* windows: revert process listing logic to that of v1.6.10
In Nomad 1.7 much of the process management code was refactored, including
a rewrite of how the process tree of an executor was determined on Windows
machines. Unfortunately that rewrite has been cursed with performance issues
and bugs. Instead, revert to the logic used in v1.6.10.
* changelog
Recently we moved from github.com/syndtr/gocapability to
github.com/moby/sys/capability due to the former package no longer being
maintainer. The new package's capability function works differently: the
known/supported functionality is split now, and the .ListSupported() call will
always return an empty list on non-linux systems. This means Nomad agents won't
start on darwin or windows.
github.com/moby/sys/capability is a fork of the (no longer maintained)
github.com/syndtr/gocapability package.
For changes since the fork took place, see
https://github.com/moby/sys/blob/main/capability/CHANGELOG.md
Note that the "workaround for RHEL6" is removed for a number of reasons.
Feel free to choose the one you like the most, either is sufficient:
1. /proc/sys/kernel/cap_last_cap is available since RHEL 6.7
(kernel 2.6.32-573.el6), released 9 years ago (2015-07-22).
2. It incorrectly returns CAP_BLOCK_SUSPEND (36), which was only added
in kernel v3.5 and was never backported to RHEL6 kernels. The
correct value for RHEL6 would be CAP_MAC_ADMIN (33).
3. As far as upstream kernels go, /proc/sys/kernel/cap_last_cap was
added in kernel v3.2, and a correct value depends on the kernel
version. It could be CAP_WAKE_ALARM (35), added to kernel v3.0, or
CAP_SYSLOG (34), added to kernel v2.6.38, or possibly a lesser value
for even older kernels.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
* drivers: move executor process out of v1 task cgroup after process starts
This PR changes the behavior of the raw exec task driver on old cgroups v1
systems such that the executor process is no longer a member of the cgroups
created for the task. Now, the executor process is placed into those
cgroups and starts the task child process (just as before), but now then
exits those cgroups and exists in the nomad parent cgroup. This change
makes the behavior sort of similar to cgroups v2 systems, where we never
have the executor enter the task cgroup to begin with (because we can
directly clone(3) the task process into it).
Fixes#23951
* executor: handle non-linux case
* cgroups: add test case for no executor process in task cgroup (v1)
* add changelog
* drivers: also move executor out of cpuset cgroup
On Windows, if the `raw_exec` driver's executor exits, the child processes are
not also killed. Create a Windows "job object" (not to be confused with a Nomad
job) and add the executor to it. Child processes of the executor will inherit
the job automatically. When the handle to the job object is freed (on executor
exit), the job itself is destroyed and this causes all processes in that job to
exit.
Fixes: https://github.com/hashicorp/nomad/issues/23668
Ref: https://learn.microsoft.com/en-us/windows/win32/procthread/job-objects
In #20619 we overhauled how we were gathering stats for Windows
processes. Unlike in Linux where we can ask for processes in a cgroup, on
Windows we have to make a single expensive syscall to get all the processes and
then build the tree ourselves. Our algorithm to do so is recursive and quadratic
in both steps and space with the number of processes on the host. For busy hosts
this hits the stack limit and panics the Nomad client.
We already build a map of parent PID to PID, so modify this to be a map of
parent PID to slice of children and then traverse that tree only from the root
we care about (the executor PID). This moves the allocations to the heap but
makes the stats gathering linear in steps and space required.
This changeset also moves as much of this code as possible into an area
not conditionally-compiled by OS, as the tagged test file was not being run in CI.
Fixes: https://github.com/hashicorp/nomad/issues/23984
This PR replaces fsouza/go-dockerclient 3rd party docker client library with
docker's official SDK.
---------
Co-authored-by: Tim Gross <tgross@hashicorp.com>
Co-authored-by: Seth Hoenig <shoenig@duck.com>
On supported platforms, the secrets directory is a 1MiB tmpfs. But some tasks
need larger space for downloading large secrets. This is especially the case for
tasks using `templates`, which need extra room to write a temporary file to the
secrets directory that gets renamed to the old file atomically.
This changeset allows increasing the size of the tmpfs in the `resources`
block. Because this is a memory resource, we need to include it in the memory we
allocate for scheduling purposes. The task is already prevented from using more
memory in the tmpfs than the `resources.memory` field allows, but can bypass
that limit by writing to the tmpfs via `template` or `artifact` blocks.
Therefore, we need to account for the size of the tmpfs in the allocation
resources. Simply adding it to the memory needed when we create the allocation
allows it to be accounted for in all downstream consumers, and then we'll
subtract that amount from the memory resources just before configuring the task
driver.
For backwards compatibility, the default value of 1MiB is "free" and ignored by
the scheduler. Otherwise we'd be increasing the allocated resources for every
existing alloc, which could cause problems across upgrades. If a user explicitly
sets `resources.secrets = 1` it will no longer be free.
Fixes: https://github.com/hashicorp/nomad/issues/2481
Ref: https://hashicorp.atlassian.net/browse/NET-10070
Whenever the "exec" task driver is being used, nomad runs a plug in that in time runs the task on a container under the hood. If by any circumstance the executor is killed, the task is reparented to the init service and wont be stopped by Nomad in case of a job updated or stop.
This commit introduces two mechanisms to avoid this behaviour:
* Adds signal catching and handling to the executor, so in case of a SIGTERM, the signal will also be passed on to the task.
* Adds a pre start clean up of the processes in the container, ensuring only the ones the executor runs are present at any given time.
We bring in `containernetworking/plugins` for the contents of a single file,
which we use in a few places for running a goroutine in a specific network
namespace. This code hasn't needed an update in a couple of years, and a good
chunk of what we need was previously vendored into `client/lib/nsutil`
already.
Updating the library via dependabot is causing errors in Docker driver tests
because it updates a lot of transient dependencies, and it's bringing in a pile
of new transient dependencies like opentelemetry. Avoid this problem going
forward by vendoring the remaining code we hadn't already.
Ref: https://github.com/hashicorp/nomad/pull/20146
* drivers/raw_exec: enable setting cgroup override values
This PR enables configuration of cgroup override values on the `raw_exec`
task driver. WARNING: setting cgroup override values eliminates any
gauruntee Nomad can make about resource availability for *any* task on
the client node.
For cgroup v2 systems, set a single unified cgroup path using `cgroup_v2_override`.
The path may be either absolute or relative to the cgroup root.
config {
cgroup_v2_override = "custom.slice/app.scope"
}
or
config {
cgroup_v2_override = "/sys/fs/cgroup/custom.slice/app.scope"
}
For cgroup v1 systems, set a per-controller path for each controller using
`cgroup_v1_override`. The path(s) may be either absolute or relative to
the controller root.
config {
cgroup_v1_override = {
"pids": "custom/app",
"cpuset": "custom/app",
}
}
or
config {
cgroup_v1_override = {
"pids": "/sys/fs/cgroup/pids/custom/app",
"cpuset": "/sys/fs/cgroup/cpuset/custom/app",
}
}
* drivers/rawexec: ensure only one of v1/v2 cgroup override is set
* drivers/raw_exec: executor should error if setting cgroup does not work
* drivers/raw_exec: create cgroups in raw_exec tests
* drivers/raw_exec: ensure we fail to start if custom cgroup set and non-root
* move custom cgroup func into shared file
---------
Co-authored-by: Michael Schurter <mschurter@hashicorp.com>
* exec2: add client support for unveil filesystem isolation mode
This PR adds support for a new filesystem isolation mode, "Unveil". The
mode introduces a "alloc_mounts" directory where tasks have user-owned
directory structure which are bind mounts into the real alloc directory
structure. This enables a task driver to use landlock (and maybe the
real unveil on openbsd one day) to isolate a task to the task owned
directory structure, providing sandboxing.
* actually create alloc-mounts-dir directory
* fix doc strings about alloc mount dir paths
The value for the executor cgroup CPU weight must be within the limits
imposed by the Linux kernel.
Nomad used the task `resource.cpu`, an unbounded value, directly as the
cgroup CPU weight, causing it to potentially go outside the imposed
values.
This commit clamps the CPU shares values to be within the limits
allowed.
Co-authored-by: Tim Gross <tgross@hashicorp.com>
On Windows, Nomad uses `syscall.NewLazyDLL` and `syscall.LoadDLL` functions to
load a few system DLL files, which does not prevent DLL hijacking
attacks. Hypothetically a local attacker on the client host that can place an
abusive library in a specific location could use this to escalate privileges to
the Nomad process. Although this attack does not fall within the Nomad security
model, it doesn't hurt to follow good practices here.
We can remove two of these DLL loads by using wrapper functions provided by the
stdlib in `x/sys/windows`
Co-authored-by: dduzgun-security <deniz.duzgun@hashicorp.com>
* drivers/raw_exec: enable configuring raw_exec task to have no memory limit
This PR makes it possible to configure a raw_exec task to not have an
upper memory limit, which is how the driver would behave pre-1.7.
This is done by setting memory_max = -1. The cluster (or node pool) must
have memory oversubscription enabled.
* cl: add cl
* Add OomKilled field to executor proto format
* Teach linux executor to detect and report OOMs
* Teach exec driver to propagate OOMKill information
* Fix data race
* use tail /dev/zero to create oom condition
* use new test framework
* minor tweaks to executor test
* add cl entry
* remove type conversion
---------
Co-authored-by: Marvin Chin <marvinchin@users.noreply.github.com>
Co-authored-by: Seth Hoenig <shoenig@duck.com>
Nomad CI checks for copywrite headers using multiple config files
for specific exemption paths. This means the top-level config file
does not take effect when running the copywrite script within
these sub-folders. Exempt files therefore need to be added to the
sub-config files, along with the top level.
* drivers/executor: set oom_score_adj for raw_exec
This might not be wholly true since I don't know all configurations of
Nomad, but in our use cases, we run some of our tasks as `raw_exec` for
reasons.
We observed that our tasks were running with `oom_score_adj = -1000`,
which prevents them from being OOM'd. This value is being inherited from
the nomad agent parent process, as configured by systemd.
Similar to #10698, we also were shocked to have this value inherited
down to every child process and believe that we should also set this
value to 0 explicitly.
I have no idea if there are other paths that might leverage this or
other ways that `raw_exec` can manifest, but this is how I was able to
observe and fix in one of our configurations.
We have been running in production our tasks wrapped in a script that
does: `echo 0 > /proc/self/oom_score_adj` to avoid this issue.
* drivers/executor: minor cleanup of setting oom adjustment
* e2e: add test for raw_exec oom adjust score
* e2e: set oom score adjust to -999
* cl: add cl
---------
Co-authored-by: Seth Hoenig <shoenig@duck.com>
