From d41213948e8f8c8f872a2cbbc3dde5364ec3bfca Mon Sep 17 00:00:00 2001 From: Jake Wharton Date: Fri, 22 Mar 2024 10:12:56 -0400 Subject: [PATCH] Gracefully handle parse failure with locking Before we would poison the map with the lock object so the second caller would get a weird ClassCastException. --- CHANGELOG.md | 2 +- .../src/test/java/retrofit2/RetrofitTest.java | 86 +++++++++++++++++++ .../src/main/java/retrofit2/Retrofit.java | 69 +++++++++------ 3 files changed, 129 insertions(+), 28 deletions(-) diff --git a/CHANGELOG.md b/CHANGELOG.md index 511a9e0516..8923355388 100644 --- a/CHANGELOG.md +++ b/CHANGELOG.md @@ -12,7 +12,7 @@ **Fixed** - - Nothing yet! + - Ensure that exceptions thrown from failure to parse method annotations can be observed by multiple threads/callers. Previously only the first caller would see the actual parsing exception and other callers would get a cryptic `ClassCastException`. ## [2.10.0] - 2024-03-18 diff --git a/retrofit/java-test/src/test/java/retrofit2/RetrofitTest.java b/retrofit/java-test/src/test/java/retrofit2/RetrofitTest.java index 20886bc785..5bd2c26138 100644 --- a/retrofit/java-test/src/test/java/retrofit2/RetrofitTest.java +++ b/retrofit/java-test/src/test/java/retrofit2/RetrofitTest.java @@ -21,6 +21,7 @@ import static org.junit.Assert.assertEquals; import static org.junit.Assert.assertNotNull; import static org.junit.Assert.assertSame; +import static org.junit.Assert.assertThrows; import static org.junit.Assert.assertTrue; import static org.junit.Assert.fail; import static retrofit2.AnnotationArraySubject.assertThat; @@ -1716,4 +1717,89 @@ public void argumentCapture() throws Exception { assertEquals("/?i=201", server.takeRequest().getPath()); } + + @Test + public void annotationParsingFailureObservedByWaitingThreads() throws InterruptedException { + AtomicInteger fails = new AtomicInteger(); + CountDownLatch startedParsing = new CountDownLatch(1); + CountDownLatch failParsing = new CountDownLatch(1); + RuntimeException failure = new RuntimeException("boom!"); + Retrofit retrofit = + new Retrofit.Builder() + .baseUrl(server.url("/")) + .addConverterFactory( + new Converter.Factory() { + @Nullable + @Override + public Converter responseBodyConverter( + Type type, Annotation[] annotations, Retrofit retrofit) { + startedParsing.countDown(); + try { + failParsing.await(); + } catch (InterruptedException e) { + throw new AssertionError(e); + } + fails.incrementAndGet(); + throw failure; + } + }) + .build(); + Annotated service = retrofit.create(Annotated.class); + + AtomicReference result1 = new AtomicReference<>(); + Thread thread1 = + new Thread( + () -> { + try { + service.method(); + } catch (RuntimeException e) { + result1.set(e); + } + }); + thread1.start(); + + // Wait for thread1 to enter the converter. This means it has inserted and taken a lock on + // parsing for the method. + startedParsing.await(); + + CountDownLatch thread2Locked = new CountDownLatch(1); + AtomicReference result2 = new AtomicReference<>(); + Thread thread2 = + new Thread( + () -> { + try { + thread2Locked.countDown(); + service.method(); + } catch (RuntimeException e) { + result2.set(e); + } + }); + thread2.start(); + thread2Locked.await(); + + // Wait for thread2 to lock on the shared object. This should be pretty fast after the last + // signal, but we have no way of knowing for sure it happened. + Thread.sleep(1_000); + + failParsing.countDown(); + thread1.join(); + thread2.join(); + + RuntimeException failure1 = result1.get(); + assertThat(failure1).isInstanceOf(IllegalArgumentException.class); + assertThat(failure1).hasCauseThat().isSameInstanceAs(failure); + + RuntimeException failure2 = result2.get(); + assertThat(failure2).isInstanceOf(IllegalArgumentException.class); + assertThat(failure2).hasCauseThat().isSameInstanceAs(failure); + + // Importantly, even though the second thread was locked waiting on the first, failure of the + // first thread caused the second thread to retry parsing. + assertThat(fails.get()).isEqualTo(2); + + // Make sure now that both threads have released the lock, new callers also retry. + RuntimeException failure3 = assertThrows(IllegalArgumentException.class, service::method); + assertThat(failure3).hasCauseThat().isSameInstanceAs(failure); + assertThat(fails.get()).isEqualTo(3); + } } diff --git a/retrofit/src/main/java/retrofit2/Retrofit.java b/retrofit/src/main/java/retrofit2/Retrofit.java index c66f821251..9e5a5bd561 100644 --- a/retrofit/src/main/java/retrofit2/Retrofit.java +++ b/retrofit/src/main/java/retrofit2/Retrofit.java @@ -212,38 +212,53 @@ private void validateServiceInterface(Class service) { } ServiceMethod loadServiceMethod(Class service, Method method) { - // Note: Once we are minSdk 24 this whole method can be replaced by computeIfAbsent. - Object lookup = serviceMethodCache.get(method); + while (true) { + // Note: Once we are minSdk 24 this whole method can be replaced by computeIfAbsent. + Object lookup = serviceMethodCache.get(method); - if (lookup instanceof ServiceMethod) { - // Happy path: method is already parsed into the model. - return (ServiceMethod) lookup; - } + if (lookup instanceof ServiceMethod) { + // Happy path: method is already parsed into the model. + return (ServiceMethod) lookup; + } - if (lookup == null) { - // Map does not contain any value. Try to put in a lock for this method. We MUST synchronize - // on the lock before it is visible to others via the map to signal we are doing the work. - Object lock = new Object(); - synchronized (lock) { - lookup = serviceMethodCache.putIfAbsent(method, lock); - if (lookup == null) { - // On successful lock insertion, perform the work and update the map before releasing. - // Other threads may be waiting on lock now and will expect the parsed model. - ServiceMethod result = ServiceMethod.parseAnnotations(this, service, method); - serviceMethodCache.put(method, result); - return result; + if (lookup == null) { + // Map does not contain any value. Try to put in a lock for this method. We MUST synchronize + // on the lock before it is visible to others via the map to signal we are doing the work. + Object lock = new Object(); + synchronized (lock) { + lookup = serviceMethodCache.putIfAbsent(method, lock); + if (lookup == null) { + // On successful lock insertion, perform the work and update the map before releasing. + // Other threads may be waiting on lock now and will expect the parsed model. + ServiceMethod result; + try { + result = ServiceMethod.parseAnnotations(this, service, method); + } catch (Throwable e) { + // Remove the lock on failure. Any other locked threads will retry as a result. + serviceMethodCache.remove(method); + throw e; + } + serviceMethodCache.put(method, result); + return result; + } } } - } - // Either the initial lookup or the attempt to put our lock in the map has returned someone - // else's lock. This means they are doing the parsing, and will update the map before releasing - // the lock. Once we can take the lock, the map is guaranteed to contain the model. - // Note: There's a chance that our effort to put a lock into the map has actually returned a - // finished model instead of a lock. In that case this code will perform a pointless lock and - // redundant lookup in the map of the same instance. This is rare, and ultimately harmless. - synchronized (lookup) { - return (ServiceMethod) serviceMethodCache.get(method); + // Either the initial lookup or the attempt to put our lock in the map has returned someone + // else's lock. This means they are doing the parsing, and will update the map before + // releasing + // the lock. Once we can take the lock, the map is guaranteed to contain the model or null. + // Note: There's a chance that our effort to put a lock into the map has actually returned a + // finished model instead of a lock. In that case this code will perform a pointless lock and + // redundant lookup in the map of the same instance. This is rare, and ultimately harmless. + synchronized (lookup) { + Object result = serviceMethodCache.get(method); + if (result == null) { + // The other thread failed its parsing. We will retry (and probably also fail). + continue; + } + return (ServiceMethod) result; + } } }