diff --git a/examples/javaweb-tomcat-sidecar/README.md b/examples/javaweb-tomcat-sidecar/README.md index bb2347664a4..1825bf3bfe9 100644 --- a/examples/javaweb-tomcat-sidecar/README.md +++ b/examples/javaweb-tomcat-sidecar/README.md @@ -45,33 +45,33 @@ This sidecar mode brings a new workflow for Java users: ![](workflow.png?raw=true "Workflow") -As you can see, user can create a `sample:v2` container as sidecar to "provide" war file to Tomcat by copying it to the shared `emptyDir` volume. And Pod will make sure the two containers compose a "atomic" scheduling unit, which is perfect for this case. Thus, your application version management will be totally seperated from web server management. +As you can see, user can create a `sample:v2` container as sidecar to "provide" war file to Tomcat by copying it to the shared `emptyDir` volume. And Pod will make sure the two containers compose an "atomic" scheduling unit, which is perfect for this case. Thus, your application version management will be totally seperated from web server management. -For example, if you gonna change the configurations of your Tomcat: +For example, if you are going to change the configurations of your Tomcat: -``` -docker exec -it /bin/bash -# do your change, and then commit it to a new image -docker commit mytomcat:7.0-dev +```sh +$ docker exec -it /bin/bash +# make some change, and then commit it to a new image +$ docker commit mytomcat:7.0-dev ``` -Done! The new Tomcat image **will not** mess up with your `sample.war` file. +Done! The new Tomcat image **will not** mess up with your `sample.war` file. You can re-use your tomcat image with lots of different war container images for lots of different apps without having to build lots of different images. -You can also upgrade your app to new version seperately, without creating a new "Tomcat plus app" image (and this image will become huge as unionfs will keep all the old war files in its layers). +Also this means that rolling out a new Tomcat to patch security or whatever else, doesn't require rebuilding N different images. -**Why don't put my `sample.war` in a host dir and mount it to tomcat container?** +**Why not put my `sample.war` in a host dir and mount it to tomcat container?** -You have to **manage the volumes** in this case, for example, when you restart or scale the Pod on another Node, your contents is not ready on that host. +You have to **manage the volumes** in this case, for example, when you restart or scale the pod on another node, your contents is not ready on that host. -Generally, we have to set up a distributed file system (NFS at least) volume to solve this (if we do not have GCE PD volume). But seriously, it's a overkill. +Generally, we have to set up a distributed file system (NFS at least) volume to solve this (if we do not have GCE PD volume). But this is generally unnecessary. -### How To +### How To Set this Up -In Kubernetes a [_Pod_](../../docs/user-guide/pods.md) is the smallest deployable unit that can be created, scheduled, and managed. Its a collocated group of containers that share an IP and storage volume. +In Kubernetes a [_Pod_](../../docs/user-guide/pods.md) is the smallest deployable unit that can be created, scheduled, and managed. It's a collocated group of containers that share an IP and storage volume. Here is the config [javaweb.yaml](javaweb.yaml) for Java Web pod: -NOTE: you should define `war` contaienr **first** as it is the "provider". +NOTE: you should define `war` container **first** as it is the "provider". @@ -98,6 +98,7 @@ spec: hostPort: 8001 volumes: - name: app-volume + emptyDir: {} ``` @@ -110,21 +111,21 @@ ADD sample.war sample.war CMD "sh" "mv.sh" ``` -And the content inf `mv.sh` is: +And the contents of `mv.sh` is: ```sh cp /sample.war /app -tail -f /etc/hosts +tail -f /dev/null ``` -#### Explaination +#### Explanation 1. 'war' container only contains the `war` file of your app -2. 'war' container's CMD try to copy `sample.war` to the `emptyDir` volume path -3. The last line of `tailf -f` is just used to hold the container, as RC does not support one-off task +2. 'war' container's CMD tries to copy `sample.war` to the `emptyDir` volume path +3. The last line of `tailf -f` is just used to hold the container, as Replication Controller does not support one-off task 4. 'tomcat' container will load the `sample.war` from volume path -What's more, if you don't want to add a build in `mv.sh` script in the `war` container, you can use Pod lifecycle handler to do the copy work, here's a example [javaweb-2.yaml](javaweb-2.yaml): +What's more, if you don't want to enclose a build-in `mv.sh` script in the `war` container, you can use Pod lifecycle handler to do the copy work, here's a example [javaweb-2.yaml](javaweb-2.yaml): @@ -159,6 +160,7 @@ spec: hostPort: 8001 volumes: - name: app-volume + emptyDir: {} ``` @@ -168,13 +170,13 @@ And the `resouer/sample:v2` Dockerfile is quite simple: ``` FROM busybox:latest ADD sample.war sample.war -CMD "tail" "-f" "/etc/hosts" +CMD "tail" "-f" "/dev/null" ``` -#### Explaination +#### Explanation 1. 'war' container only contains the `war` file of your app -2. 'war' container's CMD use `tail` to hold the container, nothing else +2. 'war' container's CMD uses `tail -f` to hold the container, nothing more 3. The `postStart` lifecycle handler will do `cp` after the `war` container is started 4. Again 'tomcat' container will load the `sample.war` from volume path @@ -185,18 +187,18 @@ Done! Now your `war` container contains nothing except `sample.war`, clean enoug Create the Java web pod: ```sh -kubectl create -f examples/javaweb-tomcat-sidecar/javaweb-2.yaml +$ kubectl create -f examples/javaweb-tomcat-sidecar/javaweb-2.yaml ``` Check status of the pod: ```sh -kubectl get -w po +$ kubectl get -w po NAME READY STATUS RESTARTS AGE javaweb-2 2/2 Running 0 7s ``` -Wait for the status to `2/2` and `Running`. Then you can visit "Hello, World" on `http://localhost:8001/sample/index.html` +Wait for the status to `2/2` and `Running`. Then you can visit "Hello, World" page on `http://localhost:8001/sample/index.html` You can also test `javaweb.yaml` in the same way. @@ -205,7 +207,7 @@ You can also test `javaweb.yaml` in the same way. All resources created in this application can be deleted: ```sh -kubectl delete -f examples/javaweb-tomcat-sidecar/javaweb-2.yaml +$ kubectl delete -f examples/javaweb-tomcat-sidecar/javaweb-2.yaml ``` diff --git a/examples/javaweb-tomcat-sidecar/javaweb-2.yaml b/examples/javaweb-tomcat-sidecar/javaweb-2.yaml index 74908189309..b34d5ab6e26 100644 --- a/examples/javaweb-tomcat-sidecar/javaweb-2.yaml +++ b/examples/javaweb-tomcat-sidecar/javaweb-2.yaml @@ -26,4 +26,6 @@ spec: - containerPort: 8080 hostPort: 8001 volumes: - - name: app-volume \ No newline at end of file + - name: app-volume + emptyDir: {} + diff --git a/examples/javaweb-tomcat-sidecar/javaweb.yaml b/examples/javaweb-tomcat-sidecar/javaweb.yaml index c29bcd7c481..d77f6a727e6 100644 --- a/examples/javaweb-tomcat-sidecar/javaweb.yaml +++ b/examples/javaweb-tomcat-sidecar/javaweb.yaml @@ -19,4 +19,6 @@ spec: - containerPort: 8080 hostPort: 8001 volumes: - - name: app-volume \ No newline at end of file + - name: app-volume + emptyDir: {} +