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# Apache Tomcat distribution for container platforms
## Configuration
Configuration is located in `conf/server.xml`, `conf/web.xml`, `conf/logging.properties`, all other configuration files, resources and context files are located in `conf`, identical to standalone Tomcat.
## Building
### Maven build
Update Tomcat version number in the `pom.xml`, customize Tomcat components in the dependencies to keep the ones needed (only the main `tomcat-catalina` is mandatory). Custom Tomcat components sources can be added to the usual Maven build path and will be included in the package that is built.
```
mvn clean; mvn package
```
### Docker build
```
docker build -t apache/tomcat-stuffed:1.0 -f ./Dockerfile .
```
Docker build arguments include `namespace` (default is `tomcat`) and `port` which should match the Tomcat port in `server.xml` (default is `8080`). Other ports that need to be exposed can be added in the `Dockerfile` as needed. Webapps should be added to the `webapps` folder where they will be auto deployed by the host if using the defaults. Otherwise, the `Dockerfile` command line can be edited like below to include the necessary resources and command line arguments to run a single or multiple hardcoded web applications.
## Running
Add a webapp as folder mywebapp (for this example, or specify another path), or a path from which a configured Host will auto deploy
```
--path: Specify a path the webapp will use
--war: Add the specified path (directory or war) as a webapp (if no path has been specified, it will be the root webapp)
```
The JULI logging manager configuration is optional but makes logging more readable and configurable:
`-Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djava.util.logging.config.file=conf/logging.properties`
The default JULI configuration uses `catalina.base`, so specifying the system property with `-Dcatalina.base=.` is also useful.
### Command line example with a single root webapp
```
java -Dcatalina.base=. -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djava.util.logging.config.file=conf/logging.properties -jar target/tomcat-stuffed-1.0.jar --war myrootwebapp
```
### Command line example with three webapps
```
java -Dcatalina.base=. -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djava.util.logging.config.file=conf/logging.properties -jar target/tomcat-stuffed-1.0.jar --war myrootwebapp --path /path1 --war mywebapp1 --path /path2 --war mywebapp2
```
## Cloud
### Deployment
An example `tomcat.yaml` is included which uses the Docker image. It uses the health check valve which can be added in `conf/server.xml`, or a similar service responding to requests on `/health`. It also declares the optional Jolokia and Prometheus ports for monitoring.
### Cluster
If using the Kubernetes cloud clustering membership provider, the pod needs to have the permission to view other pods. For example with Openshift, this is done with:
```
oc policy add-role-to-user view system:serviceaccount:$(oc project -q):default -n $(oc project -q)
```
## Native Image
The Tomcat documentation includes information on using the native-image tool (docs/graal.html).
Running in a container is possible, an example `DockerfileGraal` is given. To use a native image in a container that is not identical to the build platform,
the `native-image` call will need to use the additional `--static` parameter to statically link base libraries (this will then require zlib and glibc
static libraries). Due to TLS using dynamic libraries (SunEC for JSSE and tomcat-native for OpenSSL), TLS support is not available with static linking.
If TLS support is needed, the native image must instead be built on a platform identical to the target platform.
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