OpenStack Zaqar

openstack Queueopenstack-zaqar

Multi-tenant messaging service delivering messages at least once through worker claims, with subscriptions for broadcast observers.

Provider: openstack
Kind: Queue
Category: Messaging
Official docs: https://docs.openstack.org/zaqar/latest/
Also known as: Messaging service

Properties · 4 set by this component

property	type	values	required	kind default	this component
backoff	enum	none \| fixed \| exponential \| exponential-jitter	no	—	inherited
claimBased · component property	boolean	—	no	true	inherited
deadLetterQueue	boolean	—	no	false	inherited
delivery	enum	at-most-once \| at-least-once \| exactly-once	yes	—	▸ at-least-once
instances	integer	—	no	—	inherited
managed	boolean	—	no	false	▸ false
maxAttempts	integer	—	no	—	inherited
messageTtlExpiry · component property	boolean	—	no	true	inherited
ordering	enum	none \| per-key \| global	no	none	▸ none
persistence	boolean	—	no	true	inherited
publishSubscribe · component property	boolean	—	no	false	inherited
replay	boolean	—	no	false	inherited
retentionDays	integer	—	no	—	inherited
role	enum	work \| dlq \| retry \| offline-mailbox \| frontier	no	work	▸ work

Rules that apply · 3

Every rule whose selector covers this component's kind or its category. Whether a rule fires depends on the design: its properties, its edges and its groups.

Queue without dead-letter queueerror

queue-missing-dlq

A queue that receives asynchronous traffic and has no dead-letter queue either drops poison messages or retries them forever. Neither outcome leaves anything for a human to investigate.

— all of these hold:
— the node's `deadLetterQueue` is false
— the node has at least one asynchronous incoming edge

Retry queue without dead-letter queueerror

retry-queue-without-dlq

A retry queue is where poison messages end up. With no dead-letter queue they are retried forever or dropped in silence, and nobody ever looks at the failed payment.

— all of these hold:
— the node's `role` is "retry"
— the node's `deadLetterQueue` is false

Retry queue without backoffwarning

retry-without-backoff

Retrying a transient failure at full speed turns one slow dependency into a retry storm. A retry queue backs off, preferably exponentially and with jitter.

— all of these hold:
— the node's `role` is "retry"
— any of these hold:
— the node's `backoff` has no value
— the node's `backoff` is "none"

Use it in a design

nodes:
  - { id: "zaqar", component: "openstack-zaqar" }

Other Queue products · 23

Source

1# yaml-language-server: $schema=../../schema/component.schema.json
2# OpenStack Zaqar: multi-tenant messaging service. Per the "Getting Started Guide" only one worker can claim a
3# message so no other worker duplicates the work, and a worker that will go offline can retire the claim TTL,
4# "putting the message back into the queue for another worker to claim" - at-least-once delivery. Zaqar "is not
5# responsible for the ordering of messages" except with a single producer; subscriptions add broadcast observers.
6schemaVersion: "1"
7type: "component"
8id: "openstack-zaqar"
9kind: "queue"
10provider: "openstack"
11docs: "https://docs.openstack.org/zaqar/latest/"
12aliases: ["Messaging service"]
13defaults:
14  delivery: "at-least-once"
15  ordering: "none"
16  role: "work"
17  managed: false
18properties:
19  claimBased:
20    type: "boolean"
21    default: true
22  publishSubscribe:
23    type: "boolean"
24    default: false
25  messageTtlExpiry:
26    type: "boolean"
27    default: true

The same page as markdown, for an agent: /catalogue/components/openstack-zaqar.md