前言

docker默认的日志驱动是json-file,每一个容器都会在本地生成一个/var/lib/docker/containers/containerID/containerID-json.log,而日志驱动是支持扩展的,本章主要讲解的是Fluentd驱动收集docker日志.

Fluentd是用于统一日志记录层的开源数据收集器,是继Kubernetes、Prometheus、Envoy 、CoreDNS 和containerd后的第6个CNCF毕业项目,常用来对比的是elastic的logstash,相对而言fluentd更加轻量灵活,现在发展非常迅速社区很活跃,在编写这篇blog的时候github的star是8.8k,fork是1k就可见一斑.

前提

准备配置文件

docker-compose.yml

version: '3.7'

x-logging:
  &default-logging
  driver: fluentd
  options:
    fluentd-address: localhost:24224
    fluentd-async-connect: 'true'
    mode: non-blocking
    max-buffer-size: 4m
    tag: "kafeidou.{{.Name}}"  #配置容器的tag,以kafeidou.为前缀,容器名称为后缀,docker-compose会给容器添加副本后缀,如 fluentd_1

services:

  fluentd:
   image: fluent/fluentd:v1.3.2
   ports:
    - 24224:24224
   volumes:
    - ./:/fluentd/etc
    - /var/log/fluentd:/var/log/fluentd
   environment:
    - FLUENTD_CONF=fluentd.conf

  fluentd-worker:
   image: fluent/fluentd:v1.3.2
   depends_on:
     - fluentd
   logging: *default-logging

fluentd.conf

<source>
  @type forward
  port 24224
  bind 0.0.0.0
</source>

<match kafeidou.*>
  @type              file
  path               /var/log/fluentd/kafeidou/${tag[1]}
  append             true
  <format>
    @type            single_value
    message_key      log
  </format>
  <buffer tag,time>
    @type             file
    timekey           1d
    timekey_wait      10m
    flush_mode        interval
    flush_interval    5s
  </buffer>
</match>

<match **>
  @type              file
  path               /var/log/fluentd/${tag}
  append             true
  <format>
    @type            single_value
    message_key      log
  </format>
  <buffer tag,time>
    @type             file
    timekey           1d
    timekey_wait      10m
    flush_mode        interval
    flush_interval    5s
  </buffer>
</match>

由于fluentd需要在配置的目录中有写入的权限,所以需要先准备好存放log的目录以及给予权限.
创建目录

mkdir /var/log/fluentd

给予权限,这里用于实验演示,直接授权777

chmod -R 777 /var/log/fluentd

在docker-compose.yml和fluentd.conf的目录中执行命令:
docker-compose up -d

[root@master log]# docker-compose up -d
WARNING: The Docker Engine you're using is running in swarm mode.

Compose does not use swarm mode to deploy services to multiple nodes in a swarm. All containers will be scheduled on the current node.

To deploy your application across the swarm, use `docker stack deploy`.

Creating network "log_default" with the default driver
Creating fluentd ... done
Creating fluentd-worker ... done

查看一下日志目录下,应该就有对应的容器日志文件了:

[root@master log]# ls /var/log/fluentd/kafeidou/
fluentd-worker.20200215.log  ${tag[1]}

这是我最后的一个实验结果,会创建一个${tag[1]}目录,挺奇怪的,而且在这个目录下还会有两个文件

[root@master log]# ls /var/log/fluentd/kafeidou/\$\{tag\[1\]\}/
buffer.b59ea0804f0c1f8b6206cf76aacf52fb0.log  buffer.b59ea0804f0c1f8b6206cf76aacf52fb0.log.meta

如果有明白这块的也欢迎一起交流!