JCStress—驗證你的并發程序是否正確
作者：架構師筆記
JCStress是一個強大的工具，可以幫助開發人員測試和驗證Java并發程序的正確性。它廣泛應用于Java開發社區，并被認為是Java并發測試領域的事實標準。使用JCStress可以提高并發程序的質量和可靠性，減少并發問題的出現。
背景
JCStress（Java Concurrency Stress Tests）是一個用于測試和驗證Java并發程序正確性的工具。它是OpenJDK項目的一部分，旨在幫助開發人員發現并發程序中的競態條件、死鎖、內存可見性等問題。
JCStress提供了一組注解和API，使得編寫并發測試變得簡單和方便。使用JCStress，您可以定義和運行各種類型的并發測試，包括多線程競爭測試、內存可見性測試、有序性測試等。JCStress會自動執行大量的并發測試用例，并生成詳細的測試報告，以幫助您分析和理解并發程序的行為。
JCStress的主要特點包括：
- 并發測試：JCStress支持編寫各種類型的并發測試，包括競爭條件測試、死鎖測試、內存可見性測試等。
- 自動化測試：JCStress會自動執行大量的并發測試用例，并嘗試發現潛在的并發問題。
- 測試報告：JCStress生成詳細的測試報告，包括測試結果、執行時間、線程狀態等信息，以幫助您分析并發程序的行為。
- 高度可配置：JCStress提供了豐富的配置選項，如線程數、迭代次數、測試模式等，以滿足不同類型的并發測試需求。
JCStress使用
使用JCStress編寫和運行并發測試的一般步驟包括：
- 在測試類或測試方法上使用JCStress提供的注解，如@JCStressTest、@Actor、@Outcome等，來定義并發測試。
- 使用JCStress提供的命令行工具或API來運行并發測試，并指定相關的選項和參數。
- 分析和解釋JCStress生成的測試報告，以發現并發問題并進行修復。
JCStress使用示例
測試用例1：
/*
This is our first concurrency test. It is deliberately simplistic to show
testing approaches, introduce JCStress APIs, etc.
Suppose we want to see if the field increment is atomic. We can make test
with two actors, both actors incrementing the field and recording what
value they observed into the result object. As JCStress runs, it will
invoke these methods on the objects holding the field once per each actor
and instance, and record what results are coming from there.
Done enough times, we will get the history of observed results, and that
would tell us something about the concurrent behavior.
How to run this test:
$ java -jar jcstress-samples/target/jcstress.jar -t API_01_Simple
...
.......... [OK] org.openjdk.jcstress.samples.api.API_01_Simple
Scheduling class:
actor1: package group 0, core group 0
actor2: package group 0, core group 0
CPU allocation:
actor1: CPU #3, package #0, core #3
actor2: CPU #35, package #0, core #3
Compilation: split
actor1: C2
actor2: C2
JVM args: []
RESULT SAMPLES FREQ EXPECT DESCRIPTION
1, 1 46,946,789 10.1% Interesting Both actors came up with the same value: atomicity failure.
1, 2 110,240,149 23.8% Acceptable actor1 incremented, then actor2.
2, 1 306,529,420 66.1% Acceptable actor2 incremented, then actor1.
*/
// Mark the class as JCStress test.
@JCStressTest
// These are the test outcomes.
@Outcome(id = "1, 1", expect = ACCEPTABLE_INTERESTING, desc = "Both actors came up with the same value: atomicity failure.")
@Outcome(id = "1, 2", expect = ACCEPTABLE, desc = "actor1 incremented, then actor2.")
@Outcome(id = "2, 1", expect = ACCEPTABLE, desc = "actor2 incremented, then actor1.")
// This is a state object
@State
public class API_01_Simple {
int v;
@Actor
public void actor1(II_Result r) {
r.r1 = ++v; // record result from actor1 to field r1
}
@Actor
public void actor2(II_Result r) {
r.r2 = ++v; // record result from actor2 to field r2
}
}測試用例2：
@JCStressTest
@Outcome(id = {"1, 2", "2, 1"}, expect = ACCEPTABLE, desc = "Mutex works")
@Outcome(id = "1, 1", expect = FORBIDDEN, desc = "Mutex failure")
@State
public class Mutex_06_Semaphore {
/*
How to run this test:
$ java -jar jcstress-samples/target/jcstress.jar -t Mutex_06_Semaphore
*/
/*
----------------------------------------------------------------------------------------------------------
Single-permit Semaphore can be used as a crude mutex too. Of course, this primitive
is much more flexible, it can admit a few threads at once with more permits.
On x86_64, AArch64, PPC64:
RESULT SAMPLES FREQ EXPECT DESCRIPTION
1, 1 0 0.00% Forbidden Mutex failure
1, 2 254,394,919 50.23% Acceptable Mutex works
2, 1 252,081,625 49.77% Acceptable Mutex works
*/
private final Semaphore semaphore = new Semaphore(1);
private int v;
@Actor
public void actor1(II_Result r) {
try {
semaphore.acquire();
// critical section
r.r1 = ++v;
semaphore.release();
} catch (InterruptedException e) {
throw new IllegalStateException(e);
}
}
@Actor
public void actor2(II_Result r) {
try {
semaphore.acquire();
// critical section
r.r2 = ++v;
semaphore.release();
} catch (InterruptedException e) {
throw new IllegalStateException(e);
}
}
}JCStress總結
JCStress是一個強大的工具，可以幫助開發人員測試和驗證Java并發程序的正確性。它廣泛應用于Java開發社區，并被認為是Java并發測試領域的事實標準。使用JCStress可以提高并發程序的質量和可靠性，減少并發問題的出現。
參考資料：
【1】https://github.com/openjdk/jcstress/tree/master/jcstress-samples/src/main/java/org/openjdk/jcstress/samples。
責任編輯：姜華
來源：
今日頭條
