Introduction to the Pixiu Filter System

Introduction to the Pixiu Filter System

How to Write a Filter

For more detailed information, please refer to the Blog "Talking About Pixiu's Filter"

Let’s try writing a simple Filter that will have a basic configuration, log the request Body during the Decode phase, and return the reversed string as a Mock response. Finally, in the Encode phase, it will log the return value based on the configuration.

  1. First, create a Filter
  1. type DemoFilter struct {
  2.    logPrefix string
  3. }
  5. // Decode phase, occurs before calling Upstream
  6. func (f *DemoFilter) Decode(ctx *contexthttp.HttpContext) filter.FilterStatus {
  7.    body, _ := ioutil.ReadAll(ctx.Request.Body)
  8.    logger.Infof("request body: %s", body)
  10.    //reverse res str
  11.    runes := []rune(string(body))
  12.    for i := 0; i < len(runes)/2; i += 1 {
  13.       runes[i], runes[len(runes)-1-i] = runes[len(runes)-1-i], runes[i]
  14.    }
  15.    reverse := string(runes)
  17.    //mock response
  18.    ctx.SendLocalReply(200, []byte(reverse))
  19.    return filter.Stop
  20. }
  22. // Encode phase, at this point the Upstream Response can be accessed
  23. func (f *DemoFilter) Encode(ctx *contexthttp.HttpContext) filter.FilterStatus {
  24.    res := ctx.SourceResp.(string)
  25.    logger.Infof("%s: %s", f.logPrefix, res)
  26.    return filter.Continue
  27. }
  1. Create a Filter Factory
  1. type (
  2.     DemoFilterFactory struct {
  3.         conf *Config
  4.     }
  5.     // Config describe the config of Filter
  6.     Config struct {
  7.         LogPrefix string `yaml:"logPrefix,omitempty"`
  8.     }
  9. )
  11. func (f *DemoFilterFactory) PrepareFilterChain(ctx *contexthttp.HttpContext, chain filter.FilterChain) error {
  12.    demo := &DemoFilter{logPrefix: f.conf.LogPrefix}
  14.    chain.AppendDecodeFilters(demo)
  15.    chain.AppendEncodeFilters(demo)
  16.    return nil
  17. }
  19. func (f *DemoFilterFactory) Config() interface{} {
  20.    return f.conf
  21. }
  23. func (f *DemoFilterFactory) Apply() error {
  24.    return nil
  25. }
  1. Create a Filter Plugin and register it
  1. //important
  2. func init() {
  3.    filter.RegisterHttpFilter(&Plugin{})
  4. }
  6. type Plugin struct {
  7. }
  9. func (p *Plugin) Kind() string {
  10.    return "dgp.filters.demo"
  11. }
  13. func (p *Plugin) CreateFilterFactory() (filter.HttpFilterFactory, error) {
  14.     return &DemoFilterFactory{conf: &Config{}}, nil
  15. }
  1. Configure this Filter in the configuration file and start Pixiu
  1. static_resources:
  2.   listeners:
  3.     - name: "net/http"
  4.       protocol_type: "HTTP"
  5.       address:
  6.         socket_address:
  7.           address: "0.0.0.0"
  8.           port: 8888
  9.       filter_chains:
  10.           filters:
  11.             - name: dgp.filter.httpconnectionmanager
  12.               config:
  13.                 route_config:
  14.                   routes:
  15.                     - match:
  16.                         prefix: "/"
  17.                 http_filters:
  18.                   - name: dgp.filters.demo
  19.                     config:
  1. Access and check the logs and results
  1. curl localhost:8888/demo -d "eiv al tse’c"
  3. c’est la vie%

Logs

  1. 2022-02-19T20:20:11.900+0800    INFO    demo/demo.go:62 request body: eiv al tse’c
  2. 2022-02-19T20:20:11.900+0800    INFO    demo/demo.go:71 : eiv al tse’c

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Last modified September 30, 2024: Update & Translate Overview Docs (#3040) (d37ebceaea7)