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Fix ConfigUtil#getString ConcurrentModificationException #6841

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merged 7 commits into from
Nov 1, 2024
Merged

Fix ConfigUtil#getString ConcurrentModificationException #6841

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ab84470
Fix ConcurrentModificationException #6732
neugartf Sep 25, 2024
b115c5a
Move to stringPropertyNames in order to iterate on a stable list.
neugartf Sep 26, 2024
af48863
Improve stream handling of system property
neugartf Sep 26, 2024
329c05d
Merge branch 'open-telemetry:main' into main
neugartf Sep 26, 2024
d736406
Cloning properties in order to safely iterate over them
neugartf Sep 29, 2024
56ea3da
Add ConfigUtil#safeSystemProperties() for safe access to system prope…
jack-berg Oct 30, 2024
08d09ea
remove comment
jack-berg Oct 30, 2024
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16 changes: 15 additions & 1 deletion api/all/src/main/java/io/opentelemetry/api/internal/ConfigUtil.java
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Original file line number Diff line number Diff line change
Expand Up @@ -5,8 +5,10 @@

package io.opentelemetry.api.internal;

import java.util.ConcurrentModificationException;
import java.util.Locale;
import java.util.Map;
import java.util.Properties;
import javax.annotation.Nullable;

/**
Expand All @@ -19,6 +21,17 @@ public final class ConfigUtil {

private ConfigUtil() {}

/**
* Returns a copy of system properties which is safe to iterate over.
*
* <p>In java 8 and android environments, iterating through system properties may trigger {@link
* ConcurrentModificationException}. This method ensures callers can iterate safely without risk
* of exception. See https://github.com/open-telemetry/opentelemetry-java/issues/6732 for details.
*/
public static Properties safeSystemProperties() {
return (Properties) System.getProperties().clone();
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Cloning seems to be the simplest way to accommodate various use cases. Anything other option that returns Properties ends up mimicking the logic of clone() anyway. If clone() ends up being too expensive (I doubt it), we can cache a copy.

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I'm ok with it

ConfigUtil.getString(..) is already slow (too slow to be used on the hotpath) since it normalizes all the entry keys on each call

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If clone() ends up being too expensive

clone is only needed on jdk8 and android so we could skip it on other jdks if we so wish. Untested code follows

private static final CLONE_PROPERTIES = System.getProperty("java.version").equals("0") // android
  || System.getProperty("java.specification.version").startsWith("1."); // jdk8

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clone is only needed on jdk8 and android so we could skip it on other jdks if we so wish.

That's true. I'd prefer to keep that in our back pocket in case we need it. As a general rule, I think we avoid runtime-specific code unless we have a strong reason (subjective definition of "strong").

}

/**
* Return the system property or environment variable for the {@code key}.
*
Expand All @@ -33,8 +46,9 @@ private ConfigUtil() {}
*/
public static String getString(String key, String defaultValue) {
String normalizedKey = normalizePropertyKey(key);

String systemProperty =
System.getProperties().entrySet().stream()
safeSystemProperties().entrySet().stream()
.filter(entry -> normalizedKey.equals(normalizePropertyKey(entry.getKey().toString())))
.map(entry -> entry.getValue().toString())
.findFirst()
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49 changes: 49 additions & 0 deletions api/all/src/test/java/io/opentelemetry/api/internal/ConfigUtilTest.java
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Expand Up @@ -6,7 +6,15 @@
package io.opentelemetry.api.internal;

import static org.assertj.core.api.Assertions.assertThat;
import static org.assertj.core.api.Assertions.assertThatCode;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import org.junit.jupiter.api.Test;
import org.junitpioneer.jupiter.SetSystemProperty;

Expand Down Expand Up @@ -56,4 +64,45 @@ void defaultIfnull() {
assertThat(ConfigUtil.defaultIfNull("val1", "val2")).isEqualTo("val1");
assertThat(ConfigUtil.defaultIfNull(null, "val2")).isEqualTo("val2");
}

@Test
@SuppressWarnings("ReturnValueIgnored")
void systemPropertiesConcurrentAccess() throws ExecutionException, InterruptedException {
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This test fails on java 8 if you call System.getProperties() instead of ConfigUtil#safeSystemProperties().

int threads = 4;
ExecutorService executor = Executors.newFixedThreadPool(threads);
try {
int cycles = 1000;
CountDownLatch latch = new CountDownLatch(1);
List<Future<?>> futures = new ArrayList<>();
for (int i = 0; i < threads; i++) {
futures.add(
executor.submit(
() -> {
try {
latch.await();
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
}

for (int j = 0; j < cycles; j++) {
String property = "prop " + j;
System.setProperty(property, "a");
System.getProperties().remove(property);
}
}));
}

latch.countDown();
for (int i = 0; i < cycles; i++) {
assertThatCode(() -> ConfigUtil.getString("x", "y")).doesNotThrowAnyException();
}

for (Future<?> future : futures) {
future.get();
}

} finally {
executor.shutdownNow();
}
}
}
3 changes: 2 additions & 1 deletion ...rc/main/java/io/opentelemetry/sdk/autoconfigure/spi/internal/DefaultConfigProperties.java
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Original file line number Diff line number Diff line change
Expand Up @@ -47,7 +47,8 @@ public final class DefaultConfigProperties implements ConfigProperties {
* priority over environment variables.
*/
public static DefaultConfigProperties create(Map<String, String> defaultProperties) {
return new DefaultConfigProperties(System.getProperties(), System.getenv(), defaultProperties);
return new DefaultConfigProperties(
ConfigUtil.safeSystemProperties(), System.getenv(), defaultProperties);
}

/**
Expand Down
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