title: Apache Mesos - Weights layout: documentation

Weights

In Mesos, weights can be used to control the relative share of cluster resources that is offered to different roles.

In Mesos 0.28 and earlier, weights can only be configured by specifying the --weights command-line flag when starting the Mesos master. If a role does not have a weight specified in the --weights flag, then the default value (1.0) will be used. Weights cannot be changed without updating the flag and restarting all Mesos masters.

Mesos 1.0 contains a /weights operator endpoint that allows weights to be changed at runtime. The --weights command-line flag is deprecated.

Operator HTTP Endpoint

The master /weights HTTP endpoint enables operators to configure weights. The endpoint currently offers a REST-like interface and supports the following operations:

Updating weights with PUT.
Querying the currently set weights with GET.

The endpoint can optionally use authentication and authorization. See the authentication guide for details.

Update

The operator can update the weights by sending an HTTP PUT request to the /weights endpoint.

An example request to the /weights endpoint could look like this (using the JSON file below):

$ curl -d @weights.json -X PUT http://<master-ip>:<port>/weights

For example, to set a weight of 2.0 for role1 and set a weight of 3.5 for role2, the operator can use the following weights.json:

    [
      {
        "role": "role1",
        "weight": 2.0
      },
      {
        "role": "role2",
        "weight": 3.5
      }
    ]

If the master is configured with an explicit role whitelist, the request is only valid if all specified roles exist in the role whitelist.

Weights are now persisted in the registry on cluster bootstrap and after any updates. Once the weights are persisted in the registry, any Mesos master that subsequently starts with --weights still specified will emit a warning and use the registry value instead.

The operator will receive one of the following HTTP response codes:

200 OK: Success (the update request was successful).
400 BadRequest: Invalid arguments (e.g., invalid JSON, non-positive weights).
401 Unauthorized: Unauthenticated request.
403 Forbidden: Unauthorized request.

Query

The operator can query the configured weights by sending an HTTP GET request to the /weights endpoint.

$ curl -X GET http://<master-ip>:<port>/weights

The response message body includes a JSON representation of the current configured weights, for example:

    [
      {
        "role": "role2",
        "weight": 3.5
      },
      {
        "role": "role1",
        "weight": 2.0
      }
    ]