Provide recent syncer response lengths as a watch channel #2602
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teor2345
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jvff
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jvff
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Aug 19, 2021
Also includes metrics and logging, to make diagnosing bugs easier.
- initially empty - pruned to correct length - newest entries go first
This seems to be a nightly or beta Rust change, but hopefully stable just accepts it.
This length makes it easier to distinguish between temporary and sustained errors/syncs.
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Co-authored-by: Janito Vaqueiro Ferreira Filho <janito.vff@gmail.com>
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teor2345
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Motivation
We want Zebra to activate the mempool once it reaches the chain tip.
To find out when that happens, we need to know the recent syncer response lengths.
Specifications
We know that the mempool should only activate once Zebra reaches the chain tip, but there doesn't seem to be a specification for it.
Designs
As part of this ticket, I split the "Check Initial Sync" and "Chain Update" tokio tasks in the design.
Diagram: https://jamboard.google.com/d/1HUhdqx8afJUqgiBdBcjCw0aAfDod9R9KBJeAH24U1Qg/viewer?f=0
Scope: https://docs.google.com/document/d/10PP6wKlnS5gannRph_EQ8V9diR7byddf3W2YFZ564FU/edit#
Solution
Closes #2595.
Implementation and Tests
Monitoring
This code might be hard to test, so I've added metrics and a dashboard.
They will help us work out what happens when Zebra gets near the chain tip.
And we'll also be able to see what happens when the network or peers fail.
Review
@jvff or @upbqdn can review this PR.
(It's based on the recent heights channel from PR #2519.)
We'll do more testing as part of ticket #2592.
In ticket #2592, I wrote down what happens to the sync lengths in different situations.
Reviewer Checklist
Follow Up Work
We need to create a tokio task which turns these lengths into enable/disable mempool requests.