add an ability to run a function in a named context

Added a method to ConfigManager to run a specified function in a named context.
The named context can be a kubectl context or a pxc context.

Also,

- fixed a bug in NewConfigManagerForContext() that was preventing a context
  switch when run directly under pxc.

- added back the validations for pxc config.yaml that were commented out.
  Lack of validation was causing a seg fault if the config file was missing
  a current context etc.

Signed-off-by: Neelesh Thakur <[email protected]>

pkg/config/cm.go

@@ -71,11 +71,15 @@ func NewConfigManagerForContext(context string) (*ConfigManager, error) {
 		configManager.configrw = newPxcConfigReaderWriter()
 	}
 
-	err := configManager.Load()
-	if err != nil {
+	if err := configManager.Load(); err != nil {
 		return nil, err
 	}
 
+	if _, ok := configManager.Config.Contexts[context]; !ok {
+		return nil, fmt.Errorf("could not find the context '%s'", context)
+	}
+
+	configManager.Config.CurrentContext = context
 	return configManager, nil
 }
 
@@ -136,6 +140,31 @@ func (cm *ConfigManager) ForEachContext(
 	}
 }
 
+func (cm *ConfigManager) RunInNamedContext(contextName string, handler func() error) error {
+	// get current cluster
+	original := CM()
+	originalK := KM()
+
+	// defer resetting cluster
+	defer func() {
+		SetCM(original)
+		SetKM(originalK)
+	}()
+
+	if _, ok := cm.Config.Contexts[contextName]; !ok {
+		return fmt.Errorf("could not find the context '%s'", contextName)
+	}
+
+	newCm, err := NewConfigManagerForContext(contextName)
+	if err != nil {
+		return fmt.Errorf("failed to create manager for the context '%s'", contextName)
+	}
+	SetCM(newCm)
+	SetKM(NewKubernetesConfigManagerForContext(contextName))
+
+	return handler()
+}
+
 // GetFlags returns all the pxc persistent flags
 func (cm *ConfigManager) GetFlags() *ConfigFlags {
 	return cm.Flags

pkg/config/pxcconfig.go

@@ -227,12 +227,9 @@ func (p *pxcConfigReaderWriter) newDefaultConfig() *Config {
 }
 
 func (p *pxcConfigReaderWriter) validate(c *Config) error {
-	// REMOVED THESE LINES TO allow View for debugging. May have to check if these affect the rest of the system
-	/*
-		if len(c.CurrentContext) == 0 {
-			return fmt.Errorf("Current context missing from config file %s", CM().GetConfigFile())
-		}
-	*/
+	if len(c.CurrentContext) == 0 {
+		return fmt.Errorf("Current context missing from config file %s", CM().GetConfigFile())
+	}
 	if c.AuthInfos == nil {
 		c.AuthInfos = make(map[string]*AuthInfo)
 	}
@@ -243,21 +240,19 @@ func (p *pxcConfigReaderWriter) validate(c *Config) error {
 		c.Contexts = make(map[string]*Context)
 	}
 
-	/*
-		if _, ok := c.Contexts[c.CurrentContext]; !ok {
-			return fmt.Errorf("Context %s missing from config file %s", c.CurrentContext, CM().GetConfigFile())
-		}
+	if _, ok := c.Contexts[c.CurrentContext]; !ok {
+		return fmt.Errorf("Context %s missing from config file %s", c.CurrentContext, CM().GetConfigFile())
+	}
 
-		currentCreds := c.Contexts[c.CurrentContext].AuthInfo
-		if _, ok := c.AuthInfos[currentCreds]; !ok {
-			return fmt.Errorf("Credentials %s missing from config file %s", currentCreds, CM().GetConfigFile())
-		}
+	currentCreds := c.Contexts[c.CurrentContext].AuthInfo
+	if _, ok := c.AuthInfos[currentCreds]; !ok {
+		return fmt.Errorf("Credentials %s missing from config file %s", currentCreds, CM().GetConfigFile())
+	}
 
-		currentCluster := c.Contexts[c.CurrentContext].Cluster
-		if _, ok := c.Clusters[currentCluster]; !ok {
-			return fmt.Errorf("Cluster %s missing from config file %s", currentCluster, CM().GetConfigFile())
-		}
+	currentCluster := c.Contexts[c.CurrentContext].Cluster
+	if _, ok := c.Clusters[currentCluster]; !ok {
+		return fmt.Errorf("Cluster %s missing from config file %s", currentCluster, CM().GetConfigFile())
+	}
 
-	*/
 	return nil
 }