diff options
| author | John Rusk <John.Rusk@microsoft.com> | 2023-01-10 11:49:54 +1300 |
|---|---|---|
| committer | John Rusk <John.Rusk@microsoft.com> | 2023-01-10 11:49:54 +1300 |
| commit | 9e3dff7f401259ba557849618c446fa7e8d28c76 (patch) | |
| tree | b907a267d7e0d252f63decd4c6f4db40e981e197 /sig-scalability | |
| parent | 6241ee50b2436116f4d97397ec9b4150ef5bf3f0 (diff) | |
Small changes after additional feedback
Diffstat (limited to 'sig-scalability')
| -rw-r--r-- | sig-scalability/configs-and-limits/faq.md | 15 |
1 files changed, 7 insertions, 8 deletions
diff --git a/sig-scalability/configs-and-limits/faq.md b/sig-scalability/configs-and-limits/faq.md index d04ab5e5..33f9daa5 100644 --- a/sig-scalability/configs-and-limits/faq.md +++ b/sig-scalability/configs-and-limits/faq.md @@ -64,11 +64,11 @@ summarized as: ### How should we code client applications to improve scalability? -As noted above, LIST requests can be particularly expensive. So when working with lists -that may have more than a few thousand elements, consider the following guidelines. +As noted above, LIST requests can be particularly expensive. So consider the following guidelines when working with lists +that may have more than a few thousand small objects, or more than a few hundred large ones. 1. When defining a new resource type (new CRD) consider expected numbers -of objects that will exist (numbers of CRs). See guidelines +of objects that will exist (numbers of CRs). See guidelines for small, medium and large objects [here](https://github.com/kubernetes/enhancements/tree/master/keps/sig-api-machinery/95-custom-resource-definitions#scale-targets-for-ga). 1. When LIST-ing, the load on etcd and API Server depends primarily on the number of objects that _exist_, not the number that are _returned_. So even if you are using a field selector to filter the list and retrieve only a small number of results, these guidelines still apply. (The only exception is retrieving a single object by `metadata.name`, which is fast.) 1. If your code needs to hold an up-to-date list of objects in memory, @@ -79,13 +79,12 @@ to efficiently maintain an in-memory collection. 1. If `Informer`s don't suit your needs, consider whether you really need strong consistency. Do you really need to see the most recent data, up to the _exact moment in time_ when you issued the query? If you don't need that, set `ResourceVersion=0`. This will cause your request to be served from the API Server's cache instead of from etcd. Read the [documentation about ResourceVersions](https://kubernetes.io/docs/reference/using-api/api-concepts/#resource-versions) carefully to understand how it will affect the freshness of the data you receive. 1. If you can't use `Informer`s AND you can't use the API Server cache, then be sure to [read large lists in chunks](https://kubernetes.io/docs/reference/using-api/api-concepts/#retrieving-large-results-sets-in-chunks). -1. Additionaly, if you cannot use `Informer`s, you should also consider how _often_ your application LISTs the resources. In particular, after you read the last object in a large list, do not _immediately_ re-query the same list. Wait a while instead. Don't list more often than you need to. +1. Additionally, if you cannot use `Informer`s, you should also consider how _often_ your application LISTs the resources. In particular, after you read the last object in a large list, do not _immediately_ re-query the same list. Wait a while instead. Don't list more often than you need to. 1. Consider the number of instances of your client application which will be running. For instance, there is a big difference between having -just one controller listing objects, versus having demonsets on every node -doing the same thing. If there will be many instances of your client application -(either in daemonsets or some other form) you should be particularly careful -about LIST-related load. +just one controller listing objects, versus having pods on every node +doing the same thing (e.g. in a daemonset). If there will be many instances of your client application +periodically listing large numbers of objects, your solution will NOT scale to large clusters. ### How do you setup clusters for scalability testing? |
