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streamname.go
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streamname.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 (
"github.com/trivago/gollum/core"
"github.com/trivago/gollum/shared"
)
// StreamName formatter plugin
// StreamName is a formatter that prefixes a message with the StreamName.
// Configuration example
//
// - "stream.Broadcast":
// Formatter: "format.StreamName"
// StreamNameFormatter: "format.Envelope"
// StreamNameSeparator: " "
// StreamNameHistory: false
//
// StreamNameFormatter defines the formatter for the data transferred as
// message. By default this is set to "format.Envelope"
//
// StreamNameHistory can be set to true to not use the current but the previous
// stream name. This can be useful to e.g. get the name of the stream messages
// were dropped from. By default this is set to false.
//
// StreamNameSeparator sets the separator character placed after the stream name.
// This is set to " " by default.
type StreamName struct {
base core.Formatter
separator string
usePrevious bool
}
func init() {
shared.TypeRegistry.Register(StreamName{})
}
// Configure initializes this formatter with values from a plugin config.
func (format *StreamName) Configure(conf core.PluginConfig) error {
plugin, err := core.NewPluginWithType(conf.GetString("StreamNameFormatter", "format.Forward"), conf)
if err != nil {
return err
}
format.separator = conf.GetString("StreamNameSeparator", " ")
format.usePrevious = conf.GetBool("StreamNameHistory", false)
format.base = plugin.(core.Formatter)
return nil
}
// Format prepends the StreamName of the message to the message.
func (format *StreamName) Format(msg core.Message) ([]byte, core.MessageStreamID) {
var streamName string
data, streamID := format.base.Format(msg)
switch {
case !format.usePrevious:
streamName = core.StreamRegistry.GetStreamName(streamID)
case streamID != msg.StreamID:
streamName = core.StreamRegistry.GetStreamName(msg.StreamID)
default:
streamName = core.StreamRegistry.GetStreamName(msg.PrevStreamID)
}
payload := make([]byte, len(streamName)+len(format.separator)+len(data))
streamNameLen := copy(payload, []byte(streamName))
separatorLen := copy(payload[streamNameLen:], format.separator)
copy(payload[streamNameLen+separatorLen:], data)
return payload, streamID
}