Implement atomic deployments for Nulecule application. Fixes projectatomic#421

When there's an error during running a Nulecule application,
rollback the changes made by stopping the application.

Author: rtnpro

atomicapp/nulecule/base.py

@@ -135,22 +135,23 @@ def run(self, provider_key=None, dryrun=False):
         for component in self.components:
             component.run(provider_key, dryrun)
 
-    def stop(self, provider_key=None, dryrun=False):
+    def stop(self, provider_key=None, dryrun=False, ignore_errors=False):
         """
         Stop the Nulecule application.
 
         Args:
             provider_key (str): Provider to use for running Nulecule
                                 application
             dryrun (bool): Do not make changes to host when True
+            ignore_errors (bool): Ignore errors, if any, when True
 
         Returns:
             None
         """
         provider_key, provider = self.get_provider(provider_key, dryrun)
         # stop the Nulecule application
         for component in self.components:
-            component.stop(provider_key, dryrun)
+            component.stop(provider_key, dryrun, ignore_errors)
 
     def uninstall(self):
         # uninstall the Nulecule application
@@ -264,7 +265,7 @@ def run(self, provider_key, dryrun=False):
         provider.init()
         provider.deploy()
 
-    def stop(self, provider_key=None, dryrun=False):
+    def stop(self, provider_key=None, dryrun=False, ignore_errors=False):
         """
         Stop the Nulecule component with the specified provider.
         """
@@ -274,7 +275,7 @@ def stop(self, provider_key=None, dryrun=False):
         provider_key, provider = self.get_provider(provider_key, dryrun)
         provider.artifacts = self.rendered_artifacts.get(provider_key, [])
         provider.init()
-        provider.undeploy()
+        provider.undeploy(ignore_errors)
 
     def load_config(self, config=None, ask=False, skip_asking=False):
         """

atomicapp/nulecule/main.py

@@ -192,7 +192,7 @@ def run(self, cli_provider, answers_output, ask,
 
         self.nulecule.load_config(config=self.nulecule.config, ask=ask)
         self.nulecule.render(cli_provider, dryrun)
-        self.nulecule.run(cli_provider, dryrun)
+
         runtime_answers = self._get_runtime_answers(
             self.nulecule.config, cli_provider)
         self._write_answers(
@@ -202,12 +202,21 @@ def run(self, cli_provider, answers_output, ask,
             self._write_answers(answers_output, runtime_answers,
                                 self.answers_format)
 
-    def stop(self, cli_provider, **kwargs):
+        try:
+            self.nulecule.run(cli_provider, dryrun)
+        except Exception as e:
+            logger.error('Application run error: %s' % e)
+            logger.debug('Nulecule run error: %s' % e, exc_info=True)
+            logger.info('Rolling back changes')
+            self.stop(cli_provider, ignore_errors=True, **kwargs)
+
+    def stop(self, cli_provider, ignore_errors=False, **kwargs):
         """
         Stops a running Nulecule application.
 
         Args:
             cli_provider (str): Provider running the Nulecule application
+            ignore_errors (bool): Ignore errors, if any, when True
             kwargs (dict): Extra keyword arguments
         """
         # For stop we use the generated answer file from the run
@@ -219,7 +228,7 @@ def stop(self, cli_provider, **kwargs):
             self.app_path, config=self.answers, dryrun=dryrun)
         self.nulecule.load_config(config=self.answers)
         self.nulecule.render(cli_provider, dryrun=dryrun)
-        self.nulecule.stop(cli_provider, dryrun)
+        self.nulecule.stop(cli_provider, dryrun, ignore_errors)
 
     def uninstall(self):
         # For future use

atomicapp/plugin.py

@@ -88,7 +88,7 @@ def checkConfigFile(self):
                 "[general] section of the answers.conf file."
                 % (self.config_file, PROVIDER_CONFIG_KEY))
 
-    def undeploy(self):
+    def undeploy(self, ignore_errors=False):
         logger.warning(
             "Call to undeploy for provider %s failed - this action is not implemented",
             self.key)

atomicapp/providers/docker.py

@@ -103,7 +103,7 @@ def deploy(self):
             else:
                 subprocess.check_call(cmd)
 
-    def undeploy(self):
+    def undeploy(self, ignore_errors=False):
         logger.info("Undeploying to provider: Docker")
         artifact_names = list()
 
@@ -132,4 +132,8 @@ def undeploy(self):
                 if self.dryrun:
                     logger.info("DRY-RUN: STOPPING CONTAINER %s", " ".join(cmd))
                 else:
-                    subprocess.check_call(cmd)
+                    try:
+                        subprocess.check_call(cmd)
+                    except Exception as e:
+                        if not ignore_errors:
+                            raise e

atomicapp/providers/kubernetes.py

@@ -183,7 +183,7 @@ def deploy(self):
                 cmd.append("--kubeconfig=%s" % self.config_file)
             self._call(cmd)
 
-    def undeploy(self):
+    def undeploy(self, ignore_errors=False):
         """Undeploys the app by given resource manifests.
         Undeploy operation first scale down the replicas to 0 and then deletes
         the resource from cluster.
@@ -203,4 +203,8 @@ def undeploy(self):
             cmd = [self.kubectl, "delete", "-f", path, "--namespace=%s" % self.namespace]
             if self.config_file:
                 cmd.append("--kubeconfig=%s" % self.config_file)
-            self._call(cmd)
+            try:
+                self._call(cmd)
+            except Exception as e:
+                if not ignore_errors:
+                    raise e