Add atomic/zero-downtime index rebuilding (#358)

* Added atomic/zero-downtime index rebuilding

* Update django_elasticsearch_dsl/management/commands/search_index.py

Co-authored-by: Maksudul Haque <saad.mk112@gmail.com>

* Update django_elasticsearch_dsl/management/commands/search_index.py

Co-authored-by: Maksudul Haque <saad.mk112@gmail.com>

* Update django_elasticsearch_dsl/management/commands/search_index.py

Co-authored-by: Maksudul Haque <saad.mk112@gmail.com>

* Update django_elasticsearch_dsl/management/commands/search_index.py

Co-authored-by: Maksudul Haque <saad.mk112@gmail.com>

* Update django_elasticsearch_dsl/management/commands/search_index.py

Co-authored-by: Maksudul Haque <saad.mk112@gmail.com>

* Added index name slice to ensure index name length does not exceed 255 characters

* Updated naming of flags

* Updated arg help messages for '--use-alias' and '--use-alias-keep-index'

* Updated 'indexes' to 'indices' for verbiage consistency

* Simplified stdout messaging

* Made adjustments for better switching between using aliases and not

* Updated super() call for compatibility with Python 2

* Simplified logic for stdout messaging

* Fixed test_custom_generate_id_is_called test

* Added comment explaining need for aliases regardless of using the '--use-alias' arg

* Moved alias indices deletion for 'rebuild' without aliases to _delete()

* Added 'return False' in case of undeleted index or alias in _delete()

* Added _matches() to DocType for alias pattern matching

Co-authored-by: Maksudul Haque <saad.mk112@gmail.com>

Author: oehrlein

django_elasticsearch_dsl/documents.py

@@ -1,6 +1,7 @@
 from __future__ import unicode_literals
 
 from collections import deque
+from fnmatch import fnmatch
 from functools import partial
 
 from django import VERSION as DJANGO_VERSION
@@ -66,6 +67,18 @@ def __eq__(self, other):
     def __hash__(self):
         return id(self)
 
+    @classmethod
+    def _matches(cls, hit):
+        """
+        Determine which index or indices in a pattern to be used in a hit.
+        Overrides DSLDocument _matches function to match indices in a pattern,
+        which is needed in case of using aliases. This is needed as the
+        document class will not be used to deserialize the documents. The
+        documents will have the index set to the concrete index, whereas the
+        class refers to the alias.
+        """
+        return fnmatch(hit.get("_index", ""), cls._index._name + "*")
+
     @classmethod
     def search(cls, using=None, index=None):
         return Search(

django_elasticsearch_dsl/management/commands/search_index.py

@@ -1,5 +1,7 @@
 from __future__ import unicode_literals, absolute_import
+from datetime import datetime
 
+from elasticsearch_dsl import connections
 from django.conf import settings
 from django.core.management.base import BaseCommand, CommandError
 from six.moves import input
@@ -9,6 +11,10 @@
 class Command(BaseCommand):
     help = 'Manage elasticsearch index.'
 
+    def __init__(self, *args, **kwargs):
+        super(Command, self).__init__(*args, **kwargs)
+        self.es_conn = connections.get_connection()
+
     def add_arguments(self, parser):
         parser.add_argument(
             '--models',
@@ -63,6 +69,21 @@ def add_arguments(self, parser):
             dest='parallel',
             help='Run populate/rebuild update single threaded'
         )
+        parser.add_argument(
+            '--use-alias',
+            action='store_true',
+            dest='use_alias',
+            help='Use alias with indices'
+        )
+        parser.add_argument(
+            '--use-alias-keep-index',
+            action='store_true',
+            dest='use_alias_keep_index',
+            help="""
+                Do not delete replaced indices when used with '--rebuild' and
+                '--use-alias' args
+            """
+        )
         parser.set_defaults(parallel=getattr(settings, 'ELASTICSEARCH_DSL_PARALLEL', False))
         parser.add_argument(
             '--refresh',
@@ -107,10 +128,18 @@ def _get_models(self, args):
 
         return set(models)
 
-    def _create(self, models, options):
+    def _create(self, models, aliases, options):
         for index in registry.get_indices(models):
-            self.stdout.write("Creating index '{}'".format(index._name))
-            index.create()
+            alias_exists = index._name in aliases
+            if not alias_exists:
+                self.stdout.write("Creating index '{}'".format(index._name))
+                index.create()
+            elif options['action'] == 'create':
+                self.stdout.write(
+                    "'{}' already exists as an alias. Run '--delete' with"
+                    " '--use-alias' arg to delete indices pointed at the "
+                    "alias to make index name available.".format(index._name)
+                )
 
     def _populate(self, models, options):
         parallel = options['parallel']
@@ -123,29 +152,138 @@ def _populate(self, models, options):
             qs = doc().get_indexing_queryset()
             doc().update(qs, parallel=parallel, refresh=options['refresh'])
 
-    def _delete(self, models, options):
+    def _get_alias_indices(self, alias):
+        alias_indices = self.es_conn.indices.get_alias(name=alias)
+        return list(alias_indices.keys())
+
+    def _delete_alias_indices(self, alias):
+        alias_indices = self._get_alias_indices(alias)
+        alias_delete_actions = [
+            {"remove_index": {"index": index}} for index in alias_indices
+        ]
+        self.es_conn.indices.update_aliases({"actions": alias_delete_actions})
+        for index in alias_indices:
+            self.stdout.write("Deleted index '{}'".format(index))
+
+    def _delete(self, models, aliases, options):
         index_names = [index._name for index in registry.get_indices(models)]
 
         if not options['force']:
             response = input(
                 "Are you sure you want to delete "
-                "the '{}' indexes? [y/N]: ".format(", ".join(index_names)))
+                "the '{}' indices? [y/N]: ".format(", ".join(index_names)))
             if response.lower() != 'y':
                 self.stdout.write('Aborted')
                 return False
 
-        for index in registry.get_indices(models):
-            self.stdout.write("Deleting index '{}'".format(index._name))
-            index.delete(ignore=404)
+        if options['use_alias']:
+            for index in index_names:
+                alias_exists = index in aliases
+                if alias_exists:
+                    self._delete_alias_indices(index)
+                elif self.es_conn.indices.exists(index=index):
+                    self.stdout.write(
+                        "'{}' refers to an index, not an alias. Run "
+                        "'--delete' without '--use-alias' arg to delete "
+                        "index.".format(index)
+                    )
+                    return False
+        else:
+            for index in registry.get_indices(models):
+                alias_exists = index._name in aliases
+                if not alias_exists:
+                    self.stdout.write("Deleting index '{}'".format(index._name))
+                    index.delete(ignore=404)
+                elif options['action'] == 'rebuild':
+                    self._delete_alias_indices(index._name)
+                elif options['action'] == 'delete':
+                    self.stdout.write(
+                        "'{}' refers to an alias, not an index. Run "
+                        "'--delete' with '--use-alias' arg to delete indices "
+                        "pointed at the alias.".format(index._name)
+                    )
+                    return False
+
         return True
 
-    def _rebuild(self, models, options):
-        if not self._delete(models, options):
+    def _update_alias(self, alias, new_index, alias_exists, options):
+        alias_actions = [{"add": {"alias": alias, "index": new_index}}]
+
+        delete_existing_index = False
+        if not alias_exists and self.es_conn.indices.exists(index=alias):
+            # Elasticsearch will return an error if an index already
+            # exists with the desired alias name. Therefore, we need to
+            # delete that index.
+            delete_existing_index = True
+            alias_actions.append({"remove_index": {"index": alias}})
+
+        old_indices = []
+        alias_delete_actions = []
+        if alias_exists:
+            # Elasticsearch will return an error if we search for
+            # indices by alias but the alias doesn't exist. Therefore,
+            # we want to be sure the alias exists.
+            old_indices = self._get_alias_indices(alias)
+            alias_actions.append(
+                {"remove": {"alias": alias, "indices": old_indices}}
+            )
+            alias_delete_actions = [
+                {"remove_index": {"index": index}} for index in old_indices
+            ]
+
+        self.es_conn.indices.update_aliases({"actions": alias_actions})
+        if delete_existing_index:
+             self.stdout.write("Deleted index '{}'".format(alias))
+
+        self.stdout.write(
+            "Added alias '{}' to index '{}'".format(alias, new_index)
+        )
+
+        if old_indices:
+            for index in old_indices:
+                self.stdout.write(
+                    "Removed alias '{}' from index '{}'".format(alias, index)
+                )
+
+            if alias_delete_actions and not options['use_alias_keep_index']:
+                self.es_conn.indices.update_aliases(
+                    {"actions": alias_delete_actions}
+                )
+                for index in old_indices:
+                    self.stdout.write("Deleted index '{}'".format(index))
+
+    def _rebuild(self, models, aliases, options):
+        if (not options['use_alias']
+            and not self._delete(models, aliases, options)):
             return
 
-        self._create(models, options)
+        if options['use_alias']:
+            alias_index_pairs = []
+            index_suffix = "-" + datetime.now().strftime("%Y%m%d%H%M%S%f")
+            for index in registry.get_indices(models):
+                # The alias takes the original index name value. The
+                # index name sent to Elasticsearch will be the alias
+                # plus the suffix from above. In addition, the index
+                # name needs to be limited to 255 characters, of which
+                # 21 will always be taken by the suffix, leaving 234
+                # characters from the original index name value.
+                new_index = index._name[:234] + index_suffix
+                alias_index_pairs.append(
+                    {'alias': index._name, 'index': new_index}
+                )
+                index._name = new_index
+
+        self._create(models, aliases, options)
         self._populate(models, options)
 
+        if options['use_alias']:
+            for alias_index_pair in alias_index_pairs:
+                alias = alias_index_pair['alias']
+                alias_exists = alias in aliases
+                self._update_alias(
+                    alias, alias_index_pair['index'], alias_exists, options
+                )
+
     def handle(self, *args, **options):
         if not options['action']:
             raise CommandError(
@@ -156,14 +294,21 @@ def handle(self, *args, **options):
         action = options['action']
         models = self._get_models(options['models'])
 
+        # We need to know if and which aliases exist to mitigate naming
+        # conflicts with indices, therefore this is needed regardless
+        # of using the '--use-alias' arg.
+        aliases = []
+        for index in self.es_conn.indices.get_alias().values():
+            aliases += index['aliases'].keys()
+
         if action == 'create':
-            self._create(models, options)
+            self._create(models, aliases, options)
         elif action == 'populate':
             self._populate(models, options)
         elif action == 'delete':
-            self._delete(models, options)
+            self._delete(models, aliases, options)
         elif action == 'rebuild':
-            self._rebuild(models, options)
+            self._rebuild(models, aliases, options)
         else:
             raise CommandError(
                 "Invalid action. Must be one of"