Re-enable Agent Detection on Zos (#13730)

Co-authored-by: Jason Plumb <jplumb@splunk.com>
Co-authored-by: Lauri Tulmin <ltulmin@splunk.com>

instrumentation/resources/library/src/main/java/io/opentelemetry/instrumentation/resources/CgroupV1ContainerIdExtractor.java

@@ -20,14 +20,21 @@ final class CgroupV1ContainerIdExtractor {
       Logger.getLogger(CgroupV1ContainerIdExtractor.class.getName());
   static final Path V1_CGROUP_PATH = Paths.get("/proc/self/cgroup");
   private final ContainerResource.Filesystem filesystem;
+  private final Path inputFilePath;
 
   CgroupV1ContainerIdExtractor() {
-    this(ContainerResource.FILESYSTEM_INSTANCE);
+    this(ContainerResource.FILESYSTEM_INSTANCE, V1_CGROUP_PATH);
   }
 
   // Exists for testing
   CgroupV1ContainerIdExtractor(ContainerResource.Filesystem filesystem) {
+    this(filesystem, V1_CGROUP_PATH);
+  }
+
+  // Exists for testing
+  CgroupV1ContainerIdExtractor(ContainerResource.Filesystem filesystem, Path inputFilePath) {
     this.filesystem = filesystem;
+    this.inputFilePath = inputFilePath;
   }
 
   /**
@@ -38,10 +45,10 @@ final class CgroupV1ContainerIdExtractor {
    * @return containerId
    */
   Optional<String> extractContainerId() {
-    if (!filesystem.isReadable(V1_CGROUP_PATH)) {
+    if (!filesystem.isReadable(inputFilePath)) {
       return Optional.empty();
     }
-    try (Stream<String> lines = filesystem.lines(V1_CGROUP_PATH)) {
+    try (Stream<String> lines = filesystem.lines(inputFilePath)) {
       return lines
           .filter(line -> !line.isEmpty())
           .map(CgroupV1ContainerIdExtractor::getIdFromLine)

instrumentation/resources/library/src/main/java/io/opentelemetry/instrumentation/resources/ContainerResource.java

@@ -10,10 +10,15 @@ import io.opentelemetry.api.common.AttributeKey;
 import io.opentelemetry.api.common.Attributes;
 import io.opentelemetry.sdk.resources.Resource;
 import java.io.IOException;
+import java.nio.charset.Charset;
+import java.nio.charset.UnsupportedCharsetException;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.List;
 import java.util.Optional;
+import java.util.function.Supplier;
+import java.util.logging.Level;
+import java.util.logging.Logger;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
@@ -50,12 +55,6 @@ public final class ContainerResource {
 
   // Visible for testing
   Resource buildResource() {
-    // disable container id detection on z/os
-    // https://github.com/open-telemetry/opentelemetry-java-instrumentation/issues/12418
-    String osName = System.getProperty("os.name");
-    if (osName.equalsIgnoreCase("z/OS") || osName.equalsIgnoreCase("OS/390")) {
-      return Resource.empty();
-    }
     return getContainerId()
         .map(id -> Resource.create(Attributes.of(CONTAINER_ID, id)))
         .orElseGet(Resource::empty);
@@ -76,6 +75,17 @@ public final class ContainerResource {
 
   // Exists for testing
   static class Filesystem {
+    private static final Logger logger = Logger.getLogger(Filesystem.class.getName());
+
+    private final Supplier<String> osNameSupplier;
+
+    Filesystem() {
+      this(() -> System.getProperty("os.name"));
+    }
+
+    Filesystem(Supplier<String> osNameSupplier) {
+      this.osNameSupplier = osNameSupplier;
+    }
 
     boolean isReadable(Path path) {
       return Files.isReadable(path);
@@ -83,7 +93,19 @@ public final class ContainerResource {
 
     @MustBeClosed
     Stream<String> lines(Path path) throws IOException {
-      return Files.lines(path);
+      String osName = osNameSupplier.get();
+      if (osName.equalsIgnoreCase("z/OS") || osName.equalsIgnoreCase("OS/390")) {
+        try {
+          // On z/OS the /proc tree is always encoded with IBM1047 (Canonical name: Cp1047).
+          return Files.lines(path, Charset.forName("Cp1047"));
+        } catch (UnsupportedCharsetException e) {
+          // What charsets are available depends on the instance of the JVM
+          logger.log(Level.WARNING, "Unable to find charset Cp1047", e);
+          return Stream.empty();
+        }
+      } else {
+        return Files.lines(path);
+      }
     }
 
     List<String> lineList(Path path) throws IOException {

instrumentation/resources/library/src/test/java/io/opentelemetry/instrumentation/resources/ContainerResourceTest.java

@@ -11,6 +11,10 @@ import static org.mockito.Mockito.verifyNoInteractions;
 import static org.mockito.Mockito.when;
 
 import io.opentelemetry.sdk.resources.Resource;
+import java.io.File;
+import java.io.FileOutputStream;
+import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
 import java.util.Optional;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
@@ -50,4 +54,34 @@ class ContainerResourceTest {
     Resource resource = containerResource.buildResource();
     assertThat(resource).isSameAs(Resource.empty());
   }
+
+  @Test
+  void testAlternateEncoding() throws Exception {
+    String containerId = "ac679f8a8319c8cf7d38e1adf263bc08d231f2ff81abda3915f6e8ba4d64156a";
+    String line = "13:name=systemd:/podruntime/docker/kubepods/" + containerId + ".aaaa";
+    Charset ibmCharset = Charset.forName("Cp1047");
+    byte[] utf8 = line.getBytes(StandardCharsets.UTF_8);
+    byte[] ibm = line.getBytes(ibmCharset);
+    assertThat(ibm).isNotEqualTo(utf8);
+
+    String ibmAsString = new String(ibm, ibmCharset);
+    // Different bytes, different encoding, same semantic string value
+    assertThat(line).isEqualTo(ibmAsString);
+
+    // Make temp file that contains the IBM encoding
+    File tempFile = File.createTempFile("tmp", "mountinfo");
+    tempFile.deleteOnExit();
+    try (FileOutputStream out = new FileOutputStream(tempFile)) {
+      out.write(ibm);
+    }
+    ContainerResource.Filesystem fs =
+        // pretend we are on z/OS to trigger the routine to detect an alternative encoding
+        new ContainerResource.Filesystem(() -> "z/OS");
+    CgroupV1ContainerIdExtractor extractor =
+        new CgroupV1ContainerIdExtractor(fs, tempFile.toPath());
+    ContainerResource testClass = new ContainerResource(extractor, null);
+
+    Resource resource = testClass.buildResource();
+    assertThat(resource.getAttribute(CONTAINER_ID)).isEqualTo(containerId);
+  }
 }