From 0ef0dedf3a2daaf99eb3c90d9b42d0c0e199ac09 Mon Sep 17 00:00:00 2001 From: Sai Ramesh Vanka Date: Tue, 23 May 2023 21:54:18 +0530 Subject: [PATCH] Add a caution regarding the `exec` probe mechanism Reference Issue: https://github.com/kubernetes/website/issues/41084 1. Exec probe's implementation involves the Kubelet making a gRPC call to the underlying CRI which inturn involves in the creation of multiple processes that require a good amount of cpu usage whenever the probe is executed. 2. Whereas the other probes namely `http/gRPC/tcp` involves the Kubelet alone making a call to the container. 3. There might be a significant amount of cpu overhead in the cases of higher pod densities, lower periodic intervals when the exec probe is configured. 4. Hence, it would be a good idea to alert the user to opt for the other available probes in case of the above mentioned scenarios. Signed-off-by: Sai Ramesh Vanka --- content/en/docs/concepts/workloads/pods/pod-lifecycle.md | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/content/en/docs/concepts/workloads/pods/pod-lifecycle.md b/content/en/docs/concepts/workloads/pods/pod-lifecycle.md index b209a6a65f..1636fe3a9d 100644 --- a/content/en/docs/concepts/workloads/pods/pod-lifecycle.md +++ b/content/en/docs/concepts/workloads/pods/pod-lifecycle.md @@ -316,6 +316,10 @@ Each probe must define exactly one of these four mechanisms: the port is open. If the remote system (the container) closes the connection immediately after it opens, this counts as healthy. +{{< caution >}} Unlike the other mechanisms, `exec` probe's implementation involves the creation/forking of multiple processes each time when executed. +As a result, in case of the clusters having higher pod densities, lower intervals of `initialDelaySeconds`, `periodSeconds`, configuring any probe with exec mechanism might introduce an overhead on the cpu usage of the node. +In such scenarios, consider using the alternative probe mechanisms to avoid the overhead.{{< /caution >}} + ### Probe outcome Each probe has one of three results: