Read lines with default encoding from os

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

@@ -10,6 +10,7 @@
 import io.opentelemetry.api.common.Attributes;
 import io.opentelemetry.sdk.resources.Resource;
 import java.io.IOException;
+import java.nio.charset.Charset;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.List;
@@ -77,7 +78,11 @@ boolean isReadable(Path path) {
 
     @MustBeClosed
     Stream<String> lines(Path path) throws IOException {
-      return Files.lines(path);
+      return Files.lines(path, getDefaultCharset());
+    }
+
+    Charset getDefaultCharset() {
+      return Charset.defaultCharset();
     }
 
     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.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 +54,39 @@ void bothVersionsFail() {
     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("IBM-273");
+    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 =
+        new ContainerResource.Filesystem() {
+          @Override
+          Charset getDefaultCharset() {
+            // Override to pretend our default encoding is ibm273
+            return ibmCharset;
+          }
+        };
+    CgroupV1ContainerIdExtractor extractor =
+        new CgroupV1ContainerIdExtractor(fs, tempFile.toPath());
+    ContainerResource testClass = new ContainerResource(extractor, null);
+
+    Resource resource = testClass.buildResource();
+    assertThat(resource.getAttribute(CONTAINER_ID)).isEqualTo(containerId);
+  }
 }