ファイルに出力する

ファイルへの出力はFileOutputプラグインを使用する

docker-compose.yml

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version: '3.5'
services:
  web1:
    image: nginx:latest
    ports:
      - "8888:80" 
    depends_on:
      - fluent-bit
    command: [nginx-debug, '-g', 'daemon off;']
    logging:
      driver: fluentd
      options:
        fluentd-address: "localhost:24224"
        fluentd-async-connect: "false"
  web2:
    image: nginx:latest
    ports:
      - "8889:80" 
    depends_on:
      - fluent-bit
    command: [nginx-debug, '-g', 'daemon off;']
    logging:
      driver: fluentd
      options:
        fluentd-address: "localhost:24224"
        fluentd-async-connect: "false"
  fluent-bit:
    image: fluent/fluent-bit
    volumes:
        - ./fluent-bit.conf:/fluent-bit/etc/fluent-bit.conf
        - ./log:/log:rw
    ports:
      - "24224:24224"

fluent-bit.conf

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[SERVICE]
    Log_Level       info
    Parsers_File    parsers.conf

[INPUT]
    Name    forward
    Listen  0.0.0.0
    Port    24224

[FILTER]
    Name parser
    Match *
    Key_Name log
    Parser nginx
    Preserve_Key Off
    Reserve_Data On

[OUTPUT]
    Name file
    Match *
    Path /log/

どのように記録されるか？

標準設定で出力してみる

‘/log’ディレクトリには以下のファイルが作成された

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Mode                 LastWriteTime         Length Name
----                 -------------         ------ ----
-a---l        2021/08/15     14:15          16383 247a34282381
-a---l        2021/08/15     14:12           2205 9b0fd4a80449

ファイルにはeginxのログが記録されている

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247a34282381: [1629004368.000000000, {"source":"stdout","log":"/docker-entrypoint.sh: /docker-entrypoint.d/ is not empty, will attempt to perform configuration","container_id":"247a342823810c30c81814b59743aa4da98240b96bac829f0558770956925f67","container_name":"/output-jsonfile_web1_1"}]
247a34282381: [1629004368.000000000, {"container_id":"247a342823810c30c81814b59743aa4da98240b96bac829f0558770956925f67","container_name":"/output-jsonfile_web1_1","source":"stdout","log":"/docker-entrypoint.sh: Looking for shell scripts in /docker-entrypoint.d/"}]
247a34282381: [1629004368.000000000, {"container_name":"/output-jsonfile_web1_1","source":"stdout","log":"/docker-entrypoint.sh: Launching /docker-entrypoint.d/10-listen-on-ipv6-by-default.sh","container_id":"247a342823810c30c81814b59743aa4da98240b96bac829f0558770956925f67"}]
247a34282381: [1629004368.000000000, {"log":"10-listen-on-ipv6-by-default.sh: info: Getting the checksum of /etc/nginx/conf.d/default.conf","container_id":"247a342823810c30c81814b59743aa4da98240b96bac829f0558770956925f67","container_name":"/output-jsonfile_web1_1","source":"stdout"}]
247a34282381: [1629004368.000000000, {"log":"10-listen-on-ipv6-by-default.sh: info: Enabled listen on IPv6 in /etc/nginx/conf.d/default.conf","container_id":"247a342823810c30c81814b59743aa4da98240b96bac829f0558770956925f67","container_name":"/output-jsonfile_web1_1","source":"stdout"}]
247a34282381: [1629004368.000000000, {"log":"/docker-entrypoint.sh: Launching /docker-entrypoint.d/20-envsubst-on-templates.sh","container_id":"247a342823810c30c81814b59743aa4da98240b96bac829f0558770956925f67","container_name":"/output-jsonfile_web1_1","source":"stdout"}]
247a34282381: [1629004368.000000000, {"log":"/docker-entrypoint.sh: Launching /docker-entrypoint.d/30-tune-worker-processes.sh","container_id":"247a342823810c30c81814b59743aa4da98240b96bac829f0558770956925f67","container_name":"/output-jsonfile_web1_1","source":"stdout"}]
247a34282381: [1629004368.000000000, {"container_id":"247a342823810c30c81814b59743aa4da98240b96bac829f0558770956925f67","container_name":"/output-jsonfile_web1_1","source":"stdout","log":"/docker-entrypoint.sh: Configuration complete; ready for start up"}]
247a34282381: [1629004383.000000000, {"remote":"172.27.0.1","host":"-","user":"-","method":"GET","path":"/","code":"304","size":"0","referer":"-","agent":"Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/92.0.4515.131 Safari/537.36","container_id":"247a342823810c30c81814b59743aa4da98240b96bac829f0558770956925f67","container_name":"/output-jsonfile_web1_1","source":"stdout"}]
247a34282381: [1629004384.000000000, {"remote":"172.27.0.1","host":"-","user":"-","method":"GET","path":"/","code":"304","size":"0","referer":"-","agent":"Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/92.0.4515.131 Safari/537.36","container_id":"247a342823810c30c81814b59743aa4da98240b96bac829f0558770956925f67","container_name":"/output-jsonfile_web1_1","source":"stdout"}]

ログフォーマットは？

標準のフォーマットはtag: [time, {"key1":"value1", "key2":"value2", "key3":"value3"}]というもの。

タグがファイル名として使用され、タグとタイムスタンプ以外はJSON形式になっている。

ログファイル名をカスタマイズしたい

ログファイル名はタグが使用されるので、タグ名をファイル名として整形すれば希望のログファイル名を設定できる。
docker-composeで起動している場合、docker-composeのオプションでタグを調整する。

loggingのoptionsにtag: "logfile_name_${DATE_YYYYMMDD}.log"のような設定を行う。
dateコマンドなどでYYYYMMDD形式に整形した日付を環境変数DATE_YYYYMMDDとして定義する。

ログは/log/logfile_name_YYYYMMDD.logのようなファイルで生成される。

docker-compose.ymlタグ修正版

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version: '3.5'
services:
  web1:
    image: nginx:latest
    ports:
      - "8888:80" 
    depends_on:
      - fluent-bit
    command: [nginx-debug, '-g', 'daemon off;']
    logging:
      driver: fluentd
      options:
        fluentd-address: "localhost:24224"
        fluentd-async-connect: "false"
        tag: "logfile_name_${DATE_YYYYMMDD}.log"
  web2:
    image: nginx:latest
    ports:
      - "8889:80" 
    depends_on:
      - fluent-bit
    command: [nginx-debug, '-g', 'daemon off;']
    logging:
      driver: fluentd
      options:
        fluentd-address: "localhost:24224"
        fluentd-async-connect: "false"
        tag: "logfile_name_${DATE_YYYYMMDD}.log"
  fluent-bit:
    image: fluent/fluent-bit
    volumes:
        - ./fluent-bit.conf:/fluent-bit/etc/fluent-bit.conf
        - ./log:/log:rw
    ports:
      - "24224:24224"