Experiment: defer use of java.nio during premain

Author: mcculls

internal-api/src/main/java/datadog/trace/api/git/GitInfoProvider.java

@@ -9,7 +9,7 @@
 import datadog.trace.api.civisibility.telemetry.tag.GitShaDiscrepancyType;
 import datadog.trace.api.civisibility.telemetry.tag.GitShaMatch;
 import datadog.trace.util.Strings;
-import java.nio.file.Paths;
+import java.io.File;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
@@ -33,7 +33,7 @@ public class GitInfoProvider {
     INSTANCE.registerGitInfoBuilder(new UserSuppliedGitInfoBuilder());
   }
 
-  static final String NULL_PATH_STRING = Paths.get("").toAbsolutePath().toString();
+  static final String NULL_PATH_STRING = new File("").getAbsolutePath();
 
   private volatile Collection<GitInfoBuilder> builders = Collections.emptyList();
 

utils/container-utils/src/main/java/datadog/common/container/ContainerInfo.java

@@ -2,9 +2,9 @@
 
 import de.thetaphi.forbiddenapis.SuppressForbidden;
 import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
+import java.io.File;
 import java.io.IOException;
 import java.nio.file.Files;
-import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.text.ParseException;
 import java.util.ArrayList;
@@ -28,9 +28,9 @@ public class ContainerInfo {
 
   private static final Logger log = LoggerFactory.getLogger(ContainerInfo.class);
 
-  private static final Path CGROUP_DEFAULT_PROCFILE = Paths.get("/proc/self/cgroup");
-  private static final Path DEFAULT_CGROUP_MOUNT_PATH = Paths.get("/sys/fs/cgroup");
-  private static final Path HOST_GROUP_NAMESPACE = Paths.get("/proc/self/ns/cgroup");
+  private static final String CGROUP_DEFAULT_PROCFILE = "/proc/self/cgroup";
+  private static final String DEFAULT_CGROUP_MOUNT_PATH = "/sys/fs/cgroup";
+  private static final String HOST_GROUP_NAMESPACE = "/proc/self/ns/cgroup";
 
   // The second part is the PCF/Garden regexp. We assume no suffix ($) to avoid matching pod UIDs
   // See https://github.com/DataDog/datadog-agent/blob/7.40.x/pkg/util/cgroups/reader.go#L50
@@ -106,7 +106,7 @@ public void setcGroups(List<CGroupInfo> cGroups) {
   }
 
   static @Nullable String readEntityID(
-      ContainerInfo containerInfo, boolean isHostCgroupNamespace, Path cgroupMountPath) {
+      ContainerInfo containerInfo, boolean isHostCgroupNamespace, String cgroupMountPath) {
     String cid = containerInfo.getContainerId();
     if (cid != null && !cid.isEmpty()) {
       return "cid-" + cid;
@@ -129,13 +129,18 @@ static boolean isHostCgroupNamespace() {
    * Returns the inode of the cgroup controller if it exists, otherwise an empty string. The inode
    * is prefixed with "in-" and is used by the agent to retrieve the container ID.
    */
-  static @Nullable String getCgroupInode(Path cgroupMountPath, List<CGroupInfo> cgroups) {
+  static @Nullable String getCgroupInode(String cgroupMountPath, List<CGroupInfo> cgroups) {
     // It first tries to get the cGroupV1 "memory" controller inode, and if that fails, it tries to
     // get the cGroupV2 inode.
     for (String controller : Arrays.asList(CGROUPV1_BASE_CONTROLLER, CGROUPV2_BASE_CONTROLLER)) {
       for (CGroupInfo cgroup : cgroups) {
         if (cgroup.getControllers().contains(controller)) {
-          Path path = Paths.get(cgroupMountPath.toString(), controller, cgroup.getPath());
+          String path =
+              cgroupMountPath
+                  + File.pathSeparatorChar
+                  + controller
+                  + File.pathSeparatorChar
+                  + cgroup.getPath();
           long inode = readInode(path);
           // ignore invalid and root inode
           if (inode > 2) {
@@ -148,9 +153,10 @@ static boolean isHostCgroupNamespace() {
   }
 
   /** @return 0 - if it couldn't read inode */
-  static long readInode(Path path) {
+  static long readInode(String path) {
     try {
-      return (long) Files.getAttribute(path, "unix:ino");
+      File f = new File(path);
+      return f.exists() ? (long) Files.getAttribute(f.toPath(), "unix:ino") : 0L;
     } catch (Exception e) {
       log.debug("Unable to read cgroup inode of {} because of {}", path, e.getClass());
     }
@@ -214,15 +220,15 @@ public static String getEntityId() {
   }
 
   public static boolean isRunningInContainer() {
-    return Files.isReadable(CGROUP_DEFAULT_PROCFILE);
+    return new File(CGROUP_DEFAULT_PROCFILE).canRead();
   }
 
   public static ContainerInfo fromDefaultProcFile() throws IOException, ParseException {
     return fromProcFile(CGROUP_DEFAULT_PROCFILE);
   }
 
-  static ContainerInfo fromProcFile(Path path) throws IOException, ParseException {
-    final String content = new String(Files.readAllBytes(path));
+  static ContainerInfo fromProcFile(String path) throws IOException, ParseException {
+    final String content = new String(Files.readAllBytes(Paths.get(path)));
     if (content.isEmpty()) {
       log.debug("Proc file is empty");
       return new ContainerInfo();