containers/osbuild-composer: wait for fluentd in entrypoint

to avoid composer crashing and restarting when fluentd is not up
HMS-1496

containers/osbuild-composer/entrypoint.py

@@ -20,6 +20,9 @@ import time
 class Cli(contextlib.AbstractContextManager):
     """Command Line Interface"""
 
+    SYSLOG_RETRIES=5
+    SYSLOG_WAIT=2.0
+
     def __init__(self, argv):
         self.args = None
         self._argv = argv
@@ -241,6 +244,25 @@ class Cli(contextlib.AbstractContextManager):
             stderr=subprocess.STDOUT,
         )
 
+    @staticmethod
+    def _wait_for_syslog(addr):
+        print("Waiting for fluentd syslog server", file=sys.stderr)
+        for _ in range(Cli.SYSLOG_RETRIES):
+            sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+            try:
+                sock.connect(addr)
+            except ConnectionRefusedError:
+                time.sleep(Cli.SYSLOG_WAIT)
+                continue
+            except (NameError, ConnectionError) as ex:
+                print("Unexpected error:", ex , file=sys.stderr)
+                break
+            finally:
+                sock.close()
+
+            print("fluentd syslog server is up", file=sys.stderr)
+            break
+
     @staticmethod
     def _spawn_composer(sockets):
         cmd = [
@@ -295,6 +317,9 @@ class Cli(contextlib.AbstractContextManager):
                 proc_worker = self._spawn_worker()
 
             if any([self.args.weldr_api, self.args.composer_api, self.args.local_worker_api, self.args.remote_worker_api]):
+                if "SYSLOG_SERVER" in os.environ:
+                    addr, port = os.environ["SYSLOG_SERVER"].split(":")
+                    self._wait_for_syslog((addr, int(port)))
                 proc_composer = self._spawn_composer(sockets)
 
             if proc_composer: