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fix(v9/core): Ensure logs past MAX_LOG_BUFFER_SIZE are not swallowed #18213

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Merged
merged 3 commits into from
Nov 17, 2025
+8 −3
Merged

fix(v9/core): Ensure logs past MAX_LOG_BUFFER_SIZE are not swallowed #18213

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b3fcf83
fix(v9/core): Ensure logs past MAX_LOG_BUFFER_SIZE are not swallowed
andreiborza Nov 14, 2025
cfac0af
Add test
andreiborza Nov 14, 2025
45d7680
Ensure log that triggers flush on MAX_LOG_BUFFER_SIZE is not swallowed
andreiborza Nov 14, 2025
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6 changes: 4 additions & 2 deletions packages/core/src/logs/exports.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -90,14 +90,16 @@ function setLogAttribute(
*/
export function _INTERNAL_captureSerializedLog(client: Client, serializedLog: SerializedLog): void {
const bufferMap = _getBufferMap();

const logBuffer = _INTERNAL_getLogBuffer(client);

if (logBuffer === undefined) {
bufferMap.set(client, [serializedLog]);
} else {
bufferMap.set(client, [...logBuffer, serializedLog]);
if (logBuffer.length >= MAX_LOG_BUFFER_SIZE) {
_INTERNAL_flushLogsBuffer(client, logBuffer);
bufferMap.set(client, [serializedLog]);
} else {
bufferMap.set(client, [...logBuffer, serializedLog]);
}
}
}
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5 changes: 4 additions & 1 deletion packages/core/test/lib/logs/exports.test.ts
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Expand Up @@ -245,7 +245,10 @@ describe('_INTERNAL_captureLog', () => {
// Add one more to trigger flush
_INTERNAL_captureLog({ level: 'info', message: 'trigger flush' }, client, undefined);

expect(_INTERNAL_getLogBuffer(client)).toEqual([]);
// After flushing the 100 logs, the new log starts a fresh buffer with 1 item
const buffer = _INTERNAL_getLogBuffer(client);
expect(buffer).toHaveLength(1);
expect(buffer?.[0]?.body).toBe('trigger flush');
});

it('does not flush logs buffer when it is empty', () => {
Comment on lines 245 to 254
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@sentry sentry bot Nov 14, 2025

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Bug: New logs are silently discarded when the log buffer reaches its maximum size and triggers a flush.
Severity: CRITICAL | Confidence: 1.00

🔍 Detailed Analysis

When the log buffer reaches MAX_LOG_BUFFER_SIZE and a new log is added, the system incorrectly flushes the old buffer before the new log is fully processed. Specifically, _INTERNAL_flushLogsBuffer is called with the logBuffer (100 items) before the serializedLog is properly accounted for. Subsequently, _getBufferMap().set(client, []) clears the buffer, overwriting the newly updated buffer that contained the 101st log. This results in the most recent log being silently discarded.

💡 Suggested Fix

Modify the logic to either check the new buffer size before flushing or ensure the new log is preserved after the buffer is cleared by the flush operation.

🤖 Prompt for AI Agent 
Review the code at the location below. A potential bug has been identified by an AI
agent.
Verify if this is a real issue. If it is, propose a fix; if not, explain why it's not
valid.

Location: packages/core/test/lib/logs/exports.test.ts#L245-L254

Potential issue: When the log buffer reaches `MAX_LOG_BUFFER_SIZE` and a new log is
added, the system incorrectly flushes the old buffer before the new log is fully
processed. Specifically, `_INTERNAL_flushLogsBuffer` is called with the `logBuffer` (100
items) before the `serializedLog` is properly accounted for. Subsequently,
`_getBufferMap().set(client, [])` clears the buffer, overwriting the newly updated
buffer that contained the 101st log. This results in the most recent log being silently
discarded.

Did we get this right? 👍 / 👎 to inform future reviews.

Reference_id: 2693436

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@andreiborza andreiborza Nov 14, 2025

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Indeed, that's what this PR fixes with ba24997.

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