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docker
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Splunk Logging Driver performance improvements 

New driver options:

- `splunk-gzip` - gzip compress all requests to Splunk HEC
(enabled by default)
- `splunk-gzip-level` - change compression level.

Messages are sent in batches by 1000, with frequency of 5 seconds.
Maximum buffer is 10,000 events. If HEC will not be available, Splunk
Logging Driver will keep retrying while it can hold messages in buffer.

Added unit tests for driver.

Signed-off-by: Denis Gladkikh <denis@gladkikh.email>
This commit is contained in:
Denis Gladkikh 2016-08-25 11:27:02 -07:00
Родитель 46cb1f2601
Коммит 4907cc7793
6 изменённых файлов: 1761 добавлений и 55 удалений
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4
contrib/completion/bash/docker
Просмотреть файл

@ -520,7 +520,7 @@ __docker_complete_log_options() {
local journald_options="env labels tag"
local json_file_options="env labels max-file max-size"
local syslog_options="env labels syslog-address syslog-facility syslog-format syslog-tls-ca-cert syslog-tls-cert syslog-tls-key syslog-tls-skip-verify tag"
local splunk_options="env labels splunk-caname splunk-capath splunk-format splunk-index splunk-insecureskipverify splunk-source splunk-sourcetype splunk-token splunk-url splunk-verify-connection tag"
local splunk_options="env labels splunk-caname splunk-capath splunk-format splunk-gzip splunk-gzip-level splunk-index splunk-insecureskipverify splunk-source splunk-sourcetype splunk-token splunk-url splunk-verify-connection tag"
local all_options="$fluentd_options $gcplogs_options $gelf_options $journald_options $json_file_options $syslog_options $splunk_options"
@ -629,7 +629,7 @@ __docker_complete_log_driver_options() {
__ltrim_colon_completions "${cur}"
return
;;
splunk-insecureskipverify|splunk-verify-connection)
splunk-gzip|splunk-insecureskipverify|splunk-verify-connection)
COMPREPLY=( $( compgen -W "false true" -- "${cur##*=}" ) )
return
;;

2
contrib/completion/zsh/_docker
Просмотреть файл

@ -228,7 +228,7 @@ __docker_get_log_options() {
journald_options=("env" "labels" "tag")
json_file_options=("env" "labels" "max-file" "max-size")
syslog_options=("env" "labels" "syslog-address" "syslog-facility" "syslog-format" "syslog-tls-ca-cert" "syslog-tls-cert" "syslog-tls-key" "syslog-tls-skip-verify" "tag")
splunk_options=("env" "labels" "splunk-caname" "splunk-capath" "splunk-format" "splunk-index" "splunk-insecureskipverify" "splunk-source" "splunk-sourcetype" "splunk-token" "splunk-url" "splunk-verify-connection" "tag")
splunk_options=("env" "labels" "splunk-caname" "splunk-capath" "splunk-format" "splunk-gzip" "splunk-gzip-level" "splunk-index" "splunk-insecureskipverify" "splunk-source" "splunk-sourcetype" "splunk-token" "splunk-url" "splunk-verify-connection" "tag")
[[ $log_driver = (awslogs|all) ]] && _describe -t awslogs-options "awslogs options" awslogs_options "$@" && ret=0
[[ $log_driver = (fluentd|all) ]] && _describe -t fluentd-options "fluentd options" fluentd_options "$@" && ret=0

308
daemon/logger/splunk/splunk.go
Просмотреть файл

@ -4,6 +4,7 @@ package splunk
import (
"bytes"
"compress/gzip"
"crypto/tls"
"crypto/x509"
"encoding/json"
@ -12,7 +13,9 @@ import (
"io/ioutil"
"net/http"
"net/url"
"os"
"strconv"
"sync"
"time"
"github.com/Sirupsen/logrus"
@ -22,22 +25,47 @@ import (
)
const (
driverName = "splunk"
splunkURLKey = "splunk-url"
splunkTokenKey = "splunk-token"
splunkSourceKey = "splunk-source"
splunkSourceTypeKey = "splunk-sourcetype"
splunkIndexKey = "splunk-index"
splunkCAPathKey = "splunk-capath"
splunkCANameKey = "splunk-caname"
splunkInsecureSkipVerifyKey = "splunk-insecureskipverify"
splunkFormatKey = "splunk-format"
splunkVerifyConnectionKey = "splunk-verify-connection"
envKey = "env"
labelsKey = "labels"
tagKey = "tag"
driverName = "splunk"
splunkURLKey = "splunk-url"
splunkTokenKey = "splunk-token"
splunkSourceKey = "splunk-source"
splunkSourceTypeKey = "splunk-sourcetype"
splunkIndexKey = "splunk-index"
splunkCAPathKey = "splunk-capath"
splunkCANameKey = "splunk-caname"
splunkInsecureSkipVerifyKey = "splunk-insecureskipverify"
splunkFormatKey = "splunk-format"
splunkVerifyConnectionKey = "splunk-verify-connection"
splunkGzipCompressionKey = "splunk-gzip"
splunkGzipCompressionLevelKey = "splunk-gzip-level"
envKey = "env"
labelsKey = "labels"
tagKey = "tag"
)
const (
// How often do we send messages (if we are not reaching batch size)
defaultPostMessagesFrequency = 5 * time.Second
// How big can be batch of messages
defaultPostMessagesBatchSize = 1000
// Maximum number of messages we can store in buffer
defaultBufferMaximum = 10 * defaultPostMessagesBatchSize
// Number of messages allowed to be queued in the channel
defaultStreamChannelSize = 4 * defaultPostMessagesBatchSize
)
const (
envVarPostMessagesFrequency = "SPLUNK_LOGGING_DRIVER_POST_MESSAGES_FREQUENCY"
envVarPostMessagesBatchSize = "SPLUNK_LOGGING_DRIVER_POST_MESSAGES_BATCH_SIZE"
envVarBufferMaximum = "SPLUNK_LOGGING_DRIVER_BUFFER_MAX"
envVarStreamChannelSize = "SPLUNK_LOGGING_DRIVER_CHANNEL_SIZE"
)
type splunkLoggerInterface interface {
logger.Logger
worker()
}
type splunkLogger struct {
client *http.Client
transport *http.Transport
@ -45,6 +73,23 @@ type splunkLogger struct {
url string
auth string
nullMessage *splunkMessage
// http compression
gzipCompression bool
gzipCompressionLevel int
// Advanced options
postMessagesFrequency time.Duration
postMessagesBatchSize int
bufferMaximum int
// For synchronization between background worker and logger.
// We use channel to send messages to worker go routine.
// All other variables for blocking Close call before we flush all messages to HEC
stream chan *splunkMessage
lock sync.RWMutex
closed bool
closedCond *sync.Cond
}
type splunkLoggerInline struct {
@ -140,6 +185,29 @@ func New(ctx logger.Context) (logger.Logger, error) {
tlsConfig.ServerName = caName
}
gzipCompression := false
if gzipCompressionStr, ok := ctx.Config[splunkGzipCompressionKey]; ok {
gzipCompression, err = strconv.ParseBool(gzipCompressionStr)
if err != nil {
return nil, err
}
}
gzipCompressionLevel := gzip.DefaultCompression
if gzipCompressionLevelStr, ok := ctx.Config[splunkGzipCompressionLevelKey]; ok {
var err error
gzipCompressionLevel64, err := strconv.ParseInt(gzipCompressionLevelStr, 10, 32)
if err != nil {
return nil, err
}
gzipCompressionLevel = int(gzipCompressionLevel64)
if gzipCompressionLevel < gzip.DefaultCompression || gzipCompressionLevel > gzip.BestCompression {
err := fmt.Errorf("Not supported level '%s' for %s (supported values between %d and %d).",
gzipCompressionLevelStr, splunkGzipCompressionLevelKey, gzip.DefaultCompression, gzip.BestCompression)
return nil, err
}
}
transport := &http.Transport{
TLSClientConfig: tlsConfig,
}
@ -158,19 +226,36 @@ func New(ctx logger.Context) (logger.Logger, error) {
Index: index,
}
tag, err := loggerutils.ParseLogTag(ctx, loggerutils.DefaultTemplate)
if err != nil {
return nil, err
// Allow user to remove tag from the messages by setting tag to empty string
tag := ""
if tagTemplate, ok := ctx.Config[tagKey]; !ok || tagTemplate != "" {
tag, err = loggerutils.ParseLogTag(ctx, loggerutils.DefaultTemplate)
if err != nil {
return nil, err
}
}
attrs := ctx.ExtraAttributes(nil)
var (
postMessagesFrequency = getAdvancedOptionDuration(envVarPostMessagesFrequency, defaultPostMessagesFrequency)
postMessagesBatchSize = getAdvancedOptionInt(envVarPostMessagesBatchSize, defaultPostMessagesBatchSize)
bufferMaximum = getAdvancedOptionInt(envVarBufferMaximum, defaultBufferMaximum)
streamChannelSize = getAdvancedOptionInt(envVarStreamChannelSize, defaultStreamChannelSize)
)
logger := &splunkLogger{
client: client,
transport: transport,
url: splunkURL.String(),
auth: "Splunk " + splunkToken,
nullMessage: nullMessage,
client: client,
transport: transport,
url: splunkURL.String(),
auth: "Splunk " + splunkToken,
nullMessage: nullMessage,
gzipCompression: gzipCompression,
gzipCompressionLevel: gzipCompressionLevel,
stream: make(chan *splunkMessage, streamChannelSize),
postMessagesFrequency: postMessagesFrequency,
postMessagesBatchSize: postMessagesBatchSize,
bufferMaximum: bufferMaximum,
}
// By default we verify connection, but we allow use to skip that
@ -203,6 +288,8 @@ func New(ctx logger.Context) (logger.Logger, error) {
splunkFormat = splunkFormatInline
}
var loggerWrapper splunkLoggerInterface
switch splunkFormat {
case splunkFormatInline:
nullEvent := &splunkMessageEvent{
@ -210,18 +297,20 @@ func New(ctx logger.Context) (logger.Logger, error) {
Attrs: attrs,
}
return &splunkLoggerInline{logger, nullEvent}, nil
loggerWrapper = &splunkLoggerInline{logger, nullEvent}
case splunkFormatJSON:
nullEvent := &splunkMessageEvent{
Tag: tag,
Attrs: attrs,
}
return &splunkLoggerJSON{&splunkLoggerInline{logger, nullEvent}}, nil
loggerWrapper = &splunkLoggerJSON{&splunkLoggerInline{logger, nullEvent}}
case splunkFormatRaw:
var prefix bytes.Buffer
prefix.WriteString(tag)
prefix.WriteString(" ")
if tag != "" {
prefix.WriteString(tag)
prefix.WriteString(" ")
}
for key, value := range attrs {
prefix.WriteString(key)
prefix.WriteString("=")
@ -229,10 +318,14 @@ func New(ctx logger.Context) (logger.Logger, error) {
prefix.WriteString(" ")
}
return &splunkLoggerRaw{logger, prefix.Bytes()}, nil
loggerWrapper = &splunkLoggerRaw{logger, prefix.Bytes()}
default:
return nil, fmt.Errorf("Unexpected format %s", splunkFormat)
}
go loggerWrapper.worker()
return loggerWrapper, nil
}
func (l *splunkLoggerInline) Log(msg *logger.Message) error {
@ -244,7 +337,7 @@ func (l *splunkLoggerInline) Log(msg *logger.Message) error {
message.Event = &event
return l.postMessage(message)
return l.queueMessageAsync(message)
}
func (l *splunkLoggerJSON) Log(msg *logger.Message) error {
@ -262,7 +355,7 @@ func (l *splunkLoggerJSON) Log(msg *logger.Message) error {
message.Event = &event
return l.postMessage(message)
return l.queueMessageAsync(message)
}
func (l *splunkLoggerRaw) Log(msg *logger.Message) error {
@ -270,19 +363,124 @@ func (l *splunkLoggerRaw) Log(msg *logger.Message) error {
message.Event = string(append(l.prefix, msg.Line...))
return l.postMessage(message)
return l.queueMessageAsync(message)
}
func (l *splunkLogger) postMessage(message *splunkMessage) error {
jsonEvent, err := json.Marshal(message)
if err != nil {
return err
func (l *splunkLogger) queueMessageAsync(message *splunkMessage) error {
l.lock.RLock()
defer l.lock.RUnlock()
if l.closedCond != nil {
return fmt.Errorf("%s: driver is closed", driverName)
}
req, err := http.NewRequest("POST", l.url, bytes.NewBuffer(jsonEvent))
l.stream <- message
return nil
}
func (l *splunkLogger) worker() {
timer := time.NewTicker(l.postMessagesFrequency)
var messages []*splunkMessage
for {
select {
case message, open := <-l.stream:
if !open {
l.postMessages(messages, true)
l.lock.Lock()
defer l.lock.Unlock()
l.transport.CloseIdleConnections()
l.closed = true
l.closedCond.Signal()
return
}
messages = append(messages, message)
// Only sending when we get exactly to the batch size,
// This also helps not to fire postMessages on every new message,
// when previous try failed.
if len(messages)%l.postMessagesBatchSize == 0 {
messages = l.postMessages(messages, false)
}
case <-timer.C:
messages = l.postMessages(messages, false)
}
}
}
func (l *splunkLogger) postMessages(messages []*splunkMessage, lastChance bool) []*splunkMessage {
messagesLen := len(messages)
for i := 0; i < messagesLen; i += l.postMessagesBatchSize {
upperBound := i + l.postMessagesBatchSize
if upperBound > messagesLen {
upperBound = messagesLen
}
if err := l.tryPostMessages(messages[i:upperBound]); err != nil {
logrus.Error(err)
if messagesLen-i >= l.bufferMaximum || lastChance {
// If this is last chance - print them all to the daemon log
if lastChance {
upperBound = messagesLen
}
// Not all sent, but buffer has got to its maximum, let's log all messages
// we could not send and return buffer minus one batch size
for j := i; j < upperBound; j++ {
if jsonEvent, err := json.Marshal(messages[j]); err != nil {
logrus.Error(err)
} else {
logrus.Error(fmt.Errorf("Failed to send a message '%s'", string(jsonEvent)))
}
}
return messages[upperBound:messagesLen]
}
// Not all sent, returning buffer from where we have not sent messages
return messages[i:messagesLen]
}
}
// All sent, return empty buffer
return messages[:0]
}
func (l *splunkLogger) tryPostMessages(messages []*splunkMessage) error {
if len(messages) == 0 {
return nil
}
var buffer bytes.Buffer
var writer io.Writer
var gzipWriter *gzip.Writer
var err error
// If gzip compression is enabled - create gzip writer with specified compression
// level. If gzip compression is disabled, use standard buffer as a writer
if l.gzipCompression {
gzipWriter, err = gzip.NewWriterLevel(&buffer, l.gzipCompressionLevel)
if err != nil {
return err
}
writer = gzipWriter
} else {
writer = &buffer
}
for _, message := range messages {
jsonEvent, err := json.Marshal(message)
if err != nil {
return err
}
if _, err := writer.Write(jsonEvent); err != nil {
return err
}
}
// If gzip compression is enabled, tell it, that we are done
if l.gzipCompression {
err = gzipWriter.Close()
if err != nil {
return err
}
}
req, err := http.NewRequest("POST", l.url, bytes.NewBuffer(buffer.Bytes()))
if err != nil {
return err
}
req.Header.Set("Authorization", l.auth)
// Tell if we are sending gzip compressed body
if l.gzipCompression {
req.Header.Set("Content-Encoding", "gzip")
}
res, err := l.client.Do(req)
if err != nil {
return err
@ -301,7 +499,15 @@ func (l *splunkLogger) postMessage(message *splunkMessage) error {
}
func (l *splunkLogger) Close() error {
l.transport.CloseIdleConnections()
l.lock.Lock()
defer l.lock.Unlock()
if l.closedCond == nil {
l.closedCond = sync.NewCond(&l.lock)
close(l.stream)
for !l.closed {
l.closedCond.Wait()
}
}
return nil
}
@ -329,6 +535,8 @@ func ValidateLogOpt(cfg map[string]string) error {
case splunkInsecureSkipVerifyKey:
case splunkFormatKey:
case splunkVerifyConnectionKey:
case splunkGzipCompressionKey:
case splunkGzipCompressionLevelKey:
case envKey:
case labelsKey:
case tagKey:
@ -364,7 +572,7 @@ func parseURL(ctx logger.Context) (*url.URL, error) {
}
func verifySplunkConnection(l *splunkLogger) error {
req, err := http.NewRequest("OPTIONS", l.url, nil)
req, err := http.NewRequest(http.MethodOptions, l.url, nil)
if err != nil {
return err
}
@ -385,3 +593,29 @@ func verifySplunkConnection(l *splunkLogger) error {
}
return nil
}
func getAdvancedOptionDuration(envName string, defaultValue time.Duration) time.Duration {
valueStr := os.Getenv(envName)
if valueStr == "" {
return defaultValue
}
parsedValue, err := time.ParseDuration(valueStr)
if err != nil {
logrus.Error(fmt.Sprintf("Failed to parse value of %s as duration. Using default %v. %v", envName, defaultValue, err))
return defaultValue
}
return parsedValue
}
func getAdvancedOptionInt(envName string, defaultValue int) int {
valueStr := os.Getenv(envName)
if valueStr == "" {
return defaultValue
}
parsedValue, err := strconv.ParseInt(valueStr, 10, 32)
if err != nil {
logrus.Error(fmt.Sprintf("Failed to parse value of %s as integer. Using default %d. %v", envName, defaultValue, err))
return defaultValue
}
return int(parsedValue)
}

1302
daemon/logger/splunk/splunk_test.go Normal file
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Разница между файлами не показана из-за своего большого размера Загрузить разницу

157
daemon/logger/splunk/splunkhecmock_test.go Normal file
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@ -0,0 +1,157 @@
package splunk
import (
"compress/gzip"
"encoding/json"
"fmt"
"io"
"io/ioutil"
"net"
"net/http"
"testing"
)
func (message *splunkMessage) EventAsString() (string, error) {
if val, ok := message.Event.(string); ok {
return val, nil
}
return "", fmt.Errorf("Cannot cast Event %v to string", message.Event)
}
func (message *splunkMessage) EventAsMap() (map[string]interface{}, error) {
if val, ok := message.Event.(map[string]interface{}); ok {
return val, nil
}
return nil, fmt.Errorf("Cannot cast Event %v to map", message.Event)
}
type HTTPEventCollectorMock struct {
tcpAddr *net.TCPAddr
tcpListener *net.TCPListener
token string
simulateServerError bool
test *testing.T
connectionVerified bool
gzipEnabled *bool
messages []*splunkMessage
numOfRequests int
}
func NewHTTPEventCollectorMock(t *testing.T) *HTTPEventCollectorMock {
tcpAddr := &net.TCPAddr{IP: []byte{127, 0, 0, 1}, Port: 0, Zone: ""}
tcpListener, err := net.ListenTCP("tcp", tcpAddr)
if err != nil {
t.Fatal(err)
}
return &HTTPEventCollectorMock{
tcpAddr: tcpAddr,
tcpListener: tcpListener,
token: "4642492F-D8BD-47F1-A005-0C08AE4657DF",
simulateServerError: false,
test: t,
connectionVerified: false}
}
func (hec *HTTPEventCollectorMock) URL() string {
return "http://" + hec.tcpListener.Addr().String()
}
func (hec *HTTPEventCollectorMock) Serve() error {
return http.Serve(hec.tcpListener, hec)
}
func (hec *HTTPEventCollectorMock) Close() error {
return hec.tcpListener.Close()
}
func (hec *HTTPEventCollectorMock) ServeHTTP(writer http.ResponseWriter, request *http.Request) {
var err error
hec.numOfRequests++
if hec.simulateServerError {
if request.Body != nil {
defer request.Body.Close()
}
writer.WriteHeader(http.StatusInternalServerError)
return
}
switch request.Method {
case http.MethodOptions:
// Verify that options method is getting called only once
if hec.connectionVerified {
hec.test.Errorf("Connection should not be verified more than once. Got second request with %s method.", request.Method)
}
hec.connectionVerified = true
writer.WriteHeader(http.StatusOK)
case http.MethodPost:
// Always verify that Driver is using correct path to HEC
if request.URL.String() != "/services/collector/event/1.0" {
hec.test.Errorf("Unexpected path %v", request.URL)
}
defer request.Body.Close()
if authorization, ok := request.Header["Authorization"]; !ok || authorization[0] != ("Splunk "+hec.token) {
hec.test.Error("Authorization header is invalid.")
}
gzipEnabled := false
if contentEncoding, ok := request.Header["Content-Encoding"]; ok && contentEncoding[0] == "gzip" {
gzipEnabled = true
}
if hec.gzipEnabled == nil {
hec.gzipEnabled = &gzipEnabled
} else if gzipEnabled != *hec.gzipEnabled {
// Nothing wrong with that, but we just know that Splunk Logging Driver does not do that
hec.test.Error("Driver should not change Content Encoding.")
}
var gzipReader *gzip.Reader
var reader io.Reader
if gzipEnabled {
gzipReader, err = gzip.NewReader(request.Body)
if err != nil {
hec.test.Fatal(err)
}
reader = gzipReader
} else {
reader = request.Body
}
// Read body
var body []byte
body, err = ioutil.ReadAll(reader)
if err != nil {
hec.test.Fatal(err)
}
// Parse message
messageStart := 0
for i := 0; i < len(body); i++ {
if i == len(body)-1 || (body[i] == '}' && body[i+1] == '{') {
var message splunkMessage
err = json.Unmarshal(body[messageStart:i+1], &message)
if err != nil {
hec.test.Log(string(body[messageStart : i+1]))
hec.test.Fatal(err)
}
hec.messages = append(hec.messages, &message)
messageStart = i + 1
}
}
if gzipEnabled {
gzipReader.Close()
}
writer.WriteHeader(http.StatusOK)
default:
hec.test.Errorf("Unexpected HTTP method %s", http.MethodOptions)
writer.WriteHeader(http.StatusBadRequest)
}
}

43
docs/admin/logging/splunk.md
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@ -32,21 +32,23 @@ You can set the logging driver for a specific container by using the
You can use the `--log-opt NAME=VALUE` flag to specify these additional Splunk
logging driver options:
| Option | Required | Description |
|-----------------------------|----------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| `splunk-token` | required | Splunk HTTP Event Collector token. |
| `splunk-url` | required | Path to your Splunk Enterprise or Splunk Cloud instance (including port and scheme used by HTTP Event Collector) `https://your_splunk_instance:8088`. |
| `splunk-source` | optional | Event source. |
| `splunk-sourcetype` | optional | Event source type. |
| `splunk-index` | optional | Event index. |
| `splunk-capath` | optional | Path to root certificate. |
| `splunk-caname` | optional | Name to use for validating server certificate; by default the hostname of the `splunk-url` will be used. |
| `splunk-insecureskipverify` | optional | Ignore server certificate validation. |
| `splunk-format` | optional | Message format. Can be `inline`, `json` or `raw`. Defaults to `inline`. |
| `splunk-verify-connection` | optional | Verify on start, that docker can connect to Splunk server. Defaults to true. |
| `tag` | optional | Specify tag for message, which interpret some markup. Default value is `{{.ID}}` (12 characters of the container ID). Refer to the [log tag option documentation](log_tags.md) for customizing the log tag format. |
| `labels` | optional | Comma-separated list of keys of labels, which should be included in message, if these labels are specified for container. |
| `env` | optional | Comma-separated list of keys of environment variables, which should be included in message, if these variables are specified for container. |
| Option | Required | Description |
|-----------------------------|----------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| `splunk-token` | required | Splunk HTTP Event Collector token. |
| `splunk-url` | required | Path to your Splunk Enterprise or Splunk Cloud instance (including port and scheme used by HTTP Event Collector) `https://your_splunk_instance:8088`. |
| `splunk-source` | optional | Event source. |
| `splunk-sourcetype` | optional | Event source type. |
| `splunk-index` | optional | Event index. |
| `splunk-capath` | optional | Path to root certificate. |
| `splunk-caname` | optional | Name to use for validating server certificate; by default the hostname of the `splunk-url` will be used. |
| `splunk-insecureskipverify` | optional | Ignore server certificate validation. |
| `splunk-format` | optional | Message format. Can be `inline`, `json` or `raw`. Defaults to `inline`. |
| `splunk-verify-connection` | optional | Verify on start, that docker can connect to Splunk server. Defaults to true. |
| `splunk-gzip` | optional | Enable/disable gzip compression to send events to Splunk Enterprise or Splunk Cloud instance. Defaults to false. |
| `splunk-gzip-level` | optional | Set compression level for gzip. Valid values are -1 (default), 0 (no compression), 1 (best speed) ... 9 (best compression). Defaults to [DefaultCompression](https://golang.org/pkg/compress/gzip/#DefaultCompression). |
| `tag` | optional | Specify tag for message, which interpret some markup. Default value is `{{.ID}}` (12 characters of the container ID). Refer to the [log tag option documentation](log_tags.md) for customizing the log tag format. |
| `labels` | optional | Comma-separated list of keys of labels, which should be included in message, if these labels are specified for container. |
| `env` | optional | Comma-separated list of keys of environment variables, which should be included in message, if these variables are specified for container. |
If there is collision between `label` and `env` keys, the value of the `env` takes precedence.
Both options add additional fields to the attributes of a logging message.
@ -132,3 +134,14 @@ tag will be prefixed to the message. For example
MyImage/MyContainer env1=val1 label1=label1 my message
MyImage/MyContainer env1=val1 label1=label1 {"foo": "bar"}
```
## Advanced options
Splunk Logging Driver allows you to configure few advanced options by specifying next environment variables for the Docker daemon.
| Environment variable name | Default value | Description |
|--------------------------------------------------|---------------|----------------------------------------------------------------------------------------------------------------------------------------------------|
| `SPLUNK_LOGGING_DRIVER_POST_MESSAGES_FREQUENCY` | `5s` | If there is nothing to batch how often driver will post messages. You can think about this as the maximum time to wait for more messages to batch. |
| `SPLUNK_LOGGING_DRIVER_POST_MESSAGES_BATCH_SIZE` | `1000` | How many messages driver should wait before sending them in one batch. |
| `SPLUNK_LOGGING_DRIVER_BUFFER_MAX` | `10 * 1000` | If driver cannot connect to remote server, what is the maximum amount of messages it can hold in buffer for retries. |
| `SPLUNK_LOGGING_DRIVER_CHANNEL_SIZE` | `4 * 1000` | How many pending messages can be in the channel which is used to send messages to background logger worker, which batches them. |