TTL Lock Expired: How a Fencing Token Stops an Old Worker
On a safe model, we show why lease expiration does not stop an old process and how a monotonic fencing token prevents it from overwriting the new owner's result.
Денис
8 minViews0
GENERAL IT · JOURNAL
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Batch API Returned 200: How Not to Lose Errors for Individual Items
Check every element of the batch response: detect missing results, avoid resubmitting successful SKUs, and safely resume only temporarily failed operations.
Денис
9 minViews1
External API Returns Errors: Testing Circuit Breaker Without Cascade Timeouts
Practical guide to circuit breaker: three technical failures trip the breaker, requests stop reaching the external API, a failed probe extends the pause, and a successful one restores normal operation.
Денис
10 minViews1
Webhook Signature Is Valid: How to Stop a Replay of a Correct Request
We analyze a replay attack on a correctly signed webhook: signing the timestamp and nonce, verifying the time window, and showing why worker local memory loses protection after a restart.
Денис
8 minViews3
One Limit for Multiple Workers: Testing the Shared Token Bucket API
On a deterministic model, we compare local and shared token buckets: two workers receive four 429 responses with local limits, while a single shared limiter distributes eight requests without exceeding the limit.
Денис
8 minViews2
API Delta: How to Prevent Double-Counting of Product Quantities
On the tested model, we compare the change in product quantity against a record of its absolute value. A single operation_id prevents the same command from being applied twice, while version checking rejects stale snapshots after new product movements.
Денис
9 minViews3
Message Fails Again: Checking the Dead-Letter Queue and Safe Return
On an isolated SQLite model, we check the retry limit, move persistent errors to a dead-letter queue, handle rollback on failure between insert and delete, and perform a single return of the corrected message.
Денис
11 minViews3
Order Saved, but Webhook Not Sent: Checking the Transactional Outbox
We examine the transactional outbox using a safe model: the order and outgoing event are recorded in a single transaction; failures before and after sending do not lose the event, and retries use a stable event_id.
Денис
10 minViews3
OAuth Token Expired for Eight Requests: How to Perform a Single Update
We examine single-flight for OAuth: one request updates the access and refresh tokens, others wait for the result, and a token endpoint error does not corrupt the saved pair.
Денис
8 minViews4
How to check that a TLS certificate matches its private key
Before reloading, extract the public key from both the certificate and the private key, compare their SHA-256 hashes, and handle read errors separately. Tested with OpenSSL 3.0.13: a matching pair, a different pair, and a damaged file.
Михаил
6 minViews3
Webhook Secret Rotation: Changing Keys Without Stopping Acceptance
Practical guide: accept K1 and K2 only within a limited window, bind the signature to key_id and timestamp, verify HMAC via compare_digest, and disable the old key based on seven test results.
Денис
8 minViews0
How to check a systemd unit file before daemon-reload and starting the service
Check a complete candidate unit with systemd-analyze verify and interpret exit codes, a misspelled directive, a missing executable, and a missing dependency, without daemon-reload or starting the service.
Михаил
5 minViews1
openssl verify: why the certificate chain fails to build without an intermediate CA
A practical guide for OpenSSL 3.0: distinguishing trust anchors from intermediates, reproducing errors 20, 2, and 62, reading depth, and separately verifying the DNS name.
Михаил
7 minViews4
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