[crashtracking] add doc to outline UNIX pipe communication #1239
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BenchmarksComparisonBenchmark execution time: 2025-09-25 17:31:04 Comparing candidate commit e6d47ef in PR branch Found 15 performance improvements and 2 performance regressions! Performance is the same for 36 metrics, 2 unstable metrics. scenario:concentrator/add_spans_to_concentrator
scenario:credit_card/is_card_number/37828224631000521389798
scenario:credit_card/is_card_number/x371413321323331
scenario:credit_card/is_card_number_no_luhn/ 3782-8224-6310-005
scenario:credit_card/is_card_number_no_luhn/ 378282246310005
scenario:credit_card/is_card_number_no_luhn/378282246310005
scenario:credit_card/is_card_number_no_luhn/37828224631000521389798
scenario:credit_card/is_card_number_no_luhn/x371413321323331
scenario:normalization/normalize_name/normalize_name/good
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BaselineOmitted due to size. |
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #1239 +/- ##
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- Coverage 71.69% 71.63% -0.06%
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Files 354 355 +1
Lines 56138 56316 +178
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+ Hits 40247 40343 +96
- Misses 15891 15973 +82
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gleocadie
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Sep 24, 2025
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| **File**: `datadog-crashtracker/src/receiver/entry_points.rs:97-119` | ||
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| ```rust |
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I wonder if we need to add the code: if tomorrow the code changes, it means we have to change the doc.
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Assuming it's not too complicated, you can put it all in rustdoc instead of .MD and have the code compile.
gyuheon0h
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danielsn
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Sep 25, 2025
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| //! ┌─────────────────────┐ ┌──────────────────────┐ | ||
| //! │ Signal Handler │ │ Collector Process │ | ||
| //! │ (Original Process) │ │ (Forked Child) │ | ||
| //! │ │ │ │ | ||
| //! │ 1. Catch crash │────fork()──────────►│ 2. Setup stdio │ | ||
| //! │ 2. Fork collector │ │ 3. Create UnixStream │ | ||
| //! │ 3. Wait for child │ │ 4. Write crash data │ | ||
| //! │ │◄────wait()──────────│ 5. Exit cleanly │ | ||
| //! └─────────────────────┘ └──────────────────────┘ |
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Should you line up the fork and wait arrows with the lines of code the represent?
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| /// ┌─────────────────────────────┐ ┌─────────────────────────────┐ | ||
| /// │ 1. Catches crash signal │ │ 4. Closes stdio (0,1,2) │ | ||
| /// │ 2. Forks collector process │──►│ 5. Disables SIGPIPE │ | ||
| /// │ 3. Returns to caller │ │ 6. Creates UnixStream │ | ||
| /// │ │ │ 7. Calls emit_crashreport() │ | ||
| /// │ │ │ 8. Exits with _exit(0) │ | ||
| /// └─────────────────────────────┘ └─────────────────────────────┘ |
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The interleaving of steps here is a little confusing. Can we have whitespace to indicate which steps are concurrent?
| }; | ||
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| // Emit crashreport | ||
| // Create Unix socket stream for crash data transmission |
| //! 1. **Section Delimiters**: Uses constants from [`crate::shared::constants`] to mark boundaries | ||
| //! 2. **Structured Data**: Writes JSON, text, or binary data within sections | ||
| //! 3. **Immediate Flushing**: Flushes each section to ensure data integrity | ||
| //! 4. **Completion Marker**: Ends transmission with `DD_CRASHTRACK_DONE` |
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I found this a little confusing, because the delimiters wrap the structured data, but the list here makes them seem like they only come before.
| //! | ||
| //! ### Key Sections | ||
| //! | ||
| //! - **Stack Trace** (`emit_backtrace_by_frames`): Stack frames with optional symbol resolution |
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Do we still resolve symbols in process?
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we can pass a configuration to allow this.
| /// | ||
| /// ## Section Emission Order | ||
| /// | ||
| /// The crash report is written in this specific order: |
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Are we making this contractural? I'd say this is an implementation detail. The key part is that we try to emit more critical bits of info first, and bits that are more likely to crash last. Bits that are both critical and likely to crash are ¯\_(ツ)_/¯
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| //! ┌─────────────────┐ socketpair() ┌─────────────────┐ | ||
| //! │ Collector │◄───────────────────►│ Receiver │ | ||
| //! │ (Crashing proc) │ │ (Fork+execve) │ | ||
| //! │ │ Write End │ │ | ||
| //! │ uds_parent ────────────────────────────────► stdin (fd=0) │ | ||
| //! └─────────────────┘ └─────────────────┘ |
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| /// This function never returns - it either successfully executes the receiver binary | ||
| /// or terminates the process. |
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What does this PR do?
This PR adds a document in the
docs/folder of this repository to outline how we currently communicate over a UNIX socket to extract crash data in our two process,CollectorandReceiver, architecture in the CrashtrackerMotivation
Quality of life and DevX for developers wanting to understand Crashtracker architecture
Additional Notes
Note to reviewers: Pressing the
Display the rich diffbutton renders the Markdown, potentially making reading and reviewing easierHow to test the change?
Describe here in detail how the change can be validated.
Ticket: https://datadoghq.atlassian.net/browse/PROF-12520