chore: add backed reader, writer and pipe implementation #19147
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… to block on errors
…being closed/reconnected race conditions
separate channels for writer/reader errors moved to an interface for reconnection coordination logic for closing a pipe
…etter error tracking
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| // - readerSeqNum: how many bytes we've successfully read from remote (send to remote) | ||
| // - writerSeqNum: how many bytes we've written so far (used for validation) | ||
| readerSeqNum := bp.reader.SequenceNum() | ||
| writerSeqNum := bp.writer.SequenceNum() |
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If you read these values here, they can be out of date by the time you use them, since you release the locks and reads & writes can flow.
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| // Get sequence number and send new reader | ||
| <-seqNum | ||
| newR <- conn |
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The call to bp.reconnector.Reconnect() has to happen between reading the sequence number chan and writing the connection, so that the lock is held while we are reconnecting. And, the sequence number you psss to Reconnect has to be the one you got from the channel. Otherwise we could read more data and then get a replay from the wrong spot.
The whole point of using channels on this function on the reader is to allow this.
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| // Validate sequence numbers | ||
| if remoteReaderSeqNum > writerSeqNum { |
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The writer's Reconnect() method already handles this check, and it does so while holding the lock. Doing it here means we are subject to data races which could give false errors.
Fixes: #18101
This PR introduces a new
backedpipepackage that provides reliable bidirectional byte streams over unreliable network connections. The implementation includes:BackedPipe: Orchestrates a reader and writer to provide transparent reconnection and data replayBackedReader: Handles reading with automatic reconnection, blocking reads when disconnectedBackedWriter: Maintains a ring buffer of recent writes for replay during reconnectionRingBuffer: Efficient circular buffer implementation for storing dataThe package enables resilient connections by tracking sequence numbers and replaying missed data after reconnection. It handles connection failures gracefully, automatically reconnecting and resuming data transfer from the appropriate point.