar!myDefault, or use <#if myOptionalVar??>when-present<#else>when-missing</#if>. (These only cover the last step of the expression; to cover the whole expression, use parenthesis: (myOptionalVar.foo)!myDefault, (myOptionalVar.foo)??
----

----
FTL stack trace ("~" means nesting-related):
	- Failed at: ${error.trace}  [in template "error.ftl" at line 10, column 1]
----
	at io.undertow.servlet.spec.HttpServletResponseImpl.doErrorDispatch(HttpServletResponseImpl.java:198)
	at io.undertow.servlet.handlers.ServletInitialHandler.handleFirstRequest(ServletInitialHandler.java:276)
	at io.undertow.servlet.handlers.ServletInitialHandler.access$100(ServletInitialHandler.java:78)
	at io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:133)
	at io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:130)
	at io.undertow.servlet.core.ServletRequestContextThreadSetupAction$1.call(ServletRequestContextThreadSetupAction.java:48)
	at io.undertow.servlet.core.ContextClassLoaderSetupAction$1.call(ContextClassLoaderSetupAction.java:43)
	at io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:249)
	at io.undertow.servlet.handlers.ServletInitialHandler.access$000(ServletInitialHandler.java:78)
	at io.undertow.servlet.handlers.ServletInitialHandler$1.handleRequest(ServletInitialHandler.java:99)
	at io.undertow.server.Connectors.executeRootHandler(Connectors.java:376)
	at io.undertow.server.HttpServerExchange$1.run(HttpServerExchange.java:830)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
	at java.base/java.lang.Thread.run(Thread.java:835)
Caused by: org.springframework.web.util.NestedServletException: Request processing failed; nested exception is freemarker.core.InvalidReferenceException: The following has evaluated to null or missing:
==> error.trace  [in template "error.ftl" at line 10, column 3]

----
Tip: It's the step after the last dot that caused this error, not those before it.
----
Tip: If the failing expression is known to legally refer to something that's sometimes null or missing, either specify a default value like myOptionalVar!myDefault, or use <#if myOptionalVar??>when-present<#else>when-missing</#if>. (These only cover the last step of the expression; to cover the whole expression, use parenthesis: (myOptionalVar.foo)!myDefault, (myOptionalVar.foo)??
----

----
FTL stack trace ("~" means nesting-related):
	- Failed at: ${error.trace}  [in template "error.ftl" at line 10, column 1]
----
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1013)
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:897)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:645)
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:882)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:750)
	at io.undertow.servlet.handlers.ServletHandler.handleRequest(ServletHandler.java:74)
	at io.undertow.servlet.handlers.FilterHandler.handleRequest(FilterHandler.java:81)
	at io.undertow.servlet.handlers.security.ServletSecurityRoleHandler.handleRequest(ServletSecurityRoleHandler.java:62)
	at io.undertow.servlet.handlers.ServletChain$1.handleRequest(ServletChain.java:68)
	at io.undertow.servlet.handlers.ServletDispatchingHandler.handleRequest(ServletDispatchingHandler.java:36)
	at io.undertow.servlet.handlers.RedirectDirHandler.handleRequest(RedirectDirHandler.java:68)
	at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
	at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
	at io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:251)
	at io.undertow.servlet.handlers.ServletInitialHandler.dispatchToPath(ServletInitialHandler.java:186)
	at io.undertow.servlet.spec.RequestDispatcherImpl.error(RequestDispatcherImpl.java:501)
	at io.undertow.servlet.spec.RequestDispatcherImpl.error(RequestDispatcherImpl.java:419)
	at io.undertow.servlet.spec.HttpServletResponseImpl.doErrorDispatch(HttpServletResponseImpl.java:196)
	... 14 more
Caused by: freemarker.core.InvalidReferenceException: The following has evaluated to null or missing:
==> error.trace  [in template "error.ftl" at line 10, column 3]

----
Tip: It's the step after the last dot that caused this error, not those before it.
----
Tip: If the failing expression is known to legally refer to something that's sometimes null or missing, either specify a default value like myOptionalVar!myDefault, or use <#if myOptionalVar??>when-present<#else>when-missing</#if>. (These only cover the last step of the expression; to cover the whole expression, use parenthesis: (myOptionalVar.foo)!myDefault, (myOptionalVar.foo)??
----

----
FTL stack trace ("~" means nesting-related):
	- Failed at: ${error.trace}  [in template "error.ftl" at line 10, column 1]
----
	at freemarker.core.InvalidReferenceException.getInstance(InvalidReferenceException.java:134)
	at freemarker.core.EvalUtil.coerceModelToTextualCommon(EvalUtil.java:467)
	at freemarker.core.EvalUtil.coerceModelToStringOrMarkup(EvalUtil.java:389)
	at freemarker.core.EvalUtil.coerceModelToStringOrMarkup(EvalUtil.java:358)
	at freemarker.core.DollarVariable.calculateInterpolatedStringOrMarkup(DollarVariable.java:100)
	at freemarker.core.DollarVariable.accept(DollarVariable.java:63)
	at freemarker.core.Environment.visit(Environment.java:330)
	at freemarker.core.Environment.visit(Environment.java:336)
	at freemarker.core.Environment.process(Environment.java:309)
	at freemarker.template.Template.process(Template.java:384)
	at org.springframework.web.servlet.view.freemarker.FreeMarkerView.processTemplate(FreeMarkerView.java:389)
	at org.springframework.web.servlet.view.freemarker.FreeMarkerView.doRender(FreeMarkerView.java:302)
	at org.springframework.web.servlet.view.freemarker.FreeMarkerView.renderMergedTemplateModel(FreeMarkerView.java:253)
	at org.springframework.web.servlet.view.AbstractTemplateView.renderMergedOutputModel(AbstractTemplateView.java:178)
	at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:316)
	at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1371)
	at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1117)
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1056)
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:942)
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1005)
	... 31 more

[dkirrane]

Found the issue was the path used by the probes.
Fixed by this PR
#47

[ekoutanov]

Merged and released in 3.15.0. Massive thanks @dkirrane /\