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texttojson.go
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texttojson.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"
"encoding/json"
"github.com/trivago/gollum/core"
"github.com/trivago/tgo/tstrings"
"strconv"
"sync"
"time"
)
type jsonReaderState int
const (
jsonReadArrayEnd = jsonReaderState(iota)
jsonReadObjectEnd = jsonReaderState(iota)
jsonReadObject = jsonReaderState(iota)
jsonReadKey = jsonReaderState(iota)
jsonReadValue = jsonReaderState(iota)
jsonReadArray = jsonReaderState(iota)
jsonReadArrayAppend = jsonReaderState(iota)
)
// TextToJSON formatter
//
// This formatter uses a state machine to parse arbitrary text data and
// transform it to JSON.
//
// Parameters
//
// - StartState: Defines the name of the initial state when parsing a message.
// When set to an empty string the first state from the directives array will
// be used.
// By default this parameter is set to "".
//
// - TimestampRead: Defines a time.Parse compatible format string used to read
// time fields when using the "dat" directive.
// By default this parameter is set to "20060102150405".
//
// - TimestampWrite: Defines a time.Format compatible format string used to
// write time fields when using the "dat" directive.
// By default this parameter is set to "2006-01-02 15:04:05 MST".
//
// - UnixTimestampRead: Defines the unix timestamp format expected from fields
// that are parsed using the "dat" directive. Valid valies are "s" for seconds,
// "ms" for milliseconds, or "ns" for nanoseconds. This parameter is ignored
// unless TimestampRead is set to "".
// By default this parameter is set to "".
//
// - Directives: Defines an array of directives used to parse text data.
// Each entry must be of the format: "State:Token:NextState:Flags:Function".
// State denotes the name of the state owning this entry. Multiple entries per
// state are allowed. Token holds a string that triggers a state transition.
// NextState holds the target of the state transition. Flags is an optional
// field and is used to trigger special parser behavior. Flags can be comma
// separated if you need to use more than one.
// Function defines an action that is triggered upon state transition.
// Spaces will be stripped from all fields but Token. If a fields requires a
// colon it has to be escaped with a backslash. Other escape characters
// supported are \n, \r and \t.
// By default this parameter is set to an empty list.
//
// - Directive rules: There are some special cases which will cause the parser
// to do additional actions.
//
// * When writing a value without a key, the state name will become the key.
// * If two keys are written in a row the first key will hold a null value.
// * Writing a key while writing array elements will close the array.
//
// - Directive flags: Flags can modify the parser behavior and can be used to
// store values on a stack across multiple directives.
//
// - continue: Prepend the token to the next match.
//
// - append: Append the token to the current match and continue reading.
//
// - include: Append the token to the current match.
//
// - push: Push the current state to the stack.
//
// - pop: Pop the stack and use the returned state if possible.
//
// - Directive actions: Actions are used to write text read since the last
// transition to the JSON object.
//
// - key: Write the parsed section as a key.
//
// - val: Write the parsed section as a value without quotes.
//
// - esc: Write the parsed section as a escaped string value.
//
// - dat: Write the parsed section as a timestamp value.
//
// - arr: Start a new array.
//
// - obj: Start a new object.
//
// - end: Close an array or object.
//
// - arr+val: arr followed by val.
//
// - arr+esc: arr followed by esc.
//
// - arr+dat: arr followed by dat.
//
// - val+end: val followed by end.
//
// - esc+end: esc followed by end.
//
// - dat+end: dat followed by end.
//
// Examples
//
// The following example parses JSON data.
//
// ExampleConsumer:
// Type: consumer.Console
// Streams: console
// Modulators:
// - format.TextToJSON:
// Directives:
// - "findKey :\": key : : "
// - "findKey :}: : pop : end "
// - "key :\": findVal : : key "
// - "findVal :\\:: value : : "
// - "value :\": string : : "
// - "value :[: array : push : arr "
// - "value :{: findKey : push : obj "
// - "value :,: findKey : : val "
// - "value :}: : pop : val+end"
// - "string :\": findKey : : esc "
// - "array :[: array : push : arr "
// - "array :{: findKey : push : obj "
// - "array :]: : pop : val+end"
// - "array :,: array : : val "
// - "array :\": arrString : : "
// - "arrString :\": array : : esc "
type TextToJSON struct {
core.SimpleFormatter `gollumdoc:"embed_type"`
message *bytes.Buffer
parser tstrings.TransitionParser
state jsonReaderState
stack []jsonReaderState
parseLock *sync.Mutex
initState string `config:"StartState"`
timeRead string `config:"TimestampRead"`
timeWrite string `config:"TimestampWrite" default:"2006-01-02 15:04:05 MST"`
timeParse func(string, string) (time.Time, error)
}
func init() {
core.TypeRegistry.Register(TextToJSON{})
}
func parseUnix(layout, value string) (time.Time, error) {
s, ns := int64(0), int64(0)
switch layout {
case "s":
valueInt, err := strconv.ParseInt(value, 10, 64)
if err != nil {
return time.Time{}, err
}
s = valueInt
case "ms":
valueInt, err := strconv.ParseInt(value, 10, 64)
if err != nil {
return time.Time{}, err
}
ns = valueInt * int64(time.Millisecond)
case "ns":
valueInt, err := strconv.ParseInt(value, 10, 64)
if err != nil {
return time.Time{}, err
}
ns = valueInt
}
return time.Unix(s, ns), nil
}
// Configure initializes this formatter with values from a plugin config.
func (format *TextToJSON) Configure(conf core.PluginConfigReader) {
format.parser = tstrings.NewTransitionParser()
format.state = jsonReadObject
format.timeParse = time.Parse
format.parseLock = new(sync.Mutex)
unixRead := conf.GetString("UnixTimestampRead", "")
if format.timeRead == "" {
if unixRead == "" {
// Use default when neither are specified
format.timeRead = "20060102150405"
} else {
format.timeRead = unixRead
format.timeParse = parseUnix
}
} else if unixRead != "" {
format.Logger.Warning("Cannot use both TimestampRead and UnixTimestampRead, defaulting to TimestampRead")
}
if !conf.HasValue("Directives") {
format.Logger.Warning("JSON formatter has no directives setting")
return // ### return, no directives ###
}
directiveStrings := conf.GetStringArray("Directives", []string{})
if len(directiveStrings) == 0 {
conf.Errors.Pushf("JSON formatter has no directives")
} else {
// Parse directives
parserFunctions := make(map[string]tstrings.ParsedFunc)
parserFunctions["key"] = format.readKey
parserFunctions["val"] = format.readValue
parserFunctions["esc"] = format.readEscaped
parserFunctions["dat"] = format.readDate
parserFunctions["arr"] = format.readArray
parserFunctions["obj"] = format.readObject
parserFunctions["end"] = format.readEnd
parserFunctions["arr+val"] = format.readArrayValue
parserFunctions["arr+esc"] = format.readArrayEscaped
parserFunctions["val+end"] = format.readValueEnd
parserFunctions["esc+end"] = format.readEscapedEnd
parserFunctions["dat+end"] = format.readDateEnd
directives := []tstrings.TransitionDirective{}
for _, dirString := range directiveStrings {
directive, err := tstrings.ParseTransitionDirective(dirString, parserFunctions)
if err != nil {
conf.Errors.Pushf("%s: %s", err.Error(), dirString)
continue // ### continue, malformed directive ###
}
if format.initState == "" {
format.initState = directive.State
}
directives = append(directives, directive)
}
format.parser.AddDirectives(directives)
// Validate initstate
initStateValid := false
for i := 0; i < len(directives) && !initStateValid; i++ {
initStateValid = directives[i].State == format.initState
}
if !initStateValid {
conf.Errors.Pushf("JSONStartState does not exist in directives")
}
for _, dir := range directives {
nextStateValid := false
for i := 0; i < len(directives) && !nextStateValid; i++ {
nextStateValid = dir.NextState == directives[i].State
}
if !nextStateValid {
format.Logger.Warningf("State \"%s\" has a transition to \"%s\" which does not exist in directives", dir.State, dir.NextState)
}
}
}
}
func (format *TextToJSON) writeKey(key []byte) {
// Make sure we are not in an array anymore
for format.state == jsonReadArray || format.state == jsonReadArrayAppend {
format.readEnd(nil, 0)
}
// If no value was written, write null
if format.state > jsonReadKey {
format.message.WriteString("null")
}
// Prepend a comma except after an object has started
if format.state != jsonReadObject {
format.message.WriteByte(',')
}
format.message.WriteByte('"')
format.message.Write(key)
format.message.WriteString(`":`)
}
func (format *TextToJSON) readKey(data []byte, state tstrings.ParserStateID) {
format.writeKey(data)
format.state = jsonReadValue
}
func (format *TextToJSON) readValue(data []byte, state tstrings.ParserStateID) {
trimmedData := bytes.TrimSpace(data)
if len(trimmedData) == 0 {
switch format.state {
default:
format.state = jsonReadKey
case jsonReadArray, jsonReadArrayAppend:
}
return
}
switch format.state {
default:
format.writeKey([]byte(format.parser.GetStateName(state)))
fallthrough
case jsonReadValue:
format.message.Write(trimmedData)
format.state = jsonReadKey
case jsonReadArray:
format.message.Write(trimmedData)
format.state = jsonReadArrayAppend
case jsonReadArrayAppend:
format.message.WriteByte(',')
format.message.Write(trimmedData)
}
}
func (format *TextToJSON) readEscaped(data []byte, state tstrings.ParserStateID) {
trimmedData := bytes.TrimSpace(data)
if len(trimmedData) == 0 {
switch format.state {
default:
format.state = jsonReadKey
case jsonReadArrayAppend, jsonReadArray:
}
return
}
encodedData, _ := json.Marshal(string(trimmedData))
switch format.state {
default:
format.writeKey([]byte(format.parser.GetStateName(state)))
fallthrough
case jsonReadValue:
format.message.Write(encodedData)
format.state = jsonReadKey
case jsonReadArray:
format.message.Write(encodedData)
format.state = jsonReadArrayAppend
case jsonReadArrayAppend:
format.message.WriteString(`,`)
format.message.Write(encodedData)
}
}
func (format *TextToJSON) readDate(data []byte, state tstrings.ParserStateID) {
date, _ := format.timeParse(format.timeRead, string(bytes.TrimSpace(data)))
formattedDate := date.Format(format.timeWrite)
format.readEscaped([]byte(formattedDate), state)
}
func (format *TextToJSON) readValueEnd(data []byte, state tstrings.ParserStateID) {
formatState := format.state
format.readValue(data, state)
format.state = formatState
format.readEnd(data, state)
}
func (format *TextToJSON) readEscapedEnd(data []byte, state tstrings.ParserStateID) {
formatState := format.state
format.readEscaped(data, state)
format.state = formatState
format.readEnd(data, state)
}
func (format *TextToJSON) readDateEnd(data []byte, state tstrings.ParserStateID) {
formatState := format.state
format.readDate(data, state)
format.state = formatState
format.readEnd(data, state)
}
func (format *TextToJSON) readArrayValue(data []byte, state tstrings.ParserStateID) {
format.readArray(data, state)
format.readValue(data, state)
}
func (format *TextToJSON) readArrayEscaped(data []byte, state tstrings.ParserStateID) {
format.readArray(data, state)
format.readEscaped(data, state)
}
func (format *TextToJSON) readArrayDate(data []byte, state tstrings.ParserStateID) {
format.readArray(data, state)
format.readDate(data, state)
}
func (format *TextToJSON) readArray(data []byte, state tstrings.ParserStateID) {
switch format.state {
default:
format.writeKey([]byte(format.parser.GetStateName(state)))
fallthrough
case jsonReadValue, jsonReadArray, jsonReadObject:
format.message.WriteByte('[')
case jsonReadArrayAppend:
format.message.WriteString(",[")
}
format.stack = append(format.stack, format.state)
format.state = jsonReadArray
}
func (format *TextToJSON) readObject(data []byte, state tstrings.ParserStateID) {
switch format.state {
default:
format.writeKey([]byte(format.parser.GetStateName(state)))
fallthrough
case jsonReadValue, jsonReadObject, jsonReadArray:
format.message.WriteByte('{')
case jsonReadArrayAppend:
format.message.WriteString(",{")
}
format.stack = append(format.stack, format.state)
format.state = jsonReadObject
}
func (format *TextToJSON) readEnd(data []byte, state tstrings.ParserStateID) {
stackSize := len(format.stack)
if stackSize > 0 {
switch format.state {
case jsonReadArray, jsonReadArrayAppend:
format.message.WriteByte(']')
default:
format.message.WriteByte('}')
}
}
if stackSize > 1 {
format.state = format.stack[stackSize-1]
format.stack = format.stack[:stackSize-1] // Pop the stack
if format.state == jsonReadArray {
format.state = jsonReadArrayAppend // just finished the first entry
}
} else {
format.stack = format.stack[:0] // Clear the stack
format.state = jsonReadKey
}
}
// ApplyFormatter update message payload
func (format *TextToJSON) ApplyFormatter(msg *core.Message) error {
// The internal state is not threadsafe so we need to lock here
format.parseLock.Lock()
defer format.parseLock.Unlock()
format.message = bytes.NewBuffer(nil)
format.state = jsonReadObject
format.message.WriteString("{")
remains, state := format.parser.Parse(format.GetAppliedContent(msg), format.initState)
// Write remains as string value
if remains != nil {
format.readEscaped(remains, state)
}
// Close any open tags
if format.message.Len() > 1 {
for format.state == jsonReadArray || format.state == jsonReadArrayAppend || format.state == jsonReadObject {
format.readEnd(nil, 0)
}
}
format.message.WriteString("}\n")
format.SetAppliedContent(msg, bytes.TrimSpace(format.message.Bytes()))
return nil
}