config

README

General Config Management for Contexts

The config context provides a generic configuration feature for data contexts

type Context interface {
    datacontext.Context

    AttributesContext() datacontext.AttributesContext

    // Info provides the context for nested configuration evaluation
    Info() string
    // WithInfo provides the same context with additional nesting info
    WithInfo(desc string) Context

    ConfigTypes() ConfigTypeScheme

    // GetConfigForData deserialize configuration objects for known
    // configuration types.
    GetConfigForData(data []byte, unmarshaler runtime.Unmarshaler) (Config, error)

    // ApplyData applies the config given by a byte stream to the config store
    // If the config type is not known, a generic config is stored and returned.
    // In this case an unknown error for kind KIND_CONFIGTYPE is returned.
    ApplyData(data []byte, unmarshaler runtime.Unmarshaler, desc string) (Config, error)
    // ApplyConfig applies the config to the config store
    ApplyConfig(spec Config, desc string) error

    GetConfigForType(generation int64, typ string) (int64, []Config)
    GetConfigForName(generation int64, name string) (int64, []Config)
    GetConfig(generation int64, selector ConfigSelector) (int64, []Config)

    Generation() int64
    ApplyTo(gen int64, target interface{}) (int64, error)
}

It offers the possibility to register configuration objects of arbitrary types. This is implemented by typed objects, like for the other kinds of data context. Using this feature it is possible to decode configuration objects from yaml documents or fragments.

A Config object must implement the Config interface:

type Config interface {
    runtime.VersionedTypedObject

    ApplyTo(Context, interface{}) error
}

It can be called to be applied to a dedicated context (the second parameter) under the control of a dedicated Config context (this first parameter). If the object is not applicable for a given target context it should ignore the call. So it is the decision of the config object, whether it does something with the given context or not. It is just called for all kinds of contexts requesting a replay of configuration operations regardless of their type.

If applied using the such a configuration context by calling the appropriate Apply method on the context, the context keeps track of the sequence of applied configuration objects.

A configuration sink (any kind of data context) should keep track about the latest applied configuration sequence number from its configuration context. Whenever a non-trivial function is called on such a data context, it should request a replay of missing configuration requests.

Usage in Data Context

The update protocol for data contexts is supported by an Updater instance that can be created for a data context.

It can be set by the context constructor:

func newContext(shared datacontext.AttributesContext, configctx config.Context, reposcheme RepositoryTypeScheme, logger logging.Context) Context {
    c := &_context{
        sharedattributes:     shared,
        updater:              cfgcpi.NewUpdate(configctx),
        knownRepositoryTypes: reposcheme,
        ...
    }
    c.Context = datacontext.NewContextBase(c, CONTEXT_TYPE, key, shared.GetAttributes(), logger)
    return c
}

Then the context implementation should provide an (internal) update function called by methods based on configuration settings:

func (c *_context) ConfigContext() config.Context {
    return c.updater.GetContext()
}

func (c *_context) Update() error {
    return c.updater.Update(c)
}

This will execute the sequence of missing configuration requests applied to the configuration context used by this data context since the last update.

Providing Configuration Objects

There might be any kind of configuration objects that can apply themselves to any kind of data context.

It must implement the interface:

type Config interface {
    runtime.VersionedTypedObject

    ApplyTo(Context, interface{}) error
}

Typically, such an object SHOULD provide a serialization format. If supported it must get a unique type name, and it can be registered for the configuration context.

The following snipped shows a typical pattern, how to implement this.

const (
    MyConfigType   = "my.config" + common.TypeGroupSuffix
    MyConfigTypeV1 = MyConfigType + runtime.VersionSeparator + "v1"
)

func init() {
    config.RegisterConfigType(MyConfigType, config.NewConfigType(MyConfigType, &ConfigSpec{}))
    config.RegisterConfigType(MyConfigTypeV1, config.NewConfigType(MyConfigTypeV1, &ConfigSpec{}))
}

// ConfigSpec describes a memory based repository interface.
type ConfigSpec struct {
    runtime.ObjectVersionedType `json:",inline"`
    // Any configuration settings
    ...
}

// NewConfigSpec creates a new memory ConfigSpec
func NewConfigSpec() *ConfigSpec {
    return &ConfigSpec{
        ObjectVersionedType: runtime.NewVersionedObjectType(MyConfigType),
    }
}

func (a *ConfigSpec) GetType() string {
    return MyConfigType
}

func (a *ConfigSpec) ApplyTo(ctx config.Context, target interface{}) error {
    // check if applicable for target object
    t, ok := target.(cpi.Context)
    if !ok {
        return config.ErrNoContext(MyConfigType)
    }
    // do the needful
    return false
}

If a data context provides an own type of configuration object this should be implemented in sub package config.

Generic Configuration

The configuration context provides an own configuration object for configuring the configuration context (in sub package config), that can be used to aggregate any kind of configuration object, that is serializable.

// Config describes a memory based repository interface.
type Config struct {
  runtime.ObjectVersionedType `json:",inline"`
  Configurations              []*cpi.GenericConfig `json:"configurations"`
}

This can be used to list any sequence of configurations that will be applied in this order, if the object is applied to a configuration context. The listed configuration requests will be stored, until they are replayed by a dedicated data context.

Documentation

Index

• Constants
• Variables
• func Debug(c Context, msg string, keypairs ...interface{})
• func DefaultContext() internal.Context
• func ErrNoContext(name string) error
• func Info(c Context, msg string, keypairs ...interface{})
• func IsErrConfigNotApplicable(err error) bool
• func IsErrNoContext(err error) bool
• func IsGeneric(cfg Config) bool
• func WithConfigTypeScheme(scheme ConfigTypeScheme) internal.Builder
• func WithContext(ctx context.Context) internal.Builder
• func WithSharedAttributes(ctx datacontext.AttributesContext) internal.Builder
• type Config
  • func NewGenericConfig(data []byte, unmarshaler runtime.Unmarshaler) (Config, error)
• type ConfigApplier
• type ConfigApplierFunction
• type ConfigSelector
• type ConfigSelectorFunction
• type ConfigType
• type ConfigTypeScheme
  • func NewConfigTypeScheme() ConfigTypeScheme
• type Context
  • func DefinedForContext(ctx context.Context) (Context, bool)
  • func ForContext(ctx context.Context) Context
  • func FromProvider(p ContextProvider) Context
  • func New(mode ...datacontext.BuilderMode) Context
• type ContextProvider
• type GenericConfig
  • func ToGenericConfig(c Config) (*GenericConfig, error)

Constants

const AllGenerations = internal.AllGenerations

const CONTEXT_TYPE = internal.CONTEXT_TYPE

const KIND_CONFIGTYPE = internal.KIND_CONFIGTYPE

const OCM_CONFIG_TYPE_SUFFIX = internal.OCM_CONFIG_TYPE_SUFFIX

Variables

var AllConfigs = internal.AllConfigs

var Logger = internal.Logger

var Realm = internal.Realm

Functions

func Debug

func Debug(c Context, msg string, keypairs ...interface{})

func DefaultContext

func DefaultContext() internal.Context

func ErrNoContext

func ErrNoContext(name string) error

func Info

func Info(c Context, msg string, keypairs ...interface{})

func IsErrConfigNotApplicable

func IsErrConfigNotApplicable(err error) bool

func IsErrNoContext

func IsErrNoContext(err error) bool

func IsGeneric

func IsGeneric(cfg Config) bool

func WithConfigTypeScheme

func WithConfigTypeScheme(scheme ConfigTypeScheme) internal.Builder

func WithContext

func WithContext(ctx context.Context) internal.Builder

func WithSharedAttributes

func WithSharedAttributes(ctx datacontext.AttributesContext) internal.Builder

Types

type Config

type Config = internal.Config

func NewGenericConfig

func NewGenericConfig(data []byte, unmarshaler runtime.Unmarshaler) (Config, error)

type ConfigApplier

type ConfigApplier = internal.ConfigApplier

type ConfigApplierFunction

type ConfigApplierFunction = internal.ConfigApplierFunction

type ConfigSelector

type ConfigSelector = internal.ConfigSelector

type ConfigSelectorFunction

type ConfigSelectorFunction = internal.ConfigSelectorFunction

type ConfigType

type ConfigType = internal.ConfigType

type ConfigTypeScheme

type ConfigTypeScheme = internal.ConfigTypeScheme

func NewConfigTypeScheme

func NewConfigTypeScheme() ConfigTypeScheme

type Context

type Context = internal.Context

func DefinedForContext

func DefinedForContext(ctx context.Context) (Context, bool)

func ForContext

func ForContext(ctx context.Context) Context

func FromProvider

func FromProvider(p ContextProvider) Context

func New

func New(mode ...datacontext.BuilderMode) Context

type ContextProvider

type ContextProvider = internal.ContextProvider

type GenericConfig

type GenericConfig = internal.GenericConfig

func ToGenericConfig

func ToGenericConfig(c Config) (*GenericConfig, error)