Fallback to using unencrypted DB connection when possible (#2084)

Fix #1792.

.changeset/stupid-weeks-look.md

@@ -0,0 +1,5 @@
+---
+"@core/sync-service": patch
+---
+
+Restore the automatic fallback to unencrypted database connections when SSL isn't available.

examples/gatekeeper-auth/README.md

@@ -157,7 +157,7 @@ $ curl -sv --header "Authorization: Bearer ${AUTH_TOKEN}" \
 Note that we got an empty response when successfully proxied through to Electric above because there are no `items` in the database. If you like, you can create some, e.g. using `psql`:
 
 ```console
-$ psql "postgresql://postgres:password@localhost:54321/electric?sslmode=disable"
+$ psql "postgresql://postgres:password@localhost:54321/electric"
 psql (16.4)
 Type "help" for help.
 

packages/sync-service/lib/electric/connection/manager.ex

@@ -242,20 +242,24 @@ defmodule Electric.Connection.Manager do
 
   @impl true
   def handle_continue(:start_lock_connection, %State{lock_connection_pid: nil} = state) do
-    case Electric.Postgres.LockConnection.start_link(
-           connection_opts: state.connection_opts,
-           connection_manager: self(),
-           lock_name: Keyword.fetch!(state.replication_opts, :slot_name)
-         ) do
-      {:ok, lock_connection_pid} ->
+    opts = [
+      connection_opts: state.connection_opts,
+      connection_manager: self(),
+      lock_name: Keyword.fetch!(state.replication_opts, :slot_name)
+    ]
+
+    case start_lock_connection(opts) do
+      {:ok, pid, connection_opts} ->
+        state = %{state | lock_connection_pid: pid, connection_opts: connection_opts}
+
         Electric.StackSupervisor.dispatch_stack_event(
           state.stack_events_registry,
           state.stack_id,
           :waiting_for_connection_lock
         )
 
         Process.send_after(self(), :log_lock_connection_status, @lock_status_logging_interval)
-        {:noreply, %{state | lock_connection_pid: lock_connection_pid}}
+        {:noreply, state}
 
       {:error, reason} ->
         handle_connection_error(reason, state, "lock_connection")
@@ -445,32 +449,27 @@ defmodule Electric.Connection.Manager do
      }}
   end
 
-  defp start_replication_client(opts) do
-    case Electric.Postgres.ReplicationClient.start_link(opts) do
+  defp start_lock_connection(opts) do
+    case Electric.Postgres.LockConnection.start_link(opts) do
       {:ok, pid} ->
-        {:ok, pid, Keyword.fetch!(opts, :connection_opts)}
-
-      {:error, %Postgrex.Error{message: "ssl not available"}} = error ->
-        sslmode = get_in(opts, [:connection_opts, :sslmode])
+        {:ok, pid, opts[:connection_opts]}
 
-        if sslmode == :require do
-          error
-        else
-          if not is_nil(sslmode) do
-            # Only log a warning when there's an explicit sslmode parameter in the database
-            # config, meaning the user has requested a certain sslmode.
-            Logger.warning(
-              "Failed to connect to the database using SSL. Trying again, using an unencrypted connection."
-            )
-          end
-
-          opts
-          |> Keyword.update!(:connection_opts, &Keyword.put(&1, :ssl, false))
-          |> start_replication_client()
+      error ->
+        with {:ok, opts} <- maybe_fallback_to_no_ssl(error, opts) do
+          start_lock_connection(opts)
         end
+    end
+  end
+
+  defp start_replication_client(opts) do
+    case Electric.Postgres.ReplicationClient.start_link(opts) do
+      {:ok, pid} ->
+        {:ok, pid, opts[:connection_opts]}
 
       error ->
-        error
+        with {:ok, opts} <- maybe_fallback_to_no_ssl(error, opts) do
+          start_replication_client(opts)
+        end
     end
   end
 
@@ -488,6 +487,30 @@ defmodule Electric.Connection.Manager do
     )
   end
 
+  defp maybe_fallback_to_no_ssl(
+         {:error, %Postgrex.Error{message: "ssl not available"}} = error,
+         opts
+       ) do
+    sslmode = get_in(opts, [:connection_opts, :sslmode])
+
+    if sslmode == :require do
+      error
+    else
+      if not is_nil(sslmode) do
+        # Only log a warning when there's an explicit sslmode parameter in the database
+        # config, meaning the user has requested a certain sslmode.
+        Logger.warning(
+          "Failed to connect to the database using SSL. Trying again, using an unencrypted connection."
+        )
+      end
+
+      opts = Keyword.update!(opts, :connection_opts, &Keyword.put(&1, :ssl, false))
+      {:ok, opts}
+    end
+  end
+
+  defp maybe_fallback_to_no_ssl(error, _opts), do: error
+
   defp handle_connection_error(
          {:shutdown, {:failed_to_start_child, Electric.Postgres.ReplicationClient, error}},
          state,