Module stream 

Stream supervision: open, read, reconnect with backoff. No protocol logic here.

A server-side stream can end at any time: the server closes it, the network breaks, or it goes silent. supervise reopens it with a growing delay (backoff) and tells the consumer on every successful open, so the consumer can resend its state. It keeps trying until it is cancelled (or the receiving end of the channel is dropped), except when the broker refuses the stream in a way a repeat cannot cure: a rejected token, no permission, the limit of open streams (80001, see fatal_open). Then it reports the reason once and stops.

Examples

use std::time::Duration;
use brokapi_tbank::stream::backoff;

// 500 ms doubling up to 30 s.
assert_eq!(backoff(0), Duration::from_millis(500));
assert_eq!(backoff(2), Duration::from_secs(2));
assert_eq!(backoff(40), Duration::from_secs(30));

Structs

LastError

The last reason a stream closed, for error messages of calls that wait on a stream.

Functions

backoff

Delay before reconnect attempt n (0-based): 500 ms doubling to 30 s. The same range at BCS and Finam: none of the three brokers documents a reason for a different one.

fatal_open

Whether the refusal to open a stream is final: a repeat will not help, so the supervisor stops and reports it. Some(reason) for a rejected token (Unauthenticated), no permission (PermissionDenied) and the limit of open streams (80001, streams_limit). Everything else (the network, Unavailable, a rate limit, the lifetime limit 80005) is worth another try.

sleep_or_cancel

Sleeps d unless cancelled. false when cancelled.

supervise

Keeps one server-side stream open. connected goes out after every successful open (then the consumer knows a break happened if it is not the first), wrap turns each message into a frame. A stream silent for stale_after is closed and reopened (pings arrive on a healthy stream).