Fluentd
1.0
1.0
  • Introduction
  • Overview
    • Life of a Fluentd event
    • Support
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    • 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
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    • Multi Process Workers
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  • Container Deployment
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  • Monitoring Fluentd
    • Overview
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  • Input Plugins
    • tail
    • forward
    • udp
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    • 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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  • Parameters
  • path
  • path_suffix
  • Tips
  • Customize a filename of the buffer chunk
  • Limitation

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  1. Buffer Plugins

file

PreviousmemoryNextfile_single

Last updated 2 years ago

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

Parameters

path

type
default
version

string

nil

0.9.0

The directory path where buffer chunks are stored. Don't share this directory path with other buffers. Be sure to specify a unique path for each buffer.

<match pattern>
  ...
  <buffer>
    @type file
    path /var/log/fluent/buf
  </buffer>
</match>

This config outputs the buffer chunk files as follows. The file name is buffer.b{chunk_id}{path_suffix}.

/var/log/fluentd/buf/buffer.b58eec11d08ca8143b40e4d303510e0bb.log
/var/log/fluentd/buf/buffer.b58eec11d08ca8143b40e4d303510e0bb.log.meta
<system>
  workers 2
</system>

...

<match pattern>
  ...
  <buffer>
    @type file
    path /var/log/fluent/buf
  </buffer>
</match>

This config outputs the buffer chunk files as follows. The directory worker{worker_id} is automatically created.

/var/log/fluentd/buf/worker0/buffer.b58eec11d08ca8143b40e4d303510e0bb.log
/var/log/fluentd/buf/worker0/buffer.b58eec11d08ca8143b40e4d303510e0bb.log.meta

/var/log/fluentd/buf/worker1/buffer.b5e2a5aca2bcd9818ad6718845ddc456a.log
/var/log/fluentd/buf/worker1/buffer.b5e2a5aca2bcd9818ad6718845ddc456a.log.meta
<system>
  root_dir /var/log/fluentd
</system>

...

<match pattern>
  @id test_id
  ...
  <buffer>
    @type file
  </buffer>
</match>

This config outputs the buffer chunk files as follows. The directory {root_dir}/worker{worker_id}/{@id}/buffer is used for the path. In this case, the worker{worker_id} directory is created even for a single worker.

/var/log/fluentd/worker0/test_id/buffer/buffer.b58eec11d08ca8143b40e4d303510e0bb.log
/var/log/fluentd/worker0/test_id/buffer/buffer.b58eec11d08ca8143b40e4d303510e0bb.log.meta

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

path_suffix

type
default
version

string

.log

1.6.3

Changes the suffix of the buffer file.

# default 
/var/log/fluentd/buf/buffer.b58eec11d08ca8143b40e4d303510e0bb.log
/var/log/fluentd/buf/buffer.b58eec11d08ca8143b40e4d303510e0bb.log.meta

# with 'path_suffix .buf'
/var/log/fluentd/buf/buffer.b58eec11d08ca8143b40e4d303510e0bb.buf
/var/log/fluentd/buf/buffer.b58eec11d08ca8143b40e4d303510e0bb.buf.meta

Tips

Customize a filename of the buffer chunk

You can customize the prefix of filename (buffer by default) by adding .* to the end of the path parameter.

<match pattern>
  ...
  <buffer>
    @type file
    path /var/log/fluent/buf/custom.*
  </buffer>
</match>

This config outputs the buffer chunk files as follows. The prefix buffer is changed to custom.

/var/log/fluentd/buf/custom.b58eec11d08ca8143b40e4d303510e0bb.log
/var/log/fluentd/buf/custom.b58eec11d08ca8143b40e4d303510e0bb.log.meta

You can also customize the entire filename by adding .*. to the path parameter.

<match pattern>
  ...
  <buffer>
    @type file
    path /var/log/fluent/buf/custom_prefix.*.custom_suffix
  </buffer>
</match>

This config outputs the buffer chunk files as follows. In this case, path_suffix parameter is not used.

/var/log/fluentd/buf/custom_prefix.b58eec11d08ca8143b40e4d303510e0bb.custom_suffix
/var/log/fluentd/buf/custom_prefix.b58eec11d08ca8143b40e4d303510e0bb.custom_suffix.meta

Limitation

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

With , a directory is automatically created for each worker. So there is no need to specify a unique path for each worker.

If you specify root_dir in and of the plugin, then you can omit this parameter.

This parameter is useful when .log is not fit for your environment. See also .

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.

Common Parameters
Buffer Section Configurations
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@id