A TCP, HTTP or HTTPS check a load balancer uses to decide whether backends are healthy. For an HTTP probe, its path has to return HTTP 200.
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Each book explains Health probe in context, with comparison tables and the common traps.
Terms in this definition
- TCP
A transport protocol that is connection-oriented.
- HTTP
Hypertext Transfer Protocol, which sends data in clear text; VCF interfaces and APIs instead use HTTPS.
- HTTPS
Secure HTTP, wrapped in TLS. VCF products serve their web UIs and REST APIs this way on 443.
- ELT
Extract, load, transform: raw data lands in the target system first and is transformed there. See ETL for the opposite order.
- Probe
A check that the kubelet, or Container Apps, performs on a container. Liveness failures trigger a restart, readiness controls whether it gets traffic, and startup holds off the other checks until the app is up.
- PATH
Parent-child hierarchies in DAX rely on this function. For each row it builds one delimited text value listing the IDs of the row's ancestors, top level first and ending with the row's own ID, which PATHITEM, PATHLENGTH and friends can then pick apart.
- RETURN
Comes after the VAR definitions in DAX and holds the expression whose value the formula gives back. While debugging, pointing it at one variable for a while is a useful trick.
Related terms
- Inbound NAT rule
Forwards one port on a frontend IP to the NIC of a single VM. No backend pool, load-balancing rule or health probe is needed, but the same frontend port cannot be used by two rules on one frontend IP.
- Load-balancing rule
In Azure Load Balancer, the rule that links a frontend IP and port to a backend pool, checked by a health probe. Traffic not covered by a rule is not forwarded.
- Origin group
Collection of Front Door origins that share health probe and load-balancing settings (latency, priority and weight). Choosing an origin by path is never done at this level.