fix: preserve live collection during alias-based reindex

lib/typesense-rails.rb

@@ -270,7 +270,7 @@ class << base
     end
 
     def collection_name_with_timestamp(options)
-      "#{typesense_collection_name(options)}_#{Time.now.to_i}"
+      "#{typesense_collection_name(options)}_#{Time.now.to_i}_#{SecureRandom.hex(4)}"
     end
 
     def typesense_create_collection(collection_name, settings = nil, existing_collection: nil)
@@ -635,10 +635,11 @@ def typesense_reindex(batch_size = Typesense::IndexSettings::DEFAULT_BATCH_SIZE)
         next if typesense_indexing_disabled?(options)
 
         existing_collection_resources = {}
+        old_collection_name = nil
         begin
           master_index = typesense_ensure_init(options, settings, false)
           existing_collection_resources = typesense_collection_resources(master_index[:alias_name])
-          delete_collection(master_index[:alias_name])
+          old_collection_name = master_index[:collection_name]
         rescue ArgumentError
           @typesense_indexes[settings] = { collection_name: "", alias_name: typesense_collection_name(options) }
           master_index = @typesense_indexes[settings]
@@ -665,6 +666,7 @@ def typesense_reindex(batch_size = Typesense::IndexSettings::DEFAULT_BATCH_SIZE)
         end
 
         upsert_alias(src_index_name, master_index[:alias_name])
+        delete_collection(old_collection_name) if old_collection_name.present? && old_collection_name != src_index_name
         master_index[:collection_name] = src_index_name
       end
       nil

spec/integration_spec.rb

@@ -142,6 +142,9 @@
   create_table :misconfigured_blocks do |t|
     t.string :name
   end
+  create_table :reindex_alias_probes do |t|
+    t.string :name
+  end
   if defined?(ActiveModel::Serializer)
     create_table :serialized_objects do |t|
       t.string :name
@@ -248,6 +251,14 @@ def self.truth
   end
 end
 
+class ReindexAliasProbe < ActiveRecord::Base
+  include Typesense
+
+  typesense auto_index: false, index_name: safe_index_name("ReindexAliasProbe") do
+    attribute :name
+  end
+end
+
 module Namespaced
   def self.table_name_prefix
     "namespaced_"
@@ -991,6 +1002,33 @@ class SerializedObject < ActiveRecord::Base
       expect(Product.search("*", "", { "per_page" => Typesense::IndexSettings::DEFAULT_BATCH_SIZE }).size).to eq(n)
     end
 
+    it "does not delete the live alias target before swapping during reindex" do
+      alias_name = Product.index_name
+      old_collection_name = "#{alias_name}_old"
+      new_collection_name = "#{alias_name}_new"
+      previous_indexes = Product.instance_variable_get(:@typesense_indexes)
+
+      Product.instance_variable_set(:@typesense_indexes, {})
+
+      allow(Product).to receive(:get_collection).with(alias_name).and_return({ "name" => old_collection_name })
+      allow(Product).to receive(:typesense_collection_resources).with(alias_name).and_return({})
+      allow(Product).to receive(:collection_name_with_timestamp).and_return(new_collection_name)
+      allow(Product).to receive(:typesense_find_in_batches)
+
+      expect(Product).not_to receive(:delete_collection).with(alias_name)
+      expect(Product).to receive(:create_collection).with(
+        new_collection_name,
+        Product.typesense_settings,
+        existing_collection: {}
+      ).ordered
+      expect(Product).to receive(:upsert_alias).with(new_collection_name, alias_name).ordered
+      expect(Product).to receive(:delete_collection).with(old_collection_name).ordered
+
+      Product.reindex(Typesense::IndexSettings::DEFAULT_BATCH_SIZE)
+    ensure
+      Product.instance_variable_set(:@typesense_indexes, previous_indexes)
+    end
+
     it "should not return products that are not indexable" do
       @sekrit.index!
       @no_href.index!
@@ -1071,6 +1109,43 @@ class SerializedObject < ActiveRecord::Base
   end
 end
 
+describe "ReindexAliasProbe" do
+  before(:each) do
+    ReindexAliasProbe.delete_all
+    ReindexAliasProbe.clear_index!
+  rescue StandardError
+    ArgumentError
+  ensure
+    ReindexAliasProbe.create!(name: "alpha")
+    ReindexAliasProbe.create!(name: "beta")
+    ReindexAliasProbe.reindex(Typesense::IndexSettings::DEFAULT_BATCH_SIZE)
+  end
+
+  after(:each) do
+    ReindexAliasProbe.delete_all
+    ReindexAliasProbe.clear_index!
+  rescue StandardError
+    ArgumentError
+  end
+
+  it "keeps the alias searchable while reindex builds the replacement collection" do
+    alias_name = ReindexAliasProbe.index_name
+    search_params = { q: "alpha", query_by: "name" }
+
+    expect(ReindexAliasProbe.typesense_client.collections[alias_name].documents.search(search_params)["found"]).to eq(1)
+
+    expect(ReindexAliasProbe).to receive(:create_collection).and_wrap_original do |original, *args, **kwargs|
+      expect(
+        ReindexAliasProbe.typesense_client.collections[alias_name].documents.search(search_params)["found"]
+      ).to eq(1)
+      original.call(*args, **kwargs)
+    end
+
+    ReindexAliasProbe.reindex(Typesense::IndexSettings::DEFAULT_BATCH_SIZE)
+    expect(ReindexAliasProbe.typesense_client.collections[alias_name].documents.search(search_params)["found"]).to eq(1)
+  end
+end
+
 describe "Book" do
   before(:all) do
     Book.clear_index!