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https://github.com/ccamel/kynaptik
λ Fission Function which evaluates incoming stimulus (event/message) and determines an appropriate (configured) action (http, graphQL, ...)
https://github.com/ccamel/kynaptik
faas fission function graphql kafka kubernetes lambda notify rest serverless-functions stimulus webhook
Last synced: about 1 month ago
JSON representation
λ Fission Function which evaluates incoming stimulus (event/message) and determines an appropriate (configured) action (http, graphQL, ...)
- Host: GitHub
- URL: https://github.com/ccamel/kynaptik
- Owner: ccamel
- License: mit
- Created: 2019-07-21T20:06:48.000Z (over 5 years ago)
- Default Branch: master
- Last Pushed: 2024-10-28T13:06:49.000Z (about 2 months ago)
- Last Synced: 2024-10-28T16:50:47.130Z (about 2 months ago)
- Topics: faas, fission, function, graphql, kafka, kubernetes, lambda, notify, rest, serverless-functions, stimulus, webhook
- Language: Go
- Homepage:
- Size: 680 KB
- Stars: 2
- Watchers: 1
- Forks: 0
- Open Issues: 11
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
- awesome-ccamel - ccamel/kynaptik - λ Fission Function which evaluates incoming stimulus (event/message) and determines an appropriate (configured) action (http, graphQL, ...) (Go)
README
# Кynaptiꓘ
[](https://app.codacy.com/app/ccamel/kynaptik?utm_source=github.com&utm_medium=referral&utm_content=ccamel/kynaptik&utm_campaign=Badge_Grade_Dashboard)
[](https://circleci.com/gh/ccamel/kynaptik/tree/master)
[](https://coveralls.io/github/ccamel/kynaptik?branch=master)
[](https://codeclimate.com/github/ccamel/kynaptik/maintainability)
[](https://sonarcloud.io/dashboard?id=ccamel_kynaptik)
[](https://sonarcloud.io/dashboard?id=ccamel_kynaptik)
[](https://sonarcloud.io/dashboard?id=ccamel_kynaptik)
[](https://stackshare.io/ccamel/kynaptik)
[](https://golang.org/)
[](https://github.com/ccamel/kynaptik/releases)
> Serverless Function on [Kubernetes][kubernetes] (through [Fission][fission]) providing a generic and configurable mean to trigger _actions_ from incoming _events_.
## 👉 Purpose
`Kynaptiꓘ` is a function which specifies how a stimulus (i.e. incoming request, message) elicits a response (i.e. invocation of endpoint).
More broadly, it provides a platform with a versatile and generic Web Hook serving multiple purposes.
## 💡Principles
`Kynaptiꓘ` is a function that deploys on [Fission][fission] [FaaS](https://en.wikipedia.org/wiki/Function_as_a_service), an amazing framework for serverless functions on [Kubernetes][kubernetes].
The following diagram depicts how the main components interact:
## ✨ Features
`Kynaptiꓘ` is a simple, lean function with a deliberately limited set of features. Development is driven by the [KISS](https://en.wikipedia.org/wiki/KISS_principle) principle:
"do one thing well".
- Conditional actions: an action is executed only in case a message matches the defined condition. That condition is specified by an [expression](https://github.com/antonmedv/expr) evaluated
at running time against an environment containing the incoming message.
- Extensible configuration of actions with templating: URL, HTTP method, headers and body.
🚨 At this moment, [Fission][fission] `mqtrigger` processes incoming messages concurrently, which can cause unordered function calls. See [FISSION#1569](https://github.com/fission/fission/issues/1569). Thus, depending on the use cases, it can lead to data inconsistency.
**Out of scope:**
- No complex conditions, e.g. based on a state based on time ([CEP](https://en.wikipedia.org/wiki/Complex_event_processing))
- No content enrichment: no way to access an external data source in order to augment a message with missing information.
The incoming messages are expected to be qualified enough for the processing.
- Fire and forget behavior: the action (e.g. HTTP post) is done once, the result is not used (a log is emitted though)
- No recovery policy: no retry if the action fails
## 🚀 Actions
Here's the currently supported actions:
| Action | Description | Documentation |
| ------------- | --------------------------------------------------------------------------------- | --------------------------------------------- |
| **`http`** | Provides HTTP actions for calling external HTTP(S) resources. | [view documentation](./doc/action-http.md) |
| **`graphql`** | Provides [GraphQL][graphql] actions for calling external [GraphQL][graphql] APIs. | [view documentation](./doc/action-graphql.md) |
## 🛠 Configuration
### configmap
`Kynaptiꓘ` is configured by a k8s `ConfigMap` which defines the configuration for the function.
The `ConfigMap` _shall_ declares the key `function-spec.yml` under the key `data`, which contains the `yaml` configuration of the function.
For instance:
```yaml
apiVersion: v1
kind: ConfigMap
metadata:
namespace: default
name: kynaptik-http-configmap
data:
function-spec.yml: |
timeout: 10000
preCondition: |
data.foo == "bar"
action: |
uri: 'https://foo-bar'
method: GET
headers:
Content-Type: application/json
X-Userid: |
{{if eq .data.user.firstname "john"}}Rmlyc3Qgb3B0aW9u={{else}}U2Vjb25kIG9wdGlvbg=={{end}}
body: |
{
"message": "Hello from {{.data.user.firstname}} {{.data.user.lastname}}"
}
postCondition: |
response.StatusCode >= 200 and response.StatusCode < 300
```
The yaml configuration has the following structure:
- `preCondition`: optional, specifies the condition (textual) to be satisfied for the function to be triggered. The condition is an expression
(text) compliant with the syntax of [antonmedv/expr](https://github.com/antonmedv/expr/blob/master/docs/Language-Definition.md) engine. `true` by default.
- `action`: specifies the action to perform. The action specification is _templated_ using the [go template engine](https://golang.org/pkg/text/template/).
See section below to have details about the evaluation environment.
- `uri`: mandatory, the URI of the endpoint to invoke. Shall resolve to a URI according to [rfc3986](https://www.ietf.org/rfc/rfc3986.txt).
The scheme specifies the kind of action (see below) that will be performed: http, graphql...
- `timeout`: optional, specifies the timeout for waiting for data (in ms).
- `...`: other fields depending on the kind of action.
- `postCondition`: optional, specifies the condition (textual) to be satisfied for the response of the call be considered successful.
- `maxBodySize`: optional, defines the maximum acceptable size (in bytes) of the incoming request body. No limit by default.
- `timeout`: optional, specifies the timeout for waiting for data (in ms). No timeout by default.
The condition (either `preCondition` or `postCondition`) is an expression (text) compliant with the syntax of
[antonmedv/expr](https://github.com/antonmedv/expr/blob/master/docs/Language-Definition.md) engine.
### secrets
Along with a [ConfigMap](https://kubernetes.io/docs/tasks/configure-pod-container/configure-pod-configmap/), `Kynaptiꓘ` supports
[k8s secrets](https://kubernetes.io/docs/concepts/configuration/secret/) which allows to inject sensitive information (such as passwords)
in the function, and make them available in the execution context.
The `secret` _shall_ declares the key `function-secret.yml` under the field `data`, which contains all the `yaml` secrets of the function.
For instance:
```yaml
apiVersion: v1
kind: Secret
metadata:
namespace: default
name: kynaptik-http-secret
type: Opaque
data:
function-secret.yml: |
username: YWRtaW4=
password: c+KCrGNy4oKsdA==
```
### environment variables
Fission supports access to environment variables through `PodSpecs`, which defines the
specifications of many behaviors of functions in a declarative manner. A complete documentation can be found
[here](https://docs.fission.io/docs/spec/podspec/envvar/).
Within `Kynaptiꓘ`, environment variables can easily be retrieved using the template action `env` and providing
the name of the variable as argument:
```gotemplate
{{ env "FOO" }}
```
Variable expansion is also available as template action, as shown below:
```gotemplate
{{ "Hello $FOO" | expandenv }}
```
## 📄 Evaluation context
The _preCondition_, _postCondition_ expressions and the _action_ template are processed against a context.
The data tag available in the context is following:
| name | description | scope |
| ---------- | --------------------------------------------------------------------------------------------------------------------------- | ------------------------ |
| `data` | The incoming message (_body_ only), serialized into a map structure, with preservation of primary types (numbers, strings). | always |
| `config` | The current configuration (as loaded from the ConfigMaps). | always |
| `secret` | The current secret (if provided). | always |
| `response` | The response returned by the invocation. Datatype depends on the action performed. | only for _postCondition_ |
Some useful functions are also injected in the context covering a large set of operations: string, date, maths, encoding, environment...
The functions are mainly brought by the [Masterminds/sprig](https://github.com/Masterminds/sprig) project. The complete description of those
functions can be found [here](http://masterminds.github.io/sprig/).
[kubernetes]: https://kubernetes.io/
[fission]: https://fission.io/
[graphql]: https://graphql.org/