This PR introduces support for using Nomad on systems with cgroups v2 [1]
enabled as the cgroups controller mounted on /sys/fs/cgroups. Newer Linux
distros like Ubuntu 21.10 are shipping with cgroups v2 only, causing problems
for Nomad users.
Nomad mostly "just works" with cgroups v2 due to the indirection via libcontainer,
but not so for managing cpuset cgroups. Before, Nomad has been making use of
a feature in v1 where a PID could be a member of more than one cgroup. In v2
this is no longer possible, and so the logic around computing cpuset values
must be modified. When Nomad detects v2, it manages cpuset values in-process,
rather than making use of cgroup heirarchy inheritence via shared/reserved
parents.
Nomad will only activate the v2 logic when it detects cgroups2 is mounted at
/sys/fs/cgroups. This means on systems running in hybrid mode with cgroups2
mounted at /sys/fs/cgroups/unified (as is typical) Nomad will continue to
use the v1 logic, and should operate as before. Systems that do not support
cgroups v2 are also not affected.
When v2 is activated, Nomad will create a parent called nomad.slice (unless
otherwise configured in Client conifg), and create cgroups for tasks using
naming convention <allocID>-<task>.scope. These follow the naming convention
set by systemd and also used by Docker when cgroups v2 is detected.
Client nodes now export a new fingerprint attribute, unique.cgroups.version
which will be set to 'v1' or 'v2' to indicate the cgroups regime in use by
Nomad.
The new cpuset management strategy fixes#11705, where docker tasks that
spawned processes on startup would "leak". In cgroups v2, the PIDs are
started in the cgroup they will always live in, and thus the cause of
the leak is eliminated.
[1] https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.htmlCloses#11289Fixes#11705#11773#11933
The error output being checked depends on the linux caps supported
by the particular operating system. Fix these test cases to just
check that an error did occur.
This PR enables setting allow_caps on the exec driver
plugin configuration, as well as cap_add and cap_drop in
exec task configuration. These options replicate the
functionality already present in the docker task driver.
Important: this change also reduces the default set of
capabilities enabled by the exec driver to match the
default set enabled by the docker driver. Until v1.0.5
the exec task driver would enable all capabilities supported
by the operating system. v1.0.5 removed NET_RAW from that
list of default capabilities, but left may others which
could potentially also be leveraged by compromised tasks.
Important: the "root" user is still special cased when
used with the exec driver. Older versions of Nomad enabled
enabled all capabilities supported by the operating system
for tasks set with the root user. To maintain compatibility
with existing clusters we continue supporting this "feature",
however we maintain support for the legacy set of capabilities
rather than enabling all capabilities now supported on modern
operating systems.
The default Linux Capabilities set enabled by the docker, exec, and
java task drivers includes CAP_NET_RAW (for making ping just work),
which has the side affect of opening an ARP DoS/MiTM attack between
tasks using bridge networking on the same host network.
https://docs.docker.com/engine/reference/run/#runtime-privilege-and-linux-capabilities
This PR disables CAP_NET_RAW for the docker, exec, and java task
drivers. The previous behavior can be restored for docker using the
allow_caps docker plugin configuration option.
A future version of nomad will enable similar configurability for the
exec and java task drivers.
Introduce a new more-block friendly syntax for specifying mounts with a new `mount` block type with the target as label:
```hcl
config {
image = "..."
mount {
type = "..."
target = "target-path"
volume_options { ... }
}
}
```
The main benefit here is that by `mount` being a block, it can nest blocks and avoids the compatibility problems noted in https://github.com/hashicorp/nomad/pull/9634/files#diff-2161d829655a3a36ba2d916023e4eec125b9bd22873493c1c2e5e3f7ba92c691R128-R155 .
The intention is for us to promote this `mount` blocks and quietly deprecate the `mounts` type, while still honoring to preserve compatibility as much as we could.
This addresses the issue in https://github.com/hashicorp/nomad/issues/9604 .
The default behavior for `docker.volumes.enabled` is intended to be `false`,
but the HCL schema defaults to `true` if the value is unset. Set the default
literal value to `true`.
Additionally, Docker driver mounts of type "volume" (but not "bind") are not
being properly sandboxed with that setting. Disable Docker mounts with type
"volume" entirely whenever the `docker.volumes.enabled` flag is set to
false. Note this is unrelated to the `volume_mount` feature, which is
constrained to preconfigured host volumes or whatever is mounted by a CSI
plugin.
This changeset includes updates to unit tests that should have been failing
under the documented behavior but were not.
In the Docker driver plugin config for garbage collection, the `image_delay`
field was missing from the default we set if the entire `gc` stanza is
missing. This results in a default of 0s and immediate GC of Docker images.
Expanded docker gc config test fields.
The 'docker.config.infra_image' would default to an amd64 container.
It is possible to reference the correct image for a platform using
the `runtime.GOARCH` variable, eliminating the need to explicitly set
the `infra_image` on non-amd64 platforms.
Also upgrade to Google's pause container version 3.1 from 3.0, which
includes some enhancements around process management.
Fixes#8926
Pulling large docker containers can take longer than the default
context timeout. Without a way to change this it is very hard for
users to utilise Nomad properly without hacky work arounds.
This change adds an optional pull_timeout config parameter which
gives operators the possibility to account for increase pull times
where needed. The infra docker image also has the option to set a
custom timeout to keep consistency.
* docker: support group allocated ports
* docker: add new ports driver config to specify which group ports are mapped
* docker: update port mapping docs
Fixes#2093
Enable configuring `memory_hard_limit` in the docker config stanza for tasks.
If set, this field will be passed to the container runtime as `--memory`, and
the `memory` configuration from the task resource configuration will be passed
as `--memory_reservation`, creating hard and soft memory limits for tasks using
the docker task driver.
Fix some docker test flakiness where image cleanup process may
contaminate other tests. A clean up process may attempt to delete an
image while it's used by another test.
This fixes few cases where driver eventor goroutines are leaked during
normal operations, but especially so in tests.
This change makes few modifications:
First, it switches drivers to use `Context`s to manage shutdown events.
Previously, it relied on callers invoking `.Shutdown()` function that is
specific to internal drivers only and require casting. Using `Contexts`
provide a consistent idiomatic way to manage lifecycle for both internal
and external drivers.
Also, I discovered few places where we don't clean up a temporary driver
instance in the plugin catalog code, where we dispense a driver to
inspect and validate the schema config without properly cleaning it up.
When an allocation runs for a task driver that can't support volume mounts,
the mounting will fail in a way that can be hard to understand. With host
volumes this usually means failing silently, whereas with CSI the operator
gets inscrutable internals exposed in the `nomad alloc status`.
This changeset adds a MountConfig field to the task driver Capabilities
response. We validate this when the `csi_hook` or `volume_hook` fires and
return a user-friendly error.
Note that we don't currently have a way to get driver capabilities up to the
server, except through attributes. Validating this when the user initially
submits the jobspec would be even better than what we're doing here (and could
be useful for all our other capabilities), but that's out of scope for this
changeset.
Also note that the MountConfig enum starts with "supports all" in order to
support community plugins in a backwards compatible way, rather than cutting
them off from volume mounting unexpectedly.
* Making pull activity timeout configurable in Docker plugin config, first pass
* Fixing broken function call
* Fixing broken tests
* Fixing linter suggestion
* Adding documentation on new parameter in Docker plugin config
* Adding unit test
* Setting min value for pull_activity_timeout, making pull activity duration a private var
Operators commonly have docker logs aggregated using various tools and
don't need nomad to manage their docker logs. Worse, Nomad uses a
somewhat heavy docker api call to collect them and it seems to cause
problems when a client runs hundreds of log collections.
Here we add a knob to disable log aggregation completely for nomad.
When log collection is disabled, we avoid running logmon and
docker_logger for the docker tasks in this implementation.
The downside here is once disabled, `nomad logs ...` commands and API
no longer return logs and operators must corrolate alloc-ids with their
aggregated log info.
This is meant as a stop gap measure. Ideally, we'd follow up with at
least two changes:
First, we should optimize behavior when we can such that operators don't
need to disable docker log collection. Potentially by reverting to
using pre-0.9 syslog aggregation in linux environments, though with
different trade-offs.
Second, when/if logs are disabled, nomad logs endpoints should lookup
docker logs api on demand. This ensures that the cost of log collection
is paid sparingly.
driver.SetConfig is not appropriate for starting up reconciler
goroutine. Some ephemeral driver instances are created for validating
config and we ought not to side-effecting goroutines for those.
We currently lack a lifecycle hook to inject these, so I picked the
`Fingerprinter` function for now, and reconciler should only run after
fingerprinter started.
Use `sync.Once` to ensure that we only start reconciler loop once.
When running at scale, it's possible that Docker Engine starts
containers successfully but gets wedged in a way where API call fails.
The Docker Engine may remain unavailable for arbitrary long time.
Here, we introduce a periodic reconcilation process that ensures that any
container started by nomad is tracked, and killed if is running
unexpectedly.
Basically, the periodic job inspects any container that isn't tracked in
its handlers. A creation grace period is used to prevent killing newly
created containers that aren't registered yet.
Also, we aim to avoid killing unrelated containters started by host or
through raw_exec drivers. The logic is to pattern against containers
environment variables and mounts to infer if they are an alloc docker
container.
Lastly, the periodic job can be disabled to avoid any interference if
need be.
hclspec.NewLiteral does not quote its values, which caused `3m` to be
parsed as a nonsensical literal which broke the plugin loader during
initialization. By quoting the value here, it starts correctly.
This ensures that `port_map` along with other block like attribute
declarations (e.g. ulimit, labels, etc) can handle various hcl and json
syntax that was supported in 0.8.
In 0.8.7, the following declarations are effectively equivalent:
```
// hcl block
port_map {
http = 80
https = 443
}
// hcl assignment
port_map = {
http = 80
https = 443
}
// json single element array of map (default in API response)
{"port_map": [{"http": 80, "https": 443}]}
// json array of individual maps (supported accidentally iiuc)
{"port_map: [{"http": 80}, {"https": 443}]}
```
We achieve compatbility by using `NewAttr("...", "list(map(string))",
false)` to be serialized to a `map[string]string` wrapper, instead of using
`BlockAttrs` declaration. The wrapper merges the list of maps
automatically, to ease driver development.
This approach is closer to how v0.8.7 implemented the fields [1][2], and
despite its verbosity, seems to perserve 0.8.7 behavior in hcl2.
This is only required for built-in types that have backward
compatibility constraints. External drivers should use `BlockAttrs`
instead, as they see fit.
[1] https://github.com/hashicorp/nomad/blob/v0.8.7/client/driver/docker.go#L216
[2] https://github.com/hashicorp/nomad/blob/v0.8.7/client/driver/docker.go#L698-L700
