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Nomad creates Consul ACL tokens and service registrations to support Consul service mesh workloads, before bootstrapping the Envoy proxy. Nomad always talks to the local Consul agent and never directly to the Consul servers. But the local Consul agent talks to the Consul servers in stale consistency mode to reduce load on the servers. This can result in the Nomad client making the Envoy bootstrap request with a tokens or services that have not yet replicated to the follower that the local client is connected to. This request gets a 404 on the ACL token and that negative entry gets cached, preventing any retries from succeeding. To workaround this, we'll use a method described by our friends over on `consul-k8s` where after creating the objects in Consul we try to read them from the local agent in stale consistency mode (which prevents a failed read from being cached). This cannot completely eliminate this source of error because it's possible that Consul cluster replication is unhealthy at the time we need it, but this should make Envoy bootstrap significantly more robust. This changset adds preflight checks for the objects we create in Consul: * We add a preflight check for ACL tokens after we login via via Workload Identity and in the function we use to derive tokens in the legacy workflow. We do this check early because we also want to use this token for registering group services in the allocrunner hooks. * We add a preflight check for services right before we bootstrap Envoy in the taskrunner hook, so that we have time for our service client to batch updates to the local Consul agent in addition to the local agent sync. We've added the timeouts to be configurable via node metadata rather than the usual static configuration because for most cases, users should not need to touch or even know these values are configurable; the configuration is mostly available for testing. Fixes: https://github.com/hashicorp/nomad/issues/9307 Fixes: https://github.com/hashicorp/nomad/issues/10451 Fixes: https://github.com/hashicorp/nomad/issues/20516 Ref: https://github.com/hashicorp/consul-k8s/pull/887 Ref: https://hashicorp.atlassian.net/browse/NET-10051 Ref: https://hashicorp.atlassian.net/browse/NET-9273 Follow-up: https://hashicorp.atlassian.net/browse/NET-10138
Nomad
Nomad is a simple and flexible workload orchestrator to deploy and manage containers (docker, podman), non-containerized applications (executable, Java), and virtual machines (qemu) across on-prem and clouds at scale.
Nomad is supported on Linux, Windows, and macOS. A commercial version of Nomad, Nomad Enterprise, is also available.
- Website: https://developer.hashicorp.com/nomad
- Tutorials: HashiCorp Developer
- Forum: Discuss
Nomad provides several key features:
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Deploy Containers and Legacy Applications: Nomad’s flexibility as an orchestrator enables an organization to run containers, legacy, and batch applications together on the same infrastructure. Nomad brings core orchestration benefits to legacy applications without needing to containerize via pluggable task drivers.
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Simple & Reliable: Nomad runs as a single binary and is entirely self contained - combining resource management and scheduling into a single system. Nomad does not require any external services for storage or coordination. Nomad automatically handles application, node, and driver failures. Nomad is distributed and resilient, using leader election and state replication to provide high availability in the event of failures.
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Device Plugins & GPU Support: Nomad offers built-in support for GPU workloads such as machine learning (ML) and artificial intelligence (AI). Nomad uses device plugins to automatically detect and utilize resources from hardware devices such as GPU, FPGAs, and TPUs.
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Federation for Multi-Region, Multi-Cloud: Nomad was designed to support infrastructure at a global scale. Nomad supports federation out-of-the-box and can deploy applications across multiple regions and clouds.
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Proven Scalability: Nomad is optimistically concurrent, which increases throughput and reduces latency for workloads. Nomad has been proven to scale to clusters of 10K+ nodes in real-world production environments.
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HashiCorp Ecosystem: Nomad integrates seamlessly with Terraform, Consul, Vault for provisioning, service discovery, and secrets management.
Quick Start
Testing
See Developer: Getting Started for instructions on setting up a local Nomad cluster for non-production use.
Optionally, find Terraform manifests for bringing up a development Nomad cluster on a public cloud in the terraform directory.
Production
See Developer: Nomad Reference Architecture for recommended practices and a reference architecture for production deployments.
Documentation
Full, comprehensive documentation is available on the Nomad website: https://developer.hashicorp.com/nomad/docs
Guides are available on HashiCorp Developer.
Roadmap
A timeline of major features expected for the next release or two can be found in the Public Roadmap.
This roadmap is a best guess at any given point, and both release dates and projects in each release are subject to change. Do not take any of these items as commitments, especially ones later than one major release away.
Contributing
See the contributing directory for more developer documentation.