postpone | Postpone your resources and save some bandwidth

You could try:

It seems like you can use update() instead of finishobjects() :

The retry options apply to a single service operation performed by the Service Bus SDK and are intended to allow the SDK work around short-term transient issues, like the occasional network interruption. Other than configuring the SDK clients, the Functions infrastructure is unaware of the retries and would simply see the SDK taking a longer time to perform the requested read/publish operation.

The Functions infrastructure will apply any execution time limits imposed by the runtime or may decide to take action to guard against an unresponsive service operation. (disclaimer: I can speak to the Service Bus SDK, but don't have deep insight into the Functions runtime)

The retries from the Service Bus extensions aren't applied to your Function code; on an error in your code you'll end up in an exception scenario and, depending on configuration and trigger/binding use, will either see your message abandoned or the lock held until timeout.

I'm not sure of your exact scenario, but it seems like you may want to consider deferring the message to be read explicitly at a later time or re-enqueuing the message with a schedule so that the Function can read again at a specific point in the future.

Let's say column E is where you have your extra working days list. Then you'll have

UPDATE: Changed the solution to try and accommodate OP's notes and requests. This method utilizes the wonderful Nito.AsyncEx package, which was not explicitly named as allowed by OP.

Do MQTT brokers re-deliver un-acknowledged "QoS 1" messages from subscribers?

From [the spec]:

When a Client reconnects with CleanSession set to 0, both the Client and Server MUST re-send any unacknowledged PUBLISH Packets (where QoS > 0) and PUBREL Packets using their original Packet Identifiers [MQTT-4.4.0-1]. This is the only circumstance where a Client or Server is REQUIRED to redeliver messages.

So, yes, unacknowledged QOS1 messages will be redelivered but the only time the spec REQUIRES this to happen is when a client reconnects.

While you specificity state you are using MQTT v3.1.1 I believe it is worth noting that MQTT v5 expressly prohibits re-delivery other than following a reconnect:

When a Client reconnects with Clean Start set to 0 and a session is present, both the Client and Server MUST resend any unacknowledged PUBLISH packets (where QoS > 0) and PUBREL packets using their original Packet Identifiers. This is the only circumstance where a Client or Server is REQUIRED to resend messages. Clients and Servers MUST NOT resend messages at any other time

How much time must pass until MQTT broker re-deliver?

As per the above automatic retry is not required by the spec. Some brokers may retransmit after a period of time. emqx supports this; mosquitto used to have an option but this was removed in version 1.5 with the change log explaining:.

Outgoing messages with QoS>1 are no longer retried after a timeout period. Messages will be retried when a client reconnects. This change in behaviour can be justified by considering when the timeout may have occurred.

• If a connection is unreliable and has dropped, but without one end noticing, the messages will be retried on reconnection. Sending additional PUBLISH or PUBREL would not have changed anything.
• If a client is overloaded/unable to respond/has a slow connection then sending additional PUBLISH or PUBREL would not help the client catch up. Once the backlog has cleared the client will respond. If it is not able to catch up, sending additional duplicates would not help either

Does the MQTT broker try endlessly to re-deliver an unacknowledged message?

The 3.11 spec does not provide any guidance (so, in theory, yes) but many brokers provide some control over this (maximum number of messages queued, max size of queue etc).

Are there other ways to trigger a re-delivery?

Yes - disconnect and reconnect.

Is it a good/valid idea to postpone sending the PUBACK until a received message was successfully persisted

There was a discussion re this on the paho-dev group a couple of months ago. Its something that is being considered in the Go v5 Client (currently that client automatically acknowledges messages).

One thing to note is that the MQTT spec does have requirements with regards to the order acknowledgments are sent. Many clients ignore this requirement (and just send the acknowledgments whenever the handler returns) but some (e.g. the HiveMQ Java client) queue up ACKs so they can be sent in the correct order.

Add these two styles for your left class.

The problem is that you are trying to use the system ruby. Don’t. It doesn’t belong to you. If you have to say sudo or you see System/Library/Frameworks/Ruby in the output, you’re doing it wrong.

Install Xcode and/or the Xcode tools, install homebrew, use rbenv to install your own ruby, and use it. Then you can install the cocoapods gem and off you go.

Why not just,