Merge pull request #18737 from dvdksn/dual-logging-refresh

engine: refresh information about dual logging

content/config/containers/logging/configure.md

@@ -198,14 +198,6 @@ see more options.
 | [`gcplogs`](gcplogs.md)       | Writes log messages to Google Cloud Platform (GCP) Logging.                                                 |
 | [`logentries`](logentries.md) | Writes log messages to Rapid7 Logentries.                                                                   |
 
-> **Note**
->
-> When using Docker Engine 19.03 or older, the [`docker logs` command](../../../engine/reference/commandline/logs.md)
-> is only functional for the `local`, `json-file` and `journald` logging drivers.
-> Docker 20.10 and up introduces "dual logging", which uses a local buffer that
-> allows you to use the `docker logs` command for any logging driver. Refer to
-> [reading logs when using remote logging drivers](dual-logging.md) for details.
-
 ## Limitations of logging drivers
 
 - Reading log information requires decompressing rotated log files, which causes

content/config/containers/logging/dual-logging.md

@@ -1,46 +1,30 @@
 ---
-description:
+description: >
   Learn how to read container logs locally when using a third party logging
   solution.
-keywords:
+keywords: >
-  docker, logging, driver, dual logging, dual-logging, cache, ring-buffer,
+  docker, logging, driver, dual logging, dual logging, cache, ring-buffer,
   configuration
 title: Use docker logs with remote logging drivers
 ---
 
 ## Overview
 
-Prior to Docker Engine 20.10, the [`docker logs` command](../../../engine/reference/commandline/logs.md)
+You can use the `docker logs` command to read container logs regardless of the
-could only be used with logging drivers that supported for containers using the
+configured logging driver or plugin. Docker Engine uses the [`local`](local.md)
-`local`, `json-file`, or `journald` log drivers. However, many third party logging
+logging driver to act as cache for reading the latest logs of your containers.
-drivers had no support for locally reading logs using `docker logs`
+This is called dual logging. By default, the cache has log-file rotation
-
+enabled, and is limited to a maximum of 5 files of 20 MB each (before
-This created multiple problems when attempting to gather log data in an
-automated and standard way. Log information could only be accessed and viewed
-through the third-party solution in the format specified by that
-third-party tool.
-
-Starting with Docker Engine 20.10, you can use `docker logs` to read container
-logs regardless of the configured logging driver or plugin. This capability,
-referred to as "dual logging", allows you to use `docker logs` to read container
-logs locally in a consistent format, regardless of the log driver used, because
-the engine is configured to log information to the “local” logging driver. Refer
-to [Configure the default logging driver](configure.md) for additional information.
-
-Dual logging uses the [`local`](local.md) logging driver to act as cache for
-reading the latest logs of your containers. By default, the cache has log-file
-rotation enabled, and is limited to a maximum of 5 files of 20MB each (before
 compression) per container.
 
 Refer to the [configuration options](#configuration-options) section to customize
-these defaults, or to the [disable dual-logging](#disable-the-dual-logging-cache)
+these defaults, or to the [disable dual logging](#disable-the-dual-logging-cache)
 section to disable this feature.
 
 ## Prerequisites
 
-No configuration changes are needed to use dual logging. Docker Engine 20.10 and
+Docker Engine automatically enables dual logging if the configured logging
-up automatically enable dual logging if the configured logging driver doesn't
+driver doesn't support reading logs.
-support reading logs.
 
 The following examples show the result of running a `docker logs` command with
 and without dual logging availability:
@@ -124,7 +108,7 @@ as a default, with dual logging caching enabled:
 
 ### Configuration options
 
-The "dual logging" cache accepts the same configuration options as the
+The dual logging cache accepts the same configuration options as the
 [`local` logging driver](local.md), but with a `cache-` prefix. These options
 can be specified per container, and defaults for new containers can be set using
 the [daemon configuration file](/engine/reference/commandline/dockerd/#daemon-configuration-file).

content/config/containers/logging/gcplogs.md

@@ -40,8 +40,6 @@ You can set the logging driver for a specific container by using the
 $ docker run --log-driver=gcplogs ...
 ```
 
-The `docker logs` command isn't available for this logging driver.
-
 If Docker detects that it's running in a Google Cloud Project, it discovers
 configuration from the
 [instance metadata service](https://cloud.google.com/compute/docs/metadata).