Add a modifier for GCP cloud logging

This commit adds a modifier which will upload logs into Google Cloud
Platform's Cloud Logging.

var/ramble/repos/builtin/modifiers/gcp-cloud-logging/modifier.py

@@ -0,0 +1,55 @@
+# Copyright 2022-2024 The Ramble Authors
+#
+# Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+# https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+# <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+# option. This file may not be copied, modified, or distributed
+# except according to those terms.
+
+from ramble.modkit import *  # noqa: F403
+from ramble.util.shell_utils import last_pid_var
+
+
+class GcpCloudLogging(BasicModifier):
+    """Upload experiment logs to Google Cloud Platform Cloud Logging.
+
+    https://cloud.google.com/logging?e=48754805&hl=en
+    """
+
+    name = "gcp-cloud-logging"
+
+    tags("info")
+
+    maintainers("douglasjacobsen")
+
+    mode("standard", description="Standard execution mode")
+
+    default_mode("standard")
+
+    target_shells("bash")
+
+    modifier_variable(
+        "cloud_logging_tag",
+        default="{experiment_namespace}",
+        description="Tag to prefix cloud logging entries with",
+        modes=["standard"],
+    )
+
+    register_builtin(
+        "start_cloud_logger", required=True, injection_method="prepend"
+    )
+
+    def start_cloud_logger(self):
+        shell = ramble.config.get("config:shell")
+        last_pid_str = last_pid_var(shell)
+        return [
+            "tail -f {log_file} | logger -t {cloud_logging_tag} &",
+            f"export LOGGER_PID={last_pid_str}",
+        ]
+
+    register_builtin(
+        "kill_cloud_logger", required=True, injection_method="append"
+    )
+
+    def kill_cloud_logger(self):
+        return ["kill -9 $LOGGER_PID"]