[FIXED] Tomcat multi-context deployment stops whole process if spring-boot context fails to deploy

Issue

I have a very specific Tomcat configuration that I don't want to change and I am looking for a solution for this specific configuration.

I have declared multiple contexts (<Context>) for deployment inside the conf/server.xml file in Tomcat, something I know is not recommended. My problem is that if one of those deployments fail, the whole Tomcat process stops which terminates the rest of the applications that have successfully started. Is this behavior expected? Is there an attribute or a way to prevent this and emulate the behavior of distinct context declarations akin to the usage of context.xml file?

The error I'm getting is the following:

ConfigServletWebServerApplicationContext : Exception encountered during context initialization

with this stacktrace (for Tomcat version 8.5.24):

SEVERE [Catalina-startStop-1] org.apache.catalina.core.ContainerBase.startInternal A child container failed during start
 java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/auth-service]]
        at java.util.concurrent.FutureTask.report(FutureTask.java:122)
        at java.util.concurrent.FutureTask.get(FutureTask.java:192)
        at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:939)
        at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:872)
        at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
        at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1419)
        at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1409)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at java.lang.Thread.run(Thread.java:748)
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/auth-service]]
        at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:167)
        ... 6 more
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'authenticationController': Injection of autowired dependencies failed; nested exception is java.lang.IllegalArgumentException: Could not resolve placeholder 'app.client-html.context' in value "${app.client-html.context}"
        at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessProperties(AutowiredAnnotationBeanPostProcessor.java:405)
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1415)
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:608)
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:531)
        at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:335)
        at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234)
        at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:333)
        at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:208)
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:944)
        at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:925)
        at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:588)
        at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:144)
        at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:767)
        at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:759)
        at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:426)
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:326)
        at org.springframework.boot.web.servlet.support.SpringBootServletInitializer.run(SpringBootServletInitializer.java:173)
        at org.springframework.boot.web.servlet.support.SpringBootServletInitializer.createRootApplicationContext(SpringBootServletInitializer.java:153)
        at org.springframework.boot.web.servlet.support.SpringBootServletInitializer.onStartup(SpringBootServletInitializer.java:95)
        at org.springframework.web.SpringServletContainerInitializer.onStartup(SpringServletContainerInitializer.java:174)
        at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5196)
        at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
        ... 6 more
Caused by: java.lang.IllegalArgumentException: Could not resolve placeholder 'app.client-html.context' in value "${app.client-html.context}"
        at org.springframework.util.PropertyPlaceholderHelper.parseStringValue(PropertyPlaceholderHelper.java:178)
        at org.springframework.util.PropertyPlaceholderHelper.replacePlaceholders(PropertyPlaceholderHelper.java:124)
        at org.springframework.core.env.AbstractPropertyResolver.doResolvePlaceholders(AbstractPropertyResolver.java:239)
        at org.springframework.core.env.AbstractPropertyResolver.resolveRequiredPlaceholders(AbstractPropertyResolver.java:210)
        at org.springframework.context.support.PropertySourcesPlaceholderConfigurer.lambda$processProperties$0(PropertySourcesPlaceholderConfigurer.java:175)
        at org.springframework.beans.factory.support.AbstractBeanFactory.resolveEmbeddedValue(AbstractBeanFactory.java:931)
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1308)
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1287)
        at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:640)
        at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:119)
        at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessProperties(AutowiredAnnotationBeanPostProcessor.java:399)
        ... 27 more

Sample configuration:

<Host name="localhost" unpackWARs="true" autoDeploy="true">
    <Context docBase="../../app-that-works" path="/itworks"/>
    <Context docBase="../../app-that-fails" path="/itfails"/>
</Host>

IMPORTANT: The failing application is a spring-boot application that is packaged as a .war file and running inside a vanilla tomcat, not the embedded tomcat way. This is important because it seems that these applications have this behavior...

DISCLAIMER: I am referring to vanilla Tomcat, not spring boot or embedded tomcat etc. I am not looking for such solutions, simply a solution to this specific problem.

Solution

Basically:

• an exception during the start phase (cf. LifeCycle) of any component configured in server.xml causes the server to exit. However some exceptions (like a failed ServletContextListener) don't propagate.
• an error of a component added during runtime, does not cause the server to exit.

If you don't want the whole server to stop, when a context fails to start up, use auto-deployment: for each context defined in server.xml create a file $CATALINA_BASE/conf/<engine_name>/<host_name>/<context_path>.xml with content:

<Context docBase="/path/to/application" />

In your case you need to create $CATALINA_BASE/conf/Catalina/localhost/itworks.xml and $CATALINA_BASE/conf/Catalina/localhost/itfails.xml. See Naming for Tomcat's naming convention for XML descriptors.

Edit: Your stack trace suggests that we might be dealing with a Tomcat or Spring bug:

• On one side the StandardContext expects a ServletContainerInitializer to throw only ServletExceptions (cf. source code) and let's all unchecked exceptions through. Remark that at the same time all exceptions from ServletContextListeners are caught and just logged (cf. source code).

• On the other hand Spring's SpringServletContainerInitializer should probably wrap all unchecked exceptions into a ServletException.

What happens in your case is that an unchecked exception makes it all the way through to the StandardContext and is rethrown as a LifecycleException stopping the server. Anyway, setting:

<Context throwOnFailure="false" ... />

should stop Tomcat from propagating the exception.

Answered By - Piotr P. Karwasz