[Fix #28751] Hash stream long stream identifiers when using Postgres adapter

actioncable/CHANGELOG.md

+*   Hash long stream identifiers when using Postgres adapter.
+
+    PostgreSQL has a limit on identifiers length (63 chars, [docs](https://www.postgresql.org/docs/current/static/sql-syntax-lexical.html#SQL-SYNTAX-IDENTIFIERS)).
+    Provided fix minifies identifiers longer than 63 chars by hashing them with SHA1.
+
+    Fixes #28751.
+
+    *Vladimir Dementyev*
+
 *   ActionCable's `redis` adapter allows for other common redis-rb options (`host`, `port`, `db`, `password`) in cable.yml.
 
     Previously, it accepts only a [redis:// url](https://www.iana.org/assignments/uri-schemes/prov/redis) as an option.

actioncable/lib/action_cable/subscription_adapter/postgresql.rb

 gem "pg", "~> 0.18"
 require "pg"
 require "thread"
+require "digest/sha1"
 
 module ActionCable
   module SubscriptionAdapter
@@ -12,16 +13,16 @@ def initialize(*)
 
       def broadcast(channel, payload)
         with_connection do |pg_conn|
-          pg_conn.exec("NOTIFY #{pg_conn.escape_identifier(channel)}, '#{pg_conn.escape_string(payload)}'")
+          pg_conn.exec("NOTIFY #{pg_conn.escape_identifier(channel_identifier(channel))}, '#{pg_conn.escape_string(payload)}'")
         end
       end
 
       def subscribe(channel, callback, success_callback = nil)
-        listener.add_subscriber(channel, callback, success_callback)
+        listener.add_subscriber(channel_identifier(channel), callback, success_callback)
       end
 
       def unsubscribe(channel, callback)
-        listener.remove_subscriber(channel, callback)
+        listener.remove_subscriber(channel_identifier(channel), callback)
       end
 
       def shutdown
@@ -41,6 +42,10 @@ def with_connection(&block) # :nodoc:
       end
 
       private
+        def channel_identifier(channel)
+          channel.size > 63 ? Digest::SHA1.hexdigest(channel) : channel
+        end
+
         def listener
           @listener || @server.mutex.synchronize { @listener ||= Listener.new(self, @server.event_loop) }
         end

actioncable/test/subscription_adapter/common.rb

@@ -112,4 +112,18 @@ def test_channel_filtered_broadcast
       assert_equal "two", queue.pop
     end
   end
+
+  def test_long_identifiers
+    channel_1 = "a" * 100 + "1"
+    channel_2 = "a" * 100 + "2"
+    subscribe_as_queue(channel_1) do |queue|
+      subscribe_as_queue(channel_2) do |queue_2|
+        @tx_adapter.broadcast(channel_1, "apples")
+        @tx_adapter.broadcast(channel_2, "oranges")
+
+        assert_equal "apples", queue.pop
+        assert_equal "oranges", queue_2.pop
+      end
+    end
+  end
 end