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Make agent index generation stable irrespective of filesystem iteration order #11889

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fc7d48c
refactor(agent): Make index generation immune to filesystem unordered…
bric3 Jul 8, 2026
5d8ef78
test(agent): Replace awkward stream and for loop, with a pure stream …
bric3 Jul 9, 2026
51b20c7
refactor(agent): Remove normalization for windows
bric3 Jul 9, 2026
794f5f2
refactor(agent): Remove unused `Comparator` import
bric3 Jul 9, 2026
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70 changes: 27 additions & 43 deletions dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/AgentJarIndex.java
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Original file line number Diff line number Diff line change
Expand Up @@ -7,18 +7,17 @@
import java.io.DataOutputStream;
import java.io.File;
import java.io.IOException;
import java.nio.file.FileVisitResult;
import java.nio.file.Files;
import java.nio.file.LinkOption;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.SimpleFileVisitor;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.jar.JarFile;
import java.util.stream.Stream;
import java.util.zip.ZipEntry;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
Expand Down Expand Up @@ -90,7 +89,7 @@ public static AgentJarIndex readIndex(JarFile agentJar) {
* Generates an index from the contents of the 'build/resources' directory that makes up the agent
* jar.
*/
static class IndexGenerator extends SimpleFileVisitor<Path> {
static class IndexGenerator {
private static final Set<String> ignoredFileNames =
new HashSet<>(Arrays.asList("MANIFEST.MF", "NOTICE", "LICENSE.renamed"));

Expand All @@ -102,17 +101,31 @@ static class IndexGenerator extends SimpleFileVisitor<Path> {
private final List<String> collectedEntryKeys = new ArrayList<>();
private final List<Integer> collectedPrefixIds = new ArrayList<>();

private Path prefixRoot;
private int prefixId;

IndexGenerator(Path resourcesDir) {
this.resourcesDir = resourcesDir;

prefixTrie.put("datadog.*", 0);
}

void buildIndex() throws IOException {
Files.walkFileTree(resourcesDir, this);
Set<String> seen = new HashSet<>();
try (Stream<Path> paths = Files.walk(resourcesDir)) {
paths
.filter(path -> Files.isRegularFile(path, LinkOption.NOFOLLOW_LINKS))
.map(resourcesDir::relativize)
.sorted()
.filter(entry -> entry.getNameCount() >= 2)
.forEach(
entry -> {
String prefix = entry.getName(0) + "/";
int prefixId = prefixIdFor(prefix);
String entryKey = computeEntryKey(entry.subpath(1, entry.getNameCount()));
if (null != entryKey && seen.add(prefixId + "\0" + entryKey)) {
collectedEntryKeys.add(entryKey);
collectedPrefixIds.add(prefixId);
}
});
}

for (int i = 0; i < collectedEntryKeys.size(); i++) {
prefixTrie.put(collectedEntryKeys.get(i), collectedPrefixIds.get(i));
Expand Down Expand Up @@ -152,42 +165,13 @@ private String getPrefix(int prefixId) {
return prefixes.get(prefixId - 1);
}

@Override
public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) {
if (dir.getParent().equals(resourcesDir)) {
String prefix = dir.getFileName() + "/";
prefixRoot = dir;
prefixId = 1 + prefixes.indexOf(prefix);
if (prefixId < 1) {
prefixes.add(prefix);
prefixId = prefixes.size();
}
}
return FileVisitResult.CONTINUE;
}

@Override
public FileVisitResult postVisitDirectory(Path dir, IOException exc) {
if (dir.equals(prefixRoot)) {
prefixRoot = null;
}
return FileVisitResult.CONTINUE;
}

@Override
public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) {
if (null != prefixRoot) {
String entryKey = computeEntryKey(prefixRoot.relativize(file));
if (null != entryKey) {
collectedEntryKeys.add(entryKey);
collectedPrefixIds.add(prefixId);
if (entryKey.endsWith("*")) {
// optimization: wildcard will match everything under here so can skip
return FileVisitResult.SKIP_SIBLINGS;
}
}
private int prefixIdFor(String prefix) {
int prefixId = 1 + prefixes.indexOf(prefix);
if (prefixId < 1) {
prefixes.add(prefix);
prefixId = prefixes.size();
}
return FileVisitResult.CONTINUE;
return prefixId;
}

static String computeEntryKey(Path path) {
Expand Down
70 changes: 70 additions & 0 deletions dd-java-agent/agent-bootstrap/src/test/java/datadog/trace/bootstrap/AgentJarIndexTest.java
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Original file line number Diff line number Diff line change
@@ -1,13 +1,18 @@
package datadog.trace.bootstrap;

import static org.junit.jupiter.api.Assertions.assertArrayEquals;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertNotNull;
import static org.junit.jupiter.api.Assertions.assertNull;

import java.io.BufferedInputStream;
import java.io.DataInputStream;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.Arrays;
import java.util.List;
import java.util.jar.JarFile;
import java.util.zip.ZipEntry;
import java.util.zip.ZipOutputStream;
Expand Down Expand Up @@ -103,6 +108,25 @@ private static void createFile(Path root, String relativePath) throws IOExceptio
Files.createFile(file);
}

private static Path writeIndex(Path resourcesDir, Path indexFile) throws IOException {
AgentJarIndex.IndexGenerator generator = new AgentJarIndex.IndexGenerator(resourcesDir);
generator.buildIndex();
generator.writeIndex(indexFile);
return indexFile;
}

private static List<String> readPrefixes(Path indexFile) throws IOException {
try (DataInputStream in =
new DataInputStream(new BufferedInputStream(Files.newInputStream(indexFile)))) {
int prefixCount = in.readInt();
String[] prefixes = new String[prefixCount];
for (int i = 0; i < prefixCount; i++) {
prefixes[i] = in.readUTF();
}
return Arrays.asList(prefixes);
}
}
Comment on lines +111 to +128

@PerfectSlayer PerfectSlayer Jul 9, 2026

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🎯 suggestion: ‏What about reusing buildAndReadIndex instead?

@bric3 bric3 Jul 9, 2026

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I introduced writeIndex (returns a Path) / readPrefixes (returns a List) because these tests assert the serialized index, not only the lookup behavior after deserialization which is the goal of buildAndReadIndex (returns a AgentJarIndex) to me.
In particular for prefix ordering readPrefixes is what the test needs.


@Test
void classEntryNameResolvesBootstrapClassToTopLevel(@TempDir Path tempDir) throws Exception {
Path resources = tempDir.resolve("resources");
Expand Down Expand Up @@ -199,6 +223,52 @@ void multiplePrefixesAreIndexedIndependently(@TempDir Path tempDir) throws Excep
index.classEntryName("com.datadoghq.stats.StatsClient"));
}

@Test
void buildIndexWritesPrefixesInSortedOrder(@TempDir Path tempDir) throws Exception {
Path resources = tempDir.resolve("resources");
createFile(resources, "metrics/com/datadoghq/stats/StatsClient.classdata");
createFile(resources, "inst/datadog/trace/instrumentation/servlet/ServletAdvice.classdata");
createFile(resources, "appsec/com/datadog/appsec/Event.classdata");

Path indexFile = writeIndex(resources, tempDir.resolve("dd-java-agent.index"));

assertEquals(Arrays.asList("appsec/", "inst/", "metrics/"), readPrefixes(indexFile));
}

@Test
void buildIndexIgnoresTopLevelFilesWhenCollectingPrefixes(@TempDir Path tempDir)
throws Exception {
Path resources = tempDir.resolve("resources");
createFile(resources, "root-resource.properties");
createFile(resources, "inst/datadog/trace/instrumentation/servlet/ServletAdvice.classdata");

Path indexFile = writeIndex(resources, tempDir.resolve("dd-java-agent.index"));

assertEquals(Arrays.asList("inst/"), readPrefixes(indexFile));
}

@Test
void buildIndexIsIndependentOfDirectoryCreationOrder(@TempDir Path tempDir) throws Exception {
Path buildResources = tempDir.resolve("build-resources");
createFile(buildResources, "appsec/com/datadog/appsec/Event.classdata");
createFile(buildResources, "ci-visibility/com/datadog/ci/Visibility.classdata");
createFile(buildResources, "cws-tls/com/datadog/cws/Tls.classdata");
createFile(
buildResources, "inst/datadog/trace/instrumentation/servlet/ServletAdvice.classdata");

Path deployResources = tempDir.resolve("deploy-resources");
createFile(deployResources, "cws-tls/com/datadog/cws/Tls.classdata");
createFile(deployResources, "ci-visibility/com/datadog/ci/Visibility.classdata");
createFile(deployResources, "appsec/com/datadog/appsec/Event.classdata");
createFile(
deployResources, "inst/datadog/trace/instrumentation/servlet/ServletAdvice.classdata");

Path buildIndex = writeIndex(buildResources, tempDir.resolve("build-dd-java-agent.index"));
Path deployIndex = writeIndex(deployResources, tempDir.resolve("deploy-dd-java-agent.index"));

assertArrayEquals(Files.readAllBytes(buildIndex), Files.readAllBytes(deployIndex));
}

@Test
void buildIndexWithEmptyResourcesDirProducesWorkingIndex(@TempDir Path tempDir) throws Exception {
Path resources = tempDir.resolve("resources");
Expand Down