a74b60066c
## Problem Storage controller was observed to have unexpectedly large memory consumption when loaded with many thousands of shards. This was recently fixed: - https://github.com/neondatabase/neon/pull/7493 ...but we need a general test that the controller is well behaved with thousands of shards. Closes: https://github.com/neondatabase/neon/issues/7460 Closes: https://github.com/neondatabase/neon/issues/7463 ## Summary of changes - Add test test_storage_controller_many_tenants to exercise the system's behaviour with a more substantial workload. This test measures memory consumption and reproduces #7460 before the other changes in this PR. - Tweak reconcile_all's return value to make it nonzero if it spawns no reconcilers, but _would_ have spawned some reconcilers if they weren't blocked by the reconcile concurrency limit. This makes the test's reconcile_until_idle behave as expected (i.e. not complete until the system is nice and calm). - Fix an issue where tenant migrations would leave a spurious secondary location when migrated to some location that was not already their secondary (this was an existing low-impact bug that tripped up the test's consistency checks). On the test with 8000 shards, the resident memory per shard is about 20KiB. This is not really per-shard memory: the primary source of memory growth is the number of concurrent network/db clients we create. With 8000 shards, the test takes 125s to run on my workstation.
Running locally
First make a release build. The -s flag silences a lot of output, and makes it
easier to see if you have compile errors without scrolling up.
BUILD_TYPE=release CARGO_BUILD_FLAGS="--features=testing" make -s -j8
You may also need to run ./scripts/pysync.
Then run the tests
DEFAULT_PG_VERSION=15 NEON_BIN=./target/release poetry run pytest test_runner/performance
Some handy pytest flags for local development:
-xtells pytest to stop on first error-sshows test output-kselects a test to run--timeout=0disables our default timeout of 300s (seesetup.cfg)--preserve-database-filesto skip cleanup
What performance tests do we have and how we run them
Performance tests are built using the same infrastructure as our usual python integration tests. There are some extra fixtures that help to collect performance metrics, and to run tests against both vanilla PostgreSQL and Neon for comparison.
Tests that are run against local installation
Most of the performance tests run against a local installation. This is not very representative of a production environment. Firstly, Postgres, safekeeper(s) and the pageserver have to share CPU and I/O resources, which can add noise to the results. Secondly, network overhead is eliminated.
In the CI, the performance tests are run in the same environment as the other integration tests. We don't have control over the host that the CI runs on, so the environment may vary widely from one run to another, which makes the results across different runs noisy to compare.
Remote tests
There are a few tests that marked with pytest.mark.remote_cluster. These tests do not set up a local environment, and instead require a libpq connection string to connect to. So they can be run on any Postgres compatible database. Currently, the CI runs these tests on our staging and captest environments daily. Those are not an isolated environments, so there can be noise in the results due to activity of other clusters.
Noise
All tests run only once. Usually to obtain more consistent performance numbers, a test should be repeated multiple times and the results be aggregated, for example by taking min, max, avg, or median.
Results collection
Local test results for main branch, and results of daily performance tests, are stored in a neon project deployed in production environment. There is a Grafana dashboard that visualizes the results. Here is the dashboard. The main problem with it is the unavailability to point at particular commit, though the data for that is available in the database. Needs some tweaking from someone who knows Grafana tricks.
There is also an inconsistency in test naming. Test name should be the same across platforms, and results can be differentiated by the platform field. But currently, platform is sometimes included in test name because of the way how parametrization works in pytest. I.e. there is a platform switch in the dashboard with neon-local-ci and neon-staging variants. I.e. some tests under neon-local-ci value for a platform switch are displayed as Test test_runner/performance/test_bulk_insert.py::test_bulk_insert[vanilla] and Test test_runner/performance/test_bulk_insert.py::test_bulk_insert[neon] which is highly confusing.