Fluentd
1.0
1.0
  • Introduction
  • Overview
    • Life of a Fluentd event
    • Support
    • FAQ
    • Logo
    • fluent-package v5 vs td-agent v4
  • Installation
    • Before Installation
    • Install fluent-package
      • RPM Package (Red Hat Linux)
      • DEB Package (Debian/Ubuntu)
      • .dmg Package (macOS)
      • .msi Installer (Windows)
    • Install calyptia-fluentd
      • RPM Package (Red Hat Linux)
      • DEB Package (Debian/Ubuntu)
      • .dmg Package (macOS)
      • .msi Installer (Windows)
    • Install by Ruby Gem
    • Install from Source
    • Post Installation Guide
    • Obsolete Installation
      • Treasure Agent v4 (EOL) Installation
        • Install by RPM Package v4 (Red Hat Linux)
        • Install by DEB Package v4 (Debian/Ubuntu)
        • Install by .dmg Package v4 (macOS)
        • Install by .msi Installer v4 (Windows)
      • Treasure Agent v3 (EOL) Installation
        • Install by RPM Package v3 (Red Hat Linux)
        • Install by DEB Package v3 (Debian/Ubuntu)
        • Install by .dmg Package v3 (macOS)
        • Install by .msi Installer v3 (Windows)
  • Configuration
    • Config File Syntax
    • Config File Syntax (YAML)
    • Routing Examples
    • Config: Common Parameters
    • Config: Parse Section
    • Config: Buffer Section
    • Config: Format Section
    • Config: Extract Section
    • Config: Inject Section
    • Config: Transport Section
    • Config: Storage Section
    • Config: Service Discovery Section
  • Deployment
    • System Configuration
    • Logging
    • Signals
    • RPC
    • High Availability Config
    • Performance Tuning
    • Multi Process Workers
    • Failure Scenarios
    • Plugin Management
    • Trouble Shooting
    • Fluentd UI
    • Linux Capability
    • Command Line Option
    • Source Only Mode
    • Zero-downtime restart
  • Container Deployment
    • Docker Image
    • Docker Logging Driver
    • Docker Compose
    • Kubernetes
  • Monitoring Fluentd
    • Overview
    • Monitoring by Prometheus
    • Monitoring by REST API
  • Input Plugins
    • tail
    • forward
    • udp
    • tcp
    • unix
    • http
    • syslog
    • exec
    • sample
    • monitor_agent
    • windows_eventlog
  • Output Plugins
    • file
    • forward
    • http
    • exec
    • exec_filter
    • secondary_file
    • copy
    • relabel
    • roundrobin
    • stdout
    • null
    • s3
    • kafka
    • elasticsearch
    • opensearch
    • mongo
    • mongo_replset
    • rewrite_tag_filter
    • webhdfs
    • buffer
  • Filter Plugins
    • record_transformer
    • grep
    • parser
    • geoip
    • stdout
  • Parser Plugins
    • regexp
    • apache2
    • apache_error
    • nginx
    • syslog
    • ltsv
    • csv
    • tsv
    • json
    • msgpack
    • multiline
    • none
  • Formatter Plugins
    • out_file
    • json
    • ltsv
    • csv
    • msgpack
    • hash
    • single_value
    • stdout
    • tsv
  • Buffer Plugins
    • memory
    • file
    • file_single
  • Storage Plugins
    • local
  • Service Discovery Plugins
    • static
    • file
    • srv
  • Metrics Plugins
    • local
  • How-to Guides
    • Stream Analytics with Materialize
    • Send Apache Logs to S3
    • Send Apache Logs to Minio
    • Send Apache Logs to Mongodb
    • Send Syslog Data to Graylog
    • Send Syslog Data to InfluxDB
    • Send Syslog Data to Sematext
    • Data Analytics with Treasure Data
    • Data Collection with Hadoop (HDFS)
    • Simple Stream Processing with Fluentd
    • Stream Processing with Norikra
    • Stream Processing with Kinesis
    • Free Alternative To Splunk
    • Email Alerting like Splunk
    • How to Parse Syslog Messages
    • Cloud Data Logging with Raspberry Pi
  • Language Bindings
    • Java
    • Ruby
    • Python
    • Perl
    • PHP
    • Nodejs
    • Scala
  • Plugin Development
    • How to Write Input Plugin
    • How to Write Base Plugin
    • How to Write Buffer Plugin
    • How to Write Filter Plugin
    • How to Write Formatter Plugin
    • How to Write Output Plugin
    • How to Write Parser Plugin
    • How to Write Storage Plugin
    • How to Write Service Discovery Plugin
    • How to Write Tests for Plugin
    • Configuration Parameter Types
    • Upgrade Plugin from v0.12
  • Plugin Helper API
    • Plugin Helper: Child Process
    • Plugin Helper: Compat Parameters
    • Plugin Helper: Event Emitter
    • Plugin Helper: Event Loop
    • Plugin Helper: Extract
    • Plugin Helper: Formatter
    • Plugin Helper: Inject
    • Plugin Helper: Parser
    • Plugin Helper: Record Accessor
    • Plugin Helper: Server
    • Plugin Helper: Socket
    • Plugin Helper: Storage
    • Plugin Helper: Thread
    • Plugin Helper: Timer
    • Plugin Helper: Http Server
    • Plugin Helper: Service Discovery
  • Troubleshooting Guide
  • Appendix
    • Update from v0.12 to v1
    • td-agent v2 vs v3 vs v4
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On this page
  • Example Configuration
  • Parameters
  • path
  • calc_num_records
  • chunk_format
  • Limitation
  • chunk keys
  • Remote File System is Not Supported

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  1. Buffer Plugins

file_single

PreviousfileNextStorage Plugins

Last updated 3 years ago

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The file_single buffer plugin provides a persistent buffer implementation. It uses files to store buffer chunks on disk.

file_single is similar to file_file but it does not have the metadata file.

Example Configuration

<match pattern>
  @type forward
  # forward parameters
  <buffer>
    @type file_single
    path /var/log/fluent/out_fwd
  </buffer>
</match>

Parameters

path

type

required

default

version

string

✔

1.7.0

The directory path where buffer chunks are stored. This parameter is required.

This parameter must be unique to avoid race condition problem between output plugins. Of course, this parameter must also be unique between fluentd instances.

The actual path consists of five (5) parts:

  • path parameter

  • fsb prefix

  • tag or field value

  • chunk id

  • buf extension

# Example with <buffer tag> and tag is test.log
/path/to/buffer/fsb.test.log.b513b61c9791029c2513b61c9791029c2.buf

# Example with <buffer key> and record is {"key":"hello"}
/path/to/buffer/fsb.hello.b513b61c9791029c2513b61c9791029c2.buf

Under multi-worker environment, worker_id and plugin id are added:

/path/to/buffer/worker1/out_fwd/fsb.test.log.b513b61c9791029c2513b61c9791029c2.buf

Please make sure that you have enough space in the path directory. Running out of disk space is a problem frequently reported by users.

calc_num_records

type

required

default

version

bool

true

1.7.0

Calculate the number of records, chunk size, during chunk resume.

The buf_file_single plugin does not have the metadata file, so this plugin cannot keep the chunk size across fluentd restarts. If true, it calculates the chunk size by reading the file at startup.

If your plugin does not need the chunk size, you can set false to speedup the fluentd startup time.

This option is mainly for out_forward.

chunk_format

type

default

available values

version

enum

auto

msgpack/text/auto

1.7.0

Specifies the chunk format for calc_num_records.

With auto, the plugin decides the chunk format by formatted_to_msgpack_binary?. This option is useful when the output plugin does not implement formatted_to_msgpack_binary? correctly.

Limitation

chunk keys

buf_file_single does not have the metadata file, so buf_file_single cannot use rich metadata. The chunk keys must be the only tag or one field key for now.

<buffer>           # OK. Same as <buffer tag>
<buffer tag>       # OK
<buffer key>       # OK
<buffer time>      # NG. time is not supported
<buffer key1,key2> # NG. multiple field keys are not supported

This limitation will be removed by adding the metadata header in the file.

Remote File System is Not Supported

Caution: file_single buffer implementation depends on the characteristics of the local file system. Don't use file_single buffer on remote file systems e.g. NFS, GlusterFS, HDFS and etc. We observed major data loss by using remote file system.

If this article is incorrect or outdated, or omits critical information, please . is an open-source project under . All components are available under the Apache 2 License.

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