# Flow Queue Bus - Use this app for synchronizing messages via queues
**URL:** https://community.homey.app/t/flow-queue-bus-use-this-app-for-synchronizing-messages-via-queues/142309
**Category:** Apps
**Tags:** app, tools, flow, homey-pro
**Created:** [August 27, 2025, 10:19am UTC](https://community.homey.app/t/flow-queue-bus-use-this-app-for-synchronizing-messages-via-queues/142309 "2025-08-27T10:19:37Z")
**Posts on this page:** 8
**Page:** 1
### Author:  [@Svensei38](https://community.homey.app/u/Svensei38)
#### Post date: [August 27, 2025, 10:19am UTC](https://community.homey.app/t/flow-queue-bus-use-this-app-for-synchronizing-messages-via-queues/142309/1 "2025-08-27T10:19:37Z")
The application is live! š¤©
> **[Flow Queue Bus | Homey](https://homey.app/en-be/app/be.sierrawings.flowqueuebus/Flow-Queue-Bus/)**
>
> Queue bus for messages in flows
# Intro
This app makes it possible to synchronize messages via named queues. **Ideally for triggers that interfere with one another**.
The queuing system always works in a very straightforward way:
`QUEUE` ā `PROCESS` ā `MARK AS HANDLED/FAILED`
A queue is based on the principle āFirst In, First Outā (FIFO).
As soon as you queue a new message, processing starts right away, unless there are messages before.
**CAUTION** : you are responsible for marking messages as handled or failed manually via an action card. Otherwise the queue will become blocked and no new triggers will be fired, because the message that is being processed will remain in the first position of the queue. You can retrieve the current message that is being processed at any time via an action card, if you missed the processing trigger.
As long as a message is not being processed, it can be dequeued. As soon as a message pops from a queue (the processing trigger will fire), itās considered as processing and can only be marked as handled or as failed to remove it from its queue (with exception of the Clear Queue action card). Messages are NOT persisted. If the app would become restarted, all queues will be empty.
# Cards
## Triggers (When)
### Message dequeued from queue `Queue Name`
A message has been dequeued via the action card **Dequeue message `Message ID` from queue `Queue Name`**
This card takes following arguments:
- `Queue Name` (Text): The name of the queue to monitor
This card will provide information about that message via tokens:
- `Queue Name` (Text): The name of the queue where the message was in
- `Message ID` (Text): The unique identifier of the message
- `Message` (Text): The contents of the message
- `Attempts` (Number): The number of times this message was attempted.
Always `0` because the message is never attempted
### Message failed from queue `Queue Name`
A message has been marked as failed via the action card **Mark message `Message ID` as failed in queue `Queue Name` and process next (if any)**
This card takes following arguments:
- `Queue Name` (Text): The name of the queue to monitor
This card will provide information about that message via tokens:
- `Queue Name` (Text): The name of the queue where the message was in
- `Message ID` (Text): The unique identifier of the message
- `Message` (Text): The contents of the message
- `Attempts` (Number): The number of times this message was attempted
### Message handled from queue `Queue Name`
A message has been marked as handled via the action card **Mark message `Message ID` as handled in queue `Queue Name` and process next (if any)**
This card takes following arguments:
- `Queue Name` (Text): The name of the queue to monitor
This card will provide information about that message via tokens:
- `Queue Name` (Text): The name of the queue where the message was in
- `Message ID` (Text): The unique identifier of the message
- `Message` (Text): The contents of the message
- `Attempts` (Number): The number of times this message was attempted
### Message processing in queue `Queue Name`
A message has popped from the queue and is being handled. This is either a new message that has been added to the queue via action cards **Place `Message` in queue `Queue Name`** or **Place message in queue `Queue Name` as only message** , or a message that is being retried via action cards **Retry message `Message ID` maximum `Maximum Attempts` times in queue `Queue Name`** or **Retry `Message ID` maximum `Maximum Attempts` times, each time with a delay of `Delay` milliseconds in `Queue Name`**.
**CAUTION:** you are responsible for marking messages as handled or failed manually via an action cards **Mark message `Message ID` as handled in queue `Queue Name` and process next (if any)** or **Mark message `Message ID` as failed in queue `Queue Name` and process next (if any)**.
Retrying a message will keep it in the queue and in the first position.
This card takes following arguments:
- `Queue Name` (Text): The name of the queue to monitor
This card will provide information about that message via tokens:
- `Queue Name` (Text): The name of the queue where the message was in
- `Message ID` (Text): The unique identifier of the message
- `Message` (Text): The contents of the message
- `Attempts` (Number): The number of times this message was attempted
Always `1` for new message and a higher number for messages that are being retried
## Conditions (And)
Conditions will be added in future versions.
## Actions (Then)
### Clear queue `Queue Name`
Clears the entire named queue (including the message that is being processed). Separate triggers will fire for each message that was in the queue:
- **Message dequeued from queue `Queue Name`** (Trigger): for all messages that were dequeued
- **Message failed from queue `Queue Name` (Trigger)**: for the message that was being processed
This card takes following arguments:
- `Queue Name` (Text): The name of the queue to clear
### Dequeue message `Message ID` from queue `Queue Name`
Dequeues a message that was not being processed from a named queue. If the message is already being processed, it will not be found by this card. This card will trigger:
- **Message dequeued from queue `Queue Name`** (Trigger): for the message that was dequeued (if found)
This card takes following arguments:
- `Queue Name` (Text): The name of the queue
- `Message ID` (Text): The unique identifier of the message
### Dequeue all non-processed messages from queue `Queue Name`
Dequeues all messages that have not yet been processed. Separate triggers will fire for each message that was in the queue:
- **Message dequeued from queue `Queue Name`** (Trigger): for all messages that were queued
This card takes following arguments:
- `Queue Name` (Text): The name of the queue to clear
### Mark message `Message ID` as failed in queue Queue Name and process next (if any)
Marks the message that was being processed as failed, removes it from the named queue and starts processing the next message (if any). This card will trigger:
- **Message failed from queue `Queue Name`** (Trigger): for the message that was marked as failed
This card takes following arguments:
- `Queue Name` (Text): The name of the queue
- `Message ID` (Text): The unique identifier of the message that failed
### Get the processing message in queue `Queue Name`
Gets the message that is currently being processed (if any).
This card takes following arguments:
- `Queue Name` (Text): The name of the queue to inspect
This card will provide information about that message via tokens:
- `Queue Name` (Text): The name of the queue
- `Message ID` (Text): The unique identifier of the message
This will `"-"` if no processing message was found, otherwise the actual identifier of the message
- `Message` (Text): The contents of the message
This will `"-"` if no processing message was found, otherwise the actual contents of the message
- `Attempts` (Number): The number of times this message was attempted.
This will `0` if no processing message was found, otherwise a number higher or equal to `1`
### Get the processing message in queue `Queue Name` and with default value `Default Value` when no message is being processed
Gets the message that is currently being processed (if any) and returns a default value (for token message) when no message is being processed.
This card takes following arguments:
- `Queue Name` (Text): The name of the queue to inspect
This card will provide information about that message via tokens:
- `Queue Name` (Text): The name of the queue
- `Message ID` (Text): The unique identifier of the message
This will `"-"` if no processing message was found, otherwise the actual identifier of the message
- `Message` (Text): The contents of the message
This will `Default Value` if no processing message was found, otherwise the actual contents of the message
- `Attempts` (Number): The number of times this message was attempted.
This will `0` if no processing message was found, otherwise a number higher or equal to `1`
### Mark message `Message ID` as handled in queue `Queue Name` and process next (if any)
Marks the message that was being processed as handled, removes it from the named queue and starts processing the next message (if any). This card will trigger:
- **Message handled from queue `Queue Name`** (Trigger): for the message that was marked as failed
This card takes following arguments:
- `Queue Name` (Text): The name of the queue
- `Message ID` (Text): The unique identifier of the message that finished
### Place `Message` in queue `Queue Name`
Queues a message onto a named queue. This card will trigger:
- **Message processing in queue `Queue Name`** (Trigger): when that message reaches the first position of the queue and pops
This card takes following arguments:
- `Message` (Text): The contents of the message
- `Queue Name` (Text): The name of the queue where to place the message
### Place `Message` in queue `Queue Name` as only message
Queues a message onto a named queue and dequeues all messages that have not yet been processed. Separate triggers will fire for each message that was in the queue:
- **Message dequeued from queue `Queue Name`** (Trigger): for all messages that were dequeued
- **Message processing in queue `Queue Name`** (Trigger): when that message reaches the first position of the queue and pops
This card takes following arguments:
- `Message` (Text): The contents of the message
- `Queue Name` (Text): The name of the queue where to place the message
### Retry message `Message ID` maximum `Maximum Attempts` times in queue `Queue Name`
Retries the message that was being processed immediately with a specified maximum number of attempts. The message remains in the queue. When the maximum number of attempts is reached, the message will be marked as failed and a separate trigger will be fired:
- **Message failed from queue `Queue Name`** (Trigger): for the message that reached the maximum number of attempts
This card takes following arguments:
- `Message ID` (Text): The unique identifier of the message to retry
- `Maximum Attempts` (Number): The number of times this message can be attempted
- `Queue Name` (Text): The name of the queue
### Retry `Message ID` maximum `Maximum Attempts` times, each time with a delay of `Delay` millisonds in queue `Queue Name`
Retries the message that was being processed with a specified maximum number of attempts after the specified delay (in milliseconds). The message remains in the queue. When the maximum number of attempts is reached, the message will be marked as failed and a separate trigger will be fired:
- **Message failed from queue `Queue Name`** (Trigger): for the message that reached the maximum number of attempts
This card takes following arguments:
- `Message ID` (Text): The unique identifier of the message to retry
- `Maximum Attempts` (Number): The number of times this message can be attempted
- `Maximum Attempts` (Number): The delay (in milliseconds) between retries
- `Queue Name` (Text): The name of the queue
**CAUTION:** Using delayed retries will block the queue because the message remains in the queue.
# Example
This flow a possible application of the Flow Message Queue.
In this flow a number of triggers are being synchronized into the queue to prevent racing conditions.
> From Wikipedia: [Race condition](https://en.wikipedia.org/wiki/Race_condition)
> A race condition or race hazard is the condition of an electronics, software, or other system where the systemās substantive behavior is dependent on the sequence or timing of other uncontrollable events, leading to unexpected or inconsistent results. It becomes a bug when one or more of the possible behaviors is undesirable.
This flow handles a number of devices (lights and switches) to act like a group:
- When one or more lights go on (via the app, via a mood or via another automation), the switch (which has an LED indicator) goes on as well.
- When the switch turns on it switches on all lights (or activates the specified mood).
- When all lights turn off (via the app, via a mood or via another automation), the switch goes off too.
All of this would be impossible without a queue that synchronizes the triggers (events), because by setting the group into another state, other (new) triggers will fire.
---
### Author:  [@SingKT](https://community.homey.app/u/SingKT)
#### Post date: [September 7, 2025, 8:25am UTC](https://community.homey.app/t/flow-queue-bus-use-this-app-for-synchronizing-messages-via-queues/142309/2 "2025-09-07T08:25:57Z")
Got some samples how you use MQ with flows. Not everyone might be familiar with MQ systems. Hopefully you can implement some reporting functions to list the existing queues and the containing messages with their details. Of course persistence would be great as homey restarts and thus app restarts do happen.
---
### Author:  [@Svensei38](https://community.homey.app/u/Svensei38)
#### Post date: [September 8, 2025, 6:46pm UTC](https://community.homey.app/t/flow-queue-bus-use-this-app-for-synchronizing-messages-via-queues/142309/3 "2025-09-08T18:46:26Z")
> Got some samples how you use MQ with flows. Not everyone might be familiar with MQ systems.
Iāve updated the initial post, with better documentation and an example how I currently use in my home(y).
> Of course persistence would be great as homey restarts and thus app restarts do happen.
This was not my intention for this app. I wanted the app to be as fast as I can make it (so only in memory). But I can also see an application for persisted queues, so that would be a feature for a future version, where the Homey user can decide. In other words, I would create separate cards for persisted queues with the clear disclaimer: āSlower but saferā.
Thanks for making the suggestion.
> Hopefully you can implement some reporting functions to list the existing queues and the containing messages with their details.
That would also be a nice feature, yes. Thanks again for suggesting it.
The way it is implemented in [Chronograph](https://homey.app/en-be/app/nl.fellownet.chronograph/Chronograph/), is absolute top notch. But Iām not very anxious to do frontend developmentā¦ I will inspect [the source code from Chronograph](https://bitbucket.org/QlusterIT/nl.qluster-it.chronograph/src/master/settings/) as see if I get my head around it. Definitely something for a future version.
---
### Author:  [@Persan](https://community.homey.app/u/Persan)
#### Post date: [November 17, 2025, 9:40pm UTC](https://community.homey.app/t/flow-queue-bus-use-this-app-for-synchronizing-messages-via-queues/142309/4 "2025-11-17T21:40:33Z")
Nice that I found this app. Have been lacking the possibility to have messages queues. Unfortunately I have a lot of flows written as standard flows and not advanced onceās. Currently that makes it impossible to queue new messages. Is there a reason for not having the āPlace message in queue Queue Name asā flow card available for standard flows?
Thanks in advance!
---
### Author:  [@Svensei38](https://community.homey.app/u/Svensei38)
#### Post date: [November 18, 2025, 3:29pm UTC](https://community.homey.app/t/flow-queue-bus-use-this-app-for-synchronizing-messages-via-queues/142309/5 "2025-11-18T15:29:59Z")
Hi @Persan,
This is something that Homey does automatically. My guess is because the cards return tokens to the flow (as you can see in the documentation above). Iāve done a quick comparison between the list of āadvancedā cards in the app store and the token documentation above, and they match.
Maybe someone in the community here could help me with this: how do I mark cards forcibly as āsimpleā?
I donāt understand why Homey would _shield_ these cards from use in the simple flowsā¦.?
If you donāt want to use tokens (advanced flows) or canāt use tokens (simple flows), you can always ignore themā¦
Any thoughts anyone?
---
### Author:  [@Persan](https://community.homey.app/u/Persan)
#### Post date: [November 18, 2025, 5:53pm UTC](https://community.homey.app/t/flow-queue-bus-use-this-app-for-synchronizing-messages-via-queues/142309/6 "2025-11-18T17:53:30Z")
Thanks for your answer. Yes, what you say makes sense. But would it then be possible to have a card that places a message in a queue without giving return values?
---
### Author:  [@Tom\_ten\_Den](https://community.homey.app/u/Tom_ten_Den)
#### Post date: [March 21, 2026, 3:50pm UTC](https://community.homey.app/t/flow-queue-bus-use-this-app-for-synchronizing-messages-via-queues/142309/7 "2026-03-21T15:50:16Z")
@Svensei38 I am using this app now and was wondering why this flow already gives an error message before 3 attempts have been made?
You would expect that it only reports that it failed after 3 attempts.
> When the maximum number of attempts is reached, the message will be marked as failed and a separate trigger will be fired:
---
### Author:  [@SierraWings](https://community.homey.app/u/SierraWings)
#### Post date: [June 13, 2026, 8:51am UTC](https://community.homey.app/t/flow-queue-bus-use-this-app-for-synchronizing-messages-via-queues/142309/8 "2026-06-13T08:51:23Z")
Hi @Tom_ten_Den
Because you have not marked the message as handled or failed.
See manual above:
> **CAUTION** : you are responsible for marking messages as handled or failed manually via an action card.