# Function files

Functions files are used to assist fn to help you when creating functions.

The files can be named as:

- func.yaml
- func.json

An example of a function file:

```yaml
name: fnproject/hello
version: 0.0.1
type: sync
memory: 128
config:
  key: value
  key2: value2
  keyN: valueN
headers:
  content-type:
   - text/plain
build:
- make
- make test
```

`name` is the name and tag to which this function will be pushed to and the
route updated to use it.

`path` (optional) allows you to overwrite the calculated route from the path
position. You may use it to override the calculated route. If you plan to use
`fn test --remote=""`, this is mandatory.

`version` represents current version of the function. When deploying, it is
appended to the image as a tag.

`runtime` represents programming language runtime, for example,
'go', 'python', 'java', etc.  The runtime 'docker' will use the existing Dockerfile if one exists.

`build` (optional) is an array of local shell calls which are used to help
building the function.

`type` (optional) allows you to set the type of the route. `sync`, for functions
whose response are sent back to the requester; or `async`, for functions that
are started and return a call ID to customer while it executes in background.
Default: `sync`.

`memory` (optional) allows you to set a maximum memory threshold for this
function. If this function exceeds this limit during execution, it is stopped
and error message is logged. Default: `128`.

`timeout` (optional) is the maximum time a function will be allowed to run. Default is 30 seconds. 

`headers` (optional) is a set of HTTP headers to be returned in the response of
this function calls.

`config` (optional) is a set of configurations to be passed onto the route
setup. These configuration options shall override application configuration
during functions execution.

## Hot functions

hot functions support also adds two extra options to this configuration file.

`format` (optional) is one of the streaming formats covered at [function-format.md](function-format.md).

`idle_timeout` (optional) is the time in seconds a container will remain alive without receiving any new requests; 
hot functions will stay alive as long as they receive a request in this interval. Default: `30`. 

## Testing functions

`tests` (optional) is an array of tests that can be used to valid functions both
locally and remotely. It has the following structure

```yaml
tests:
- name: envvar
  in: "inserted stdin"
  out: "expected stdout"
  err: "expected stderr"
  env:
    envvar: trololo
```

`in` (optional) is a string that is going to be sent to the file's declared
function.

`out` (optional) is the expected output for this function test. It is present
both in local and remote executions.

`err` (optional) similar to `out`, however it read from `stderr`. It is only
available for local machine tests.

`env` (optional) is a map of environment variables that are injected during
tests.