github.com/niedbalski/juju@v0.0.0-20190215020005-8ff100488e47/apiserver/common/block.go (about)

     1  // Copyright 2014 Canonical Ltd.
     2  // Licensed under the AGPLv3, see LICENCE file for details.
     3  
     4  package common
     5  
     6  import (
     7  	"github.com/juju/errors"
     8  
     9  	"github.com/juju/juju/state"
    10  )
    11  
    12  type BlockGetter interface {
    13  	GetBlockForType(t state.BlockType) (state.Block, bool, error)
    14  }
    15  
    16  // BlockChecker checks for current blocks if any.
    17  type BlockChecker struct {
    18  	getter BlockGetter
    19  }
    20  
    21  func NewBlockChecker(s BlockGetter) *BlockChecker {
    22  	return &BlockChecker{s}
    23  }
    24  
    25  // ChangeAllowed checks if change block is in place.
    26  // Change block prevents all operations that may change
    27  // current model in any way from running successfully.
    28  func (c *BlockChecker) ChangeAllowed() error {
    29  	return c.checkBlock(state.ChangeBlock)
    30  }
    31  
    32  // RemoveAllowed checks if remove block is in place.
    33  // Remove block prevents removal of machine, service, unit
    34  // and relation from current model.
    35  func (c *BlockChecker) RemoveAllowed() error {
    36  	if err := c.checkBlock(state.RemoveBlock); err != nil {
    37  		return err
    38  	}
    39  	// Check if change block has been enabled
    40  	return c.checkBlock(state.ChangeBlock)
    41  }
    42  
    43  // DestroyAllowed checks if destroy block is in place.
    44  // Destroy block prevents destruction of current model.
    45  func (c *BlockChecker) DestroyAllowed() error {
    46  	if err := c.checkBlock(state.DestroyBlock); err != nil {
    47  		return err
    48  	}
    49  	// Check if remove block has been enabled
    50  	if err := c.checkBlock(state.RemoveBlock); err != nil {
    51  		return err
    52  	}
    53  	// Check if change block has been enabled
    54  	return c.checkBlock(state.ChangeBlock)
    55  }
    56  
    57  // checkBlock checks if specified operation must be blocked.
    58  // If it does, the method throws specific error that can be examined
    59  // to stop operation execution.
    60  func (c *BlockChecker) checkBlock(blockType state.BlockType) error {
    61  	aBlock, isEnabled, err := c.getter.GetBlockForType(blockType)
    62  	if err != nil {
    63  		return errors.Trace(err)
    64  	}
    65  	if isEnabled {
    66  		return OperationBlockedError(aBlock.Message())
    67  	}
    68  	return nil
    69  }