feat: lib/daemon.py can return daemon stdout/stderr content so far

3 files changed, 114 insertions, 2 deletions

diff --git a/share/python/lib/daemon.md b/share/python/lib/daemon.md
index 4d91bd1..9484926 100644
--- a/share/python/lib/daemon.md
+++ b/share/python/lib/daemon.md
@@ -69,6 +69,41 @@ then there is no "/bin/sleep 12765" process
 ~~~
 
 
+# Daemon stdout and stderr are retrievable
+
+Sometimes it's useful for the step functions to be able to retrieve
+the stdout or stderr of of the daemon, after it's started, or even
+after it's terminated. This scenario verifies that `lib/daemon` can do
+that.
+
+~~~scenario
+given a daemon helper shell script chatty-daemon.sh
+given there is no "chatty-daemon" process
+when I start "./chatty-daemon.sh" as a background process as chatty-daemon
+when daemon chatty-daemon has produced output
+when I stop background process chatty-daemon
+then there is no "chatty-daemon" process
+then daemon chatty-daemon stdout is "hi there\n"
+then daemon chatty-daemon stderr is "hola\n"
+~~~
+
+We make for the daemon to exit, to work around a race condition: if
+the test program retrieves the daemon's output too fast, it may not
+have had time to produce it yet.
+
+
+~~~{#chatty-daemon.sh .file .sh .numberLines}
+#!/bin/bash
+
+set -euo pipefail
+
+trap 'exit 0' TERM
+
+echo hola 1>&2
+echo hi there
+~~~
+
+
 ---
 title: Acceptance criteria for the lib/daemon Subplot library
 author: The Subplot project
diff --git a/share/python/lib/daemon.py b/share/python/lib/daemon.py
index 4ba1987..160da0a 100644
--- a/share/python/lib/daemon.py
+++ b/share/python/lib/daemon.py
@@ -62,6 +62,7 @@ def _daemon_start(ctx, path=None, args=None, name=None):
     runcmd_get_stderr = globals()["runcmd_get_stderr"]
     runcmd_prepend_to_path = globals()["runcmd_prepend_to_path"]
 
+    path = os.path.abspath(path)
     argv = [path] + args.split()
 
     logging.debug(f"Starting daemon {name}")
@@ -154,10 +155,17 @@ def daemon_wait_for_port(host, port, timeout=5.0):
 # Stop a daemon.
 def daemon_stop(ctx, name=None):
     logging.debug(f"Stopping daemon {name}")
+
     ns = ctx.declare("_daemon")
     logging.debug(f"  ns={ns}")
     pid = ns[name]["pid"]
-    signo = signal.SIGKILL
+    signo = signal.SIGTERM
+
+    this = ns[name]
+    data = open(this["stdout"]).read()
+    logging.debug(f"{name} stdout, before: {data!r}")
+    data = open(this["stderr"]).read()
+    logging.debug(f"{name} stderr, before: {data!r}")
 
     logging.debug(f"Terminating process {pid} with signal {signo}")
     try:
@@ -165,6 +173,20 @@ def daemon_stop(ctx, name=None):
     except ProcessLookupError:
         logging.warning("Process did not actually exist (anymore?)")
 
+    while True:
+        try:
+            os.kill(pid, 0)
+            logging.debug(f"Daemon {name}, pid {pid} still exists")
+            time.sleep(1)
+        except ProcessLookupError:
+            break
+    logging.debug(f"Daemon {name} is gone")
+
+    data = open(this["stdout"]).read()
+    logging.debug(f"{name} stdout, after: {data!r}")
+    data = open(this["stderr"]).read()
+    logging.debug(f"{name} stderr, after: {data!r}")
+
 
 def daemon_no_such_process(ctx, args=None):
     assert not _daemon_pgrep(args)
@@ -176,7 +198,7 @@ def daemon_process_exists(ctx, args=None):
 
 def _daemon_pgrep(pattern):
     logging.info(f"checking if process exists: pattern={pattern}")
-    exit = subprocess.call(["pgrep", "-laf", pattern])
+    exit = subprocess.call(["pgrep", "-laf", pattern], stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)
     logging.info(f"exit code: {exit}")
     return exit == 0
 
@@ -187,3 +209,48 @@ def daemon_start_fails_with(ctx, message=None):
     logging.debug(f"daemon_start_fails_with: error={error!r}")
     logging.debug(f"daemon_start_fails_with: message={message!r}")
     assert message.lower() in error.lower()
+
+
+def daemon_get_stdout(ctx, name):
+    return _daemon_get_output(ctx, name, "stdout")
+
+
+def daemon_get_stderr(ctx, name):
+    return _daemon_get_output(ctx, name, "stderr")
+
+
+def _daemon_get_output(ctx, name, which):
+    ns = ctx.declare("_daemon")
+    this = ns[name]
+    filename = this[which]
+    data = open(filename).read()
+    logging.debug(f"Read {which} of daemon {name} from {filename}: {data!r}")
+    return data
+
+
+def daemon_has_produced_output(ctx, name=None):
+    started = time.time()
+    timeout = 5.0
+    while time.time() < started + timeout:
+        stdout = daemon_get_stdout(ctx, name)
+        stderr = daemon_get_stderr(ctx, name)
+        if stdout and stderr:
+            break
+        time.sleep(0.1)
+
+
+def daemon_stdout_is(ctx, name=None, text=None):
+    daemon_get_stdout = globals()["daemon_get_stdout"]
+    _daemon_output_is(ctx, name, text, daemon_get_stdout)
+
+
+def daemon_stderr_is(ctx, name=None, text=None):
+    daemon_get_stderr = globals()["daemon_get_stderr"]
+    _daemon_output_is(ctx, name, text, daemon_get_stderr)
+
+
+def _daemon_output_is(ctx, name, text, getter):
+    assert_eq = globals()["assert_eq"]
+    text = bytes(text, "UTF-8").decode("unicode_escape")
+    output = getter(ctx, name)
+    assert_eq(text, output)
diff --git a/share/python/lib/daemon.yaml b/share/python/lib/daemon.yaml
index f72ba1a..4fab1f6 100644
--- a/share/python/lib/daemon.yaml
+++ b/share/python/lib/daemon.yaml
@@ -17,6 +17,9 @@
 - when: I stop background process {name}
   function: daemon_stop
 
+- when: daemon {name} has produced output
+  function: daemon_has_produced_output
+
 - then: a process "{args:text}" is running
   function: daemon_process_exists
 
@@ -25,3 +28,10 @@
 
 - then: starting daemon fails with "{message:text}"
   function: daemon_start_fails_with
+
+- then: daemon {name} stdout is "{text:text}"
+  function: daemon_stdout_is
+
+- then: daemon {name} stderr is "{text:text}"
+  function: daemon_stderr_is
+