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Edit the custom spawners doc

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Carol Willing
2016-01-27 16:48:59 -08:00
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# Writing a custom Spawner # Writing a custom Spawner
Each single-user server is started by a [Spawner][]. [Spawner][] starts each single-user notebook server.
The Spawner represents an abstract interface to a process, The Spawner represents an abstract interface to a process,
and a custom Spawner needs to be able to take three actions: and a custom Spawner needs to be able to take three actions:
1. start the process - start the process
2. poll whether the process is still running - poll whether the process is still running
3. stop the process - stop the process
See a list of custom Spawners [on the wiki](https://github.com/jupyter/jupyterhub/wiki/Spawners). ## Examples
Custom Spawners for JupyterHub can be found on the [JupyterHub wiki](https://github.com/jupyter/jupyterhub/wiki/Spawners). Some examples include:
- [DockerSpawner](https://github.com/jupyter/dockerspawner) for spawning user servers in Docker containers
* dockerspawner.DockerSpawner for spawning identical Docker containers for
each users
* dockerspawner.SystemUserSpawner for spawning Docker containers with an
environment and home directory for each users
- [SudoSpawner](https://github.com/jupyter/sudospawner) enables JupyterHub to
run without being root, by spawning an intermediate process via `sudo`
- [BatchSpawner](https://github.com/mbmilligan/batchspawner) for spawning remote
servers using batch systems
- [RemoteSpawner](https://github.com/zonca/remotespawner) to spawn notebooks
and a remote server and tunnel the port via SSH
- [SwarmSpawner](https://github.com/compmodels/jupyterhub/blob/master/swarmspawner.py)
for spawning containers using Docker Swarm
## Spawner control methods
## Spawner.start ### Spawner.start
`Spawner.start` should start the single-user server for a single user. `Spawner.start` should start the single-user server for a single user.
Information about the user can be retrieved from `self.user`, Information about the user can be retrieved from `self.user`,
@@ -20,8 +35,9 @@ an object encapsulating the user's name, authentication, and server info.
When `Spawner.start` returns, it should have stored the IP and port When `Spawner.start` returns, it should have stored the IP and port
of the single-user server in `self.user.server`. of the single-user server in `self.user.server`.
**NOTE:** when writing coroutines, *never* `yield` in between a db change and a commit. **NOTE:** When writing coroutines, *never* `yield` in between a database change and a commit.
Most `Spawner.start`s should have something looking like:
Most `Spawner.start` functions will look similar to this example:
```python ```python
def start(self): def start(self):
@@ -36,33 +52,30 @@ not just requested. JupyterHub can handle `Spawner.start` being very slow
(such as PBS-style batch queues, or instantiating whole AWS instances) (such as PBS-style batch queues, or instantiating whole AWS instances)
via relaxing the `Spawner.start_timeout` config value. via relaxing the `Spawner.start_timeout` config value.
### Spawner.poll
## Spawner.poll
`Spawner.poll` should check if the spawner is still running. `Spawner.poll` should check if the spawner is still running.
It should return `None` if it is still running, It should return `None` if it is still running,
and an integer exit status, otherwise. and an integer exit status, otherwise.
For the local process case, this uses `os.kill(PID, 0)` For the local process case, `Spawner.poll` uses `os.kill(PID, 0)`
to check if the process is still around. to check if the local process is still running.
## Spawner.stop ### Spawner.stop
`Spawner.stop` should stop the process. It must be a tornado coroutine,
and should return when the process has finished exiting.
`Spawner.stop` should stop the process. It must be a tornado coroutine, which should return when the process has finished exiting.
## Spawner state ## Spawner state
JupyterHub should be able to stop and restart without having to teardown JupyterHub should be able to stop and restart without tearing down
single-user servers. This means that a Spawner may need to persist single-user notebook servers. To do this task, a Spawner may need to persist
some information that it can be restored. some information that can be restored later.
A dictionary of JSON-able state can be used to store this information. A JSON-able dictionary of state can be used to store persisted information.
Unlike start/stop/poll, the state methods must not be coroutines. Unlike start, stop, and poll methods, the state methods must not be coroutines.
In the single-process case, this is only the process ID of the server: For the single-process case, the Spawner state is only the process ID of the server:
```python ```python
def get_state(self): def get_state(self):
@@ -94,11 +107,11 @@ or docker-based deployments where users can select from a list of base images.
This feature is enabled by setting `Spawner.options_form`, which is an HTML form snippet This feature is enabled by setting `Spawner.options_form`, which is an HTML form snippet
inserted unmodified into the spawn form. inserted unmodified into the spawn form.
If the `Spawner.options_form` is defined, when a user would start their server, they will be directed to a form page, like this: If the `Spawner.options_form` is defined, when a user tries to start their server, they will be directed to a form page, like this:
![spawn-form](images/spawn-form.png) ![spawn-form](images/spawn-form.png)
If `Spawner.options_form` is undefined, the users server is spawned directly, and no spawn page is rendered. If `Spawner.options_form` is undefined, the user's server is spawned directly, and no spawn page is rendered.
See [this example](https://github.com/jupyter/jupyterhub/blob/master/examples/spawn-form/jupyterhub_config.py) for a form that allows custom CLI args for the local spawner. See [this example](https://github.com/jupyter/jupyterhub/blob/master/examples/spawn-form/jupyterhub_config.py) for a form that allows custom CLI args for the local spawner.
@@ -115,9 +128,9 @@ Options from this form will always be a dictionary of lists of strings, e.g.:
} }
``` ```
When formdata arrives, it is passed through `Spawner.options_from_form(formdata)`, When `formdata` arrives, it is passed through `Spawner.options_from_form(formdata)`,
which is a method to turn the form data into the correct structure. which is a method to turn the form data into the correct structure.
This method must return a dictionary, and is meant to interpret the lists-of-strings into the correct types, e.g. for the above form it would look like: This method must return a dictionary, and is meant to interpret the lists-of-strings into the correct types. For example, the `options_from_form` for the above form would look like:
```python ```python
def options_from_form(self, formdata): def options_from_form(self, formdata):
@@ -140,7 +153,7 @@ which would return:
} }
``` ```
When `Spawner.spawn` is called, this dict is accessible as `self.user_options`. When `Spawner.spawn` is called, this dictionary is accessible as `self.user_options`.