diff --git a/contributing/mock-driver.md b/contributing/mock-driver.md new file mode 100644 index 000000000..d54af361f --- /dev/null +++ b/contributing/mock-driver.md @@ -0,0 +1,128 @@ +# Mock Driver + +This repo includes a mock task driver in the [`drivers/mock`][] package that +implements a minimal task driver interface for development work. This driver is +loaded as the other [built-in drivers][] are, but only when Nomad is [not +compiled with the release tag][]. + +## Task Configuration + +```hcl +task "mocktask" { + driver = "mock_driver" + + config { + run_for = "10s" + exit_code = 7 + exit_err_msg = "the application crashed" + } +} +``` + +The `mock_driver` driver supports the following configuration in the job spec: + +- `run_for` `(duration: "0s")` - The duration for which the fake task runs + for. After this period the driver responds indicating the task has terminated. +- `signal_error` `(string: "")` - The error message the task returns if signalled. +- `stderr_repeat_duration` `(duration: "0s")` - The duration between repeated stderr outputs. +- `stderr_repeat` `(number: 0)` - The number of times the `stderr_string` will be written. +- `stderr_string` `(string: "")` - The string that the task writes to stderr. +- `stdout_repeat_duration` `(string: "")` - The duration between repeated stdout outputs. +- `stdout_repeat` `(number: 0)` - The number of times the `stdout_string` will be written. +- `stdout_string` `(string: "")` - The string that the task writes to stdout. + +The driver has configurable startup and shutdown for the tasks: + +- `exit_code` `(number: 0)` - The exit code the driver should return for the exiting task. +- `exit_err_msg` `(string: "")` - The error message the task returns while exiting. +- `exit_signal` `(number: 0)` - The signal with which the driver indicates the + task has been killed. +- `kill_after` `(duration: "0s")` - Duration after which the driver indicates + the task has exited with `SIGINT`. +- `plugin_exit_after` `(string: "")` - Duration after which the driver indicates + the plugin exited via the `WaitTask` call. +- `start_block_for` `(duration: "0s")` - Duration to block before returning when started. +- `start_error_recoverable` `(bool: false)` - Marks whether the error returned + when starting the driver is recoverable. +- `start_error` `(string: "")` - The error that is returned when starting the driver. + +The driver can present information to the client about the task as though it had networking: + +- `driver_advertise` `(bool: false)` - Returned as `DriverNetwork.AutoAdvertise` from `Start()` +- `driver_ip` `(string: "")` - The address returned as the `DriverNetwork.IP` from `Start()` +- `driver_port_map` `(string: "")` - Parse a label:number pair and return it as + `DriverNetwork.PortMap` from `Start()`. + + +## Plugin Options + +```hcl +plugin "mock_driver" { + fs_isolation = "none" + shutdown_periodic_after = false + shutdown_periodic_duration = 0 +} +``` + +- `fs_isolation` `(string: "none")` - The type of file system isolation to + report to the client. Must be one of `"none"`, `"chroot"`, or `"image"`. +- `shutdown_periodic_after` `(bool: false)` - A toggle that can be used during + tests to "stop" a previously-functioning driver, allowing for testing of + periodic drivers and fingerprinters. +- `shutdown_periodic_duration` `(number: 0)` - The duration after which to stop + a previously-functioning driver, in seconds. + + +## Example + +An example job that could be used for testing task `kill_timeout`: + +``` +job "mock" { + + group "group" { + + task "task" { + + driver = "mock_driver" + + kill_timeout = "5s" + + config { + exit_code = 0 + exit_err_msg = "error on exit" + exit_signal = 9 + kill_after = "3s" + run_for = "30s" + signal_error = "got signal" + start_block_for = "1s" + stdout_repeat = 1 + stdout_repeat_duration = "10s" + stdout_string = "hello, world!\n" + } + + resources { + cpu = 128 + memory = 128 + } + + } + } +} +``` + +This results in the following allocation events: + +``` +Recent Events: +Time Type Description +2023-03-20T16:22:39-04:00 Restarting Task restarting in 17.426443129s +2023-03-20T16:22:39-04:00 Terminated Exit Code: 0, Signal: 9, Exit Message: "error on exit" +2023-03-20T16:22:09-04:00 Started Task started by client +2023-03-20T16:22:07-04:00 Task Setup Building Task Directory +2023-03-20T16:22:07-04:00 Received Task received by client +``` + +[built-in drivers]: https://github.com/hashicorp/nomad/blob/main/helper/pluginutils/catalog/register.go +[not compiled with the release tag]: https://github.com/hashicorp/nomad/blob/main/helper/pluginutils/catalog/register_testing.go +[`drivers/mock`]: https://github.com/hashicorp/nomad/tree/main/drivers/mock