03818c4aa9
The direct failure detector design is simplistic. It sends pings sequentially and times out listeners that reached the threshold (i.e. didn't hear from a given endpoint for too long) in-between pings. Given the sequential nature, the previous ping must finish so the next ping can start. We timeout pings that take too long. The timeout was hardcoded and set to 300ms. This is too low for wide-area setups -- latencies across the Earth can indeed go up to 300ms. 3 subsequent timed out pings to a given node were sufficient for the Raft listener to "mark server as down" (the listener used a threshold of 1s). Increase the ping timeout to 600ms which should be enough even for pinging the opposite side of Earth, and make it tunable. Increase the Raft listener threshold from 1s to 2s. Without the increased threshold, one timed out ping would be enough to mark the server as down. Increasing it to 2s requires 3 timed out pings which makes it more robust in presence of transient network hiccups. In the future we'll most likely want to decrease the Raft listener threshold again, if we use Raft for data path -- so leader elections start quickly after leader failures. (Faster than 2s). To do that we'll have to improve the design of the direct failure detector. Ref: scylladb/scylladb#16410 Fixes: scylladb/scylladb#16607 --- I tested the change manually using `tc qdisc ... netem delay`, setting network delay on local setup to ~300ms with jitter. Without the change, the result is as observed in scylladb/scylladb#16410: interleaving ``` raft_group_registry - marking Raft server ... as dead for Raft groups raft_group_registry - marking Raft server ... as alive for Raft groups ``` happening once every few seconds. The "marking as dead" happens whenever we get 3 subsequent failed pings, which is happens with certain (high) probability depending on the latency jitter. Then as soon as we get a successful ping, we mark server back as alive. With the change, the phenomenon no longer appears. Closes scylladb/scylladb#18443
Scylla in-source tests.
For details on how to run the tests, see docs/dev/testing.md
Shared C++ utils, libraries are in lib/, for Python - pylib/
alternator - Python tests which connect to a single server and use the DynamoDB API unit, boost, raft - unit tests in C++ cql-pytest - Python tests which connect to a single server and use CQL topology* - tests that set up clusters and add/remove nodes cql - approval tests that use CQL and pre-recorded output rest_api - tests for Scylla REST API Port 9000 scylla-gdb - tests for scylla-gdb.py helper script nodetool - tests for C++ implementation of nodetool
If you can use an existing folder, consider adding your test to it. New folders should be used for new large categories/subsystems, or when the test environment is significantly different from some existing suite, e.g. you plan to start scylladb with different configuration, and you intend to add many tests and would like them to reuse an existing Scylla cluster (clusters can be reused for tests within the same folder).
To add a new folder, create a new directory, and then
copy & edit its suite.ini.