fix: sync HubStorage on post-init isolation_level change; stabilize specs

SeanLF · claude · SeanLF · commit 3ce928c677a7 · 2026-07-11T10:09:00.000-04:00
Two follow-ups from review:

- Configuration#isolation_level= now applies the level to HubStorage when
  the SDK is already initialized, so changing Sentry.configuration.isolation_level
  after Sentry.init takes effect instead of leaving the SDK on the old backend.
  The default is assigned to the ivar directly in initialize so a throwaway
  Configuration.new cannot clobber the active isolation level (only Sentry.init
  builds the live config).

- Make the :fiber isolation_level specs deterministic across Ruby versions by
  stubbing fiber_storage_available?, and add an explicit downgrade-to-:thread
  spec. Previously these asserted :fiber unconditionally and would fail on the
  Ruby &lt; 3.2 CI cells, where :fiber correctly falls back to :thread.

Co-Authored-By: Claude Opus 4.8 (1M context) &lt;noreply@anthropic.com&gt;
diff --git a/sentry-ruby/lib/sentry/configuration.rb b/sentry-ruby/lib/sentry/configuration.rb
@@ -555,7 +555,10 @@ def initialize
       self.capture_queue_time = true
       self.org_id = nil
       self.strict_trace_continuation = false
-      self.isolation_level = :thread
+      # Assign the ivar directly rather than through the setter: the default must
+      # not sync HubStorage (a throwaway Configuration.new would otherwise clobber
+      # the active isolation level). init and the setter handle syncing.
+      @isolation_level = :thread
 
       spotlight_env = ENV["SENTRY_SPOTLIGHT"]
       spotlight_bool = Sentry::Utils::EnvHelper.env_to_bool(spotlight_env, strict: true)
@@ -634,6 +637,11 @@ def isolation_level=(level)
       end
 
       @isolation_level = applied
+
+      # Keep the active hub storage in sync when the level is changed after the
+      # SDK is initialized. During `Sentry.init` the config block runs before the
+      # SDK is initialized, so init applies the level to HubStorage itself.
+      Sentry::HubStorage.isolation_level = applied if Sentry.initialized?
     end
 
     def breadcrumbs_logger=(logger)
diff --git a/sentry-ruby/spec/sentry/configuration_spec.rb b/sentry-ruby/spec/sentry/configuration_spec.rb
@@ -702,6 +702,9 @@ class SentryConfigurationSample < Sentry::Configuration
     end
 
     it "accepts :thread and :fiber" do
+      # stub availability so the :fiber assertion is deterministic on Rubies < 3.2
+      allow(Sentry::HubStorage).to receive(:fiber_storage_available?).and_return(true)
+
       subject.isolation_level = :fiber
       expect(subject.isolation_level).to eq(:fiber)
 
@@ -710,6 +713,7 @@ class SentryConfigurationSample < Sentry::Configuration
     end
 
     it "coerces string values" do
+      allow(Sentry::HubStorage).to receive(:fiber_storage_available?).and_return(true)
       subject.isolation_level = "fiber"
       expect(subject.isolation_level).to eq(:fiber)
     end
@@ -719,6 +723,14 @@ class SentryConfigurationSample < Sentry::Configuration
         .to raise_error(ArgumentError, /isolation_level must be one of/)
     end
 
+    context "when Fiber storage is available" do
+      it "keeps :fiber" do
+        allow(Sentry::HubStorage).to receive(:fiber_storage_available?).and_return(true)
+        subject.isolation_level = :fiber
+        expect(subject.isolation_level).to eq(:fiber)
+      end
+    end
+
     context "when Fiber storage is unavailable" do
       it "falls back to :thread with a warning" do
         allow(Sentry::HubStorage).to receive(:fiber_storage_available?).and_return(false)
@@ -727,13 +739,6 @@ class SentryConfigurationSample < Sentry::Configuration
         expect(subject.isolation_level).to eq(:thread)
       end
     end
-
-    context "when Fiber storage is available", when: { fiber_storage?: [] } do
-      it "keeps :fiber" do
-        subject.isolation_level = :fiber
-        expect(subject.isolation_level).to eq(:fiber)
-      end
-    end
   end
 
   describe "#validate" do
diff --git a/sentry-ruby/spec/sentry/hub_storage_spec.rb b/sentry-ruby/spec/sentry/hub_storage_spec.rb
@@ -16,11 +16,18 @@
       expect(described_class.isolation_level).to eq(:thread)
     end
 
-    it "accepts :fiber" do
+    it "accepts :fiber when Fiber storage is available" do
+      allow(described_class).to receive(:fiber_storage_available?).and_return(true)
       described_class.isolation_level = :fiber
       expect(described_class.isolation_level).to eq(:fiber)
     end
 
+    it "downgrades :fiber to :thread when Fiber storage is unavailable" do
+      allow(described_class).to receive(:fiber_storage_available?).and_return(false)
+      described_class.isolation_level = :fiber
+      expect(described_class.isolation_level).to eq(:thread)
+    end
+
     it "raises ArgumentError for an unknown level" do
       expect { described_class.isolation_level = :process }
         .to raise_error(ArgumentError, /isolation_level must be one of/)
diff --git a/sentry-ruby/spec/sentry_spec.rb b/sentry-ruby/spec/sentry_spec.rb
@@ -110,6 +110,20 @@
     end
   end
 
+  describe "changing isolation_level after init", when: { fiber_storage?: [] } do
+    before { perform_basic_setup }
+
+    after { Sentry::HubStorage.isolation_level = :thread }
+
+    it "applies the change to the active hub storage" do
+      expect(Sentry::HubStorage.isolation_level).to eq(:thread)
+
+      Sentry.configuration.isolation_level = :fiber
+
+      expect(Sentry::HubStorage.isolation_level).to eq(:fiber)
+    end
+  end
+
   describe "fiber isolation", when: { fiber_storage?: [] } do
     before do
       perform_basic_setup { |config| config.isolation_level = :fiber }
