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Interface: Priority

common.Priority

Priority contains metadata that controls relative ordering of task processing when tasks are backlogged in a queue. Initially, Priority will be used in activity and workflow task queues, which are typically where backlogs exist. Priority is (for now) attached to workflows and activities. Activities and child workflows inherit Priority from the workflow that created them, but may override fields when they are started or modified. For each field of a Priority on an activity/workflow, not present or equal to zero/empty string means to inherit the value from the calling workflow, or if there is no calling workflow, then use the default (documented on the field). The overall semantics of Priority are:

  1. First, consider "priority_key": lower number goes first.
  2. Then, consider fairness: the fairness mechanism attempts to dispatch tasks for a given key in proportion to its weight.

Properties​

fairnessKey​

• Optional fairnessKey: string

FairnessKey is a short string that's used as a key for a fairness balancing mechanism. It may correspond to a tenant id, or to a fixed string like "high" or "low". The default is the empty string.

The fairness mechanism attempts to dispatch tasks for a given key in proportion to its weight. For example, using a thousand distinct tenant ids, each with a weight of 1.0 (the default) will result in each tenant getting a roughly equal share of task dispatch throughput.

Fairness keys are limited to 64 bytes.

fairnessWeight​

• Optional fairnessWeight: number

FairnessWeight for a task can come from multiple sources for flexibility. From highest to lowest precedence:

  1. Weights for a small set of keys can be overridden in task queue configuration with an API.
  2. It can be attached to the workflow/activity in this field.
  3. The default weight of 1.0 will be used.

Weight values are clamped to the range [0.001, 1000].

priorityKey​

• Optional priorityKey: number

Priority key is a positive integer from 1 to n, where smaller integers correspond to higher priorities (tasks run sooner). In general, tasks in a queue should be processed in close to priority order, although small deviations are possible.

The maximum priority value (minimum priority) is determined by server configuration, and defaults to 5.

The default priority is (min+max)/2. With the default max of 5 and min of 1, that comes out to 3.