fix: make observation additive and reference-counted per webview (#54) - #55
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@velocitysystems @yokuze This attempts to resolve this issue: #54 |
velocitysystems
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Jul 30, 2026
jjhafer
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This was referenced Jul 30, 2026
…vermine#54) Observation was destructive: any observe() call dropped the existing broker, and with it the sole broadcast sender, ending every current subscriber's stream with no error and no attributable cause. Since observe() is exposed over IPC, one window could silently kill another window's change stream just by observing the same database, which made multi-window use impossible. Observation is now shared rather than replaced. The broker is created once per database and reused, requested tables are merged into it, and each window holds its own registration so teardown waits for the last one to be released. Correctness depends on the registrations and the broker staying in step, so the lock order protecting them is enforced by the compiler rather than by convention - the registration methods require proof that the caller holds the database lock. The same ordering defect had been reintroduced four times while the rule lived only in a comment. Fixes issue silvermine#54. BREAKING CHANGE: DatabaseWrapper::enable_observation() no longer tears down the existing broker. Callers who re-called it to shed subscribers, or to change channel_capacity/capture_values on a live database, must now call disable_observation() first. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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@velocitysystems Updated, can you review again? |
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Observation was destructive: any observe() call dropped the existing broker, and with it the sole broadcast sender, ending every current subscriber's stream with no error and no attributable cause. Since observe() is exposed over IPC, one window could silently kill another window's change stream just by observing the same database, which made multi-window use impossible.
Observation is now shared rather than replaced. The broker is created once per database and reused, requested tables are merged into it, and each window holds its own registration so teardown waits for the last one to be released.
Correctness depends on the registrations and the broker staying in step, so the lock order protecting them is enforced by the compiler rather than by convention - the registration methods require proof that the caller holds the database lock. The same ordering defect had been reintroduced four times while the rule lived only in a comment.
Fixes issue #54.
BREAKING CHANGE: DatabaseWrapper::enable_observation() no longer tears down the existing broker. Callers who re-called it to shed subscribers, or to change channel_capacity/capture_values on a live database, must now call disable_observation() first.