From b79552567ea281ef33acad87283fcfd4dffb77c6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Edgar=20Ram=C3=ADrez-Mondrag=C3=B3n?= <edgarrm358@gmail.com>
Date: Wed, 21 Aug 2024 20:22:07 -0600
Subject: [PATCH] feat: Interruption and termination signals in taps and
 targets

---
 samples/sample_target_csv/csv_target.py |  2 +-
 singer_sdk/plugin_base.py               | 25 ++++++++++++++++++++++++-
 singer_sdk/tap_base.py                  | 15 +++++++++++++++
 singer_sdk/target_base.py               | 19 +++++++++++++++++++
 4 files changed, 59 insertions(+), 2 deletions(-)

diff --git a/samples/sample_target_csv/csv_target.py b/samples/sample_target_csv/csv_target.py
index d52b76f48..906c430ae 100644
--- a/samples/sample_target_csv/csv_target.py
+++ b/samples/sample_target_csv/csv_target.py
@@ -12,7 +12,7 @@ class SampleTargetCSV(Target):
 
     name = "target-csv"
     config_jsonschema = th.PropertiesList(
-        th.Property("target_folder", th.StringType, required=True),
+        th.Property("target_folder", th.StringType, default="output"),
         th.Property("file_naming_scheme", th.StringType),
     ).to_dict()
     default_sink_class = SampleCSVTargetSink
diff --git a/singer_sdk/plugin_base.py b/singer_sdk/plugin_base.py
index eb5b39de3..9272fba34 100644
--- a/singer_sdk/plugin_base.py
+++ b/singer_sdk/plugin_base.py
@@ -5,12 +5,13 @@
 import abc
 import logging
 import os
+import signal
 import sys
 import time
 import typing as t
 from importlib import metadata
 from pathlib import Path, PurePath
-from types import MappingProxyType
+from types import FrameType, MappingProxyType
 
 import click
 
@@ -176,6 +177,10 @@ def __init__(
         # Initialization timestamp
         self.__initialized_at = int(time.time() * 1000)
 
+        # Signal handling
+        signal.signal(signal.SIGINT, self._handle_termination)
+        signal.signal(signal.SIGTERM, self._handle_termination)
+
     def setup_mapper(self) -> None:
         """Initialize the plugin mapper for this tap."""
         self._mapper = PluginMapper(
@@ -402,6 +407,24 @@ def _validate_config(self, *, raise_errors: bool = True) -> list[str]:
 
         return errors
 
+    def _handle_termination(  # pragma: no cover
+        self,
+        signum: int,  # noqa: ARG002
+        frame: FrameType | None,  # noqa: ARG002
+    ) -> None:
+        """Handle termination signal.
+
+        Args:
+            signum: Signal number.
+            frame: Frame.
+
+        Raises:
+            click.Abort: If the termination signal is received.
+        """
+        self.logger.info("Gracefully shutting down...")
+        errmsg = "Received termination signal"
+        raise click.Abort(errmsg)
+
     @classmethod
     def print_version(
         cls: type[PluginBase],
diff --git a/singer_sdk/tap_base.py b/singer_sdk/tap_base.py
index d69fa5f38..293eb5358 100644
--- a/singer_sdk/tap_base.py
+++ b/singer_sdk/tap_base.py
@@ -31,6 +31,7 @@
 
 if t.TYPE_CHECKING:
     from pathlib import PurePath
+    from types import FrameType
 
     from singer_sdk.connectors import SQLConnector
     from singer_sdk.mapper import PluginMapper
@@ -473,6 +474,20 @@ def sync_all(self) -> None:
 
     # Command Line Execution
 
+    def _handle_termination(  # pragma: no cover
+        self,
+        signum: int,
+        frame: FrameType | None,
+    ) -> None:
+        """Handle termination signal.
+
+        Args:
+            signum: Signal number.
+            frame: Frame.
+        """
+        self.write_message(StateMessage(value=self.state))
+        super()._handle_termination(signum, frame)
+
     @classmethod
     def invoke(  # type: ignore[override]
         cls: type[Tap],
diff --git a/singer_sdk/target_base.py b/singer_sdk/target_base.py
index 22ad28176..ca551b728 100644
--- a/singer_sdk/target_base.py
+++ b/singer_sdk/target_base.py
@@ -32,6 +32,7 @@
 
 if t.TYPE_CHECKING:
     from pathlib import PurePath
+    from types import FrameType
 
     from singer_sdk.connectors import SQLConnector
     from singer_sdk.mapper import PluginMapper
@@ -540,6 +541,24 @@ def _write_state_message(self, state: dict) -> None:
 
     # CLI handler
 
+    def _handle_termination(  # pragma: no cover
+        self,
+        signum: int,
+        frame: FrameType | None,
+    ) -> None:
+        """Handle termination signals.
+
+        Args:
+            signum: Signal number.
+            frame: Frame object.
+        """
+        self.logger.info(
+            "Received termination signal %d, draining all sinks...",
+            signum,
+        )
+        self.drain_all(is_endofpipe=True)
+        super()._handle_termination(signum, frame)
+
     @classmethod
     def invoke(  # type: ignore[override]
         cls: type[Target],