github.com/xmidt-org/webpa-common@v1.11.9/service/servicehttp/hashFilter.go (about)

     1  package servicehttp
     2  
     3  import (
     4  	"net/http"
     5  
     6  	"github.com/go-kit/kit/log/level"
     7  	"github.com/xmidt-org/webpa-common/device"
     8  	"github.com/xmidt-org/webpa-common/logging"
     9  	"github.com/xmidt-org/webpa-common/service"
    10  	"github.com/xmidt-org/webpa-common/xhttp/xfilter"
    11  )
    12  
    13  // NewHashFilter constructs an xfilter that enforces device hashing to an instance that represents this server process.
    14  // Any request that does not pass the self predicate will be rejected with the reject error.
    15  //
    16  // The returned filter will check the request's context for a device id, using that to hash with if one is found.
    17  // Otherwise, the device key is parsed from the request via device.IDHashParser.
    18  func NewHashFilter(a service.Accessor, reject error, self func(string) bool) xfilter.Interface {
    19  	// allow any nil parameter to simply disable the filtering
    20  	if a == nil || reject == nil || self == nil {
    21  		return xfilter.Allow()
    22  	}
    23  
    24  	return xfilter.Func(func(r *http.Request) error {
    25  		var key []byte
    26  
    27  		if id, ok := device.GetID(r.Context()); ok {
    28  			key = id.Bytes()
    29  		} else {
    30  			var err error
    31  			if key, err = device.IDHashParser(r); err != nil {
    32  				return err
    33  			}
    34  		}
    35  
    36  		i, err := a.Get(key)
    37  		if err != nil {
    38  			return err
    39  		}
    40  
    41  		if !self(i) {
    42  			logging.GetLogger(r.Context()).Log(level.Key(), level.ErrorValue(), logging.MessageKey(), "device does not hash to this instance", "hashKey", string(key), logging.ErrorKey(), reject, "instance", i)
    43  			return reject
    44  		}
    45  
    46  		return nil
    47  	})
    48  }