Merge pull request #5561 from matrix-org/rav/docker/refactor

Refactor the docker/start.py script

changelog.d/5561.feature

@@ -0,0 +1 @@
+Update Docker image to deprecate the use of environment variables for configuration, and make the use of a static configuration the default.

docker/start.py

@@ -1,75 +1,81 @@
 #!/usr/local/bin/python
 
-import jinja2
-import os
-import sys
-import subprocess
-import glob
 import codecs
+import glob
+import os
+import subprocess
+import sys
+
+import jinja2
+
 
 # Utility functions
-convert = lambda src, dst, environ: open(dst, "w").write(
-    jinja2.Template(open(src).read()).render(**environ)
-)
+def log(txt):
+    print(txt, file=sys.stderr)
 
 
-def check_arguments(environ, args):
-    for argument in args:
-        if argument not in environ:
-            print("Environment variable %s is mandatory, exiting." % argument)
+def error(txt):
+    log(txt)
     sys.exit(2)
 
 
-def generate_secrets(environ, secrets):
+def convert(src, dst, environ):
+    """Generate a file from a template
+
+    Args:
+        src (str): path to input file
+        dst (str): path to file to write
+        environ (dict): environment dictionary, for replacement mappings.
+    """
+    with open(src) as infile:
+        template = infile.read()
+    rendered = jinja2.Template(template).render(**environ)
+    with open(dst, "w") as outfile:
+        outfile.write(rendered)
+
+
+def generate_config_from_template(environ, ownership):
+    """Generate a homeserver.yaml from environment variables
+
+    Args:
+        environ (dict): environment dictionary
+        ownership (str): "<user>:<group>" string which will be used to set
+            ownership of the generated configs
+
+    Returns:
+        path to generated config file
+    """
+    for v in ("SYNAPSE_SERVER_NAME", "SYNAPSE_REPORT_STATS"):
+        if v not in environ:
+            error(
+                "Environment variable '%s' is mandatory when generating a config "
+                "file on-the-fly." % (v,)
+            )
+
+    # populate some params from data files (if they exist, else create new ones)
+    environ = environ.copy()
+    secrets = {
+        "registration": "SYNAPSE_REGISTRATION_SHARED_SECRET",
+        "macaroon": "SYNAPSE_MACAROON_SECRET_KEY",
+    }
+
     for name, secret in secrets.items():
         if secret not in environ:
             filename = "/data/%s.%s.key" % (environ["SYNAPSE_SERVER_NAME"], name)
+
+            # if the file already exists, load in the existing value; otherwise,
+            # generate a new secret and write it to a file
+
             if os.path.exists(filename):
                 with open(filename) as handle:
                     value = handle.read()
             else:
-                print("Generating a random secret for {}".format(name))
+                log("Generating a random secret for {}".format(name))
                 value = codecs.encode(os.urandom(32), "hex").decode()
                 with open(filename, "w") as handle:
                     handle.write(value)
             environ[secret] = value
 
-
-# Prepare the configuration
-mode = sys.argv[1] if len(sys.argv) > 1 else None
-environ = os.environ.copy()
-ownership = "{}:{}".format(environ.get("UID", 991), environ.get("GID", 991))
-args = ["python", "-m", "synapse.app.homeserver"]
-
-# In generate mode, generate a configuration, missing keys, then exit
-if mode == "generate":
-    check_arguments(
-        environ, ("SYNAPSE_SERVER_NAME", "SYNAPSE_REPORT_STATS", "SYNAPSE_CONFIG_PATH")
-    )
-    args += [
-        "--server-name",
-        environ["SYNAPSE_SERVER_NAME"],
-        "--report-stats",
-        environ["SYNAPSE_REPORT_STATS"],
-        "--config-path",
-        environ["SYNAPSE_CONFIG_PATH"],
-        "--generate-config",
-    ]
-    os.execv("/usr/local/bin/python", args)
-
-# In normal mode, generate missing keys if any, then run synapse
-else:
-    if "SYNAPSE_CONFIG_PATH" in environ:
-        config_path = environ["SYNAPSE_CONFIG_PATH"]
-    else:
-        check_arguments(environ, ("SYNAPSE_SERVER_NAME", "SYNAPSE_REPORT_STATS"))
-        generate_secrets(
-            environ,
-            {
-                "registration": "SYNAPSE_REGISTRATION_SHARED_SECRET",
-                "macaroon": "SYNAPSE_MACAROON_SECRET_KEY",
-            },
-        )
     environ["SYNAPSE_APPSERVICES"] = glob.glob("/data/appservices/*.yaml")
     if not os.path.exists("/compiled"):
         os.mkdir("/compiled")
@@ -85,18 +91,63 @@ else:
             if tlsanswerstring in ("false", "off", "0", "no"):
                 environ["SYNAPSE_NO_TLS"] = False
             else:
-                    print(
+                error(
                     'Environment variable "SYNAPSE_NO_TLS" found but value "'
                     + tlsanswerstring
                     + '" unrecognized; exiting.'
                 )
-                    sys.exit(2)
 
     convert("/conf/homeserver.yaml", config_path, environ)
     convert("/conf/log.config", "/compiled/log.config", environ)
     subprocess.check_output(["chown", "-R", ownership, "/data"])
+    return config_path
 
-    args += [
+
+def run_generate_config(environ):
+    """Run synapse with a --generate-config param to generate a template config file
+
+    Args:
+        environ (dict): environment dictionary
+
+    Never returns.
+    """
+    for v in ("SYNAPSE_SERVER_NAME", "SYNAPSE_REPORT_STATS", "SYNAPSE_CONFIG_PATH"):
+        if v not in environ:
+            error("Environment variable '%s' is mandatory in `generate` mode." % (v,))
+
+    args = [
+        "python",
+        "-m",
+        "synapse.app.homeserver",
+        "--server-name",
+        environ["SYNAPSE_SERVER_NAME"],
+        "--report-stats",
+        environ["SYNAPSE_REPORT_STATS"],
+        "--config-path",
+        environ["SYNAPSE_CONFIG_PATH"],
+        "--generate-config",
+    ]
+    os.execv("/usr/local/bin/python", args)
+
+
+def main(args, environ):
+    mode = args[1] if len(args) > 1 else None
+    ownership = "{}:{}".format(environ.get("UID", 991), environ.get("GID", 991))
+
+    # In generate mode, generate a configuration, missing keys, then exit
+    if mode == "generate":
+        return run_generate_config(environ)
+
+    # In normal mode, generate missing keys if any, then run synapse
+    if "SYNAPSE_CONFIG_PATH" in environ:
+        config_path = environ["SYNAPSE_CONFIG_PATH"]
+    else:
+        config_path = generate_config_from_template(environ, ownership)
+
+    args = [
+        "python",
+        "-m",
+        "synapse.app.homeserver",
         "--config-path",
         config_path,
         # tell synapse to put any generated keys in /data rather than /compiled
@@ -107,3 +158,7 @@ else:
     # Generate missing keys and start synapse
     subprocess.check_output(args + ["--generate-keys"])
     os.execv("/sbin/su-exec", ["su-exec", ownership] + args)
+
+
+if __name__ == "__main__":
+    main(sys.argv, os.environ)