Fluentd Logging Driver Configuration Options and Usage

`fluentd-address` option to connect to a different address. `tcp`(default) and `unix` sockets are supported. ```console $ docker run --log-driver=fluentd --log-opt fluentd-address=fluentdhost:24224 $ docker run --log-driver=fluentd --log-opt fluentd-address=tcp://fluentdhost:24224 $ docker run --log-driver=fluentd --log-opt fluentd-address=unix:///path/to/fluentd.sock ``` Two of the above specify the same address, because `tcp` is default. ### tag By default, Docker uses the first 12 characters of the container ID to tag log messages. Refer to the [log tag option documentation](log_tags.md) for customizing the log tag format. ### labels, labels-regex, env, and env-regex The `labels` and `env` options each take a comma-separated list of keys. If there is collision between `label` and `env` keys, the value of the `env` takes precedence. Both options add additional fields to the extra attributes of a logging message. The `env-regex` and `labels-regex` options are similar to and compatible with respectively `env` and `labels`. Their values are regular expressions to match logging-related environment variables and labels. It is used for advanced [log tag options](log_tags.md). ### fluentd-async Docker connects to Fluentd in the background. Messages are buffered until the connection is established. Defaults to `false`. ### fluentd-async-reconnect-interval When `fluentd-async` is enabled, the `fluentd-async-reconnect-interval` option defines the interval, in milliseconds, at which the connection to `fluentd-address` is re-established. This option is useful if the address resolves to one or more IP addresses, for example a Consul service address. ### fluentd-buffer-limit Sets the number of events buffered on the memory. Records will be stored in memory up to this number. If the buffer is full, the call to record logs will fail. The default is 1048576. (https://github.com/fluent/fluent-logger-golang/tree/master#bufferlimit) ### fluentd-retry-wait How long to wait between retries. Defaults to 1 second. ### fluentd-max-retries The maximum number of retries. Defaults to `4294967295` (2\*\*32 - 1). ### fluentd-sub-second-precision Generates event logs in nanosecond resolution. Defaults to `false`. ## Fluentd daemon management with Docker About `Fluentd` itself, see [the project webpage](https://www.fluentd.org) and [its documents](https://docs.fluentd.org). To use this logging driver, start the `fluentd` daemon on a host. We recommend that you use [the Fluentd docker image](https://hub.docker.com/r/fluent/fluentd/). This image is especially useful if you want to aggregate multiple container logs on each host then, later, transfer the logs to another Fluentd node to create an aggregate store. ### Test container loggers 1. Write a configuration file (`test.conf`) to dump input logs: ```text <source> @type forward </source> <match *> @type stdout </match> ``` 2. Launch Fluentd container with this configuration file: ```console $ docker run -it -p 24224:24224 -v /path/to/conf/test.conf:/fluentd/etc/test.conf -e FLUENTD_CONF=test.conf fluent/fluentd:latest ``` 3. Start one or more containers with the `fluentd` logging driver: ```console $ docker run --log-driver=fluentd your/application ```

This section provides a comprehensive guide to configuring the Fluentd logging driver in Docker. It covers various options, including `fluentd-address` for specifying the Fluentd daemon's address, `tag` for customizing log tags, and `labels`/`env` options for adding extra attributes to log messages. It also details advanced options like `fluentd-async` for asynchronous logging, `fluentd-async-reconnect-interval` for reconnection intervals, `fluentd-buffer-limit` for memory buffering, and retry-related options like `fluentd-retry-wait` and `fluentd-max-retries`. Additionally, it includes instructions on setting up a Fluentd daemon using a Docker image and testing the logging driver by writing a sample configuration file and launching containers with the `fluentd` logging driver.