patch: Fix Kolibri blocking after starting

Makefile

@@ -74,6 +74,7 @@ src/kolibri: clean
 	sed -i 's/if name.endswith(".py"):/if name.endswith(".py") or name.endswith(".pyc"):/g' src/kolibri/dist/django/db/migrations/loader.py
 	# Apply kolibri patches
 	patch -d src/ -p1 < patches/0001-server-Set-STATUS_RUNNING-just-once.patch
+	patch -d src/ -p1 < patches/0002-Fix-Kolibri-blocking-after-starting-with-port-0.patch
 
 .PHONY: apps-bundle.zip
 apps-bundle.zip:

patches/0002-Fix-Kolibri-blocking-after-starting-with-port-0.patch

@@ -0,0 +1,157 @@
+From 609b938945f614bd9d086eb33e8652ea697543c6 Mon Sep 17 00:00:00 2001
+From: Dylan McCall <dylan@endlessos.org>
+Date: Thu, 7 Apr 2022 11:27:01 -0700
+Subject: [PATCH] Fix Kolibri blocking after starting with port 0
+
+After the server starts, BaseServerPlugin waits for it to respond on the
+expected port number. For this feature to work, we need it to see the
+bind address from the associated httpserver, which is different from the
+original bind address when binding to port 0.
+
+For clarity, we will not initialize the cheroot.wsgi Server with a
+bind_addr. Instead, it will be controlled by ServerPlugin itself.
+
+With this change in place, we can remove PortCache because we no longer
+need to reuse port numbers.
+---
+ kolibri/utils/server.py | 89 ++++++++++-------------------------------
+ 1 file changed, 21 insertions(+), 68 deletions(-)
+
+diff --git a/kolibri/utils/server.py b/kolibri/utils/server.py
+index d9080d0073..bc582f69ef 100644
+--- a/kolibri/utils/server.py
++++ b/kolibri/utils/server.py
+@@ -61,9 +61,6 @@ PID_FILE = os.path.join(conf.KOLIBRI_HOME, "server.pid")
+ # File used to activate profiling middleware and get profiler PID
+ PROFILE_LOCK = os.path.join(conf.KOLIBRI_HOME, "server_profile.lock")
+
+-# File used to store previously available ports
+-PORT_CACHE = os.path.join(conf.KOLIBRI_HOME, "port_cache")
+-
+ # File used to send a state transition command to the server process
+ PROCESS_CONTROL_FLAG = os.path.join(conf.KOLIBRI_HOME, "process_control.flag")
+
+@@ -129,73 +126,31 @@ def port_is_available_on_host(host, port):
+     return True
+
+
+-class PortCache:
+-    def __init__(self):
+-        self.values = {}
+-        self.occupied_ports = set()
+-        self.load()
+-
+-    def lock_port(self, port):
+-        if port:
+-            self.occupied_ports.add(port)
+-
+-    def register_port(self, port):
+-        self.values[port] = True
+-        self.save()
+-
+-    def get_port(self, host):
+-        if self.values:
+-            try:
+-                port = next(
+-                    p
+-                    for p in self.values
+-                    if not self.values[p] and p not in self.occupied_ports
+-                )
+-                if port:
+-                    if port_is_available_on_host(host, port):
+-                        self.values[port] = True
+-                        return port
+-            except StopIteration:
+-                pass
+-        return None
+-
+-    def save(self):
+-        with open(PORT_CACHE, "w") as f:
+-            f.write("\n".join(str(p) for p in self.values))
+-
+-    def load(self):
+-        try:
+-            with open(PORT_CACHE, "r") as f:
+-                for port in f.readlines():
+-                    self.values[int(port)] = False
+-        except IOError:
+-            pass
+-
+-
+-port_cache = PortCache()
+-
+-
+ class ServerPlugin(BaseServerPlugin):
+-    def subscribe(self):
+-        super(ServerPlugin, self).subscribe()
+-        self.bus.subscribe("ENTER", self.ENTER)
++    def __init__(self, *args, **kwargs):
++        httpserver = kwargs.get("httpserver")
++        if not isinstance(httpserver, BaseServer):
++            raise TypeError("httpserver must be a cheroot.wsgi.BaseServer")
++        super(ServerPlugin, self).__init__(*args, **kwargs)
++        self._default_bind_addr = self.bind_addr
+
+-    def unsubscribe(self):
+-        super(ServerPlugin, self).unsubscribe()
+-        self.bus.unsubscribe("ENTER", self.ENTER)
++    @property
++    def bind_addr(self):
++        # Instead of using our own copy of bind_addr, mirror httpserver.
++        # This is necessary because methods in BaseServerPlugin expect
++        # bind_addr to match the bind address the server is using, such as
++        # when binding to port 0.
++        return self.httpserver.bind_addr
+
+-    def ENTER(self):
+-        host, bind_port = self.bind_addr
+-        if bind_port == 0:
+-            port = port_cache.get_port(host)
+-            if port:
+-                self.bind_addr = (host, port)
+-                self.httpserver.bind_addr = (host, port)
++    @bind_addr.setter
++    def bind_addr(self, value):
++        self.httpserver.bind_addr = value
+
+     def START(self):
++        # Reset httpserver bind_addr. This value changes if httpserver has
++        # been started before.
++        self.httpserver.bind_addr = self._default_bind_addr
+         super(ServerPlugin, self).START()
+-        _, port = self.httpserver.bind_addr
+-        port_cache.register_port(port)
+
+     @property
+     def interface(self):
+@@ -594,9 +549,7 @@ class KolibriProcessBus(ProcessBus):
+         self.background = background
+         self.serve_http = serve_http
+         self.port = int(port)
+-        port_cache.lock_port(self.port)
+         self.zip_port = int(zip_port)
+-        port_cache.lock_port(self.zip_port)
+         # On Mac, Python crashes when forking the process, so prevent daemonization until we can figure out
+         # a better fix. See https://github.com/learningequality/kolibri/issues/4821
+         if sys.platform == "darwin":
+@@ -724,7 +677,7 @@ class KolibriProcessBus(ProcessBus):
+
+             kolibri_server = KolibriServerPlugin(
+                 self,
+-                httpserver=Server(kolibri_address, application, **server_config),
++                httpserver=Server(None, application, **server_config),
+                 bind_addr=kolibri_address,
+             )
+
+@@ -735,7 +688,7 @@ class KolibriProcessBus(ProcessBus):
+
+             alt_port_server = ZipContentServerPlugin(
+                 self,
+-                httpserver=Server(alt_port_addr, alt_application, **server_config),
++                httpserver=Server(None, alt_application, **server_config),
+                 bind_addr=alt_port_addr,
+             )
+             # Subscribe these servers
+-- 
+2.35.1
+