Start work on migration script for v5.0.0

Author: morgante

helpers/migrate.py

@@ -0,0 +1,305 @@
+#!/usr/bin/env python3
+
+# Copyright 2019 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import argparse
+import copy
+import subprocess
+import sys
+import shutil
+import re
+
+MIGRATIONS = [
+    {
+        "resource_type": "google_container_cluster",
+        "name": "zonal_primary",
+        "rename": "primary",
+        "replace": True,
+        "module": ""
+    },
+]
+
+class ModuleMigration:
+    """
+    Migrate the resources from a flat project factory to match the new
+    module structure created by the G Suite refactor.
+    """
+
+    def __init__(self, source_module):
+        self.source_module = source_module
+
+    def moves(self):
+        """
+        Generate the set of old/new resource pairs that will be migrated
+        to the `destination` module.
+        """
+        resources = self.targets()
+        moves = []
+        for (old, migration) in resources:
+            new = copy.deepcopy(old)
+            new.module += migration["module"]
+
+            print("new", new.name)
+
+            # Update the copied resource with the "rename" value if it is set
+            if "rename" in migration:
+                new.name = migration["rename"]
+
+            pair = (old.path(), new.path())
+            moves.append(pair)
+
+        print("moves", moves)
+        return moves
+
+    def targets(self):
+        """
+        A list of resources that will be moved to the new module        """
+        to_move = []
+
+        for migration in MIGRATIONS:
+            resource_type = migration["resource_type"]
+            resource_name = migration["name"]
+            matching_resources = self.source_module.get_resources(
+                resource_type,
+                resource_name)
+            to_move += [(r, migration) for r in matching_resources]
+
+        return to_move
+
+class TerraformModule:
+    """
+    A Terraform module with associated resources.
+    """
+
+    def __init__(self, name, resources):
+        """
+        Create a new module and associate it with a list of resources.
+        """
+        self.name = name
+        self.resources = resources
+
+    def get_resources(self, resource_type=None, resource_name=None):
+        """
+        Return a list of resources matching the given resource type and name.
+        """
+
+        ret = []
+        for resource in self.resources:
+            matches_type = (resource_type is None or
+                            resource_type == resource.resource_type)
+
+            name_pattern = re.compile(r'%s(\[\d+\])?' % resource_name)
+            matches_name = (resource_name is None or
+                            name_pattern.match(resource.name))
+
+            if matches_type and matches_name:
+                ret.append(resource)
+
+        return ret
+
+    def has_resource(self, resource_type=None, resource_name=None):
+        """
+        Does this module contain a resource with the matching type and name?
+        """
+        for resource in self.resources:
+            matches_type = (resource_type is None or
+                            resource_type == resource.resource_type)
+
+            matches_name = (resource_name is None or
+                            resource_name in resource.name)
+
+            if matches_type and matches_name:
+                return True
+
+        return False
+
+    def __repr__(self):
+        return "{}({!r}, {!r})".format(
+            self.__class__.__name__,
+            self.name,
+            [repr(resource) for resource in self.resources])
+
+
+class TerraformResource:
+    """
+    A Terraform resource, defined by the the identifier of that resource.
+    """
+
+    @classmethod
+    def from_path(cls, path):
+        """
+        Generate a new Terraform resource, based on the fully qualified
+        Terraform resource path.
+        """
+        if re.match(r'\A[\w.\[\]-]+\Z', path) is None:
+            raise ValueError(
+                "Invalid Terraform resource path {!r}".format(path))
+
+        parts = path.split(".")
+        name = parts.pop()
+        resource_type = parts.pop()
+        module = ".".join(parts)
+        return cls(module, resource_type, name)
+
+    def __init__(self, module, resource_type, name):
+        """
+        Create a new TerraformResource from a pre-parsed path.
+        """
+        self.module = module
+        self.resource_type = resource_type
+
+        find_suffix = re.match('(^.+)\[(\d+)\]', name)
+        if find_suffix:
+            self.name = find_suffix.group(1)
+            self.index = find_suffix.group(2)
+        else:
+            self.name = name
+            self.index = -1
+
+    def path(self):
+        """
+        Return the fully qualified resource path.
+        """
+        parts = [self.module, self.resource_type, self.name]
+        if parts[0] == '':
+            del parts[0]
+        path = ".".join(parts)
+        if self.index is not -1:
+            path = "{0}[{1}]".format(path, self.index)
+        return path
+
+    def __repr__(self):
+        return "{}({!r}, {!r}, {!r})".format(
+            self.__class__.__name__,
+            self.module,
+            self.resource_type,
+            self.name)
+
+def group_by_module(resources):
+    """
+    Group a set of resources according to their containing module.
+    """
+
+    groups = {}
+    for resource in resources:
+        if resource.module in groups:
+            groups[resource.module].append(resource)
+        else:
+            groups[resource.module] = [resource]
+
+    return [
+        TerraformModule(name, contained)
+        for name, contained in groups.items()
+    ]
+
+
+def read_state(statefile):
+    """
+    Read the terraform state at the given path.
+    """
+    argv = ["terraform", "state", "list", "-state", statefile]
+    result = subprocess.run(argv,
+                            capture_output=True,
+                            check=True,
+                            encoding='utf-8')
+    elements = result.stdout.split("\n")
+    elements.pop()
+    return elements
+
+
+def state_changes_for_module(module, statefile):
+    """
+    Compute the Terraform state changes (deletions and moves) for a single
+    module.
+    """
+    commands = []
+
+    migration = ModuleMigration(module)
+
+    for (old, new) in migration.moves():
+        wrapper = '"{0}"'
+        argv = ["terraform", "state", "mv", "-state", statefile, wrapper.format(old), wrapper.format(new)]
+        commands.append(argv)
+
+    return commands
+
+
+def migrate(statefile, dryrun=False):
+    """
+    Migrate the terraform state in `statefile` to match the post-refactor
+    resource structure.
+    """
+
+    # Generate a list of Terraform resource states from the output of
+    # `terraform state list`
+    resources = [
+        TerraformResource.from_path(path)
+        for path in read_state(statefile)
+    ]
+
+    # Group resources based on the module where they're defined.
+    modules = group_by_module(resources)
+    print('modules', len(modules))
+
+    # Filter our list of Terraform modules down to anything that looks like a
+    # zonal GKE module. We key this off the presence off of
+    # `google_container_cluster.zonal_primary` since that should almost always be
+    # unique to a GKE module.
+    modules_to_migrate = [
+        module for module in modules
+        if module.has_resource("google_container_cluster", "zonal_primary")
+    ]
+
+    print("---- Migrating the following modules:")
+    for module in modules_to_migrate:
+        print("-- " + module.name)
+
+    # Collect a list of resources for each module
+    commands = []
+    for module in modules_to_migrate:
+        commands += state_changes_for_module(module, statefile)
+
+    for argv in commands:
+        if dryrun:
+            print(" ".join(argv))
+        else:
+            subprocess.run(argv, check=True, encoding='utf-8')
+
+def main(argv):
+    parser = argparser()
+    args = parser.parse_args(argv[1:])
+
+    print("cp {} {}".format(args.oldstate, args.newstate))
+    shutil.copy(args.oldstate, args.newstate)
+
+    migrate(args.newstate, dryrun=args.dryrun)
+    print("State migration complete, verify migration with "
+          "`terraform plan -state '{}'`".format(args.newstate))
+
+def argparser():
+    parser = argparse.ArgumentParser(description='Migrate Terraform state')
+    parser.add_argument('oldstate', metavar='oldstate.json',
+                        help='The current Terraform state (will not be '
+                             'modified)')
+    parser.add_argument('newstate', metavar='newstate.json',
+                        help='The path to the new state file')
+    parser.add_argument('--dryrun', action='store_true',
+                        help='Print the `terraform state mv` commands instead '
+                             'of running the commands.')
+    return parser
+
+
+if __name__ == "__main__":
+    main(sys.argv)