According to Kubernetes documentation
The metadata in an annotation can be small or large, structured or unstructured, and can include characters not permitted by labels.
Annotations, like labels, are key/value maps
Then there is a detailed explanation on the syntax of the annotation keys. But it says nothing about the value part.
Where can I find more about the allowed length and character set for the value of an annotation in Kubernetes?
Here you can find the code that validates annotations in current master:
func ValidateAnnotations(annotations map[string]string, fldPath *field.Path) field.ErrorList {
allErrs := field.ErrorList{}
for k := range annotations {
for _, msg := range validation.IsQualifiedName(strings.ToLower(k)) {
allErrs = append(allErrs, field.Invalid(fldPath, k, msg))
}
}
if err := ValidateAnnotationsSize(annotations); err != nil {
allErrs = append(allErrs, field.TooLong(fldPath, "", TotalAnnotationSizeLimitB))
}
return allErrs
}
The keys are validated according to the rules that you mentioned.
The only validation applied to the values is the total length of all annotations (size of keys + size of values for all annotations) that can't be longer than 256Kb.
const TotalAnnotationSizeLimitB int = 256 * (1 << 10) // 256 kB
...
func ValidateAnnotationsSize(annotations map[string]string) error {
var totalSize int64
for k, v := range annotations {
totalSize += (int64)(len(k)) + (int64)(len(v))
}
if totalSize > (int64)(TotalAnnotationSizeLimitB) {
return fmt.Errorf("annotations size %d is larger than limit %d", totalSize, TotalAnnotationSizeLimitB)
}
return nil
}