agent

Eru's per-node agent. It watches the workloads a node runs — containerd containers, systemd process pods and cocoon VMs — health checks them, forwards their logs, exports their metrics and reports node and workload status back to eru-core.

Documentation: projecteru2.github.io/agent (source in docs/)

Highlights

• Node heartbeat — reports the node alive to core on an interval, with a ttl three times the interval so one lost report does not evict the node; a clean shutdown removes the status, a SIGUSR1 restart keeps it.
• Workload health checks — TCP and HTTP probes declared per workload, run on every runtime event and on a periodic sweep, with the result published through core.
• Log forwarding — ships each line as a JSON record to tcp://, udp:// or journal:// targets, sharded over several targets by workload id, read from the node's journal with a persisted cursor, or read straight off a VM's serial console. Container output reaches the journal through eru-agent log-shim, containerd's binary logger; console output is written there by the agent itself, so every workload kind has the same history.
• Live log tailing — GET /log/?app=<name> streams the logs of one application straight off the node.
• Prometheus metrics — per-workload cpu, memory, per-nic network and per-device block io gauges on /metrics, optionally pushed to statsd as well. Sampled straight from cgroup v2 files, so a tick makes no call to any daemon.
• Runtimes per node — a node declares the runtimes it hosts under a required runtimes: section: containerd containers, systemd process pods, cocoon VMs, or several at once; the heartbeat needs every one of them alive. The old runtime: and docker: keys are gone, with no compatibility shim. A mock runtime and store cover development.
• Node-side helper modes — the same binary is containerd's task logger (eru-agent log-shim) and its CNI hook (eru-agent oci-hook), so a container node needs no eru daemon beyond the agent.

Quick start

make build
cp agent.yaml.sample /etc/eru/agent.yaml   # edit core, runtimes and log settings
./eru-agent --config /etc/eru/agent.yaml

Or from the published image:

docker run -d --name eru-agent --net host --privileged --restart always \
  --cgroupns=host \
  -v /sys/fs/cgroup:/sys/fs/cgroup:ro \
  -v /sys:/sys:ro \
  -v /run/containerd/containerd.sock:/run/containerd/containerd.sock \
  -v /proc/:/hostProc/ \
  -v /etc/eru:/etc/eru \
  projecteru2/agent /usr/bin/eru-agent

See installation for the systemd unit and configuration for every option.

Related projects

• core — the scheduler this agent reports to
• cli — command line client for core
• resource-extend — extra resource plugins for core
• quickstart — Ansible playbook that stands up a cluster, this agent included
• footstone — the build and lambda images Eru runs code in

Development

make build    # build the eru-agent binary
make test     # go vet plus tests with the race detector
make lint     # golangci-lint on linux and darwin
make fmt      # gofumpt + goimports
make mock     # regenerate the testify mocks
make all      # deps, fmt, lint, test, build

License

This project is licensed under the MIT License. See LICENSE.