hive

Documentation

Overview

Package hive provides the infrastructure for building Cilium applications from modular components (cells).

Hive is implemented using the uber/dig library, which provides the dependency injection for objects in the hive. It is similar to uber/fx, but adds an opinionated approach to configuration.

The configuration for cells is extracted from Viper. By default the field names are assumed to correspond to flag names, e.g. field 'MyOption' corresponds to '--my-option' flag.

The hive constructor, New(), takes the viper instance and the pflag FlagSet as parameters and registers the flags from all cells and binds them to viper variables. Once the FlagSet and viper configuration has been parsed one can call Populate() to pull the values from viper and construct the application. The hive can then be Run().

Example

For a runnable example see pkg/hive/example.

Try running:

example$ go run .
(ctrl-c stops)

example$ go run . --dot-graph | dot -Tx11

Try also commenting out cell.Provide lines and seeing what the dependency errors look like.

Index

• func AddConfigOverride[Cfg cell.Flagger](h *Hive, override func(*Cfg))
• type Hive
  • func New(cells ...cell.Cell) *Hive
  • func (h *Hive) AppendInvoke(invoke func() error)
  • func (h *Hive) Command() *cobra.Command
  • func (h *Hive) Populate() error
  • func (h *Hive) PrintDotGraph()
  • func (h *Hive) PrintObjects()
  • func (h *Hive) RegisterFlags(flags *pflag.FlagSet)
  • func (h *Hive) Run() error
  • func (h *Hive) SetEnvPrefix(prefix string)
  • func (h *Hive) SetTimeouts(start, stop time.Duration)
  • func (h *Hive) Shutdown(opts ...ShutdownOption)
  • func (h *Hive) Start(ctx context.Context) error
  • func (h *Hive) Stop(ctx context.Context) error
  • func (h *Hive) Viper() *viper.Viper
• type ShutdownOption
  • func ShutdownWithError(err error) ShutdownOption
• type Shutdowner

Functions

func AddConfigOverride

func AddConfigOverride[Cfg cell.Flagger](h *Hive, override func(*Cfg))

AddConfigOverride appends a config override function to modify a configuration after it has been parsed.

This method is only meant to be used in tests.

Types

type Hive

type Hive struct {
	// contains filtered or unexported fields
}

Hive is a framework building modular applications.

It implements dependency injection using the dig library.

See pkg/hive/example for a runnable example application.

func New

func New(cells ...cell.Cell) *Hive

New returns a new hive that can be run, or inspected. The command-line flags from the cells are registered as part of this.

The object graph is not constructed until methods of the hive are invoked.

Applications should call RegisterFlags() to register the hive's command-line flags. Likewise if configuration settings come from configuration files, then the Viper() method can be used to populate the hive's viper instance.

func (*Hive) AppendInvoke

func (h *Hive) AppendInvoke(invoke func() error)

func (*Hive) Command

func (h *Hive) Command() *cobra.Command

Command constructs the cobra command for hive. The hive command can be used to inspect the dependency graph.

func (*Hive) Populate

func (h *Hive) Populate() error

Populate instantiates the hive. Use for testing that the hive can be instantiated.

func (*Hive) PrintDotGraph

func (h *Hive) PrintDotGraph()

func (*Hive) PrintObjects

func (h *Hive) PrintObjects()

func (*Hive) RegisterFlags

func (h *Hive) RegisterFlags(flags *pflag.FlagSet)

RegisterFlags adds all flags in the hive to the given flag set. Fatals if a flag already exists in the given flag set. Use with e.g. cobra.Command:

cmd := &cobra.Command{...}
h.RegisterFlags(cmd.Flags())

func (*Hive) Run

func (h *Hive) Run() error

Run populates the cell configurations and runs the hive cells. Interrupt signal or call to Shutdowner.Shutdown() will cause the hive to stop.

func (*Hive) SetEnvPrefix

func (h *Hive) SetEnvPrefix(prefix string)

func (*Hive) SetTimeouts

func (h *Hive) SetTimeouts(start, stop time.Duration)

func (*Hive) Shutdown

func (h *Hive) Shutdown(opts ...ShutdownOption)

Shutdown implements the Shutdowner interface and is provided for the cells to use for triggering a early shutdown.

func (*Hive) Start

func (h *Hive) Start(ctx context.Context) error

Start starts the hive. The context allows cancelling the start. If context is cancelled and the start hooks do not respect the cancellation then after 5 more seconds the process will be terminated forcefully.

func (*Hive) Stop

func (h *Hive) Stop(ctx context.Context) error

Stop stops the hive. The context allows cancelling the stop. If context is cancelled and the stop hooks do not respect the cancellation then after 5 more seconds the process will be terminated forcefully.

func (*Hive) Viper

func (h *Hive) Viper() *viper.Viper

Viper returns the hive's viper instance.

type ShutdownOption

type ShutdownOption interface {
	// contains filtered or unexported methods
}

func ShutdownWithError

func ShutdownWithError(err error) ShutdownOption

ShutdownWithError shuts down with an error.

type Shutdowner

type Shutdowner interface {
	Shutdown(...ShutdownOption)
}

Shutdowner provides Shutdown(), which is a way to trigger stop for hive.

To shut down with an error, call Shutdown with ShutdownWithError(err). This error will be returned from Run().