Vigilmon vs Sensu Go: Agentless External Uptime vs Agent-Based Infrastructure Event Processing 2026

Vigilmon vs Sensu Go is a comparison between two monitoring tools that approach infrastructure observability from opposite architectural directions. Sensu Go is an agent-based infrastructure event processing platform — a Kubernetes-native observability pipeline where agents run inside your infrastructure, execute checks, collect metrics, and feed an event stream that routes through handlers, filters, and mutators. Vigilmon is an agentless, outside-in uptime monitoring service — no agents to install, no pipelines to configure, just external checks from multiple probe locations that alert when a majority independently confirm a failure.

The difference goes deeper than agent vs agentless. It's a difference in philosophy: Sensu processes events from inside your infrastructure; Vigilmon validates reachability from outside it.

What Is Sensu Go?

Sensu Go is the current generation of the Sensu open-source monitoring framework, rewritten from scratch in Go. It is designed around an event-driven pipeline model for infrastructure monitoring, metrics collection, and alerting.

Key characteristics of Sensu Go:

Agent-based: Sensu agents run on every host, container, or Kubernetes pod you want to monitor. The agent executes check plugins, collects the output, and forwards events to the Sensu backend.
Event pipeline architecture: Events flow through a configurable pipeline — check results become events, which pass through filters (to suppress noise), mutators (to transform format), and handlers (to route to PagerDuty, Slack, InfluxDB, etc.)
Check plugins: Sensu uses community and custom check scripts/binaries. Hundreds of Sensu plugins exist for everything from disk checks to application health to Kubernetes pod status.
Kubernetes-native: Sensu Go runs natively in Kubernetes with a SensuAgent DaemonSet, SensuBackend StatefulSet, and CRD-based configuration. It's a common choice for Kubernetes-first infrastructure teams.
Metrics collection: Agents collect and forward metrics in Graphite, InfluxDB, Nagios PerfData, OpenMetrics/Prometheus, and other formats.
Multi-tenancy: Sensu supports namespaces, RBAC, and multi-tenant deployments — useful for MSPs or large organizations with isolated environments.
Self-hosted: The open-source Sensu Go backend is self-hosted. Sensu's commercial tier (Sensu Enterprise) adds SSO, audit logging, and support, but the core platform requires you to run and maintain the backend.

Sensu Go is a powerful tool for teams that need a flexible event processing pipeline inside their infrastructure. The tradeoff: it requires substantial setup — deploying the backend, configuring agents, writing or sourcing check definitions, and building the handler pipeline.

What Is Vigilmon?

Vigilmon is an agentless, outside-in uptime monitoring service. Nothing runs inside your infrastructure. Vigilmon dispatches checks from multiple geographically distributed probe nodes, validates that your services respond correctly from the internet, and alerts only when a majority of probes independently confirm the failure — eliminating false positives from single-probe transient failures.

Vigilmon monitors:

HTTP/HTTPS endpoints — status code validation, response body keyword matching, SSL certificate expiry warnings
TCP ports — raw socket checks for databases, mail servers, game servers, and custom services
Cron job heartbeats — detect silent background job failures when expected pings stop arriving

The free tier is permanent: 5 monitors, no credit card, no expiry. A full production monitoring setup can be running in minutes.

Feature Comparison

| Feature | Sensu Go | Vigilmon | |---|---|---| | HTTP/HTTPS availability checks | ✅ (via plugin) | ✅ | | TCP port checks | ✅ (via plugin) | ✅ | | Cron / heartbeat monitoring | ✅ (keepalive model) | ✅ | | SSL certificate monitoring | ✅ (via plugin) | ✅ | | Agent required on each host | ✅ (required) | ❌ (agentless) | | Outside-in internet checks | ❌ | ✅ | | Multi-region consensus alerting | ❌ | ✅ | | Kubernetes-native deployment | ✅ | ❌ | | Internal infrastructure metrics | ✅ | ❌ | | Custom check plugins | ✅ | ❌ | | Event pipeline (filters/mutators/handlers) | ✅ | ❌ | | Self-hosted backend | ✅ | ❌ (SaaS) | | Multi-tenancy / RBAC | ✅ | ❌ | | Slack / PagerDuty integrations | ✅ (via handler) | ✅ (native) | | Status pages | ❌ | ✅ | | Zero-configuration setup | ❌ | ✅ | | Free tier | ✅ (open-source) | ✅ (5 monitors, permanent) | | Managed SaaS | ❌ | ✅ |

Pricing Comparison

Sensu Go Pricing

Sensu Go open-source is free to use with no license cost. You provide and operate the infrastructure:

Backend: Requires a database (etcd, bundled or external), load balancer if running HA, and compute resources. A production HA backend needs at least 3 etcd nodes.
Agents: Run on every monitored host — no per-agent license cost in open-source.
Operations cost: Engineering time to deploy, configure, maintain, and upgrade the Sensu backend cluster. The total cost of ownership for a fully maintained Sensu deployment includes the labor to keep it running.

Sensu Enterprise (the commercial tier) adds support, SSO, audit logging, and enterprise features at quoted pricing.

For small teams, the operational cost of running a self-hosted monitoring backend often exceeds the cost of a managed SaaS alternative.

Vigilmon Pricing

Vigilmon's free tier is permanent and requires no credit card:

Free: 5 monitors (HTTP, TCP, heartbeats), 5-minute check intervals, multi-region consensus alerting, email and webhook notifications, response time history

Paid plans scale with monitor count and check frequency. Zero infrastructure to run, zero backend to maintain.

The Core Difference: Inside-Out Pipeline vs Outside-In Consensus

Sensu Go: Inside-Out Event Processing

Sensu's model is inside-out: agents run inside your infrastructure, execute checks, and produce events. The value is in the pipeline — events from dozens of check types across your entire fleet flow into a single processing stream where you apply business logic: suppress noise during maintenance windows, route critical events to PagerDuty and non-critical to Slack, transform formats to feed time-series databases, and correlate events across services.

For infrastructure teams managing large fleets of hosts, containers, and Kubernetes workloads, this pipeline model is powerful. A single Sensu deployment can replace Nagios, collect Prometheus metrics, and route everything through a unified handler.

What Sensu cannot do well: Validate that your service is actually reachable from the internet. Sensu agents run inside your infrastructure and execute checks from inside the network. An HTTP check run by a Sensu agent on your application server validates that the service is reachable from inside the server — not that it's reachable to your users. A firewall misconfiguration, a routing issue at your CDN, or an SSL error specific to external certificate trust chains will not be caught by an internal Sensu agent.

This is not a gap in Sensu's design — it's a fundamental property of inside-out monitoring. Sensu doesn't model the outside-in perspective because that's not what it's built for.

Vigilmon: Outside-In Consensus

Vigilmon's model is outside-in: checks run from geographically distributed probe nodes across the internet, simulating what your users actually experience when they try to reach your service. The consensus model — requiring a majority of independent probes to confirm a failure before alerting — filters out the transient routing blips and single-probe anomalies that would generate false alerts from simpler monitoring tools.

What Vigilmon cannot do: Run custom check plugins, process an event stream from your internal infrastructure, collect host metrics, or monitor Kubernetes pods from inside the cluster. Vigilmon checks what's externally reachable. It knows nothing about what's happening inside your servers.

The Setup Complexity Gap

This is the most practical difference for most teams evaluating these tools.

Sensu Go setup sequence (production, HA):

Deploy etcd cluster (3 nodes) or configure external etcd
Deploy Sensu backend (1–3 nodes behind a load balancer)
Configure TLS between backend and agents
Install Sensu agent on every host/container/pod
Write or source check definitions (nagios plugins, sensu plugins, custom scripts)
Configure filters for maintenance windows and event suppression
Configure handlers for PagerDuty, Slack, InfluxDB, etc.
Set up RBAC and namespaces for team isolation
Configure monitoring for Sensu's own backend components (recursive monitoring problem)

For experienced infrastructure engineers, this is manageable. For a small team without dedicated ops, this is weeks of work before the first alert fires.

Vigilmon setup sequence:

Create account
Add a URL, TCP host:port, or heartbeat endpoint
Done — alerts fire when consensus confirms a failure

For teams that need uptime monitoring, not a full observability pipeline, the setup complexity difference is the decisive factor.

Kubernetes: Where Sensu Shines (and Its Limits)

Sensu Go has genuine strengths in Kubernetes environments. The Sensu operator deploys agents as a DaemonSet, check definitions become Kubernetes CRDs, and the backend integrates with Kubernetes service discovery. For teams running Kubernetes-native infrastructure who need a unified event processing pipeline for internal checks, Sensu is one of the more mature options.

But Kubernetes workloads still need external availability monitoring. Your Kubernetes service may be running perfectly inside the cluster while an Ingress misconfiguration, an expired certificate, or a cloud load balancer configuration error makes your service unreachable to external users. Sensu's Kubernetes-native checks run inside the cluster and will not catch these external failure modes.

The complement: Sensu monitors what's happening inside the Kubernetes cluster; Vigilmon monitors whether the service endpoints are reachable from outside it.

Agent Keepalive vs Heartbeat Monitoring

Both Sensu and Vigilmon have a model for detecting silent failures where something that should be running isn't.

Sensu keepalives: Sensu agents send keepalive messages to the backend on a configurable interval. If the backend doesn't hear from an agent within the timeout, it generates a keepalive failure event. This detects that the Sensu agent itself has stopped — which usually means the host is down, the network path to the backend is broken, or the agent process died.

Vigilmon heartbeats: Vigilmon heartbeat monitors wait for your application or job to send a ping. Your cron job, background worker, or scheduled task sends a POST to a Vigilmon URL on each successful completion. If the ping doesn't arrive within the timeout, Vigilmon alerts. This detects silent job failures — the cron job ran but failed mid-execution, the scheduler dropped the job, or the job is completing but the work it's doing is wrong (if your check is embedded in the job itself).

These models are complementary. Sensu keepalives tell you whether your infrastructure nodes are still alive. Vigilmon heartbeats tell you whether your jobs are still doing work.

When to Choose Sensu Go

Sensu Go is the better choice when:

You need a unified event processing pipeline across a large fleet of hosts and containers
Kubernetes-native deployment with CRD-based configuration is a requirement
Custom check plugins for bespoke infrastructure components are required
Multi-tenant RBAC for team or customer isolation is needed
You have the infrastructure team to deploy and maintain a self-hosted backend cluster
Routing events to time-series databases (InfluxDB, Prometheus remote write) is part of your observability stack
You're replacing a Nagios/Icinga deployment and need a compatible plugin ecosystem

When to Choose Vigilmon

Vigilmon is the better choice when:

You need to know whether your services are reachable from the internet
Setup in minutes matters more than a full event pipeline
You don't have the ops capacity to run a self-hosted monitoring backend
Multi-region consensus before alerting is required to suppress false positives
Background job and cron heartbeat monitoring is needed without running agent infrastructure
You need to monitor third-party APIs or partner endpoints you don't control
Your monitoring budget is limited or zero — the free tier is permanent with no trial expiry

Using Both Together

Sensu and Vigilmon are complementary. Running both is reasonable for teams with both internal infrastructure monitoring needs and external availability requirements:

Sensu Go handles internal infrastructure event processing: host health checks, Kubernetes pod status, application-layer checks from inside the cluster, and metric collection into time-series databases
Vigilmon handles external availability monitoring: internet-facing HTTP and TCP checks with consensus alerting, SSL certificate monitoring, and heartbeat monitoring for critical background jobs

The boundary is clear: Sensu covers what's happening inside your infrastructure; Vigilmon covers what your users experience from outside it.

Side-by-Side Summary

| Dimension | Sensu Go | Vigilmon | |---|---|---| | Primary purpose | Infrastructure event processing pipeline | External availability monitoring | | Perspective | Inside-out (agents in your infra) | Outside-in (internet probes) | | Agent required | ✅ (per host/pod) | ❌ (agentless) | | Setup complexity | High (backend + agents + config) | Minimal (minutes) | | Kubernetes-native | ✅ | ❌ | | Custom check plugins | ✅ | ❌ | | Event pipeline (filters/handlers) | ✅ | ❌ | | Consensus alerting | ❌ | ✅ | | Outside-in internet checks | ❌ | ✅ | | Status pages | ❌ | ✅ | | Self-hosted vs SaaS | Self-hosted | SaaS | | Free tier | ✅ (open-source) | ✅ (5 monitors, permanent) | | Best for | Large fleet infrastructure monitoring | Simple, reliable external availability |

Conclusion

Sensu Go vs Vigilmon is not a close call — they solve fundamentally different problems. Sensu Go is a sophisticated inside-out event processing pipeline for teams managing large infrastructure fleets, Kubernetes clusters, and custom check ecosystems. It requires real operational investment to deploy and maintain, and delivers a correspondingly powerful observability platform.

Vigilmon is an outside-in availability monitoring service that runs in minutes, requires nothing inside your infrastructure, and provides multi-region consensus alerting for HTTP, TCP, and heartbeat monitors. It's not trying to be a pipeline — it's trying to tell you when your services stop being reachable.

For teams that need both, the combination is standard practice: Sensu inside, Vigilmon outside, with each tool covering the failure modes the other can't see.

Try Vigilmon free at vigilmon.online — no agents, no backend to deploy, no credit card, multi-region consensus alerting from the first monitor.

Tags: #monitoring #uptime #sensu #sensugo #kubernetes #vigilmon #devops #sre #infrastructure #eventprocessing #2026