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71 lines
4.0 KiB
Markdown
71 lines
4.0 KiB
Markdown
# etcd Robustness Testing
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Purpose of etcd robustness tests is to validate that etcd upholds
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[API guarantees] and [watch guarantees] under any condition or failure.
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Robustness tests achieve that comparing etcd cluster behavior against a simplified model.
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Multiple test encompass different etcd cluster setups, client traffic types and failures experienced by cluster.
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During a single test we create a cluster and inject failures while sending and recording client traffic.
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Correctness is validated by running collected history of client operations against the etcd model and a set of validators.
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Upon failure tests generate a report that can be used to attribute whether failure was caused by bug in etcd or test framework.
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[API guarantees]: https://etcd.io/docs/latest/learning/api_guarantees/
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[watch guarantees]: https://etcd.io/docs/latest/learning/api/#watch-streams
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## Running locally
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1. Build etcd with failpoints
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```bash
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make gofail-enable
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make build
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make gofail-disable
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```
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2. Run the tests
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```bash
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make test-robustness
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```
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Optionally you can pass environment variables:
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* `GO_TEST_FLAGS` - to pass additional arguments to `go test`.
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It is recommended to run tests multiple times with failfast enabled. this can be done by setting `GO_TEST_FLAGS='--count=100 --failfast'`.
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* `EXPECT_DEBUG=true` - to get logs from the cluster.
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* `RESULTS_DIR` - to change location where results report will be saved.
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## Analysing failure
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If robustness tests fails we want to analyse the report to confirm if the issue is on etcd side. Location of this report
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is included in test logs. One of log lines should look like:
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```
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history.go:34: Model is not linearizable
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logger.go:130: 2023-03-18T12:18:03.244+0100 INFO Saving member data dir {"member": "TestRobustnessIssue14370-test-0", "path": "/tmp/TestRobustness_Issue14370/TestRobustnessIssue14370-test-0"}
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logger.go:130: 2023-03-18T12:18:03.244+0100 INFO Saving watch responses {"path": "/tmp/TestRobustness_Issue14370/TestRobustnessIssue14370-test-0/responses.json"}
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logger.go:130: 2023-03-18T12:18:03.247+0100 INFO Saving watch events {"path": "/tmp/TestRobustness_Issue14370/TestRobustnessIssue14370-test-0/events.json"}
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logger.go:130: 2023-03-18T12:18:03.248+0100 INFO Saving operation history {"path": "/tmp/TestRobustness_Issue14370/full-history.json"}
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logger.go:130: 2023-03-18T12:18:03.252+0100 INFO Saving operation history {"path": "/tmp/TestRobustness_Issue14370/patched-history.json"}
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logger.go:130: 2023-03-18T12:18:03.256+0100 INFO Saving visualization {"path": "/tmp/TestRobustness_Issue14370/history.html"}
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```
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Report includes multiple types of files:
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* Member db files, can be used to verify disk/memory corruption.
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* Watch responses saved as json, can be used to validate [watch guarantees].
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* Operation history saved as both html visualization and a json, can be used to validate [API guarantees].
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### Example analysis of linearization issue
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Let's analyse issue [#14370].
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To reproduce the issue by yourself run `make test-robustness-issue14370`.
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After a couple of tries robustness tests should report `Model is not linearizable` and save report locally.
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Lineralization issues are easiest to analyse via history visualization.
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Open `/tmp/TestRobustness_Issue14370/history.html` file in your browser.
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Jump to the error in linearization by clicking `[ jump to first error ]` on the top of the page.
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You should see a graph similar to the one on the image below.
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Last correct request (connected with grey line) is a `Put` request that succeeded and got revision `168`.
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All following requests are invalid (connected with red line) as they have revision `167`.
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Etcd guarantee that revision is non-decreasing, so this shows a bug in etcd as there is no way revision should decrease.
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This is consistent with the root cause of [#14370] as it was issue with process crash causing last write to be lost.
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[#14370]: https://github.com/etcd-io/etcd/issues/14370 |