» Upgrade Guides

The upgrading page covers the details of doing a standard upgrade. However, specific versions of Nomad may have more details provided for their upgrades as a result of new features or changed behavior. This page is used to document those details separately from the standard upgrade flow.

» Nomad 0.10.0

» Deployments

Nomad 0.10 enables rolling deployments for service jobs by default and adds a default update stanza when a service job is created or updated. This does not affect jobs with an update stanza.

In pre-0.10 releases, when updating a service job without an update stanza, all existing allocations are stopped while new allocations start up, and this may cause a service degradation or an outage. You can regain this behavior and disable deployments by setting max_parallel to 0.

For more information, see update stanza.

» Nomad 0.9.5

» Template Rendering

Nomad 0.9.5 includes security fixes for privilege escalation vulnerabilities in handling of job template stanzas:

  • The client host's environment variables are now cleaned before rendering the template. If a template includes the env function, the job should include an env stanza to allow access to the variable in the template.
  • The plugin function is no longer permitted by default and will raise an error if used in a template. Operator can opt-in to permitting this function with the new template.function_blacklist field in the client configuration.
  • The file function has been changed to restrict paths to fall inside the task directory by default. Paths that used the NOMAD_TASK_DIR environment variable to prefix file paths should work unchanged. Relative paths or symlinks that point outside the task directory will raise an error. An operator can opt-out of this protection with the new template.disable_file_sandbox field in the client configuration.

» Nomad 0.9.0

» Preemption

Nomad 0.9 adds preemption support for system jobs. If a system job is submitted that has a higher priority than other running jobs on the node, and the node does not have capacity remaining, Nomad may preempt those lower priority allocations to place the system job. See preemption for more details.

» Task Driver Plugins

All task drivers have become plugins in Nomad 0.9.0. There are two user visible differences between 0.8 and 0.9 drivers:

  • LXC is now community supported and distributed independently.
  • Task driver config stanzas are no longer validated by the nomad job validate command. This is a regression that will be fixed in a future release.

There is a new method for client driver configuration options, but existing client.options settings are supported in 0.9. See plugin configuration for details.

» LXC

LXC is now an external plugin and must be installed separately. See the LXC driver's documentation for details.

» Structured Logging

Nomad 0.9.0 switches to structured logging. Any log processing on the pre-0.9 log output will need to be updated to match the structured output.

Structured log lines have the format:

# <Timestamp> [<Level>] <Component>: <Message>: <KeyN>=<ValueN> ...

2019-01-29T05:52:09.221Z [INFO ] client.plugin: starting plugin manager: plugin-type=device

Values containing whitespace will be quoted:

... starting plugin: task=redis args="[/opt/gopath/bin/nomad logmon]"

» HCL2 Transition

Nomad 0.9.0 begins a transition to HCL2, the next version of the HashiCorp configuration language. While Nomad has begun integrating HCL2, users will need to continue to use HCL1 in Nomad 0.9.0 as the transition is incomplete.

If you interpolate variables in your task.config containing consecutive dots in their name, you will need to change your job specification to use the env map. See the following example:

env {
  # Note the multiple consecutive dots
  image...version = "3.2"

  # Valid in both v0.8 and v0.9
  image.version = "3.2"
}

# v0.8 task config stanza:
task {
  driver = "docker"
  config {
    image = "redis:${image...version}"
  }
}

# v0.9 task config stanza:
task {
  driver = "docker"
  config {
    image = "redis:${env["image...version"]}"
  }
}

This only affects users who interpolate unusual variables with multiple consecutive dots in their task config stanza. All other interpolation is unchanged.

Since HCL2 uses dotted object notation for interpolation users should transition away from variable names with multiple consecutive dots.

» Downgrading clients

Due to the large refactor of the Nomad client in 0.9, downgrading to a previous version of the client after upgrading it to Nomad 0.9 is not supported. To downgrade safely, users should erase the Nomad client's data directory.

» Nomad 0.8.0

» Raft Protocol Version Compatibility

When upgrading to Nomad 0.8.0 from a version lower than 0.7.0, users will need to set the raft_protocol option in their server stanza to 1 in order to maintain backwards compatibility with the old servers during the upgrade. After the servers have been migrated to version 0.8.0, raft_protocol can be moved up to 2 and the servers restarted to match the default.

The Raft protocol must be stepped up in this way; only adjacent version numbers are compatible (for example, version 1 cannot talk to version 3). Here is a table of the Raft Protocol versions supported by each Nomad version:

Version Supported Raft Protocols
0.6 and earlier 0
0.7 1
0.8 and later 1, 2, 3

In order to enable all Autopilot features, all servers in a Nomad cluster must be running with Raft protocol version 3 or later.

» Upgrading to Raft Protocol 3

This section provides details on upgrading to Raft Protocol 3 in Nomad 0.8 and higher. Raft protocol version 3 requires Nomad running 0.8.0 or newer on all servers in order to work. See Raft Protocol Version Compatibility for more details. Also the format of peers.json used for outage recovery is different when running with the latest Raft protocol. See Manual Recovery Using peers.json for a description of the required format.

Please note that the Raft protocol is different from Nomad's internal protocol as shown in commands like nomad server members. To see the version of the Raft protocol in use on each server, use the nomad operator raft list-peers command.

The easiest way to upgrade servers is to have each server leave the cluster, upgrade its raft_protocol version in the server stanza, and then add it back. Make sure the new server joins successfully and that the cluster is stable before rolling the upgrade forward to the next server. It's also possible to stand up a new set of servers, and then slowly stand down each of the older servers in a similar fashion.

When using Raft protocol version 3, servers are identified by their node-id instead of their IP address when Nomad makes changes to its internal Raft quorum configuration. This means that once a cluster has been upgraded with servers all running Raft protocol version 3, it will no longer allow servers running any older Raft protocol versions to be added. If running a single Nomad server, restarting it in-place will result in that server not being able to elect itself as a leader. To avoid this, either set the Raft protocol back to 2, or use Manual Recovery Using peers.json to map the server to its node ID in the Raft quorum configuration.

» Node Draining Improvements

Node draining via the node drain command or the drain API has been substantially changed in Nomad 0.8. In Nomad 0.7.1 and earlier draining a node would immediately stop all allocations on the node being drained. Nomad 0.8 now supports a migrate stanza in job specifications to control how many allocations may be migrated at once and the default will be used for existing jobs.

The drain command now blocks until the drain completes. To get the Nomad 0.7.1 and earlier drain behavior use the command: nomad node drain -enable -force -detach <node-id>

See the migrate stanza documentation and Decommissioning Nodes guide for details.

» Periods in Environment Variable Names No Longer Escaped

Applications which expect periods in environment variable names to be replaced with underscores must be updated.

In Nomad 0.7 periods (.) in environment variables names were replaced with an underscore in both the env and template stanzas.

In Nomad 0.8 periods are not replaced and will be included in environment variables verbatim.

For example the following stanza:

env {
  registry.consul.addr = "${NOMAD_IP_http}:8500"
}

In Nomad 0.7 would be exposed to the task as registry_consul_addr=127.0.0.1:8500. In Nomad 0.8 it will now appear exactly as specified: registry.consul.addr=127.0.0.1:8500.

» Client APIs Unavailable on Older Nodes

Because Nomad 0.8 uses a new RPC mechanism to route node-specific APIs like nomad alloc fs through servers to the node, 0.8 CLIs are incompatible using these commands on clients older than 0.8.

To access these commands on older clients either continue to use a pre-0.8 version of the CLI, or upgrade all clients to 0.8.

» CLI Command Changes

Nomad 0.8 has changed the organization of CLI commands to be based on subcommands. An example of this change is the change from nomad alloc-status to nomad alloc status. All commands have been made to be backwards compatible, but operators should update any usage of the old style commands to the new style as the old style will be deprecated in future versions of Nomad.

» RPC Advertise Address

The behavior of the advertised RPC address has changed to be only used to advertise the RPC address of servers to client nodes. Server to server communication is done using the advertised Serf address. Existing cluster's should not be effected but the advertised RPC address may need to be updated to allow connecting client's over a NAT.

» Nomad 0.6.0

» Default advertise address changes

When no advertise address was specified and Nomad's bind_addr was loopback or 0.0.0.0, Nomad attempted to resolve the local hostname to use as an advertise address.

Many hosts cannot properly resolve their hostname, so Nomad 0.6 defaults advertise to the first private IP on the host (e.g. 10.1.2.3).

If you manually configure advertise addresses no changes are necessary.

» Nomad Clients

The change to the default, advertised IP also effect clients that do not specify which network_interface to use. If you have several routable IPs, it is advised to configure the client's network interface such that tasks bind to the correct address.

» Nomad 0.5.5

» Docker load changes

Nomad 0.5.5 has a backward incompatible change in the docker driver's configuration. Prior to 0.5.5 the load configuration option accepted a list images to load, in 0.5.5 it has been changed to a single string. No functionality was changed. Even if more than one item was specified prior to 0.5.5 only the first item was used.

To do a zero-downtime deploy with jobs that use the load option:

  • Upgrade servers to version 0.5.5 or later.

  • Deploy new client nodes on the same version as the servers.

  • Resubmit jobs with the load option fixed and a constraint to only run on version 0.5.5 or later:

    constraint {
      attribute = "${attr.nomad.version}"
      operator  = "version"
      value     = ">= 0.5.5"
    }
  • Drain and shutdown old client nodes.

» Validation changes

Due to internal job serialization and validation changes you may run into issues using 0.5.5 command line tools such as nomad run and nomad validate with 0.5.4 or earlier agents.

It is recommended you upgrade agents before or alongside your command line tools.

» Nomad 0.4.0

Nomad 0.4.0 has backward incompatible changes in the logic for Consul deregistration. When a Task which was started by Nomad v0.3.x is uncleanly shut down, the Nomad 0.4 Client will no longer clean up any stale services. If an in-place upgrade of the Nomad client to 0.4 prevents the Task from gracefully shutting down and deregistering its Consul-registered services, the Nomad Client will not clean up the remaining Consul services registered with the 0.3 Executor.

We recommend draining a node before upgrading to 0.4.0 and then re-enabling the node once the upgrade is complete.

» Nomad 0.3.1

Nomad 0.3.1 removes artifact downloading from driver configurations and places them as a first class element of the task. As such, jobs will have to be rewritten in the proper format and resubmitted to Nomad. Nomad clients will properly re-attach to existing tasks but job definitions must be updated before they can be dispatched to clients running 0.3.1.

» Nomad 0.3.0

Nomad 0.3.0 has made several substantial changes to job files included a new log block and variable interpretation syntax (${var}), a modified restart policy syntax, and minimum resources for tasks as well as validation. These changes require a slight change to the default upgrade flow.

After upgrading the version of the servers, all previously submitted jobs must be resubmitted with the updated job syntax using a Nomad 0.3.0 binary.

  • All instances of $var must be converted to the new syntax of ${var}

  • All tasks must provide their required resources for CPU, memory and disk as well as required network usage if ports are required by the task.

  • Restart policies must be updated to indicate whether it is desired for the task to restart on failure or to fail using mode = "delay" or mode = "fail" respectively.

  • Service names that include periods will fail validation. To fix, remove any periods from the service name before running the job.

After updating the Servers and job files, Nomad Clients can be upgraded by first draining the node so no tasks are running on it. This can be verified by running nomad node status <node-id> and verify there are no tasks in the running state. Once that is done the client can be killed, the data_dir should be deleted and then Nomad 0.3.0 can be launched.