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