Update Jenkins documentation.

hack/jenkins/README.md

 # Jenkins
 
 [Jenkins](http://jenkins-ci.org/) is a pluggable continuous
-integration system. The Google team is running a Jenkins server on a
-private GCE instance for the Kubernetes project in order to run longer
-integration tests, continuously, on different providers. Currently, we
-are running tests on GCE, GKE, and AWS.
+integration system. The Google team is running two Jenkins servers in GCE for
+the Kubernetes project. The post-commit instance runs continuous builds, unit
+tests, integration tests, code verification tests, and end-to-end tests on
+multiple providers using the latest commits to the Kubernetes repo from the
+master and release branches. The PR Jenkins instance runs these tests on each
+PR by a trusted contributor, it but only runs a subset of the end-to-end tests
+and only on GCE.
 
 ## General flow
-The flow of the Google Jenkins server:
+The flow of the post-commit Jenkins instance:
 * Under the `kubernetes-build` job: Every 2 minutes, Jenkins polls for a batch
   of new commits, after which it runs the `build.sh` script (in this directory)
   on the latest tip. This results in build assets getting pushed to GCS and the
@@ -18,9 +21,7 @@ The flow of the Google Jenkins server:
   * `kubernetes-e2e-gce`: Standard GCE e2e.
   * `kubernetes-e2e-gke`: GKE provider e2e, with head k8s client and GKE
     creating clusters at its default version.
-  * `kubernetes-e2e-gke-ci`: GKE provider e2e, with head k8s client and GKE
-    creating clusters at the head k8s version.
-  * `kubernetes-e2e-aws`: AWS provider e2e.
+  * `kubernetes-e2e-aws`: AWS provider e2e. This only runs once a day.
 * Each job will not run concurrently with itself, so, for instance,
   Jenkins executor will only ever run one `kubernetes-build`
   job. However, it may run the jobs in parallel,
@@ -41,6 +42,42 @@ outside this repository, it's tricky to keep documentation for it up
 to date quickly. However, the scripts themselves attempt to provide
 color for the configuration(s) that each script runs in.
 
+## GCS Log Format
+
+Our `upload-to-gcs.sh` script runs at the start and end of every job. Logs on
+post-commit Jenkins go under `gs://kubernetes-jenkins/logs/`. Logs on PR
+Jenkins go under `gs://kubernetes-jenkins-pull/pr-logs/pull/PULL_NUMBER/`.
+Individual run logs go into the `JOB_NAME/BUILD_NUMBER` folder.
+
+At the start of the job, it uploads `started.json` containing the version of
+Kubernetes under test and the timestamp.
+
+At the end, it uploads `finished.json` containing the result and timestamp, as
+well as the build log into `build-log.txt`. Under `artifacts/` we put our
+test results in `junit_XY.xml`, along with gcp resource lists and cluster logs.
+
+It also updates `latest-build.txt` at the end to point to this build number.
+In the end, the directory structure looks like this:
+
+```
+gs://kubernetes-jenkins/logs/kubernetes-e2e-gce/
+  latest-build.txt
+  12345/
+    build-log.txt
+    started.json
+    finished.json
+    artifacts/
+      gcp-resources-{before, after}.txt
+      junit_{00, 01, ...}.xml
+      jenkins-e2e-master/{kube-apiserver.log, ...}
+      jenkins-e2e-minion-abcd/{kubelet.log, ...}
+  12344/
+    ...
+```
+
+The munger uses `latest-build.txt` and the JUnit reports to figure out whether
+or not the job is healthy.
+
 ## Job Builder
 
 New jobs should be specified as YAML files to be processed by [Jenkins Job
@@ -51,4 +88,11 @@ in a Docker container defined in `job-builder-image`, and triggers it using
 [jenkins_jobs.ini](http://docs.openstack.org/infra/jenkins-job-builder/execution.html)
 which contains the location and credentials of the Jenkins server.
 
+E2E Job definitions are templated to avoid code duplication. To add a new job,
+add a new entry to the appropriate `project`.
+[This](https://github.com/kubernetes/kubernetes/commit/eb273e5a4bdd3905f881563ada4e6543c7eb96b5)
+is an example of a commit which does this. If necessary, create a new project, as in
+[this](https://github.com/kubernetes/kubernetes/commit/09c27cdabc300e0420a2914100bedb565c23ed73)
+commit.
+
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