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Log Management

logs <app> [-h] [-t|--tail] [-n|--num num] [-q|--quiet] [-p|--ps process]  # Display recent log output
logs:failed [--all|<app>]                                                  # Shows the last failed deploy logs
logs:report [<app>] [<flag>]                                               # Displays a logs report for one or more apps
logs:set [--global|<app>] <key> <value>                                    # Set or clear a logs property for an app
logs:vector-logs [--num num] [--tail]                                      # Display vector log output
logs:vector-start                                                          # Start the vector logging container
logs:vector-stop                                                           # Stop the vector logging container

Usage

Application logs

You can easily get logs of an app using the logs command:

dokku logs node-js-app

Behavioral modifiers

Dokku also supports certain command-line arguments that augment the log command's behavior.

-n, --num NUM        # the number of lines to display
-p, --ps PS          # only display logs from the given process
-t, --tail           # continually stream logs
-q, --quiet          # display raw logs without colors, time and names

You can use these modifiers as follows:

dokku logs node-js-app -t -p web

will show logs continually from the web process.

Failed deploy logs

Warning: The default docker-local scheduler will "store" these until the next deploy or until the old containers are garbage collected - whichever runs first. If you require the logs beyond this point in time, please ship the logs to a centralized log server.

In some cases, it may be useful to retrieve the logs from a previously failed deploy.

You can retrieve these logs by using the logs:failed command.

dokku logs:failed node-js-app

You may also fetch all failed app logs by using the --all flag.

dokku logs:failed --all

Docker Log Retention

Docker log retention can be specified via the logs:set command by specifying a value for max-size. Log retention is set via injected docker options for all applications, but is also available via the logs-get-property trigger for alternative schedulers.

dokku logs:set node-js-app max-size 20m

The default value may be set by passing an empty value for the option:

dokku logs:set node-js-app max-size

Valid values include any integer number followed by a unit of measure (k, m, or g) or the string unlimited. Setting to unlimited will result in Dokku omitting the log option.

The max-size property can also be set globally. The global default is 10m, and the global value is used when no app-specific value is set.

dokku logs:set --global max-size 20m

The default value may be set by passing an empty value for the option.

dokku logs:set --global max-size

Vector Logging Shipping

New as of 0.22.6

Vector is an open-source, lightweight and ultra-fast tool for building observability pipelines. Dokku integrates with it for shipping container logs for the docker-local scheduler. Users may configure log-shipping on a per-app or global basis, neither of which interfere with the dokku logs commands.

Starting the Vector container

Warning: While the default vector image may be updated over time, this will not impact running vector containers. Users are encouraged to view any Dokku and Vector changelogs to ensure their system will continue running as expected.

Vector may be started via the logs:vector-start command.

dokku logs:vector-start

This will start a new container named vector with Dokku's vector config mounted and ready for use. If a running container already exists, this command will do nothing. Additionally, if a container exists but is not running, this command will attempt to start the container.

While the default vector image is hardcoded, users may specify an alternative via the --vector-image flag:

dokku logs:vector-start --vector-image timberio/vector:latest-debian

The vector container will be started with the following volume mounts:

  • /var/lib/dokku/data/logs/vector.json:/etc/vector/vector.json
  • /var/run/docker.sock:/var/run/docker.sock
  • /var/log/dokku/apps:/var/log/dokku/apps

The final volume mount - /var/log/dokku/apps - may be used for users that wish to ship logs to a file on disk that may be later logrotated. This directory is owned by the dokku user and group, with permissions set to 0755. At this time, log-rotation is not configured for this directory.

Stopping the Vector container

Vector may be stopped via the logs:vector-stop command.

dokku logs:vector-stop

The vector container will be stopped and removed from the system. If the container is not running, this command will do nothing.

Configuring a log sink

Vector uses the concept of log "sinks" to send logs to a given endpoint. Log sinks may be configured globally or on a per-app basis by specifying a vector-sink in DSN form with the logs:set command. Specifying a sink value will reload any running vector container.

# setting the sink value in quotes is encouraged to avoid
# issues with ampersand encoding in shell commands
dokku logs:set node-js-app vector-sink "console://?encoding[codec]=json"

A sink may be removed by setting an empty value, which will also reload the running vector container.

dokku logs:set node-js-app vector-sink

Only one sink may be specified on a per-app basis at a given time.

Log sinks can also be specified globally by specifying the --global flag to logs:set with no app name specified:

dokku logs:set --global vector-sink "console://?encoding[codec]=json"

As with app-specific sink settings, the global value may also be cleared by setting no value.

dokku logs:set --global vector-sink
Log Sink DSN Format

The DSN form of a sink is as follows:

SINK_TYPE://?SINK_OPTIONS

Valid values for SINK_TYPE include all log vector log sinks, while SINK_OPTIONS is a query-string form for the sink's options. The following is a short description on how to set various values:

  • bool: form: key=bool
  • string: form: key=string
  • int: form: key=int
  • [string]: form: key[]=string
  • [int]: form: key[]=int
  • table: form: `option[key]=value

Please read the sink documentation for your sink of choice to configure the sink as desired.

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