Using metadata in Cloud Foundry

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You can use metadata in Cloud Foundry and gives you instructions for adding, updating, removing, and viewing metadata.

About metadata

Cloud Foundry Application Runtime allows you to add metadata to resources such as spaces and apps. You can use metadata to provide additional information about the resources in your Cloud Foundry deployment. This can help with operating, monitoring, and auditing.

For example, you can tag resources with metadata that describes the type of environment they belong to. You can also use metadata to describe app characteristics, such as front end or back end. Other examples include billing codes, points of contact, resource consumption, and information about security or risk.

Methods of adding metadata

You can add metadata to resources using any of the following methods:

Cloud Foundry Command Line Interface (cf CLI) v7: For procedures using this method of adding metadata, see cf CLI Procedures. For more information about cf CLI v7, see Upgrading to cf CLI v7.
Cloud Foundry API (CAPI): For procedures using this method of adding metadata, see API procedures. For more information about adding metadata with CAPI, see Metadata in the CAPI documentation.

Types of metadata

You can add two types of metadata to resources in Cloud Foundry:

Labels: Labels allow you to identify and select Cloud Foundry resources. For example, if you label all apps running in production or all spaces that contain Internet-facing apps, you can then search for them.
Annotations: Annotations allow you to add non-identifying metadata to Cloud Foundry resources. You cannot query based on annotations. Also, there are fewer restrictions for key-value pairs of annotations than there are for labels. For example, you can include contact information of persons responsible for the resource, or tool information for debugging purposes.

Annotations sent to service brokers

For installations using CAPI v1.108.0 and later, Cloud Foundry sends annotations with key prefixes to service brokers when service instances and service bindings are created.

When a service instance is created, Cloud Foundry sends the following annotations to service brokers:

organization_annotations
space_annotations
instance_annotations

When a service instance is bound to an app, Cloud Foundry also sends app_annotations to service brokers.

For more information about the annotations listed above, see Cloud Foundry Context Object in the Open Service Broker API Profile on GitHub.

For more general information about annotations, see Annotations in the CAPI documentation.

Metadata Requirements

The following tables describe requirements for creating metadata.

Requirements for labels

The following table describes the requirements for creating labels:

Label requirements
Part of Label	Length in characters	Allowed characters	Other Requirements
(Optional) Key Prefix	0-253	Alphanumeric ( \[a-z0-9A-Z\] ) `-` `.`	DNS subdomain format, with at least one `.` Must end with `/`
Key Name	1-63	Alphanumeric ( \[a-z0-9A-Z\] ) `-` `_` `.`	Must begin and end with an alphanumeric character
Value	0-63	Alphanumeric `-` `_` `.`	Must begin and end with an alphanumeric character Empty values allowed

Requirements for annotations

The following table describes the requirements for creating annotations:

Annotation Requirements
Part of Annotation	Length in characters	Allowed characters	Other Requirements
(Optional) Key Prefix	0-253	Alphanumeric ( \[a-z0-9A-Z\] ) `-` `.`	DNS subdomain format, with at least one `.` Must end with `/`
Key Name	1-63	Alphanumeric ( \[a-z0-9A-Z\] ) `-` `_` `.`	Must begin and end with an alphanumeric character
Value	0-5000	Any unicode character	n/a

Metadata key prefixes

You can ensure that a label or annotation key is easily differentiated from other keys by using a prefix. A prefix is a namespacing pattern that helps you more clearly identify resources. Prefixes are in DNS subdomain format. For example, prefix.example.com.

Consider an example in which you have two scanner tools: one for security and one for compliance. Both tools use a scanned label or annotation. You can disambiguate between the two tools using a prefix. The security tool can prefix a label or annotation with security.example.com/scanned and the compliance tool can prefix a label or annotation with compliance.example.com/scanned.

cf CLI procedures

The following sections describe how to add, update, view, and list metadata using the cf CLI.

To see which resources are supported for this feature, run cf labels -h. cf CLI v7 supports adding labels to apps, orgs, spaces, buildpacks, stacks, routes, domains, and various service resources.

Add metadata to a resource

This section describes how to add metadata using the cf CLI.

Add a label

To add a label to a resource:

Run:
```
cf set-label RESOURCE RESOURCE-NAME KEY=VALUE
```
Where:
- RESOURCE is the type of resource you want to label, such as app or space.
- RESOURCE-NAME is the name of the resource you want to label, such as example-app.
- KEY is the key for the label.
- VALUE is the corresponding value for the label key. You can enter multiple key-value pairs in the same command.

Update metadata for a resource

To update metadata for a resource, follow the procedure for adding metadata and provide a new value for an existing key. For more information, see Add metadata to a resource.

Remove metadata from a resource

This section describes how to remove metadata using the cf CLI.

Remove a label

To remove a label from a resource:

Run:
```
cf unset-label RESOURCE RESOURCE-NAME KEY
```
Where:
- RESOURCE is the type of resource you want to remove the label from, such as app or space.
- RESOURCE-NAME is the name of the resource you want to remove the label from , such as example-app.
- KEY is the key for the label.

View metadata for a resource

This section describes how to view metadata with the cf CLI.

View labels

To view labels for a resource:

Run:
```
cf labels RESOURCE RESOURCE-NAME
```
Where:
- RESOURCE is the type of resource you want to remove the label from, such as app or space.
- RESOURCE-NAME is the name of the resource you want to remove the label from , such as example-app.

Select resources by labels

To select resources by labels:

Run:

cf apps --labels 'environment in (production,staging),tier in (backend)'

API procedures

The following sections describe how to add, update, remove, list, and query metadata using CAPI.

Add metadata to a resource

The following sections describe how to add labels and annotations to resources.

Add a label

To add a label to a resource using CAPI:

Run:
```
cf curl v3/RESOURCE-ENDPOINT/GUID \
  -X PATCH \
  -d '{
    "metadata": {
      "labels": {
        "LABEL-KEY": "LABEL-VALUE"
      }
    }
  }'
```
Where:
- RESOURCE-ENDPOINT is the CAPI endpoint for the type of resource you want to label, such as apps or organizations.
- GUID is the GUID of the resource you want to label.
- LABEL-KEY is the key for the label.
- LABEL-VALUE is the corresponding value for the label key.

Add an annotation

To add an annotation:

Run:
```
cf curl v3/RESOURCE-ENDPOINT/GUID \
  -X PATCH \
  -d '{
    "metadata": {
      "annotations": {
        "ANNOTATION-KEY": "ANNOTATION-VALUE"
      }
    }
  }'
```
Where:
- RESOURCE-ENDPOINT is the CAPI endpoint for the type of resource you want to label, such as apps or organizations.
- GUID is the GUID of the resource you want to label.
- ANNOTATION-KEY is the key for the label.
- ANNOTATION-VALUE is the corresponding value for the annotation key.

Update metadata for a resource

To update metadata for a resource, follow the procedure for adding metadata and provide a new value for an existing key. For more information, see Add metadata to a resource.

Remove metadata from a resource

To remove metadata from a resource, follow the procedure for adding metadata and provide a null value for an existing key. For more information, see Add metadata to a resource.

View metadata for a resource

To view metadata using the list endpoint of a resource:

Run:
```
cf curl /v3/RESOURCE-ENDPOINT/GUID
```
Where:
- RESOURCE-ENDPOINT is the CAPI endpoint for the type of resource you want to view, such as apps or organizations.
- GUID is the GUID of the resource you want to view.

List resources by querying labels

To list resources by querying label metadata:

To query a resource by using the label_selector parameter on its list endpoint, run:
```
cf curl /v3/RESOURCE-ENDPOINT/?label_selector=SELECTOR-REQUIREMENTS
```
Where:
- RESOURCE-ENDPOINT is the CAPI endpoint for the type of resource you want to view, such as apps or organizations.
- SELECTOR-REQUIREMENTS is one of requirement types specified in Selector Requirement Reference. You can add multiple selector requirements using a comma-separated list.
  Ensure that this part of the URL is appropriately escaped.

Selector requirement reference

The following table describes how to form selector requirements:

Requirement	Format	Description
existence	`KEY`	Returns all resources labeled with the given key
inexistence	`!KEY`	Returns all resources not labeled with the given key
equality	`KEY==VALUE` or `KEY=VALUE`	Returns all resources labeled with the given key and value
inequality	`KEY!=VALUE`	Returns all resources not labeled with the given key and value
set inclusion	`KEY in (VALUE1,VALUE2...)`	Returns all resources labeled with the given key and one of the specified values
set exclusion	`KEY notin (VALUE1,VALUE2...)`	Returns all resources not labeled with the given key and one of the specified values

Example: Label resources with a git commit

This section provides the following:

A procedure for labeling an app, package, and droplet with a Git commit SHA. For more information, see Manually Label Resources.
A script that automates the procedure. For more information, see Automate Labeling Resources.

Labeling your app and related resources with a Git commit SHA allows you to track which version of your code is running on Cloud Foundry.

For more information about app packages and droplets, see the CAPI documentation.

Manually label resources

To label an app, droplet, and package with a Git commit SHA:

Run:
```
cf app APP-NAME --guid
```
Where APP-NAME is the name of the app.
Record the app GUID you retrieved in the previous step,
Return the GUID of the droplet and package associated with the app by running:
```
cf curl /v3/apps/APP-GUID/droplets/current
```
Where APP-GUID is the GUID of the app.
Record the GUID of the droplet and package:
- The droplet GUID is the value for the "guid" key.
- The package GUID is the end of the "href" URL for the "package" key.
For example, the droplet and package GUIDs are highlighted in blue in the following output:
```
{
  "guid": "fd35633f-5c5c-4e4e-a5a9-0722c970a9d2",
  ...
  "links": {
    "package": {
      "href": "https://api.run.pivotal.io/v3/packages/fd35633f-5c5c-4e4e-a5a9-0722c970a9d2"
    }
  }
```
Label the app with a Git commit SHA by running:
```
cf curl /v3/apps/APP-GUID -X PATCH -d '{"metadata": { "labels": { "commit": COMMIT-SHA } } }'
```
Where:
- APP-GUID is the GUID of the app.
- COMMIT-SHA is the SHA of the Git commit.
Label the app droplet with the same Git commit SHA by running:
```
cf curl /v3/droplets/DROPLET-GUID -X PATCH -d '{"metadata": { "labels": { "commit": COMMIT-SHA } } }'
```
Where:
- DROPLET-GUID is the GUID of the droplet.
- COMMIT-SHA is the SHA of the Git commit.
Label the app package with the same Git commit SHA by running:
```
cf curl /v3/packages/PACKAGE-GUID -X PATCH -d '{"metadata": { "labels": { "commit": COMMIT-SHA } } }'
```
Where:
- PACKAGE-GUID is the GUID of the package.
- COMMIT-SHA is the SHA of the Git commit.

Automate labeling resources

You can automate labeling resources by running a script either programmatically or manually in the app repository.

Prerequisite

To run the following example script, you must install jq. To download jq, see jq.

Example script

The following script retrieves the GUID of the app, droplet, and package. It then curls CAPI to label each resource with the current Git commit SHA.

Replace APP-NAME with the name of your app.

#!/usr/bin/env bash

set -ex

APP_GUID="$(cf app APP-NAME --guid)"
APP_URI="/v3/apps/${APP_GUID}"

DROPLET_GUID="$(cf curl "/v3/apps/${APP_GUID}/droplets/current" | jq -r .guid)"
DROPLET_URI="/v3/droplets/${DROPLET_GUID}"

PACKAGE_GUID="$(cf curl "/v3/droplets/${DROPLET_GUID}" | jq -r .links.package.href | xargs basename)"
PACKAGE_URI="/v3/packages/${PACKAGE_GUID}"

COMMIT_SHA="$(git rev-parse --short HEAD)"
REQUEST_BODY="$(jq -nc --arg commit "${COMMIT_SHA}" '{"metadata": { "labels": { "commit": $commit } } }')"

cf curl "${APP_URI}" -X PATCH -d "${REQUEST_BODY}"
cf curl "${PACKAGE_URI}" -X PATCH -d "${REQUEST_BODY}"
cf curl "${DROPLET_URI}" -X PATCH -d "${REQUEST_BODY}"

Example: Add custom tags to log and metric envelopes

Log and metric envelopes emitted by applications are tagged with information about the application, such as the application name, for example.

You can define additional custom log and metric tags by adding a label with a specific prefix. The default prefix is metric.tag.cloudfoundry.org. Following a restart of the application, the custom metric tag is visible in the logs and metrics emitted for processes associated with that application.

The following commands add a tag named custom_tag with the value some_value for logs and metrics emitted for the application sample-app:

$ cf set-label app sample-app metric.tag.cloudfoundry.org/custom_tag=some_value
$ cf restart sample-app

You can verify that the custom tag has been applied by querying Log Cache with the log-cache cf CLI plug-in. The following commands assume that you have the jq command line utility.

$ cf install-plugin -r CF-Community 'log-cache'

$ cf tail sample-app --json --follow | jq -r '.tags.custom_tag'
some_value
some_value
some_value

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