java: Raise JattachSocketMissing if the attach socket is missing (HS only for now)

gprofiler/profilers/java.py

@@ -162,6 +162,20 @@ def __str__(self) -> str:
         )
 
 
+class JattachSocketMissingException(JattachExceptionBase):
+    def __str__(self) -> str:
+        # the attach listener is initialized once, then it is marked as initialized:
+        # (https://github.com/openjdk/jdk/blob/3d07b3c7f01b60ff4dc38f62407c212b48883dbf/src/hotspot/share/services/attachListener.cpp#L388)
+        # and will not be initialized again:
+        # https://github.com/openjdk/jdk/blob/3d07b3c7f01b60ff4dc38f62407c212b48883dbf/src/hotspot/os/linux/attachListener_linux.cpp#L509
+        # since openjdk 2870c9d55efe, the attach socket will be recreated even when removed (and this exception
+        # won't happen).
+        return super().__str__() + (
+            "\nJVM attach socket is missing and jattach could not create it. It has most"
+            " likely been removed; the process has to be restarted for a new socket to be created."
+        )
+
+
 _JAVA_VERSION_TIMEOUT = 5
 
 
@@ -443,6 +457,9 @@ def _run_async_profiler(self, cmd: List[str]) -> None:
             args = e.returncode, e.cmd, e.stdout, e.stderr, self.process.pid, ap_log, is_loaded
             if isinstance(e, CalledProcessTimeoutError):
                 raise JattachTimeout(*args, timeout=self._jattach_timeout) from None
+            elif e.stderr == b"Could not start attach mechanism: No such file or directory\n":
+                # this is true for jattach_hotspot
+                raise JattachSocketMissingException(*args) from None
             else:
                 raise JattachException(*args) from None
 

tests/test_java.py

@@ -19,6 +19,7 @@
 import pytest
 from docker.models.containers import Container
 from granulate_utils.linux.elf import get_elf_buildid
+from granulate_utils.linux.ns import get_process_nspid
 from packaging.version import Version
 from pytest import LogCaptureFixture, MonkeyPatch
 
@@ -507,3 +508,26 @@ def start_async_profiler_and_interrupt(self: AsyncProfiledProcess, *args: Any, *
     assert profile.appid == "java: Fibonacci.jar"
     # and application metadata for java
     assert profile.app_metadata is not None and "java_version" in profile.app_metadata
+
+
+@pytest.mark.parametrize("in_container", [True])  # only in container is enough
+def test_java_attach_socket_missing(
+    tmp_path: Path,
+    application_pid: int,
+) -> None:
+    """
+    Tests that we get the proper JattachMissingSocketException when the attach socket is deleted.
+    """
+
+    with make_java_profiler(
+        storage_dir=str(tmp_path),
+        duration=1,
+    ) as profiler:
+        snapshot_one_profile(profiler)
+
+        # now the attach socket is created, remove it
+        Path(f"/proc/{application_pid}/root/tmp/.java_pid{get_process_nspid(application_pid)}").unlink()
+
+        profile = snapshot_one_profile(profiler)
+        assert len(profile.stacks) == 1
+        assert next(iter(profile.stacks.keys())) == "java;[Profiling error: exception JattachSocketMissingException]"