[[configmap-propertysource]]
= Using a `ConfigMap` `PropertySource`

Kubernetes provides a resource named https://kubernetes.io/docs/concepts/configuration/configmap/[`ConfigMap`] to externalize the
parameters to pass to your application in the form of key-value pairs or embedded `application.properties` or `application.yaml` files.
The link:https://github.com/spring-cloud/spring-cloud-kubernetes/tree/master/spring-cloud-kubernetes-fabric8-config[Spring Cloud Kubernetes Config] project makes Kubernetes `ConfigMap` instances available
during application startup and triggers hot reloading of beans or Spring context when changes are detected on
observed `ConfigMap` instances.

Everything that follows is explained mainly referring to examples using ConfigMaps, but the same stands for
Secrets, i.e.: every feature is supported for both.

The default behavior is to create a `Fabric8ConfigMapPropertySource` (or a `KubernetesClientConfigMapPropertySource`) based on a Kubernetes `ConfigMap` that has `metadata.name` of either:

- value of `spring.cloud.kubernetes.config.name`
- value of your Spring application (as defined by `spring.application.name` property)
- the String literal `"application"`

However, more advanced configuration is possible where you can use multiple `ConfigMap` instances.
The `spring.cloud.kubernetes.config.sources` list makes this possible.
For example, you could define the following `ConfigMap` instances:

[source,yaml]
----
spring:
  application:
    name: cloud-k8s-app
  cloud:
    kubernetes:
      config:
        name: default-name
        namespace: default-namespace
        sources:
         # Spring Cloud Kubernetes looks up a ConfigMap named c1 in namespace default-namespace
         - name: c1
         # Spring Cloud Kubernetes looks up a ConfigMap named default-name in whatever namespace n2
         - namespace: n2
         # Spring Cloud Kubernetes looks up a ConfigMap named c3 in namespace n3
         - namespace: n3
           name: c3
----

In the preceding example, if `spring.cloud.kubernetes.config.namespace` had not been set,
the `ConfigMap` named `c1` would be looked up in the namespace that the application runs.
See xref:property-source-config/namespace-resolution.adoc[Namespace resolution] to get a better understanding of how the namespace
of the application is resolved.


Any matching `ConfigMap` that is found is processed as follows:

* Apply individual configuration properties.
* Apply as `yaml` (or `properties`) the content of any property that is named by the value of `spring.application.name`
  (if it's not present, by `application.yaml/properties`)
* Apply as a properties file the content of the above name + each active profile.

An example should make a lot more sense. Let's suppose that `spring.application.name=my-app` and that
we have a single active profile called `k8s`. For a configuration as below:


[source]
----
kind: ConfigMap
apiVersion: v1
metadata:
  name: my-app
data:
  my-app.yaml: |-
    ...
  my-app-k8s.yaml: |-
    ..
  my-app-dev.yaml: |-
    ..
  not-my-app.yaml: |-
   ..
  someProp: someValue
----

This is what we will end-up loading:

 - `my-app.yaml` treated as a file
 - `my-app-k8s.yaml` treated as a file
 - `my-app-dev.yaml` _ignored_, since `dev` is _not_ an active profile
 - `not-my-app.yaml` _ignored_, since it does not match `spring.application.name`
 - `someProp: someValue` plain property

The order of loading properties is a as follows:

- first load all properties from `my-app.yaml`
- then all from profile-based sources: `my-app-k8s.yaml`
- then all plain properties `someProp: someValue`

This means that profile based sources take precedence over non-profile based sources (just like in a vanilla Spring app); and plain properties take precedence over both profile and non-profile based sources. Here is an example:

====
[source]
----
kind: ConfigMap
apiVersion: v1
metadata:
  name: my-app
data:
  my-app-k8s.yaml: |-
    key1=valueA
	key2=valueB
  my-app.yaml: |-
    key1=valueC
    key2=valueA
  key1: valueD
----
====

After processing such a ConfigMap, this is what you will get in the properties: `key1=valueD`, `key2=valueB`.

The single exception to the aforementioned flow is when the `ConfigMap` contains a *single* key that indicates
the file is a YAML or properties file. In that case, the name of the key does NOT have to be `application.yaml` or
`application.properties` (it can be anything) and the value of the property is treated correctly.
This features facilitates the use case where the `ConfigMap` was created by using something like the following:

[source]
----
kubectl create configmap game-config --from-file=/path/to/app-config.yaml
----

Assume that we have a Spring Boot application named `demo` that uses the following properties to read its thread pool
configuration.

* `pool.size.core`
* `pool.size.maximum`

This can be externalized to config map in `yaml` format as follows:

[source,yaml]
----
kind: ConfigMap
apiVersion: v1
metadata:
  name: demo
data:
  pool.size.core: 1
  pool.size.max: 16
----

Individual properties work fine for most cases. However, sometimes, embedded `yaml` is more convenient. In this case, we
use a single property named `application.yaml` to embed our `yaml`, as follows:

[source,yaml]
----
kind: ConfigMap
apiVersion: v1
metadata:
  name: demo
data:
  application.yaml: |-
    pool:
      size:
        core: 1
        max:16
----

The following example also works:

[source,yaml]
----
kind: ConfigMap
apiVersion: v1
metadata:
  name: demo
data:
  custom-name.yaml: |-
    pool:
      size:
        core: 1
        max:16
----

You can also define the search to happen based on labels, for example:


[source,yaml]
----
spring:
  application:
    name: labeled-configmap-with-prefix
  cloud:
    kubernetes:
      config:
        enableApi: true
        useNameAsPrefix: true
        namespace: spring-k8s
        sources:
          - labels:
              letter: a
----

This will search for every configmap in namespace `spring-k8s` that has labels `{letter : a}`. The important
thing to notice here is that unlike reading a configmap by name, this can result in _multiple_ config maps read.
As usual, the same feature is supported for secrets.

You can also configure Spring Boot applications differently depending on active profiles that are merged together
when the `ConfigMap` is read. You can provide different property values for different profiles by using an
`application.properties` or `application.yaml` property, specifying profile-specific values, each in their own document
(indicated by the `---` sequence), as follows:

[source,yaml]
----
kind: ConfigMap
apiVersion: v1
metadata:
  name: demo
data:
  application.yml: |-
    greeting:
      message: Say Hello to the World
    farewell:
      message: Say Goodbye
    ---
    spring:
      profiles: development
    greeting:
      message: Say Hello to the Developers
    farewell:
      message: Say Goodbye to the Developers
    ---
    spring:
      profiles: production
    greeting:
      message: Say Hello to the Ops
----

In the preceding case, the configuration loaded into your Spring Application with the `development` profile is as follows:

[source,yaml]
----
  greeting:
    message: Say Hello to the Developers
  farewell:
    message: Say Goodbye to the Developers
----

However, if the `production` profile is active, the configuration becomes:

[source,yaml]
----
  greeting:
    message: Say Hello to the Ops
  farewell:
    message: Say Goodbye
----

If both profiles are active, the property that appears last within the `ConfigMap` overwrites any preceding values.

Another option is to create a different config map per profile and spring boot will automatically fetch it based
on active profiles

[source,yaml]
----
kind: ConfigMap
apiVersion: v1
metadata:
  name: demo
data:
  application.yml: |-
    greeting:
      message: Say Hello to the World
    farewell:
      message: Say Goodbye
----
[source,yaml]
----
kind: ConfigMap
apiVersion: v1
metadata:
  name: demo-development
data:
  application.yml: |-
    spring:
      profiles: development
    greeting:
      message: Say Hello to the Developers
    farewell:
      message: Say Goodbye to the Developers
----
[source,yaml]
----
kind: ConfigMap
apiVersion: v1
metadata:
  name: demo-production
data:
  application.yml: |-
    spring:
      profiles: production
    greeting:
      message: Say Hello to the Ops
    farewell:
      message: Say Goodbye
----


To tell Spring Boot which `profile` should be enabled see the https://docs.spring.io/spring-boot/docs/current/reference/html/features.html#features.profiles[Spring Boot documentation].
One option for activating a specific profile when deploying to Kubernetes is to launch your Spring Boot application with an environment variable that you can define in the PodSpec at the container specification.
 Deployment resource file, as follows:

[source,yaml]
----
apiVersion: apps/v1
kind: Deployment
metadata:
  name: deployment-name
  labels:
    app: deployment-name
spec:
  replicas: 1
  selector:
    matchLabels:
      app: deployment-name
  template:
    metadata:
      labels:
        app: deployment-name
	spec:
		containers:
		- name: container-name
		  image: your-image
		  env:
		  - name: SPRING_PROFILES_ACTIVE
			value: "development"
----

You could run into a situation where there are multiple configs maps that have the same property names. For example:

[source,yaml]
----
kind: ConfigMap
apiVersion: v1
metadata:
  name: config-map-one
data:
  application.yml: |-
    greeting:
      message: Say Hello from one
----

and

[source,yaml]
----
kind: ConfigMap
apiVersion: v1
metadata:
  name: config-map-two
data:
  application.yml: |-
    greeting:
      message: Say Hello from two
----

Depending on the order in which you place these in `bootstrap.yaml|properties`, you might end up with an un-expected result (the last config map wins). For example:

[source,yaml]
----
spring:
  application:
    name: cloud-k8s-app
  cloud:
    kubernetes:
      config:
        namespace: default-namespace
        sources:
         - name: config-map-two
         - name: config-map-one
----

will result in property `greetings.message` being `Say Hello from one`.

There is a way to change this default configuration by specifying `useNameAsPrefix`. For example:

[source,yaml]
----
spring:
  application:
    name: with-prefix
  cloud:
    kubernetes:
      config:
        useNameAsPrefix: true
        namespace: default-namespace
        sources:
          - name: config-map-one
            useNameAsPrefix: false
          - name: config-map-two
----

Such a configuration will result in two properties being generated:

 - `greetings.message` equal to `Say Hello from one`.

 - `config-map-two.greetings.message` equal to `Say Hello from two`

Notice that `spring.cloud.kubernetes.config.useNameAsPrefix` has a _lower_ priority than `spring.cloud.kubernetes.config.sources.useNameAsPrefix`.
This allows you to set a "default" strategy for all sources, at the same time allowing to override only a few.

If using the config map name is not an option, you can specify a different strategy, called : `explicitPrefix`. Since this is an _explicit_ prefix that
you select, it can only be supplied to the `sources` level. At the same time it has a higher priority than `useNameAsPrefix`. Let's suppose we have a third config map with these entries:


[source,yaml]
----
kind: ConfigMap
apiVersion: v1
metadata:
  name: config-map-three
data:
  application.yml: |-
    greeting:
      message: Say Hello from three
----

A configuration like the one below:

[source,yaml]
----
spring:
  application:
    name: with-prefix
  cloud:
    kubernetes:
      config:
        useNameAsPrefix: true
        namespace: default-namespace
        sources:
          - name: config-map-one
            useNameAsPrefix: false
          - name: config-map-two
            explicitPrefix: two
          - name: config-map-three
----

will result in three properties being generated:

 - `greetings.message` equal to `Say Hello from one`.

 - `two.greetings.message` equal to `Say Hello from two`.

 - `config-map-three.greetings.message` equal to `Say Hello from three`.

The same way you configure a prefix for configmaps, you can do it for secrets also; both for secrets that are based on name
and the ones based on labels. For example:

[source.yaml]
----
spring:
  application:
    name: prefix-based-secrets
  cloud:
    kubernetes:
      secrets:
        enableApi: true
        useNameAsPrefix: true
        namespace: spring-k8s
        sources:
          - labels:
              letter: a
            useNameAsPrefix: false
          - labels:
              letter: b
            explicitPrefix: two
          - labels:
              letter: c
          - labels:
              letter: d
            useNameAsPrefix: true
          - name: my-secret
----

The same processing rules apply when generating property source as for config maps. The only difference is that
potentially, looking up secrets by labels can mean that we find more than one source. In such a case, prefix (if specified via `useNameAsPrefix`)
will be the name of the secret found for those particular labels.

One more thing to bear in mind is that we support `prefix` per _secret_. The easiest way to explain this is via an example:

[source.yaml]
----
spring:
  application:
    name: prefix-based-secrets
  cloud:
    kubernetes:
      secrets:
        enableApi: true
        useNameAsPrefix: true
        namespace: spring-k8s
        sources:
          - labels:
              color: blue
            useNameAsPrefix: true
----

Suppose that a query matching such a label will return two secrets as a result: `secretA` and `secretB`.
Both of these secrets have the same property name: `color=sea-blue` and `color=ocean-blue`. Because `useNamesAsPrefix=true`, there will be two property sources loaded:

 - `secretA.color=sea-blue`
 - `secretB.color=ocean-blue`

By default, besides reading the config map that is specified in the `sources` configuration, Spring will also try to read
all properties from "profile aware" sources. The easiest way to explain this is via an example. Let's suppose your application
enables a profile called "dev" and you have a configuration like the one below:

[source,yaml]
----
spring:
  application:
    name: spring-k8s
  cloud:
    kubernetes:
      config:
        namespace: default-namespace
        sources:
          - name: config-map-one
----

Besides reading the `config-map-one`, Spring will also try to read `config-map-one-dev`; in this particular order. Each active profile
generates such a profile aware config map.

Though your application should not be impacted by such a config map, it can be disabled if needed:

[source,yaml]
----
spring:
  application:
    name: spring-k8s
  cloud:
    kubernetes:
      config:
        includeProfileSpecificSources: false
        namespace: default-namespace
        sources:
          - name: config-map-one
            includeProfileSpecificSources: false
----

Notice that just like before, there are two levels where you can specify this property: for all config maps or
for individual ones; the latter having a higher priority.

NOTE: You should check the security configuration section. To access config maps from inside a pod you need to have the correct
Kubernetes service accounts, roles and role bindings.

Another option for using `ConfigMap` instances is to mount them into the Pod by running the Spring Cloud Kubernetes application
and having Spring Cloud Kubernetes read them from the file system.

NOTE: This feature is deprecated and will be removed in a future release (Use `spring.config.import` instead).
This behavior is controlled by the `spring.cloud.kubernetes.config.paths` property. You can use it in
addition to or instead of the mechanism described earlier.
`spring.cloud.kubernetes.config.paths` expects a List of full paths to each property file, because directories are not being recursively parsed. For example:

```
spring:
  cloud:
    kubernetes:
      config:
        paths:
          - /tmp/application.properties
          - /var/application.yaml
```

NOTE:  If you use `spring.cloud.kubernetes.config.paths` or `spring.cloud.kubernetes.secrets.path` the automatic reload
functionality will not work.  You will need to make a `POST` request to the `/actuator/refresh` endpoint or
restart/redeploy the application.

[#config-map-fail-fast]
In some cases, your application may be unable to load some of your `ConfigMaps` using the Kubernetes API.
If you want your application to fail the start-up process in such cases, you can set
`spring.cloud.kubernetes.config.fail-fast=true` to make the application start-up fail with an Exception.

[#config-map-retry]
You can also make your application retry loading `ConfigMap` property sources on a failure. First, you need to
set `spring.cloud.kubernetes.config.fail-fast=true`. Then you need to add `spring-retry` 
and `spring-boot-starter-aop` to your classpath. You can configure retry properties such as
the maximum number of attempts, backoff options like initial interval, multiplier, max interval by setting the
`spring.cloud.kubernetes.config.retry.*` properties.

NOTE: If you already have `spring-retry` and `spring-boot-starter-aop` on the classpath for some reason
and want to enable fail-fast, but do not want retry to be enabled; you can disable retry for `ConfigMap` `PropertySources`
by setting `spring.cloud.kubernetes.config.retry.enabled=false`.

.Properties:
[options="header,footer"]
|===
| Name                                                    | Type      | Default                      | Description
| `spring.cloud.kubernetes.config.enabled`                | `Boolean` | `true`                       | Enable ConfigMaps `PropertySource`
| `spring.cloud.kubernetes.config.name`                   | `String`  | `${spring.application.name}` | Sets the name of `ConfigMap` to look up
| `spring.cloud.kubernetes.config.namespace`              | `String`  | Client namespace             | Sets the Kubernetes namespace where to lookup
| `spring.cloud.kubernetes.config.paths`                  | `List`    | `null`                       | Sets the paths where `ConfigMap` instances are mounted
| `spring.cloud.kubernetes.config.enableApi`              | `Boolean` | `true`                       | Enable or disable consuming `ConfigMap` instances through APIs
| `spring.cloud.kubernetes.config.fail-fast`              | `Boolean` | `false`                      | Enable or disable failing the application start-up when an error occurred while loading a `ConfigMap`
| `spring.cloud.kubernetes.config.retry.enabled`          | `Boolean` | `true`                       | Enable or disable config retry.
| `spring.cloud.kubernetes.config.retry.initial-interval` | `Long`    | `1000`                       | Initial retry interval in milliseconds.
| `spring.cloud.kubernetes.config.retry.max-attempts`     | `Integer` | `6`                          | Maximum number of attempts.
| `spring.cloud.kubernetes.config.retry.max-interval`     | `Long`    | `2000`                       | Maximum interval for backoff.
| `spring.cloud.kubernetes.config.retry.multiplier`       | `Double`  | `1.1`                        | Multiplier for next interval.
|===

