[Core]Add runtime context for python worker (#10309)

* add runtime context for python

* fixed

* code fixed

* test added

* lint

* lint

python/ray/runtime_context.py

@@ -0,0 +1,57 @@
+import ray.worker
+import logging
+
+logger = logging.getLogger(__name__)
+
+
+class RuntimeContext(object):
+    """A class used for getting runtime context."""
+
+    def __init__(self, worker):
+        assert worker is not None
+        self.worker = worker
+
+    @property
+    def current_job_id(self):
+        """Get current job ID for this worker or driver.
+
+        Returns:
+            If called by a driver, this returns the job ID. If called in
+                a task, return the job ID of the associated driver.
+        """
+        return self.worker.current_job_id
+
+    @property
+    def current_actor_id(self):
+        """Get the current actor ID in this worker.
+
+        Returns:
+            The current driver id in this worker.
+        """
+        # only worker mode has actor_id
+        assert self.worker.mode == ray.worker.WORKER_MODE, (
+            f"This method is only available when the process is a\
+                 worker. Current mode: {self.worker.mode}")
+        return self.worker.actor_id
+
+    @property
+    def was_current_actor_reconstructed(self):
+        """Check whether this actor has been restarted
+
+        Returns:
+            Whether this actor has been ever restarted.
+        """
+        # TODO: this method should not be called in a normal task.
+        actor_info = ray.state.actors(self.current_actor_id.hex())
+        return actor_info and actor_info["NumRestarts"] != 0
+
+
+_runtime_context = None
+
+
+def get_runtime_context():
+    global _runtime_context
+    if _runtime_context is None:
+        _runtime_context = RuntimeContext(ray.worker.global_worker)
+
+    return _runtime_context