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fix(win): buffer attachment updates - #174
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Expose `CrashpadClient::RegisterHandlers()` so sentry-native can restore the Windows crash handlers after another runtime replaces them, such as Unity installing its own handlers. Without access to this method, `sentry_reinstall_backend()` shuts down and starts the backend again. This launches another handler process and reloads breadcrumbs into the existing ring, duplicating them. Exposing the registration method lets the SDK preserve its client, handler process, IPC pipe, and breadcrumb state. Ref: getsentry/sentry-native#2182
The attachment IPC round trip waits for acknowledgment, which is sent before the request's disk write. The write then continues on the pipe service thread, keeping that pipe instance occupied. Later breadcrumb or scope updates can block on disk I/O from earlier requests when both instances are busy. Acknowledging before storing also allows consecutive updates to reach the delegate out of order, so a truncating write can erase a later append. Buffer each writable file under `attachments_lock_` before acknowledging its update. Writes replace pending content and appends extend it. Flush the buffers while the client is suspended, before resolving attachments or reading the external crash reporter envelope. Both crash dumps and `DumpWithoutCrash` use this path. Append-only updates extend preloaded file contents, while truncation keeps breadcrumb buffers bounded as the ring rotates. The handler kept across sentry-native backend reinstall preserves these pending updates. Ref: getsentry/sentry-native#2182
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The external crash reporter path deletes the database report, so the envelope is the only artifact. Flush again under the envelope lock so an update stored during the dump is included. The map is empty after the first flush, so only late arrivals are written.
JoshuaMoelans
approved these changes
Oct 12, 2026
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An attachment IPC update waits for acknowledgment, which is correctly sent before the request's disk write. However, when the handler proceeds to the disk write, it keeps the instance busy and therefore indirectly blocks any potential other incoming updates during the I/O. In essence, during heavy congestion, later IPC updates can block on disk I/O from earlier requests when both instances are busy.
Avoid that by buffering attachment IPC updates before acknowledging them. Writes replace pending content and appends extend it, and flush the buffers when appropriate.
Note:
RegisterHandlersis made public on Windows to allow sentry-native's backend reinstall to preserve the attachment IPC update buffer.Ref: getsentry/sentry-native#2182