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etcd-quorum-read flag: explicitly default to off for v2 #4792

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merged 1 commit into from
Mar 25, 2018

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Kubernetes 1.9 changed the default for etcd-quorum-read flag value to
true, in the hope of fixing some of the edge-case controller issues.

However, while this is cheap on etcd3, that fix was not backported to
etcd2, and performance there of quorum reads is poor.

For non-HA clusters with etcd2, it still goes through raft, but does not
need to - we set etcd-quorum-read to false, as this is just a missed
optimization in etcd2.

For HA clusters with etcd2, it's trickier, but at least for now we're
going to avoid the (crippling) performance regression. kops 1.10 should
have etcd-manager (allowing upgrades to etcd3), and the ability to
configure IOPS on the etcd volume, so we can revisit this in 1.10 /
1.11.

@k8s-ci-robot k8s-ci-robot added size/M Denotes a PR that changes 30-99 lines, ignoring generated files. approved Indicates a PR has been approved by an approver from all required OWNERS files. cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. labels Mar 25, 2018
Kubernetes 1.9 changed the default for etcd-quorum-read flag value to
true, in the hope of fixing some of the edge-case controller issues.

However, while this is cheap on etcd3, that fix was not backported to
etcd2, and performance there of quorum reads is poor.

For non-HA clusters with etcd2, it still goes through raft, but does not
need to - we set etcd-quorum-read to false, as this is just a missed
optimization in etcd2.

For HA clusters with etcd2, it's trickier, but at least for now we're
going to avoid the (crippling) performance regression.  kops 1.10 should
have etcd-manager (allowing upgrades to etcd3), and the ability to
configure IOPS on the etcd volume, so we can revisit this in 1.10 /
1.11.
@justinsb justinsb changed the title etcd-quroum-read flag: explicitly default to off for v2 etcd-quorum-read flag: explicitly default to off for v2 Mar 25, 2018
@chrislovecnm
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Merging this since @justinsb is going to send in a test for e2e.

@chrislovecnm
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/lgtm

@k8s-ci-robot k8s-ci-robot added the lgtm "Looks good to me", indicates that a PR is ready to be merged. label Mar 25, 2018
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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: chrislovecnm, justinsb

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4 participants