Requests Overview

In the context of the Kameo, requests are the means through which actors communicate and interact with each other. These interactions are encapsulated in two primary forms: ask requests and tell requests. Understanding the nuances between these two types of requests is crucial for effectively managing actor behaviors and ensuring the robustness of your application.

Ask Requests

Ask requests are a form of message sending where the sender waits for a response from the receiver. This pattern is useful when the sender requires data or confirmation that an action has been completed before proceeding. Unlike tell requests, ask requests inherently support handling responses and errors, providing a direct way to deal with exceptional conditions.

Key Features of Ask Requests:

• Reply Awaited: The sender pauses its execution and waits for a reply, making it synchronous in nature within an asynchronous execution model.
• Error Handling: If an actor encounters an error while processing an ask request, the responsibility of handling these errors falls to the caller. This allows for more granular error management strategies.
• Timeouts:
  • Mailbox Timeout: For actors with a bounded mailbox, an optional mailbox_timeout can be specified. This timeout represents the maximum duration the request will wait in the queue before being processed. If the mailbox is full beyond this duration, the request may be dropped or an error returned.
  • Reply Timeout: A reply_timeout can also be set, indicating how long the sender will wait for a response. This is particularly useful for avoiding indefinite blocking in scenarios where the receiver might be unable to process the request promptly.

Tell Requests

Tell requests, on the other hand, are the "fire-and-forget" type of messages. When a tell request is sent, the sender does not wait for any acknowledgment or reply from the receiver. This approach is ideal for notifications or commands where the outcome does not directly influence the sender's immediate actions.

Characteristics of Tell Requests:

• No Reply: The sender continues its execution without waiting for a response, embodying a truly asynchronous interaction pattern.
• Error Handling: Errors encountered by the actor while processing a tell request are treated as panics. By default, such panics may lead to the stopping of the actor, although this behavior can be customized via the Actor::on_panic hook to allow for error recovery or logging.
• Mailbox Timeout: Similar to ask requests, a mailbox_timeout can be set for tell requests sent to actors with bounded mailboxes. This timeout helps manage the queuing behavior in scenarios where the actor's mailbox might be at capacity, ensuring that the system can gracefully handle backpressure.

Summary

Requests, encompassing both the ask and tell patterns, offer versatile communication strategies within Kameo. This duality provides the flexibility to either await responses for critical operations or to proceed without direct feedback for more autonomous actions. Such versatility is key to supporting a broad spectrum of application requirements, from straightforward notifications to intricate data exchanges and control flows, enhancing the dynamism and efficiency of your actor interactions.