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Helm Charts
The HelmChart
API defines a Source to produce an Artifact for a Helm chart
archive with a set of specific configurations.
Example
The following is an example of a HelmChart. It fetches and/or packages a Helm
chart and exposes it as a tarball (.tgz
) Artifact for the specified
configuration:
---
apiVersion: source.toolkit.fluxcd.io/v1beta2
kind: HelmChart
metadata:
name: podinfo
namespace: default
spec:
interval: 5m0s
chart: podinfo
reconcileStrategy: ChartVersion
sourceRef:
kind: HelmRepository
name: podinfo
version: '5.*'
In the above example:
- A HelmChart named
podinfo
is created, indicated by the.metadata.name
field. - The source-controller fetches the Helm chart every five minutes from the
podinfo
HelmRepository source reference, indicated by the.spec.sourceRef.kind
and.spec.sourceRef.name
fields. - The fetched Helm chart version is the latest available chart
version in the range specified in
spec.version
. This version is also used as Artifact revision, reported in-cluster in the.status.artifact.revision
field. - When the current Helm Chart version differs from the latest available chart in the version range, it is fetched and/or packaged as a new Artifact.
- The new Artifact is reported in the
.status.artifact
field.
You can run this example by saving the manifest into helmchart.yaml
.
NOTE: HelmChart is usually used by the helm-controller. Based on the HelmRelease configuration, an associated HelmChart is created by the helm-controller.
Apply the resource on the cluster:
kubectl apply -f helmchart.yaml
Run
kubectl get helmchart
to see the HelmChart:NAME CHART VERSION SOURCE KIND SOURCE NAME AGE READY STATUS podinfo podinfo 5.* HelmRepository podinfo 53s True pulled 'podinfo' chart with version '5.2.1'
Run
kubectl describe helmchart podinfo
to see the Artifact and Conditions in the HelmChart’s Status:Status: Observed Source Artifact Revision: sha256:83a3c595163a6ff0333e0154c790383b5be441b9db632cb36da11db1c4ece111 Artifact: Digest: sha256:6c3cc3b955bce1686036ae6822ee2ca0ef6ecb994e3f2d19eaf3ec03dcba84b3 Last Update Time: 2022-02-13T11:24:10Z Path: helmchart/default/podinfo/podinfo-5.2.1.tgz Revision: 5.2.1 Size: 14166 URL: http://source-controller.flux-system.svc.cluster.local./helmchart/default/podinfo/podinfo-5.2.1.tgz Conditions: Last Transition Time: 2022-02-13T11:24:10Z Message: pulled 'podinfo' chart with version '5.2.1' Observed Generation: 1 Reason: ChartPullSucceeded Status: True Type: Ready Last Transition Time: 2022-02-13T11:24:10Z Message: pulled 'podinfo' chart with version '5.2.1' Observed Generation: 1 Reason: ChartPullSucceeded Status: True Type: ArtifactInStorage Observed Chart Name: podinfo Observed Generation: 1 URL: http://source-controller.flux-system.svc.cluster.local./helmchart/default/podinfo/latest.tar.gz Events: Type Reason Age From Message ---- ------ ---- ---- ------- Normal ChartPullSucceeded 2m51s source-controller pulled 'podinfo' chart with version '5.2.1'
Writing a HelmChart spec
As with all other Kubernetes config, a HelmChart needs apiVersion
, kind
, and
metadata
fields. The name of a HelmChart object must be a valid
DNS subdomain name.
A HelmChart also needs a
.spec
section.
Source reference
.spec.sourceRef
is a required field that specifies a reference to the Source
the chart is available at.
Supported references are:
Although there are three kinds of source references, there are only two
underlying implementations. The artifact building process for GitRepository
and Bucket
are the same as they are already built source artifacts. In case
of HelmRepository
, a chart is fetched and/or packaged based on the
configuration of the Helm chart.
For a HelmChart
to be reconciled, the associated artifact in the source
reference must be ready. If the source artifact is not ready, the HelmChart
reconciliation is retried.
When the metadata.generation
of the HelmChart
don’t match with the
status.observedGeneration
, the chart is fetched from source and/or packaged.
If there’s no .spec.valuesFiles
specified, the chart is only fetched from the
source, and not packaged. If .spec.valuesFiles
are specified, the chart is
fetched and packaged with the values files. When the metadata.generation
matches the status.observedGeneration
, the chart is only fetched from source
or from the cache if available, and not packaged.
When using a HelmRepository
source reference, the secret reference defined in
the Helm repository is used to fetch the chart.
The HelmChart reconciliation behavior varies depending on the source reference kind, see reconcile strategy.
The attributes of the generated artifact also varies depending on the source reference kind, see artifact.
Chart
.spec.chart
is a required field that specifies the name or path the Helm chart
is available at in the
Source reference.
For HelmRepository
Source reference, it’ll be just the name of the chart.
spec:
chart: podinfo
sourceRef:
name: podinfo
kind: HelmRepository
For GitRepository
and Bucket
Source reference, it’ll be the path to the
Helm chart directory.
spec:
chart: ./charts/podinfo
sourceRef:
name: podinfo
kind: <GitRepository|Bucket>
Version
.spec.version
is an optional field to specify the version of the chart in
semver. It is applicable only when the Source reference is a HelmRepository
.
It is ignored for GitRepository
and Bucket
Source reference. It defaults to
the latest version of the chart with value *
.
Version can be a fixed semver, minor or patch semver range of a specific
version (i.e. 4.0.x
) or any semver range (i.e. >=4.0.0 <5.0.0
).
Values files
.spec.valuesFiles
is an optional field to specify an alternative list of
values files to use as the chart values (values.yaml). The file paths are
expected to be relative to the Source reference. Values files are merged in the
order of the list with the last file overriding the first. It is ignored when
omitted. When values files are specified, the chart is fetched and packaged
with the provided values.
spec:
chart:
spec:
chart: podinfo
...
valuesFiles:
- values.yaml
- values-production.yaml
Values files also affect the generated artifact revision, see artifact.
Reconcile strategy
.spec.reconcileStrategy
is an optional field to specify what enables the
creation of a new Artifact. Valid values are ChartVersion
and Revision
.
ChartVersion
is used for creating a new artifact when the chart version
changes in a HelmRepository
. Revision
is used for creating a new artifact
when the source revision changes in a GitRepository
or a Bucket
Source. It
defaults to ChartVersion
.
NOTE: If the reconcile strategy is ChartVersion
and the source reference
is a GitRepository
or a Bucket
, no new chart artifact is produced on updates
to the source unless the version
in Chart.yaml
is incremented. To produce
new chart artifact on change in source revision, set the reconcile strategy to
Revision
.
Reconcile strategy also affects the artifact version, see artifact for more details.
Interval
.spec.interval
is a required field that specifies the interval at which the
Helm Chart source must be checked for updates.
After successfully reconciling a HelmChart object, the source-controller
requeues the object for inspection after the specified interval. The value must
be in a
Go recognized duration string format,
e.g. 10m0s
to look at the source for updates every 10 minutes.
If the .metadata.generation
of a resource changes (due to e.g. applying a
change to the spec), this is handled instantly outside the interval window.
Suspend
.spec.suspend
is an optional field to suspend the reconciliation of a
HelmChart. When set to true
, the controller will stop reconciling the
HelmChart, and changes to the resource or the Helm chart Source will not result
in a new Artifact. When the field is set to false
or removed, it will resume.
For practical information, see suspending and resuming.
Verification
Note: This feature is available only for Helm charts fetched from an OCI Registry.
.spec.verify
is an optional field to enable the verification of
Cosign
signatures. The field offers two subfields:
.provider
, to specify the verification provider. Only supportscosign
at present..secretRef.name
, to specify a reference to a Secret in the same namespace as the HelmChart, containing the Cosign public keys of trusted authors.
---
apiVersion: source.toolkit.fluxcd.io/v1beta2
kind: HelmChart
metadata:
name: podinfo
spec:
verify:
provider: cosign
secretRef:
name: cosign-public-keys
When the verification succeeds, the controller adds a Condition with the
following attributes to the HelmChart’s .status.conditions
:
type: SourceVerified
status: "True"
reason: Succeeded
Public keys verification
To verify the authenticity of HelmChart hosted in an OCI Registry, create a Kubernetes secret with the Cosign public keys:
---
apiVersion: v1
kind: Secret
metadata:
name: cosign-public-keys
type: Opaque
data:
key1.pub: <BASE64>
key2.pub: <BASE64>
Note that the keys must have the .pub
extension for Flux to make use of them.
Flux will loop over the public keys and use them to verify a HelmChart’s signature. This allows for older HelmCharts to be valid as long as the right key is in the secret.
Keyless verification
For publicly available HelmCharts, which are signed using the
Cosign Keyless procedure,
you can enable the verification by omitting the .verify.secretRef
field.
Example of verifying HelmCharts signed by the Cosign GitHub Action with GitHub OIDC Token:
apiVersion: source.toolkit.fluxcd.io/v1beta2
kind: HelmChart
metadata:
name: podinfo
spec:
interval: 5m
chart: podinfo
reconcileStrategy: ChartVersion
sourceRef:
kind: HelmRepository
name: podinfo
version: ">=6.1.6"
verify:
provider: cosign
---
apiVersion: source.toolkit.fluxcd.io/v1beta2
kind: HelmRepository
metadata:
name: podinfo
spec:
interval: 1m0s
url: oci://ghcr.io/stefanprodan/charts
type: "oci"
The controller verifies the signatures using the Fulcio root CA and the Rekor instance hosted at rekor.sigstore.dev.
Note that keyless verification is an experimental feature, using custom root CAs or self-hosted Rekor instances are not currently supported.
Working with HelmCharts
Triggering a reconcile
To manually tell the source-controller to reconcile a HelmChart outside the
specified interval window, a HelmCHart can be annotated with
reconcile.fluxcd.io/requestedAt: <arbitrary value>
. Annotating the resource
queues the object for reconciliation if the <arbitrary-value>
differs from
the last value the controller acted on, as reported in
.status.lastHandledReconcileAt
.
Using kubectl
:
kubectl annotate --field-manager=flux-client-side-apply --overwrite helmchart/<chart-name> reconcile.fluxcd.io/requestedAt="$(date +%s)"
Waiting for Ready
When a change is applied, it is possible to wait for the HelmChart to reach a
ready state using kubectl
:
kubectl wait helmchart/<chart-name> --for=condition=ready --timeout=1m
Suspending and resuming
When you find yourself in a situation where you temporarily want to pause the
reconciliation of a HelmChart, you can suspend it using the
.spec.suspend
field.
Suspend a HelmChart
In your YAML declaration:
---
apiVersion: source.toolkit.fluxcd.io/v1beta2
kind: HelmChart
metadata:
name: <chart-name>
spec:
suspend: true
Using kubectl
:
kubectl patch helmchart <chart-name> --field-manager=flux-client-side-apply -p '{\"spec\": {\"suspend\" : true }}'
Note: When a HelmChart has an Artifact and is suspended, and this Artifact later disappears from the storage due to e.g. the source-controller Pod being evicted from a Node, this will not be reflected in the HelmChart’s Status until it is resumed.
Resume a HelmChart
In your YAML declaration, comment out (or remove) the field:
---
apiVersion: source.toolkit.fluxcd.io/v1beta2
kind: HelmChart
metadata:
name: <chart-name>
spec:
# suspend: true
Note: Setting the field value to false
has the same effect as removing
it, but does not allow for “hot patching” using e.g. kubectl
while practicing
GitOps; as the manually applied patch would be overwritten by the declared
state in Git.
Using kubectl
:
kubectl patch helmchart <chart-name> --field-manager=flux-client-side-apply -p '{\"spec\" : {\"suspend\" : false }}'
Debugging a HelmChart
There are several ways to gather information about a HelmChart for debugging purposes.
Describe the HelmChart
Describing a HelmChart using kubectl describe helmchart <chart-name>
displays
the latest recorded information for the resource in the Status
and Events
sections:
...
Status:
...
Conditions:
Last Transition Time: 2022-02-13T14:06:27Z
Message: invalid chart reference: failed to get chart version for remote reference: no 'podinfo' chart with version matching '9.*' found
Observed Generation: 3
Reason: InvalidChartReference
Status: True
Type: Stalled
Last Transition Time: 2022-02-13T14:06:27Z
Message: invalid chart reference: failed to get chart version for remote reference: no 'podinfo' chart with version matching '9.*' found
Observed Generation: 3
Reason: InvalidChartReference
Status: False
Type: Ready
Last Transition Time: 2022-02-13T14:06:27Z
Message: invalid chart reference: failed to get chart version for remote reference: no 'podinfo' chart with version matching '9.*' found
Observed Generation: 3
Reason: InvalidChartReference
Status: True
Type: FetchFailed
Last Handled Reconcile At: 1644759954
Observed Chart Name: podinfo
Observed Generation: 3
URL: http://source-controller.flux-system.svc.cluster.local./helmchart/default/podinfo/latest.tar.gz
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Warning InvalidChartReference 11s source-controller invalid chart reference: failed to get chart version for remote reference: no 'podinfo' chart with ver
sion matching '9.*' found
Trace emitted Events
To view events for specific HelmChart(s), kubectl events
can be used in
combination with --for
to list the Events for specific objects. For example,
running
kubectl events --for HelmChart/<chart-name>
lists
LAST SEEN TYPE REASON OBJECT MESSAGE
22s Warning InvalidChartReference helmchart/<chart-name> invalid chart reference: failed to get chart version for remote reference: no 'podinfo' chart with version matching '9.*' found
2s Normal ChartPullSucceeded helmchart/<chart-name> pulled 'podinfo' chart with version '6.0.3'
2s Normal ArtifactUpToDate helmchart/<chart-name> artifact up-to-date with remote revision: '6.0.3'
Besides being reported in Events, the reconciliation errors are also logged by
the controller. The Flux CLI offer commands for filtering the logs for a
specific HelmChart, e.g. flux logs --level=error --kind=HelmChart --name=<chart-name>
.
Improving resource consumption by enabling the cache
When using a HelmRepository
as Source for a HelmChart
, the controller loads
the repository index in memory to find the latest version of the chart.
The controller can be configured to cache Helm repository indexes in memory.
The cache is used to avoid loading repository indexes for every HelmChart
reconciliation.
The following flags are provided to enable and configure the cache:
helm-cache-max-size
: The maximum size of the cache in number of indexes. If0
, then the cache is disabled.helm-cache-ttl
: The TTL of an index in the cache.helm-cache-purge-interval
: The interval at which the cache is purged of expired items.
The caching strategy is to pull a repository index from the cache if it is
available, otherwise to load the index, retrieve and build the chart,
then cache the index. The cached index TTL is refreshed every time the
Helm repository index is loaded with the helm-cache-ttl
value.
The cache is purged of expired items every helm-cache-purge-interval
.
When the cache is full, no more items can be added to the cache, and the source-controller will report a warning event instead.
In order to use the cache, set the related flags in the source-controller Deployment config:
spec:
containers:
- args:
- --watch-all-namespaces
- --log-level=info
- --log-encoding=json
- --enable-leader-election
- --storage-path=/data
- --storage-adv-addr=source-controller.$(RUNTIME_NAMESPACE).svc.cluster.local.
## Helm cache with up to 10 items, i.e. 10 indexes.
- --helm-cache-max-size=10
## TTL of an index is 1 hour.
- --helm-cache-ttl=1h
## Purge expired index every 10 minutes.
- --helm-cache-purge-interval=10m
HelmChart Status
Artifact
The HelmChart reports the last built chart as an Artifact object in the
.status.artifact
of the resource.
The Artifact file is a gzip compressed TAR archive (<chart-name>-<chart-version>.tgz
),
and can be retrieved in-cluster from the .status.artifact.url
HTTP address.
Artifact example
---
apiVersion: source.toolkit.fluxcd.io/v1beta2
kind: HelmChart
metadata:
name: <chart-name>
status:
artifact:
digest: sha256:e30b95a08787de69ffdad3c232d65cfb131b5b50c6fd44295f48a078fceaa44e
lastUpdateTime: "2022-02-10T18:53:47Z"
path: helmchart/<source-namespace>/<chart-name>/<chart-name>-<chart-version>.tgz
revision: 6.0.3
size: 14166
url: http://source-controller.flux-system.svc.cluster.local./helmchart/<source-namespace>/<chart-name>/<chart-name>-<chart-version>.tgz
When using a HelmRepository
as the source reference and values files are
provided, the value of status.artifact.revision
is the chart version combined
with the HelmChart
object generation. For example, if the chart version is
6.0.3
and the HelmChart
object generation is 1
, the
status.artifact.revision
value will be 6.0.3+1
.
---
apiVersion: source.toolkit.fluxcd.io/v1beta2
kind: HelmChart
metadata:
name: <chart-name>
status:
artifact:
digest: sha256:ee68224ded207ebb18a8e9730cf3313fa6bc1f31e6d8d3943ab541113559bb52
lastUpdateTime: "2022-02-28T08:07:12Z"
path: helmchart/<source-namespace>/<chart-name>/<chart-name>-6.0.3+1.tgz
revision: 6.0.3+1
size: 14166
url: http://source-controller.flux-system.svc.cluster.local./helmchart/<source-namespace>/<chart-name>/<chart-name>-6.0.3+1.tgz
observedGeneration: 1
...
When using a GitRepository
or a Bucket
as the source reference and
Revision
as the reconcile strategy, the value of status.artifact.revision
is
the chart version combined with the first 12 characters of the revision of the
GitRepository
or Bucket
. For example if the chart version is 6.0.3
and the
revision of the Bucket
is 4e5cbb7b97d00a8039b8810b90b922f4256fd3bd8f78b934b4892dae13f7ca87
,
the status.artifact.revision
value will be 6.0.3+4e5cbb7b97d0
.
---
apiVersion: source.toolkit.fluxcd.io/v1beta2
kind: HelmChart
metadata:
name: <chart-name>
status:
artifact:
digest: sha256:8d1f0ac3f4b0e8759a32180086f17ac87ca04e5d46c356e67f97e97616ef4718
lastUpdateTime: "2022-02-28T08:07:12Z"
path: helmchart/<source-namespace>/<chart-name>/<chart-name>-6.0.3+4e5cbb7b97d0.tgz
revision: 6.0.3+4e5cbb7b97d0
size: 14166
url: http://source-controller.flux-system.svc.cluster.local./helmchart/<source-namespace>/<chart-name>/<chart-name>-6.0.3+4e5cbb7b97d0.tgz
Conditions
A HelmChart enters various states during its lifecycle, reflected as Kubernetes Conditions. It can be reconciling while fetching or building the chart, it can be ready, it can fail during reconciliation, or it can stall.
The HelmChart API is compatible with the
kstatus
specification,
and reports Reconciling
and Stalled
conditions where applicable to
provide better (timeout) support to solutions polling the HelmChart to become
Ready
.
Reconciling HelmChart
The source-controller marks a HelmChart as reconciling when one of the following is true:
- There is no current Artifact for the HelmChart, or the reported Artifact is determined to have disappeared from the storage.
- The generation of the HelmChart is newer than the Observed Generation.
- The newly fetched Artifact revision differs from the current Artifact.
When the HelmChart is “reconciling”, the Ready
Condition status becomes
Unknown
when the controller detects drift, and the controller adds a Condition
with the following attributes to the HelmChart’s .status.conditions
:
type: Reconciling
status: "True"
reason: Progressing
|reason: ProgressingWithRetry
If the reconciling state is due to a new version, it adds an additional Condition with the following attributes:
type: ArtifactOutdated
status: "True"
reason: NewChart
Both Conditions have a
“negative polarity”,
and are only present on the HelmChart while their status value is "True"
.
Ready HelmChart
The source-controller marks a HelmChart as ready when it has the following characteristics:
- The HelmChart reports an Artifact.
- The reported Artifact exists in the controller’s Artifact storage.
- The controller was able to fetch and build the Helm chart using the current spec.
- The version/revision of the reported Artifact is up-to-date with the latest version/revision of the Helm chart.
When the HelmChart is “ready”, the controller sets a Condition with the
following attributes in the HelmChart’s .status.conditions
:
type: Ready
status: "True"
reason: Succeeded
This Ready
Condition will retain a status value of "True"
until the
HelmChart is marked as
reconciling, or e.g.
a
transient error occurs due to a temporary network issue.
When the HelmChart Artifact is archived in the controller’s Artifact
storage, the controller sets a Condition with the following attributes in the
HelmChart’s .status.conditions
:
type: ArtifactInStorage
status: "True"
reason: Succeeded
This ArtifactInStorage
Condition will retain a status value of "True"
until
the Artifact in the storage no longer exists.
Failed HelmChart
The source-controller may get stuck trying to produce an Artifact for a HelmChart without completing. This can occur due to some of the following factors:
- The Helm chart Source is temporarily unavailable.
- The credentials in the Source reference Secret are invalid.
- The HelmChart spec contains a generic misconfiguration.
- A storage related failure when storing the artifact.
When this happens, the controller sets the Ready
Condition status to False
,
and adds a Condition with the following attributes to the HelmChart’s
.status.conditions
:
type: FetchFailed
|type: StorageOperationFailed
status: "True"
reason: AuthenticationFailed
|reason: StorageOperationFailed
|reason: URLInvalid
|reason: IllegalPath
|reason: Failed
This condition has a
“negative polarity”,
and is only present on the HelmChart while the status value is "True"
.
There may be more arbitrary values for the reason
field to provide accurate
reason for a condition.
While the HelmChart has this Condition, the controller will continue to attempt to produce an Artifact for the resource with an exponential backoff, until it succeeds and the HelmChart is marked as ready.
Note that a HelmChart can be
reconciling
while failing at the same time, for example due to a newly introduced
configuration issue in the HelmChart spec. When a reconciliation fails, the
Reconciling
Condition reason would be ProgressingWithRetry
. When the
reconciliation is performed again after the failure, the reason is updated to
Progressing
.
Stalled HelmChart
The source-controller can mark a HelmChart as stalled when it determines that without changes to the spec, the reconciliation can not succeed. For example because a HelmChart Version is set to a non-existing version.
When this happens, the controller sets the same Conditions as when it
fails, but adds another Condition with the following
attributes to the HelmChart’s .status.conditions
:
type: Stalled
status: "True"
reason: InvalidChartReference
While the HelmChart has this Condition, the controller will not requeue the resource any further, and will stop reconciling the resource until a change to the spec is made.
Observed Source Artifact Revision
The source-controller reports the revision of the last
Source reference’s Artifact the current chart was fetched
from in the HelmChart’s .status.observedSourceArtifactRevision
. It is used to
keep track of the source artifact revision and detect when a new source
artifact is available.
Observed Chart Name
The source-controller reports the last resolved chart name of the Artifact
for the
.spec.chart
field in the HelmChart’s
.status.observedChartName
. It is used to keep track of the chart and detect
when a new chart is found.
Observed Generation
The source-controller reports an
observed generation
in the HelmChart’s .status.observedGeneration
. The observed generation is the
latest .metadata.generation
which resulted in either a
ready state,
or stalled due to error it can not recover from without human
intervention.
Last Handled Reconcile At
The source-controller reports the last reconcile.fluxcd.io/requestedAt
annotation value it acted on in the .status.lastHandledReconcileAt
field.
For practical information about this field, see triggering a reconcile.