From ccc39a4ad605d2bd5f6d85fbb8067046961cdecb Mon Sep 17 00:00:00 2001
From: Donal McBreen <donal@basecamp.com>
Date: Thu, 12 Oct 2023 10:25:16 +0200
Subject: [PATCH] Run solid_queue with SQLite

Update the tests to run solid_queue on SQLite.

They can be triggered by:
```
TARGET_DB=sqlite rails test
```

The adapter is prone to raising `SQLite3::BusyException`s when
concurrent transactions occur. Preventing this requires a couple of
patches to the adapter.

1. Implement retry with backoff - add a `retries` config setting
to the adapter and sleep progressively longer for each retry. This
setting is currently in the Rails main branch, but that implementation
has no backoff. That doesn't work well in our case.
1. Always create immediate transactions - SQLite by default creates
deferred transactions, which don't take a write lock. Then later if
there is a write it tries to upgrade the lock. This won't work if the
transaction has a stale read so retrying the write by itself is not
possible. Starting with an immediate transaction moves the write lock to
that point and ensures that we only get blocked on a retryable
transaction.
---
 .github/workflows/main.yml                |  2 +-
 lib/solid_queue/supervisor.rb             |  1 +
 test/dummy/config/database.yml            | 18 ++++++++++++++
 test/dummy/config/initializers/sqlite3.rb | 30 +++++++++++++++++++++++
 test/dummy/config/solid_queue.yml         |  2 +-
 test/test_helper.rb                       | 10 ++++++++
 6 files changed, 61 insertions(+), 2 deletions(-)
 create mode 100644 test/dummy/config/initializers/sqlite3.rb

diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 29819e64..1c798f83 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -9,7 +9,7 @@ jobs:
       fail-fast: false
       matrix:
         ruby-version: [3.2.2]
-        database: [mysql]
+        database: [mysql, sqlite]
     services:
       mysql:
         image: mysql:8.0.31
diff --git a/lib/solid_queue/supervisor.rb b/lib/solid_queue/supervisor.rb
index c053e803..3f2a1444 100644
--- a/lib/solid_queue/supervisor.rb
+++ b/lib/solid_queue/supervisor.rb
@@ -117,6 +117,7 @@ def start_runner(runner)
 
         pid = fork do
           runner.start
+          exit!
         end
 
         forks[pid] = runner
diff --git a/test/dummy/config/database.yml b/test/dummy/config/database.yml
index 8af24d93..cc9551a1 100644
--- a/test/dummy/config/database.yml
+++ b/test/dummy/config/database.yml
@@ -5,6 +5,22 @@
 #   gem "mysql2"
 #
 
+<% if ENV["TARGET_DB"] == "sqlite" %>
+default: &default
+  adapter: sqlite3
+  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 50 } %>
+  retries: 100
+
+development:
+  <<: *default
+  database: db/development.sqlite
+
+test:
+  <<: *default
+  pool: 20
+  database: db/test.sqlite
+
+<% else %>
 default: &default
   adapter: mysql2
   username: root
@@ -20,3 +36,5 @@ test:
   <<: *default
   pool: 20
   database: solid_queue_test
+<% end %>
+
diff --git a/test/dummy/config/initializers/sqlite3.rb b/test/dummy/config/initializers/sqlite3.rb
new file mode 100644
index 00000000..80d0fec0
--- /dev/null
+++ b/test/dummy/config/initializers/sqlite3.rb
@@ -0,0 +1,30 @@
+module SqliteImmediateTransactions
+  def begin_db_transaction
+    log("begin immediate transaction", "TRANSACTION") do
+      with_raw_connection(allow_retry: true, materialize_transactions: false) do |conn|
+        conn.transaction(:immediate)
+      end
+    end
+  end
+end
+
+module SQLite3Configuration
+  private
+    def configure_connection
+      super
+
+      if @config[:retries]
+        retries = self.class.type_cast_config_to_integer(@config[:retries])
+        raw_connection.busy_handler do |count|
+          (count <= retries).tap { |result| sleep count * 0.001 if result }
+        end
+      end
+    end
+end
+
+ActiveSupport.on_load :active_record do
+  if defined?(ActiveRecord::ConnectionAdapters::SQLite3Adapter)
+    ActiveRecord::ConnectionAdapters::SQLite3Adapter.prepend SqliteImmediateTransactions
+    ActiveRecord::ConnectionAdapters::SQLite3Adapter.prepend SQLite3Configuration
+  end
+end
diff --git a/test/dummy/config/solid_queue.yml b/test/dummy/config/solid_queue.yml
index df780efe..9ce3cdad 100644
--- a/test/dummy/config/solid_queue.yml
+++ b/test/dummy/config/solid_queue.yml
@@ -5,7 +5,7 @@ default: &default
     default:
       pool_size: 5
   scheduler:
-    polling_interval: 300
+    polling_interval: 1
     batch_size: 500
 
 development:
diff --git a/test/test_helper.rb b/test/test_helper.rb
index eb7974f6..e74b20a5 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -15,6 +15,16 @@
   ActiveSupport::TestCase.fixtures :all
 end
 
+module BlockLogDeviceTimeoutExceptions
+  def write(...)
+    # Prevents TimeoutExceptions from occurring during log writing, where they will be swallowed
+    # See https://bugs.ruby-lang.org/issues/9115
+    Thread.handle_interrupt(Timeout::Error => :never, Timeout::ExitException => :never) { super }
+  end
+end
+
+Logger::LogDevice.prepend(BlockLogDeviceTimeoutExceptions)
+
 class ActiveSupport::TestCase
   setup do
     SolidQueue.logger = ActiveSupport::Logger.new(nil)