Make Subchannel internal state handling clearer #1949
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Motivation: The subchannel conflates closing (recoverable) with shutting down (terminal). Shutting down is initiated by a higher level (load-balancer, user) while closing happens when the subchannel closes unexpectedtly or is no longer required (i.e. becomes idle). A closed subchannel can be re-opeend, a shutdown subchannel can't. This distinction isn't clear enough in the state handling. Modifications: - Rename 'close' to 'shutDown' where applicable - Add a new 'shutting down' state and renaming the 'closing' state to 'going away'. - Add a state machine diagram - Fix up a few state transitions Result: More robust state handling
gjcairo
approved these changes
Jun 24, 2024
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| /// ┌───────────────┐ | ||
| /// ┌───────▶│ NOT CONNECTED │───────────shutDown─────────────┐ | ||
| /// │ └───────────────┘ │ | ||
| /// │ │ │ | ||
| /// │ connFailed──┤connect │ | ||
| /// │ /backedOff │ │ | ||
| /// │ │ ▼ │ | ||
| /// │ │ ┌───────────────┐ │ | ||
| /// │ └──│ CONNECTING │──────┐ │ | ||
| /// │ └───────────────┘ │ │ | ||
| /// │ │ │ │ | ||
| /// closed connSucceeded │ │ | ||
| /// │ │ │ │ | ||
| /// │ ▼ │ │ | ||
| /// │ ┌───────────────┐ │ ┌───────────────┐ │ | ||
| /// │ │ CONNECTED │──shutDown──▶│ SHUTTING DOWN │ │ | ||
| /// │ └───────────────┘ │ └───────────────┘ │ | ||
| /// │ │ │ │ │ | ||
| /// │ goAway │ closed │ | ||
| /// │ │ │ │ │ | ||
| /// │ ▼ │ ▼ │ | ||
| /// │ ┌───────────────┐ │ ┌───────────────┐ │ | ||
| /// └────────│ GOING AWAY │──────┘ │ SHUT DOWN │◀─┘ | ||
| /// └───────────────┘ └───────────────┘ |
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np, it was helpful for me too! 😅
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Motivation:
The subchannel conflates closing (recoverable) with shutting down (terminal). Shutting down is initiated by a higher level (load-balancer, user) while closing happens when the subchannel closes unexpectedtly or is no longer required (i.e. becomes idle). A closed subchannel can be re-opeend, a shutdown subchannel can't. This distinction isn't clear enough in the state handling.
Modifications:
Result:
More robust state handling