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JCStress—驗(yàn)證你的并發(fā)程序是否正確
背景
JCStress（Java Concurrency Stress Tests）是一個(gè)用于測試和驗(yàn)證Java并發(fā)程序正確性的工具。它是OpenJDK項(xiàng)目的一部分，旨在幫助開發(fā)人員發(fā)現(xiàn)并發(fā)程序中的競態(tài)條件、死鎖、內(nèi)存可見性等問題。
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JCStress提供了一組注解和API，使得編寫并發(fā)測試變得簡單和方便。使用JCStress，您可以定義和運(yùn)行各種類型的并發(fā)測試，包括多線程競爭測試、內(nèi)存可見性測試、有序性測試等。JCStress會自動執(zhí)行大量的并發(fā)測試用例，并生成詳細(xì)的測試報(bào)告，以幫助您分析和理解并發(fā)程序的行為。
JCStress的主要特點(diǎn)包括：
- 并發(fā)測試：JCStress支持編寫各種類型的并發(fā)測試，包括競爭條件測試、死鎖測試、內(nèi)存可見性測試等。
- 自動化測試：JCStress會自動執(zhí)行大量的并發(fā)測試用例，并嘗試發(fā)現(xiàn)潛在的并發(fā)問題。
- 測試報(bào)告：JCStress生成詳細(xì)的測試報(bào)告，包括測試結(jié)果、執(zhí)行時(shí)間、線程狀態(tài)等信息，以幫助您分析并發(fā)程序的行為。
- 高度可配置：JCStress提供了豐富的配置選項(xiàng)，如線程數(shù)、迭代次數(shù)、測試模式等，以滿足不同類型的并發(fā)測試需求。
JCStress使用
使用JCStress編寫和運(yùn)行并發(fā)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(fā)測試。
- 使用JCStress提供的命令行工具或API來運(yùn)行并發(fā)測試，并指定相關(guān)的選項(xiàng)和參數(shù)。
- 分析和解釋JCStress生成的測試報(bào)告，以發(fā)現(xiàn)并發(fā)問題并進(jìn)行修復(fù)。
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(jié)
JCStress是一個(gè)強(qiáng)大的工具，可以幫助開發(fā)人員測試和驗(yàn)證Java并發(fā)程序的正確性。它廣泛應(yīng)用于Java開發(fā)社區(qū)，并被認(rèn)為是Java并發(fā)測試領(lǐng)域的事實(shí)標(biāo)準(zhǔn)。使用JCStress可以提高并發(fā)程序的質(zhì)量和可靠性，減少并發(fā)問題的出現(xiàn)。
參考資料：
【1】https://github.com/openjdk/jcstress/tree/master/jcstress-samples/src/main/java/org/openjdk/jcstress/samples。
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