mirror of
https://github.com/fnproject/fn.git
synced 2022-10-28 21:29:17 +03:00
92 lines
3.0 KiB
Markdown
92 lines
3.0 KiB
Markdown
# Writing Functions
|
|
|
|
This will give you the basic overview of writing base level functions. You can also use higher level
|
|
abstractions that make it easier such as [lambda](lambda/README.md).
|
|
|
|
Also, for complete examples in various languages, see the [examples directory](/examples).
|
|
We have language libraries for [Go](https://github.com/funcy/functions_go), [Javascript](https://github.com/treeder/functions_js) and
|
|
[Ruby](https://github.com/treeder/functions_ruby).
|
|
|
|
## Code
|
|
|
|
The most basic code layout in any language is as follows, this is pseudo code and is not meant to run.
|
|
|
|
```ruby
|
|
# Read and parse from STDIN
|
|
body = JSON.parse(STDIN)
|
|
|
|
# Do something
|
|
return_struct = doSomething(body)
|
|
|
|
# If sync, respond:
|
|
STDOUT.write(JSON.generate(return_struct))
|
|
# If async, update something:
|
|
db.update(return_struct)
|
|
```
|
|
|
|
## Inputs
|
|
|
|
Inputs are provided through standard input and environment variables. We'll just talk about the default input format here, but you can find others [here](function-format.md).
|
|
To read in the function body, just read from STDIN.
|
|
|
|
You will also have access to a set of environment variables.
|
|
|
|
* REQUEST_URL - the full URL for the request
|
|
* APP_NAME - the name of the application that matched this route, eg: `myapp`
|
|
* ROUTE - the matched route, eg: `/hello`
|
|
* METHOD - the HTTP method for the request, eg: `GET` or `POST`
|
|
* HEADER_X - the HTTP headers that were set for this request. Replace X with the upper cased name of the header and replace dashes in the header with underscores.
|
|
* X - any [configuration values](https://gitlab.oracledx.com/odx/functions/blob/master/fn/README.md#application-level-configuration) you've set
|
|
for the Application or the Route. Replace X with the upper cased name of the config variable you set. Ex: `minio_secret=secret` will be exposed via MINIO_SECRET env var.
|
|
|
|
Warning: these may change before release.
|
|
|
|
## Logging
|
|
|
|
Standard out is where you should write response data for synchronous functions. Standard error
|
|
is where you should write for logging, as [it was intended](http://www.jstorimer.com/blogs/workingwithcode/7766119-when-to-use-stderr-instead-of-stdout).
|
|
|
|
So to write output to logs, simply log to STDERR. Here are some examples in a few languages.
|
|
|
|
In Go, simply use the [log](https://golang.org/pkg/log/) package, it writes to STDERR by default.
|
|
|
|
```go
|
|
log.Println("hi")
|
|
```
|
|
|
|
In Node.js:
|
|
|
|
```node
|
|
console.error("hi");
|
|
```
|
|
|
|
[More details for Node.js here](http://stackoverflow.com/a/27576486/105562).
|
|
|
|
In Ruby:
|
|
|
|
```ruby
|
|
STDERR.puts("hi")
|
|
```
|
|
|
|
## Using Lambda Functions
|
|
|
|
### Lambda everywhere
|
|
|
|
Lambda support for Oracle Functios enables you to take your AWS Lambda functions and run them
|
|
anywhere. You should be able to take your code and run them without any changes.
|
|
|
|
Creating Lambda functions is not much different than using regular functions, just use
|
|
the `lambda-node` runtime.
|
|
|
|
```sh
|
|
fn init --runtime lambda-node <DOCKER_HUB_USERNAME>/lambda-node
|
|
```
|
|
|
|
Be sure the filename for your main handler is `func.js`.
|
|
|
|
TODO: Make Java and Python use the new workflow too.
|
|
|
|
## Next Steps
|
|
|
|
* [Packaging your function](packaging.md)
|