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streamroute.go
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streamroute.go
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// Copyright 2015-2017 trivago GmbH
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package format
import (
"bytes"
"github.com/trivago/gollum/core"
)
// StreamRoute formatter plugin
//
// StreamRoute is a formatter that modifies a message's stream by reading a
// prefix from the message's data (and discarding it).
// The prefix is defined as everything before a given delimiter in the
// message. If no delimiter is found or the prefix is empty the message stream
// is not changed.
//
// Parameters
//
// - Delimiter: This value defines the delimiter to search when extracting the stream name.
// By default this parameter is set to ":".
//
// - StreamModulator: A list of further modulators to format and filter the extracted stream name.
// By default this parameter is "empty".
//
// Examples
//
// This example sets the stream name for messages like `<error>:a message string` to `error`
// and `a message string` as payload:
//
// exampleConsumer:
// Type: consumer.Console
// Streams: "*"
// Modulators:
// - format.StreamRoute:
// Delimiter: ":"
// StreamModulator:
// - format.Trim:
// LeftSeparator: <
// RightSeparator: >
type StreamRoute struct {
core.SimpleFormatter `gollumdoc:"embed_type"`
streamModulators core.ModulatorArray `config:"StreamModulator"`
delimiter []byte `config:"Delimiter" default:":"`
}
func init() {
core.TypeRegistry.Register(StreamRoute{})
}
// Configure initializes this formatter with values from a plugin config.
func (format *StreamRoute) Configure(conf core.PluginConfigReader) {
}
// ApplyFormatter update message payload
func (format *StreamRoute) ApplyFormatter(msg *core.Message) error {
content := format.GetAppliedContent(msg)
delimiterIdx := bytes.Index(content, format.delimiter)
switch delimiterIdx {
case 0:
content = content[len(format.delimiter):]
format.SetAppliedContent(msg, content)
case -1:
// no prefix
default:
streamName := content[:delimiterIdx]
streamMsg := core.NewMessage(nil, []byte(streamName), nil, msg.GetStreamID())
content = content[(delimiterIdx + len(format.delimiter)):]
format.SetAppliedContent(msg, content)
switch result := format.streamModulators.Modulate(streamMsg); result {
case core.ModulateResultDiscard, core.ModulateResultFallback:
return nil // ### return, rule based early out ###
}
targetStreamID := core.GetStreamID(streamMsg.String())
if msg.GetStreamID() != targetStreamID {
msg.SetStreamID(targetStreamID)
}
}
return nil
}