test: wait for ewww to start, and log stderr if it doesn't

When the ewww daemon starts successfully, it'll listen on the assigned
port. We wait for that port to be open, for up to five seconds. If
that fails, then ewww didn't start successfully, and hopefully there
is something useful in its stderr so we read and log that.

1 files changed, 20 insertions, 1 deletions

diff --git a/ewww.py b/ewww.py
index ded5064..8a6e453 100644
--- a/ewww.py
+++ b/ewww.py
@@ -8,6 +8,7 @@ import random
 import re
 import shutil
 import signal
+import socket
 import subprocess
 import time
 import urllib.parse
@@ -82,7 +83,7 @@ def start_server(ctx, filename=None):
     logging.debug(f"Starting ewww with config file {filename}")
     config = get_file(filename).decode("UTF-8")
     config = yaml.safe_load(config)
-    config["port"] = random.randint(2000, 30000)
+    port = config["port"] = random.randint(2000, 30000)
     logging.debug(f"Picked randomly port for ewww: {config['port']}")
     ctx["config"] = config
     config = yaml.safe_dump(config)
@@ -90,6 +91,24 @@ def start_server(ctx, filename=None):
 
     start_daemon(ctx, "ewww", [_binary("ewww"), filename])
 
+    if not port_open("localhost", port, 5.0):
+        stderr = open(ctx["daemon"]["ewww"]["stderr"]).read()
+        logging.debug(f"Stderr from daemon: {stderr!r}")
+
+
+# Wait for a port to be open
+def port_open(host, port, timeout):
+    logging.debug(f"Waiting for port localhost:{port} to be available")
+    started = time.time()
+    while time.time() < started + timeout:
+        try:
+            socket.create_connection((host, port), timeout=timeout)
+            return True
+        except socket.error:
+            pass
+    logging.error(f"Port localhost:{port} is not open")
+    return False
+
 
 # Stop previously started server.
 def stop_server(ctx):