appcfg.py not working in command line

问题:

I'm just having a bit of trouble understanding why this command:

>appcfg.py -A adept-box-109804 update app.yaml

as given by the Try Google App Engine Now page does not work. I have downloaded the App Engine SDK for Python, and have Path set up to point to the location of appcfg.py, but running appcfg.py in my projects root directory does not work in the command line. I either have to navigate to the folder containing appcfg.py and do

>python appcfg.py help

or do

>python "C:\Program Files (x86)\Google\google_appengine\appcfg.py" help

to get a command to work from anywhere. I used the latter method to deploy my test app, but was just wondering if someone could explain why the command as given by the simple Google tutorial did not do anything. I also checked to make sure that .py files are automatically opened with the Python 2.7 interpreter, such that a file hello.py will be executed in the command line by simply typing

>hello.py

and it will output its print statement. On the other hand, using appcfg.py in a similar manner gives the same output no matter the arguments (please note I truncated the output, but rest assured that they are identical no matter the arguments:

C:\>appcfg.py help backends
Usage: appcfg.py [options] <action>

Action must be one of:
  backends: Perform a backend action.
  backends configure: Reconfigure a backend without stopping it.
  backends delete: Delete a backend.
  backends list: List all backends configured for the app.
  backends rollback: Roll back an update of a backend.
  backends start: Start a backend.
  backends stop: Stop a backend.
  backends update: Update one or more backends.
  create_bulkloader_config: Create a bulkloader.yaml from a running application.
  cron_info: Display information about cron jobs.
  delete_version: Delete the specified version for an app.
  download_app: Download a previously-uploaded app.
  download_data: Download entities from datastore.
  help: Print help for a specific action.
  list_versions: List all uploaded versions for an app.
  request_logs: Write request logs in Apache common log format.
  resource_limits_info: Get the resource limits.
  rollback: Rollback an in-progress update.
  set_default_version: Set the default (serving) version.
  start_module_version: Start a module version.
  stop_module_version: Stop a module version.
  update: Create or update an app version.
  update_cron: Update application cron definitions.
  update_dispatch: Update application dispatch definitions.
  update_dos: Update application dos definitions.
  update_indexes: Update application indexes.
  update_queues: Update application task queue definitions.
  upload_data: Upload data records to datastore.
  vacuum_indexes: Delete unused indexes from application.
Use 'help <action>' for a detailed description.

C:\>appcfg.py help update
Usage: appcfg.py [options] <action>

Action must be one of:
  backends: Perform a backend action.
  backends configure: Reconfigure a backend without stopping it.
  backends delete: Delete a backend.
  backends list: List all backends configured for the app.
  backends rollback: Roll back an update of a backend.
  backends start: Start a backend.
  backends stop: Stop a backend.
  backends update: Update one or more backends.
  create_bulkloader_config: Create a bulkloader.yaml from a running application.
  cron_info: Display information about cron jobs.
  delete_version: Delete the specified version for an app.
  download_app: Download a previously-uploaded app.
  download_data: Download entities from datastore.
  help: Print help for a specific action.
  list_versions: List all uploaded versions for an app.
  request_logs: Write request logs in Apache common log format.
  resource_limits_info: Get the resource limits.
  rollback: Rollback an in-progress update.
  set_default_version: Set the default (serving) version.
  start_module_version: Start a module version.
  stop_module_version: Stop a module version.
  update: Create or update an app version.
  update_cron: Update application cron definitions.
  update_dispatch: Update application dispatch definitions.
  update_dos: Update application dos definitions.
  update_indexes: Update application indexes.
  update_queues: Update application task queue definitions.
  upload_data: Upload data records to datastore.
  vacuum_indexes: Delete unused indexes from application.
Use 'help <action>' for a detailed description.

回答1:

Your confusion probably stems from mixing up 2 possible invocations styles:

1. python appcfg.py ...
2. appcfg.py ...

The 1st one can't make use of the fact that the location of the appcfg.py is in the path, it is just an argument to the python executable, which can not locate the appcfg.py file unless either:

• it finds it in the current directory
• the appcfg.py file is specified using a full path or a path relative to the current working directory from which python is invoked

This is the reason for which your 2nd and 3rd commands don't work as you'd expect. Using the 2nd invocation style instead should work if the location of the appcfg.py is in the path - just as your last command invocation does.

Key point to remember: the path configuration applies to the command executable only, not to its arguments (which BTW each executable may process as it wishes, some executables may combine arguments with the path configuration to obtain location of files).

Similarly appcfg.py itself (once successfully invoked using either of the 2 invocation styles) needs to be able to locate your app.yaml file specified as argument. It cannot do so unless either:

• it finds it in the current directory
• the app.yaml file (or its directory) is specified using a full path or a path relative to the current working directory from which appcfg.py is invoked

I suspect appcfg.py's inability to locate your app.yaml file may be the reason for which the 1st command you mentioned didn't work. If not you should provide details about the failure.

Regarding why the output of your last command is identical regardless of the arguments, I'm not sure, it could be a bug in the windows version of the SDK. In linux the output is different:

> appcfg.py help backends
Usage: appcfg.py [options] backends <directory> <action>

Perform a backend action.

The 'backends' command will perform a backends action.

Options:
  -h, --help            Show the help message and exit.
  -q, --quiet           Print errors only.
  -v, --verbose         Print info level logs.
  --noisy               Print all logs.
  -s SERVER, --server=SERVER
                        The App Engine server.
  -e EMAIL, --email=EMAIL
                        The username to use. Will prompt if omitted.
  -H HOST, --host=HOST  Overrides the Host header sent with all RPCs.
  --no_cookies          Do not save authentication cookies to local disk.
  --skip_sdk_update_check
                        Do not check for SDK updates.
  -A APP_ID, --application=APP_ID
                        Set the application, overriding the application value
                        from app.yaml file.
  -M MODULE, --module=MODULE
                        Set the module, overriding the module value from
                        app.yaml.
  -V VERSION, --version=VERSION
                        Set the (major) version, overriding the version value
                        from app.yaml file.
  -r RUNTIME, --runtime=RUNTIME
                        Override runtime from app.yaml file.
  -E NAME:VALUE, --env_variable=NAME:VALUE
                        Set an environment variable, potentially overriding an
                        env_variable value from app.yaml file (flag may be
                        repeated to set multiple variables).
  -R, --allow_any_runtime
                        Do not validate the runtime in app.yaml
  --oauth2              Ignored (OAuth2 is the default).
  --oauth2_refresh_token=OAUTH2_REFRESH_TOKEN
                        An existing OAuth2 refresh token to use. Will not
                        attempt interactive OAuth approval.
  --oauth2_access_token=OAUTH2_ACCESS_TOKEN
                        An existing OAuth2 access token to use. Will not
                        attempt interactive OAuth approval.
  --authenticate_service_account
                        Authenticate using the default service account for the
                        Google Compute Engine VM in which appcfg is being
                        called
  --noauth_local_webserver
                        Do not run a local web server to handle redirects
                        during OAuth authorization.

回答2:

I finally tracked down the real reason, and it wasn't a bug with the AppEngine SDK. Rather it was with my Python interpreter, as I noticed it wasn't accepting arguments for any .py files. It turned out to be a registry error, located at [HKEY_CLASSES_ROOT\Applications\python.exe\shell\open\command] where I had to change the value from "C:\Python27\python.exe" "%1" to "C:\Python27\python.exe" "%1" %*

How this happened, whether it be the Python 2.7 installer, or maybe the AppEngine SDK, I'm not sure though.

回答3:

I had this problem, and is deepened in local variable python version that different from app engine python version. So the solution is just to add before the script the current python version location:

C:\Python27\python.exe "C:\Program Files (x86)\Google\google_appengine\appcfg.py"

And it just return to work well.