Sentry

Sentry catches errors in production and tells you exactly where they happened: stack trace, request, user, and the release that broke it. It also does tracing, session replay, profiling, logs, uptime and cron monitoring, with SDKs for most languages and frameworks. The code is source-available under the Functional Source License, and each release becomes Apache 2.0 two years later.

Self-hosting runs on Docker Compose with a heavy stack (Kafka, ClickHouse, Redis, Postgres, Snuba, Relay and more) and wants 4 cores and 16 GB of RAM plus 16 GB of swap, ideally 32 GB. An errors-only profile cuts that to about 7 GB. Sentry itself pitches self-hosted for low-volume and proof-of-concept use, and it leaves out the Seer AI debugger, spike protection and some mobile symbolication.

The cloud free plan is one user with 5,000 errors, 5 million spans and 50 replays a month. Team is $29 a month ($26 billed annually) for unlimited users and 50,000 errors; Business is $89 ($80 annually) with the same base quotas plus SAML and SCIM, unlimited dashboards and advanced quota management. Seer is $40 per active contributor on top. Solo: free cloud. Small teams: Team is cheap insurance. Large orgs: Business for SAML and SCIM.

The catch: the license. You can self-host for internal use, but you can't offer Sentry, or anything substantially similar built on it, as a commercial product, so it isn't open source until each version's two-year clock runs out. GlitchTip (glitchtip/glitchtip-backend) is the lighter, open option.