Add suffix ID to memfd file name (#9796)

* Update to add ID suffix

* Update dd-trace-core/src/main/java/datadog/trace/core/servicediscovery/ServiceDiscovery.java

Co-authored-by: Stuart McCulloch <[email protected]>

* fix import

---------

Co-authored-by: Stuart McCulloch <[email protected]>

Author: raphaelgavache

dd-java-agent/agent-tooling/src/main/java/datadog/trace/agent/tooling/servicediscovery/MemFDUnixWriter.java

@@ -33,29 +33,29 @@ private interface LibC extends Library {
   private static final int F_SEAL_GROW = 0x0004;
 
   @Override
-  public void write(byte[] payload) {
+  public void write(String fileName, byte[] payload) {
     final LibC libc = Native.load("c", LibC.class);
 
-    int memFd = libc.memfd_create("datadog-tracer-info-", MFD_CLOEXEC | MFD_ALLOW_SEALING);
+    int memFd = libc.memfd_create(fileName, MFD_CLOEXEC | MFD_ALLOW_SEALING);
     if (memFd < 0) {
-      log.warn("datadog-tracer-info memfd create failed, errno={}", Native.getLastError());
+      log.warn("{} memfd create failed, errno={}", fileName, Native.getLastError());
       return;
     }
 
-    log.debug("datadog-tracer-info memfd created (fd={})", memFd);
+    log.debug("{} memfd created (fd={})", fileName, memFd);
 
     Memory buf = new Memory(payload.length);
     buf.write(0, payload, 0, payload.length);
 
     NativeLong written = libc.write(memFd, buf, new NativeLong(payload.length));
     if (written.longValue() != payload.length) {
-      log.warn("write to datadog-tracer-info memfd failed errno={}", Native.getLastError());
+      log.warn("write to {} memfd failed errno={}", fileName, Native.getLastError());
       return;
     }
     log.debug("wrote {} bytes to memfd {}", written.longValue(), memFd);
     int returnCode = libc.fcntl(memFd, F_ADD_SEALS, F_SEAL_SHRINK | F_SEAL_GROW | F_SEAL_SEAL);
     if (returnCode == -1) {
-      log.warn("failed to add seal to datadog-tracer-info memfd errno={}", Native.getLastError());
+      log.warn("failed to add seal to {} memfd errno={}", fileName, Native.getLastError());
       return;
     }
     // memfd is not closed to keep it readable for the lifetime of the process.

dd-trace-core/src/main/java/datadog/trace/core/servicediscovery/ForeignMemoryWriter.java

@@ -2,5 +2,5 @@
 
 @FunctionalInterface
 public interface ForeignMemoryWriter {
-  void write(byte[] payload);
+  void write(String fileName, byte[] payload);
 }

dd-trace-core/src/main/java/datadog/trace/core/servicediscovery/ServiceDiscovery.java

@@ -9,6 +9,7 @@
 import datadog.trace.api.Config;
 import datadog.trace.api.ProcessTags;
 import datadog.trace.bootstrap.instrumentation.api.UTF8BytesString;
+import datadog.trace.util.RandomUtils;
 import java.nio.ByteBuffer;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -35,12 +36,17 @@ public void writeTracerMetadata(Config config) {
               ProcessTags.getTagsForSerialization(),
               ContainerInfo.get().getContainerId());
 
-      foreignMemoryWriter.write(payload);
+      foreignMemoryWriter.write(generateFileName(), payload);
     } catch (Throwable t) {
       log.debug("service discovery memfd write failed", t);
     }
   }
 
+  private static String generateFileName() {
+    String suffix = RandomUtils.randomUUID().toString().substring(0, 8);
+    return "datadog-tracer-info-" + suffix;
+  }
+
   static byte[] encodePayload(
       String tracerVersion,
       String hostname,

dd-trace-core/src/test/groovy/datadog/trace/core/servicediscovery/ServiceDiscoveryTest.groovy

@@ -44,4 +44,12 @@ class ServiceDiscoveryTest extends DDCoreSpecification {
     and:
     map.toString() == '{"schema_version":2,"tracer_language":"java","tracer_version":"1.2.3","hostname":"my_host"}'
   }
+  def "generateFileName"() {
+    when:
+    String name = ServiceDiscovery.generateFileName()
+
+    then:
+    name.startsWith("datadog-tracer-info-")
+    name.length() == "datadog-tracer-info-".length() + 8
+  }
 }