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Added proposal with priority but assured concurrency and fairness #930

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Added proposal with priority but assured concurrency and fairness #930

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MikeSpreitzer
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@k8s-ci-robot k8s-ci-robot added cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. kind/kep Categorizes KEP tracking issues and PRs modifying the KEP directory sig/api-machinery Categorizes an issue or PR as relevant to SIG API Machinery. labels Apr 2, 2019
@k8s-ci-robot k8s-ci-robot added the size/XL Denotes a PR that changes 500-999 lines, ignoring generated files. label Apr 2, 2019
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[APPROVALNOTIFIER] This PR is NOT APPROVED

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@MikeSpreitzer
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CC @yue9944882
CC @wojtek-t

@MikeSpreitzer
Exempt priority zero requests from being counted
eb4dd50 
.. to make the management like today's max-in-flight handler.
yue9944882
yue9944882 reviewed Apr 2, 2019
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keps/sig-api-machinery/20190228-priority-and-fairness.md
queueLengthLimit: 100
```

Some flow schemata.
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I believe the api model of flow schema here can be simplified by:

  • removing support for patternMatch and nonPatternMatch. additionally, all controllers are sharing the same user identity as system:kube-controller-manager but differs in user-agent http header.
  • make the field matchingPriority optional and only filled to resolve conflicts among multiple flow schemas. A default value will be working for most cases I suppose.
  • instead of defining explicit boolean tests in the api model. consider make it a bit simpler by costing a bit ambiguity. as the yaml examples in the following shows:
kind: FlowSchema
meta:
  name: system-top
spec:
  matchingPriority: 500 // default to 500, override if necessary
  requestPriority:
    name: system-top
  matchRules:
  - field: groups
     valueSet: [ "system:masters" ]
---
kind: FlowSchema
meta:
  name: system-high-node-heartbeat
spec:
  matchingPriority: 500 // default to 500, override if necessary
  requestPriority:
    name: system-high
  flowDistinguisher:
    source: user
    # no transformation in this case
    matchRules:
  - field: groups
     valueSet: [ "system:nodes" ]
  - field: resource
     valueSet: [ "nodes" ]
---
kind: FlowSchema
meta:
  name: system-high-system-objects
spec:
  matchingPriority: 500 // default to 500, override if necessary
  requestPriority:
    name: system-high
  flowDistinguisher:
    source: user
    # no transformation in this case
    matchRules:
  - field: groups
     valueSet: [ "system:nodes" ]
  - field: namespace
     valueSet: [ "kube-system" ]
---
kind: FlowSchema
meta:
  name: system-high-system-objects
spec:
  matchingPriority: 500 // default to 500, override if necessary
  requestPriority:
    name: system-high
  flowDistinguisher:
    source: user
    # no transformation in this case
    matchRules:
  - field: groups
     valueSet: [ "system:nodes" ]
  - field: namespace
     valueSet: [ "kube-system" ]
---
kind: FlowSchema
meta:
  name: workload-low-serviceaccounts
spec:
  matchingPriority: 500 // default to 500, override if necessary
  requestPriority:
    name: workload-high
  flowDistinguisher:
    source: namespace
    # no transformation in this case
  matchRules:
  - field: groups
     valueSet: [ "system:serviceaccounts" ]
....

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  • all controllers are sharing the same user identity as system:kube-controller-manager but differs in user-agent http header.

that's not generally accurate... typically, each controller loop gets a distinct identity

yue9944882
yue9944882 reviewed Apr 2, 2019
View reviewed changes
keps/sig-api-machinery/20190228-priority-and-fairness.md
(ACV), which is calculated as follows.

```
ACV(l) = ceil( SCL * ACS(l) / (100 + sum[priority levels k] ACS(k) ) )
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why is it 100? i have a complex feeling about introducing more magic numbers..

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This number is not particularly magic. It just establishes a magnitude standard to compare the ACS values with. All that matters is their ratios. We could create another configuration parameter to define the share for shared concurrency. But, without loss of generality, we can fix it at a particular number.

@MikeSpreitzer
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In the meeting today we agreed to start simpler, and #933 is an attempt to capture that agreement.
I expect we will soon want to restore borrowing between priority levels.
Nobody was confident that we will want to restore the distinction between mutating and read-only.

@MikeSpreitzer MikeSpreitzer mentioned this pull request Apr 2, 2019
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@MikeSpreitzer MikeSpreitzer mentioned this pull request Apr 12, 2019
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@MikeSpreitzer: PR needs rebase.

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@k8s-ci-robot k8s-ci-robot added the needs-rebase Indicates a PR cannot be merged because it has merge conflicts with HEAD. label May 5, 2019
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wojtek-t commented May 6, 2019

@MikeSpreitzer - should this one be closed now?

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It is not something we are trying to merge now. OTOH, it has a more advanced design that I think we will want to look at second.

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@k8s-ci-robot k8s-ci-robot added the lifecycle/stale Denotes an issue or PR has remained open with no activity and has become stale. label Aug 4, 2019
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/lifecycle rotten

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@fejta-bot: Closed this PR.

In response to this:

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