Merge pull request #434 from liori/tmpfs_workspace

tmpfs_workspace: Plugin for having workspace on tmpfs for speed

bootstrapvz/plugins/tmpfs_workspace/README.rst

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+tmpfs workspace
+---------------
+
+The ``tmpfs workspace`` plugin mounts a tmpfs filesystem for the
+workspace temporary files. This is useful when the workspace directory
+is placed on a slow medium (e.g. a hard disk drive), the build process
+performs lots of local I/O (e.g. building a vagrant box), and there is
+enough RAM to store data necessary for the build process. For example,
+the ``stretch-vagrant.yml`` manifest file from the examples directory
+takes 33 minutes to build on the plugin author's home server. Using
+this plugin reduces this time to 3 minutes at the cost of 1.2GB of
+additional RAM usage.
+
+Settings
+~~~~~~~~
+
+This plugin has no settings. To enable it add ``"tmpfs_workspace":{}``
+to the plugin section of the manifest.

bootstrapvz/plugins/tmpfs_workspace/__init__.py

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+from bootstrapvz.common.tasks.workspace import CreateWorkspace, DeleteWorkspace
+from tasks import CreateTmpFsWorkspace, MountTmpFsWorkspace, UnmountTmpFsWorkspace, DeleteTmpFsWorkspace
+
+
+def resolve_tasks(taskset, manifest):
+    taskset.discard(CreateWorkspace)
+    taskset.discard(DeleteWorkspace)
+
+    taskset.add(CreateTmpFsWorkspace)
+    taskset.add(MountTmpFsWorkspace)
+    taskset.add(UnmountTmpFsWorkspace)
+    taskset.add(DeleteTmpFsWorkspace)
+
+
+def resolve_rollback_tasks(taskset, manifest, completed, counter_task):
+    counter_task(taskset, MountTmpFsWorkspace, UnmountTmpFsWorkspace)
+    counter_task(taskset, CreateTmpFsWorkspace, DeleteTmpFsWorkspace)

bootstrapvz/plugins/tmpfs_workspace/tasks.py

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+from os import makedirs, rmdir
+
+from bootstrapvz.base import Task
+from bootstrapvz.common.tasks.workspace import CreateWorkspace, DeleteWorkspace
+from bootstrapvz.common import phases
+from bootstrapvz.common.tools import log_check_call
+
+
+class CreateTmpFsWorkspace(Task):
+    description = 'Creating directory for tmpfs-based workspace'
+    phase = phases.preparation
+
+    @classmethod
+    def run(cls, info):
+        makedirs(info.workspace)
+
+
+class MountTmpFsWorkspace(Task):
+    description = 'Mounting tmpfs-based workspace'
+    phase = phases.preparation
+
+    # CreateWorkspace is explicitly skipped (see the plugin's resolve_task function). Several other tasks
+    # depend on CreateWorkspace to put their own files inside the workspace. We position MountTmpFs before
+    # CreateWorkspace to leverage these dependencies. See also UnmountTmpFs/DeleteWorkspace below.
+    successors = [CreateWorkspace]
+    predecessors = [CreateTmpFsWorkspace]
+
+    @classmethod
+    def run(cls, info):
+        log_check_call(['mount', '--types', 'tmpfs', 'none', info.workspace])
+
+
+class UnmountTmpFsWorkspace(Task):
+    description = 'Unmounting tmpfs-based workspace'
+    phase = phases.cleaning
+    predecessors = [DeleteWorkspace]
+
+    @classmethod
+    def run(cls, info):
+        log_check_call(['umount', info.workspace])
+
+
+class DeleteTmpFsWorkspace(Task):
+    description = 'Deleting directory for tmpfs-based workspace'
+    phase = phases.cleaning
+    predecessors = [UnmountTmpFsWorkspace]
+
+    @classmethod
+    def run(cls, info):
+        rmdir(info.workspace)