Chapter 8. Triggering and modifying builds
The following sections outline how to trigger builds and modify builds using build hooks.
8.1. Build triggers
When defining a BuildConfig
, you can define triggers to control the circumstances in which the BuildConfig
should be run. The following build triggers are available:
- Webhook
- Image change
- Configuration change
8.1.1. Webhook triggers
Webhook triggers allow you to trigger a new build by sending a request to the OpenShift Container Platform API endpoint. You can define these triggers using GitHub, GitLab, Bitbucket, or Generic webhooks.
Currently, OpenShift Container Platform webhooks only support the analogous versions of the push event for each of the Git-based Source Code Management (SCM) systems. All other event types are ignored.
When the push events are processed, the OpenShift Container Platform control plane host confirms if the branch reference inside the event matches the branch reference in the corresponding BuildConfig
. If so, it then checks out the exact commit reference noted in the webhook event on the OpenShift Container Platform build. If they do not match, no build is triggered.
oc new-app
and oc new-build
create GitHub and Generic webhook triggers automatically, but any other needed webhook triggers must be added manually. You can manually add triggers by setting triggers.
For all webhooks, you must define a secret with a key named WebHookSecretKey
and the value being the value to be supplied when invoking the webhook. The webhook definition must then reference the secret. The secret ensures the uniqueness of the URL, preventing others from triggering the build. The value of the key is compared to the secret provided during the webhook invocation.
For example here is a GitHub webhook with a reference to a secret named mysecret
:
type: "GitHub" github: secretReference: name: "mysecret"
The secret is then defined as follows. Note that the value of the secret is base64 encoded as is required for any data
field of a Secret
object.
- kind: Secret apiVersion: v1 metadata: name: mysecret creationTimestamp: data: WebHookSecretKey: c2VjcmV0dmFsdWUx
8.1.1.1. Adding unauthenticated users to the system:webhook role binding
As a cluster administrator, you can add unauthenticated users to the system:webhook
role binding in OpenShift Container Platform for specific namespaces. The system:webhook
role binding allows users to trigger builds from external systems that do not use an OpenShift Container Platform authentication mechanism. Unauthenticated users do not have access to non-public role bindings by default. This is a change from OpenShift Container Platform versions before 4.16.
Adding unauthenticated users to the system:webhook
role binding is required to successfully trigger builds from GitHub, GitLab, and Bitbucket.
If it is necessary to allow unauthenticated users access to a cluster, you can do so by adding unauthenticated users to the system:webhook
role binding in each required namespace. This method is more secure than adding unauthenticated users to the system:webhook
cluster role binding. However, if you have a large number of namespaces, it is possible to add unauthenticated users to the system:webhook
cluster role binding which would apply the change to all namespaces.
Always verify compliance with your organization’s security standards when modifying unauthenticated access.
Prerequisites
-
You have access to the cluster as a user with the
cluster-admin
role. -
You have installed the OpenShift CLI (
oc
).
Procedure
Create a YAML file named
add-webhooks-unauth.yaml
and add the following content:apiVersion: rbac.authorization.k8s.io/v1 kind: RoleBinding metadata: annotations: rbac.authorization.kubernetes.io/autoupdate: "true" name: webhook-access-unauthenticated namespace: <namespace> 1 roleRef: apiGroup: rbac.authorization.k8s.io kind: Role name: "system:webhook" subjects: - apiGroup: rbac.authorization.k8s.io kind: Group name: "system:unauthenticated"
- 1
- The namespace of your
BuildConfig
.
Apply the configuration by running the following command:
$ oc apply -f add-webhooks-unauth.yaml
Additional resources
8.1.1.2. Using GitHub webhooks
GitHub webhooks handle the call made by GitHub when a repository is updated. When defining the trigger, you must specify a secret, which is part of the URL you supply to GitHub when configuring the webhook.
Example GitHub webhook definition:
type: "GitHub" github: secretReference: name: "mysecret"
The secret used in the webhook trigger configuration is not the same as the secret
field you encounter when configuring webhook in GitHub UI. The secret in the webhook trigger configuration makes the webhook URL unique and hard to predict. The secret configured in the GitHub UI is an optional string field that is used to create an HMAC hex digest of the body, which is sent as an X-Hub-Signature
header.
The payload URL is returned as the GitHub Webhook URL by the oc describe
command (see Displaying Webhook URLs), and is structured as follows:
Example output
https://<openshift_api_host:port>/apis/build.openshift.io/v1/namespaces/<namespace>/buildconfigs/<name>/webhooks/<secret>/github
Prerequisites
-
Create a
BuildConfig
from a GitHub repository. -
system:unauthenticated
has access to thesystem:webhook
role in the required namespaces. Or,system:unauthenticated
has access to thesystem:webhook
cluster role.
Procedure
Configure a GitHub Webhook.
After creating a
BuildConfig
object from a GitHub repository, run the following command:$ oc describe bc/<name_of_your_BuildConfig>
This command generates a webhook GitHub URL.
Example output
https://api.starter-us-east-1.openshift.com:443/apis/build.openshift.io/v1/namespaces/<namespace>/buildconfigs/<name>/webhooks/<secret>/github
- Cut and paste this URL into GitHub, from the GitHub web console.
-
In your GitHub repository, select Add Webhook from Settings
Webhooks. - Paste the URL output into the Payload URL field.
-
Change the Content Type from GitHub’s default
application/x-www-form-urlencoded
toapplication/json
. Click Add webhook.
You should see a message from GitHub stating that your webhook was successfully configured.
Now, when you push a change to your GitHub repository, a new build automatically starts, and upon a successful build a new deployment starts.
NoteGogs supports the same webhook payload format as GitHub. Therefore, if you are using a Gogs server, you can define a GitHub webhook trigger on your
BuildConfig
and trigger it by your Gogs server as well.
Given a file containing a valid JSON payload, such as
payload.json
, you can manually trigger the webhook with the followingcurl
command:$ curl -H "X-GitHub-Event: push" -H "Content-Type: application/json" -k -X POST --data-binary @payload.json https://<openshift_api_host:port>/apis/build.openshift.io/v1/namespaces/<namespace>/buildconfigs/<name>/webhooks/<secret>/github
The
-k
argument is only necessary if your API server does not have a properly signed certificate.
The build will only be triggered if the ref
value from GitHub webhook event matches the ref
value specified in the source.git
field of the BuildConfig
resource.
Additional resources
8.1.1.3. Using GitLab webhooks
GitLab webhooks handle the call made by GitLab when a repository is updated. As with the GitHub triggers, you must specify a secret. The following example is a trigger definition YAML within the BuildConfig
:
type: "GitLab" gitlab: secretReference: name: "mysecret"
The payload URL is returned as the GitLab Webhook URL by the oc describe
command, and is structured as follows:
Example output
https://<openshift_api_host:port>/apis/build.openshift.io/v1/namespaces/<namespace>/buildconfigs/<name>/webhooks/<secret>/gitlab
Prerequisites
-
system:unauthenticated
has access to thesystem:webhook
role in the required namespaces. Or,system:unauthenticated
has access to thesystem:webhook
cluster role.
Procedure
Configure a GitLab Webhook.
Get the webhook URL by entering the following command:
$ oc describe bc <name>
-
Copy the webhook URL, replacing
<secret>
with your secret value. - Follow the GitLab setup instructions to paste the webhook URL into your GitLab repository settings.
Given a file containing a valid JSON payload, such as
payload.json
, you can manually trigger the webhook with the followingcurl
command:$ curl -H "X-GitLab-Event: Push Hook" -H "Content-Type: application/json" -k -X POST --data-binary @payload.json https://<openshift_api_host:port>/apis/build.openshift.io/v1/namespaces/<namespace>/buildconfigs/<name>/webhooks/<secret>/gitlab
The
-k
argument is only necessary if your API server does not have a properly signed certificate.
8.1.1.4. Using Bitbucket webhooks
Bitbucket webhooks handle the call made by Bitbucket when a repository is updated. Similar to GitHub and GitLab triggers, you must specify a secret. The following example is a trigger definition YAML within the BuildConfig
:
type: "Bitbucket" bitbucket: secretReference: name: "mysecret"
The payload URL is returned as the Bitbucket Webhook URL by the oc describe
command, and is structured as follows:
Example output
https://<openshift_api_host:port>/apis/build.openshift.io/v1/namespaces/<namespace>/buildconfigs/<name>/webhooks/<secret>/bitbucket
Prerequisites
-
system:unauthenticated
has access to thesystem:webhook
role in the required namespaces. Or,system:unauthenticated
has access to thesystem:webhook
cluster role.
Procedure
Configure a Bitbucket Webhook.
Get the webhook URL by entering the following command:
$ oc describe bc <name>
-
Copy the webhook URL, replacing
<secret>
with your secret value. - Follow the Bitbucket setup instructions to paste the webhook URL into your Bitbucket repository settings.
Given a file containing a valid JSON payload, such as
payload.json
, you can manually trigger the webhook by entering the followingcurl
command:$ curl -H "X-Event-Key: repo:push" -H "Content-Type: application/json" -k -X POST --data-binary @payload.json https://<openshift_api_host:port>/apis/build.openshift.io/v1/namespaces/<namespace>/buildconfigs/<name>/webhooks/<secret>/bitbucket
The
-k
argument is only necessary if your API server does not have a properly signed certificate.
8.1.1.5. Using generic webhooks
Generic webhooks are called from any system capable of making a web request. As with the other webhooks, you must specify a secret, which is part of the URL that the caller must use to trigger the build. The secret ensures the uniqueness of the URL, preventing others from triggering the build. The following is an example trigger definition YAML within the BuildConfig
:
type: "Generic"
generic:
secretReference:
name: "mysecret"
allowEnv: true 1
- 1
- Set to
true
to allow a generic webhook to pass in environment variables.
Procedure
To set up the caller, supply the calling system with the URL of the generic webhook endpoint for your build.
Example generic webhook endpoint URL
https://<openshift_api_host:port>/apis/build.openshift.io/v1/namespaces/<namespace>/buildconfigs/<name>/webhooks/<secret>/generic
The caller must call the webhook as a
POST
operation.To call the webhook manually, enter the following
curl
command:$ curl -X POST -k https://<openshift_api_host:port>/apis/build.openshift.io/v1/namespaces/<namespace>/buildconfigs/<name>/webhooks/<secret>/generic
The HTTP verb must be set to
POST
. The insecure-k
flag is specified to ignore certificate validation. This second flag is not necessary if your cluster has properly signed certificates.The endpoint can accept an optional payload with the following format:
git: uri: "<url to git repository>" ref: "<optional git reference>" commit: "<commit hash identifying a specific git commit>" author: name: "<author name>" email: "<author e-mail>" committer: name: "<committer name>" email: "<committer e-mail>" message: "<commit message>" env: 1 - name: "<variable name>" value: "<variable value>"
- 1
- Similar to the
BuildConfig
environment variables, the environment variables defined here are made available to your build. If these variables collide with theBuildConfig
environment variables, these variables take precedence. By default, environment variables passed by webhook are ignored. Set theallowEnv
field totrue
on the webhook definition to enable this behavior.
To pass this payload using
curl
, define it in a file namedpayload_file.yaml
and run the following command:$ curl -H "Content-Type: application/yaml" --data-binary @payload_file.yaml -X POST -k https://<openshift_api_host:port>/apis/build.openshift.io/v1/namespaces/<namespace>/buildconfigs/<name>/webhooks/<secret>/generic
The arguments are the same as the previous example with the addition of a header and a payload. The
-H
argument sets theContent-Type
header toapplication/yaml
orapplication/json
depending on your payload format. The--data-binary
argument is used to send a binary payload with newlines intact with thePOST
request.
OpenShift Container Platform permits builds to be triggered by the generic webhook even if an invalid request payload is presented, for example, invalid content type, unparsable or invalid content, and so on. This behavior is maintained for backwards compatibility. If an invalid request payload is presented, OpenShift Container Platform returns a warning in JSON format as part of its HTTP 200 OK
response.
8.1.1.6. Displaying webhook URLs
You can use the oc describe
command to display webhook URLs associated with a build configuration. If the command does not display any webhook URLs, then no webhook trigger is currently defined for that build configuration.
Procedure
-
To display any webhook URLs associated with a
BuildConfig
, run the following command:
$ oc describe bc <name>
8.1.2. Using image change triggers
As a developer, you can configure your build to run automatically every time a base image changes.
You can use image change triggers to automatically invoke your build when a new version of an upstream image is available. For example, if a build is based on a RHEL image, you can trigger that build to run any time the RHEL image changes. As a result, the application image is always running on the latest RHEL base image.
Image streams that point to container images in v1 container registries only trigger a build once when the image stream tag becomes available and not on subsequent image updates. This is due to the lack of uniquely identifiable images in v1 container registries.
Procedure
Define an
ImageStream
that points to the upstream image you want to use as a trigger:kind: "ImageStream" apiVersion: "v1" metadata: name: "ruby-20-centos7"
This defines the image stream that is tied to a container image repository located at
<system-registry>/<namespace>/ruby-20-centos7
. The<system-registry>
is defined as a service with the namedocker-registry
running in OpenShift Container Platform.If an image stream is the base image for the build, set the
from
field in the build strategy to point to theImageStream
:strategy: sourceStrategy: from: kind: "ImageStreamTag" name: "ruby-20-centos7:latest"
In this case, the
sourceStrategy
definition is consuming thelatest
tag of the image stream namedruby-20-centos7
located within this namespace.Define a build with one or more triggers that point to
ImageStreams
:type: "ImageChange" 1 imageChange: {} type: "ImageChange" 2 imageChange: from: kind: "ImageStreamTag" name: "custom-image:latest"
- 1
- An image change trigger that monitors the
ImageStream
andTag
as defined by the build strategy’sfrom
field. TheimageChange
object here must be empty. - 2
- An image change trigger that monitors an arbitrary image stream. The
imageChange
part, in this case, must include afrom
field that references theImageStreamTag
to monitor.
When using an image change trigger for the strategy image stream, the generated build is supplied with an immutable docker tag that points to the latest image corresponding to that tag. This new image reference is used by the strategy when it executes for the build.
For other image change triggers that do not reference the strategy image stream, a new build is started, but the build strategy is not updated with a unique image reference.
Since this example has an image change trigger for the strategy, the resulting build is:
strategy: sourceStrategy: from: kind: "DockerImage" name: "172.30.17.3:5001/mynamespace/ruby-20-centos7:<immutableid>"
This ensures that the triggered build uses the new image that was just pushed to the repository, and the build can be re-run any time with the same inputs.
You can pause an image change trigger to allow multiple changes on the referenced image stream before a build is started. You can also set the paused
attribute to true when initially adding an ImageChangeTrigger
to a BuildConfig
to prevent a build from being immediately triggered.
type: "ImageChange" imageChange: from: kind: "ImageStreamTag" name: "custom-image:latest" paused: true
In addition to setting the image field for all Strategy
types, for custom builds, the OPENSHIFT_CUSTOM_BUILD_BASE_IMAGE
environment variable is checked. If it does not exist, then it is created with the immutable image reference. If it does exist, then it is updated with the immutable image reference.
If a build is triggered due to a webhook trigger or manual request, the build that is created uses the <immutableid>
resolved from the ImageStream
referenced by the Strategy
. This ensures that builds are performed using consistent image tags for ease of reproduction.
Additional resources
8.1.3. Identifying the image change trigger of a build
As a developer, if you have image change triggers, you can identify which image change initiated the last build. This can be useful for debugging or troubleshooting builds.
Example BuildConfig
apiVersion: build.openshift.io/v1 kind: BuildConfig metadata: name: bc-ict-example namespace: bc-ict-example-namespace spec: # ... triggers: - imageChange: from: kind: ImageStreamTag name: input:latest namespace: bc-ict-example-namespace - imageChange: from: kind: ImageStreamTag name: input2:latest namespace: bc-ict-example-namespace type: ImageChange status: imageChangeTriggers: - from: name: input:latest namespace: bc-ict-example-namespace lastTriggerTime: "2021-06-30T13:47:53Z" lastTriggeredImageID: image-registry.openshift-image-registry.svc:5000/bc-ict-example-namespace/input@sha256:0f88ffbeb9d25525720bfa3524cb1bf0908b7f791057cf1acfae917b11266a69 - from: name: input2:latest namespace: bc-ict-example-namespace lastTriggeredImageID: image-registry.openshift-image-registry.svc:5000/bc-ict-example-namespace/input2@sha256:0f88ffbeb9d25525720bfa3524cb2ce0908b7f791057cf1acfae917b11266a69 lastVersion: 1
This example omits elements that are not related to image change triggers.
Prerequisites
- You have configured multiple image change triggers. These triggers have triggered one or more builds.
Procedure
In the
BuildConfig
CR, instatus.imageChangeTriggers
, identify thelastTriggerTime
that has the latest timestamp.This
ImageChangeTriggerStatus
Then you use the `name` and `namespace` from that build to find the corresponding image change trigger in `buildConfig.spec.triggers`.
-
Under
imageChangeTriggers
, compare timestamps to identify the latest
Image change triggers
In your build configuration, buildConfig.spec.triggers
is an array of build trigger policies, BuildTriggerPolicy
.
Each BuildTriggerPolicy
has a type
field and set of pointers fields. Each pointer field corresponds to one of the allowed values for the type
field. As such, you can only set BuildTriggerPolicy
to only one pointer field.
For image change triggers, the value of type
is ImageChange
. Then, the imageChange
field is the pointer to an ImageChangeTrigger
object, which has the following fields:
-
lastTriggeredImageID
: This field, which is not shown in the example, is deprecated in OpenShift Container Platform 4.8 and will be ignored in a future release. It contains the resolved image reference for theImageStreamTag
when the last build was triggered from thisBuildConfig
. -
paused
: You can use this field, which is not shown in the example, to temporarily disable this particular image change trigger. -
from
: Use this field to reference theImageStreamTag
that drives this image change trigger. Its type is the core Kubernetes type,OwnerReference
.
The from
field has the following fields of note:
-
kind
: For image change triggers, the only supported value isImageStreamTag
. -
namespace
: Use this field to specify the namespace of theImageStreamTag
. -
name
: Use this field to specify theImageStreamTag
.
Image change trigger status
In your build configuration, buildConfig.status.imageChangeTriggers
is an array of ImageChangeTriggerStatus
elements. Each ImageChangeTriggerStatus
element includes the from
, lastTriggeredImageID
, and lastTriggerTime
elements shown in the preceding example.
The ImageChangeTriggerStatus
that has the most recent lastTriggerTime
triggered the most recent build. You use its name
and namespace
to identify the image change trigger in buildConfig.spec.triggers
that triggered the build.
The lastTriggerTime
with the most recent timestamp signifies the ImageChangeTriggerStatus
of the last build. This ImageChangeTriggerStatus
has the same name
and namespace
as the image change trigger in buildConfig.spec.triggers
that triggered the build.
Additional resources
8.1.4. Configuration change triggers
A configuration change trigger allows a build to be automatically invoked as soon as a new BuildConfig
is created.
The following is an example trigger definition YAML within the BuildConfig
:
type: "ConfigChange"
Configuration change triggers currently only work when creating a new BuildConfig
. In a future release, configuration change triggers will also be able to launch a build whenever a BuildConfig
is updated.
8.1.4.1. Setting triggers manually
Triggers can be added to and removed from build configurations with oc set triggers
.
Procedure
To set a GitHub webhook trigger on a build configuration, enter the following command:
$ oc set triggers bc <name> --from-github
To set an image change trigger, enter the following command:
$ oc set triggers bc <name> --from-image='<image>'
To remove a trigger, enter the following command:
$ oc set triggers bc <name> --from-bitbucket --remove
When a webhook trigger already exists, adding it again regenerates the webhook secret.
For more information, consult the help documentation by entering the following command:
$ oc set triggers --help
8.2. Build hooks
Build hooks allow behavior to be injected into the build process.
The postCommit
field of a BuildConfig
object runs commands inside a temporary container that is running the build output image. The hook is run immediately after the last layer of the image has been committed and before the image is pushed to a registry.
The current working directory is set to the image’s WORKDIR
, which is the default working directory of the container image. For most images, this is where the source code is located.
The hook fails if the script or command returns a non-zero exit code or if starting the temporary container fails. When the hook fails it marks the build as failed and the image is not pushed to a registry. The reason for failing can be inspected by looking at the build logs.
Build hooks can be used to run unit tests to verify the image before the build is marked complete and the image is made available in a registry. If all tests pass and the test runner returns with exit code 0
, the build is marked successful. In case of any test failure, the build is marked as failed. In all cases, the build log contains the output of the test runner, which can be used to identify failed tests.
The postCommit
hook is not only limited to running tests, but can be used for other commands as well. Since it runs in a temporary container, changes made by the hook do not persist, meaning that running the hook cannot affect the final image. This behavior allows for, among other uses, the installation and usage of test dependencies that are automatically discarded and are not present in the final image.
8.2.1. Configuring post commit build hooks
There are different ways to configure the post-build hook. All forms in the following examples are equivalent and run bundle exec rake test --verbose
.
Procedure
Use one of the following options to configure post-build hooks:
Option Description Shell script
postCommit: script: "bundle exec rake test --verbose"
The
script
value is a shell script to be run with/bin/sh -ic
. Use this option when a shell script is appropriate to execute the build hook. For example, for running unit tests as above. To control the image entry point or if the image does not have/bin/sh
, usecommand
, orargs
, or both.NoteThe additional
-i
flag was introduced to improve the experience working with CentOS and RHEL images, and may be removed in a future release.Command as the image entry point
postCommit: command: ["/bin/bash", "-c", "bundle exec rake test --verbose"]
In this form,
command
is the command to run, which overrides the image entry point in the exec form, as documented in the Dockerfile reference. This is needed if the image does not have/bin/sh
, or if you do not want to use a shell. In all other cases, usingscript
might be more convenient.Command with arguments
postCommit: command: ["bundle", "exec", "rake", "test"] args: ["--verbose"]
This form is equivalent to appending the arguments to
command
.
Providing both script
and command
simultaneously creates an invalid build hook.
8.2.2. Using the CLI to set post commit build hooks
The oc set build-hook
command can be used to set the build hook for a build configuration.
Procedure
Complete one of the following actions:
To set a command as the post-commit build hook, enter the following command:
$ oc set build-hook bc/mybc \ --post-commit \ --command \ -- bundle exec rake test --verbose
To set a script as the post-commit build hook, enter the following command:
$ oc set build-hook bc/mybc --post-commit --script="bundle exec rake test --verbose"