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Diffstat (limited to 'nixos/tests/cockroachdb.nix')
| -rw-r--r-- | nixos/tests/cockroachdb.nix | 124 |
1 files changed, 124 insertions, 0 deletions
diff --git a/nixos/tests/cockroachdb.nix b/nixos/tests/cockroachdb.nix new file mode 100644 index 00000000000..d793842f0ab --- /dev/null +++ b/nixos/tests/cockroachdb.nix @@ -0,0 +1,124 @@ +# This performs a full 'end-to-end' test of a multi-node CockroachDB cluster +# using the built-in 'cockroach workload' command, to simulate a semi-realistic +# test load. It generally takes anywhere from 3-5 minutes to run and 1-2GB of +# RAM (though each of 3 workers gets 2GB allocated) +# +# CockroachDB requires synchronized system clocks within a small error window +# (~500ms by default) on each node in order to maintain a multi-node cluster. +# Cluster joins that are outside this window will fail, and nodes that skew +# outside the window after joining will promptly get kicked out. +# +# To accomodate this, we use QEMU/virtio infrastructure and load the 'ptp_kvm' +# driver inside a guest. This driver allows the host machine to pass its clock +# through to the guest as a hardware clock that appears as a Precision Time +# Protocol (PTP) Clock device, generally /dev/ptp0. PTP devices can be measured +# and used as hardware reference clocks (similar to an on-board GPS clock) by +# NTP software. In our case, we use Chrony to synchronize to the reference +# clock. +# +# This test is currently NOT enabled as a continuously-checked NixOS test. +# Ideally, this test would be run by Hydra and Borg on all relevant changes, +# except: +# +# - Not every build machine is compatible with the ptp_kvm driver. +# Virtualized EC2 instances, for example, do not support loading the ptp_kvm +# driver into guests. However, bare metal builders (e.g. Packet) do seem to +# work just fine. In practice, this means x86_64-linux builds would fail +# randomly, depending on which build machine got the job. (This is probably +# worth some investigation; I imagine it's based on ptp_kvm's usage of paravirt +# support which may not be available in 'nested' environments.) +# +# - ptp_kvm is not supported on aarch64, otherwise it seems likely Cockroach +# could be tested there, as well. This seems to be due to the usage of +# the TSC in ptp_kvm, which isn't supported (easily) on AArch64. (And: +# testing stuff, not just making sure it builds, is important to ensure +# aarch64 support remains viable.) +# +# For future developers who are reading this message, are daring and would want +# to fix this, some options are: +# +# - Just test a single node cluster instead (boring and less thorough). +# - Move all CI to bare metal packet builders, and we can at least do x86_64-linux. +# - Get virtualized clocking working in aarch64, somehow. +# - Add a 4th node that acts as an NTP service and uses no PTP clocks for +# references, at the client level. This bloats the node and memory +# requirements, but would probably allow both aarch64/x86_64 to work. +# + +let + + # Creates a node. If 'joinNode' parameter, a string containing an IP address, + # is non-null, then the CockroachDB server will attempt to join/connect to + # the cluster node specified at that address. + makeNode = locality: myAddr: joinNode: + { nodes, pkgs, lib, config, ... }: + + { + # Bank/TPC-C benchmarks take some memory to complete + virtualisation.memorySize = 2048; + + # Install the KVM PTP "Virtualized Clock" driver. This allows a /dev/ptp0 + # device to appear as a reference clock, synchronized to the host clock. + # Because CockroachDB *requires* a time-synchronization mechanism for + # the system time in a cluster scenario, this is necessary to work. + boot.kernelModules = [ "ptp_kvm" ]; + + # Enable and configure Chrony, using the given virtualized clock passed + # through by KVM. + services.chrony.enable = true; + services.chrony.servers = lib.mkForce [ ]; + services.chrony.extraConfig = '' + refclock PHC /dev/ptp0 poll 2 prefer require refid KVM + makestep 0.1 3 + ''; + + # Enable CockroachDB. In order to ensure that Chrony has performed its + # first synchronization at boot-time (which may take ~10 seconds) before + # starting CockroachDB, we block the ExecStartPre directive using the + # 'waitsync' command. This ensures Cockroach doesn't have its system time + # leap forward out of nowhere during startup/execution. + # + # Note that the default threshold for NTP-based skew in CockroachDB is + # ~500ms by default, so making sure it's started *after* accurate time + # synchronization is extremely important. + services.cockroachdb.enable = true; + services.cockroachdb.insecure = true; + services.cockroachdb.openPorts = true; + services.cockroachdb.locality = locality; + services.cockroachdb.listen.address = myAddr; + services.cockroachdb.join = lib.mkIf (joinNode != null) joinNode; + + systemd.services.chronyd.unitConfig.ConditionPathExists = "/dev/ptp0"; + + # Hold startup until Chrony has performed its first measurement (which + # will probably result in a full timeskip, thanks to makestep) + systemd.services.cockroachdb.preStart = '' + ${pkgs.chrony}/bin/chronyc waitsync + ''; + }; + +in import ./make-test-python.nix ({ pkgs, ...} : { + name = "cockroachdb"; + meta.maintainers = with pkgs.lib.maintainers; + [ thoughtpolice ]; + + nodes = { + node1 = makeNode "country=us,region=east,dc=1" "192.168.1.1" null; + node2 = makeNode "country=us,region=west,dc=2b" "192.168.1.2" "192.168.1.1"; + node3 = makeNode "country=eu,region=west,dc=2" "192.168.1.3" "192.168.1.1"; + }; + + # NOTE: All the nodes must start in order and you must NOT use startAll, because + # there's otherwise no way to guarantee that node1 will start before the others try + # to join it. + testScript = '' + for node in node1, node2, node3: + node.start() + node.wait_for_unit("cockroachdb") + node1.succeed( + "cockroach sql --host=192.168.1.1 --insecure -e 'SHOW ALL CLUSTER SETTINGS' 2>&1", + "cockroach workload init bank 'postgresql://root@192.168.1.1:26257?sslmode=disable'", + "cockroach workload run bank --duration=1m 'postgresql://root@192.168.1.1:26257?sslmode=disable'", + ) + ''; +}) |