1 files changed, 84 insertions, 0 deletions
diff --git a/subplot/daemon.py b/subplot/daemon.py
new file mode 100644
index 0000000..e223505
--- /dev/null
+++ b/subplot/daemon.py
@@ -0,0 +1,84 @@
+#############################################################################
+# Start and stop daemons, or background processes.
+
+
+import logging
+import os
+import signal
+import time
+
+
+# Start a process in the background.
+def start_daemon(ctx, name, argv):
+    runcmd = globals()["runcmd"]
+    exit_code_is = globals()["exit_code_is"]
+
+    logging.debug(f"Starting daemon {name}")
+    logging.debug(f"  ctx={ctx.as_dict()}")
+    logging.debug(f"  name={name}")
+    logging.debug(f"  argv={argv}")
+
+    if "daemon" not in ctx.as_dict():
+        ctx["daemon"] = {}
+    assert name not in ctx["daemon"]
+    this = ctx["daemon"][name] = {
+        "pid-file": f"{name}.pid",
+        "stderr": f"{name}.stderr",
+        "stdout": f"{name}.stdout",
+    }
+    runcmd(
+        ctx,
+        [
+            "/usr/sbin/daemonize",
+            "-c",
+            os.getcwd(),
+            "-p",
+            this["pid-file"],
+            "-e",
+            this["stderr"],
+            "-o",
+            this["stdout"],
+        ]
+        + argv,
+    )
+
+    # Wait for a bit for daemon to start and maybe find a problem and die.
+    time.sleep(3)
+    if ctx["exit"] != 0:
+        logging.error(f"obnam-server stderr: {ctx['stderr']}")
+
+    exit_code_is(ctx, 0)
+    this["pid"] = int(open(this["pid-file"]).read().strip())
+    assert process_exists(this["pid"])
+
+    logging.debug(f"Started daemon {name}")
+    logging.debug(f"  ctx={ctx.as_dict()}")
+
+
+# Stop a daemon.
+def stop_daemon(ctx, name):
+    logging.debug(f"Stopping daemon {name}")
+    logging.debug(f"  ctx={ctx.as_dict()}")
+    logging.debug(f"  ctx['daemon']={ctx.as_dict()['daemon']}")
+
+    this = ctx["daemon"][name]
+    terminate_process(this["pid"], signal.SIGKILL)
+
+
+# Does a process exist?
+def process_exists(pid):
+    try:
+        os.kill(pid, 0)
+    except ProcessLookupError:
+        return False
+    return True
+
+
+# Terminate process.
+def terminate_process(pid, signalno):
+    logging.debug(f"Terminating process {pid} with signal {signalno}")
+    try:
+        os.kill(pid, signalno)
+    except ProcessLookupError:
+        logging.debug("Process did not actually exist (anymore?)")
+        pass