Applications

An application in Juju is a collection of identical application units that are installed via a charm.

Application management

Common application management tasks are summarised below.

The most important ones are Deploying applications and Managing relations.

Application groups

Application groups allow an operator to manage groups of the same application by providing custom application names during deployment.

See the Application groups page for details.

Application high availability

Application high availability pertains to the distribution of units over availability zones.

See the Application high availability page for full information.

Application metrics

Metrics for applications can be collected for the purposes of model-level assessment of application utilisation and capacity planning.

See the Application metrics page to learn more.

Configure applications

Applications can have their configuration options set during, or after, deployment.

The Configuring applications page explains how this is done.

Deploy applications

The Deploying applications page covers an array of methods for getting your applications deployed.

The Deploying applications - advanced page contains more advanced use cases.

See the Deploying charms offline page for guidance when deploying in a network-restricted environment.

Applications can be deployed and configured as a collection of charms. This subject is treated on the Charm bundles page.

Display information for deployed applications

Once an application is deployed it is possible to display information on it. This is done with the show-application command. For example:

juju deploy postgresql pgsql
juju show-application pgsql

Sample output:

pgsql:
  charm: postgresql
  series: bionic
  channel: stable
  principal: true
  exposed: false
  remote: false
  endpoint-bindings:
    coordinator: ""
    data: ""
    db: ""
    db-admin: ""
    local-monitors: ""
    master: ""
    nrpe-external-master: ""
    replication: ""
    syslog: ""
Relate applications

When an application requires another application in order to fulfil its purpose they need to be logically linked together. In Juju, such a link is called a relation.

The Managing relations page explains this important concept.

Scale applications

Juju horizontally scales applications up and down by adding and removing application units.

The Scaling applications page for details.

Upgrade an application

Upgrading an application in Juju means to upgrade the application's charm.

See the Upgrading applications page for in-depth coverage.

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