openstack
/
charm-nova-cloud-controller
Code Issues Proposed changes

Switch knownhost caching on by default 

This change "flips the switch" by changing the default for caching
knownhosts to true.  This means that during deployment host lookups are
only performed once for each related unit.  This was experimental for
the previous charm release.

Release note is change-id: Ib3d17b4057dd7f671f123b1da7df21c9f3d7e182

Change-Id: I644df508563f93b661af6bfd5fb668f0e31d5e4d
This commit is contained in:
Alex Kavanagh 2019-08-16 17:51:41 +01:00
parent f98a6bd962
commit 9d8ccd169a
2 changed files with 20 additions and 20 deletions
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14
README.md
View File

@ -88,14 +88,16 @@ quota-key_pairs - 100
quota-server_groups - 10 (only available after Icehouse)
quota-server_group_members - 10 (only available after Icehouse)
## EXPERIMENTAL: SSH knownhosts caching
## SSH knownhosts caching
This section covers an EXPERIMENTAL option involving the caching of SSH
host lookups (knownhosts) on each nova-compute unit.
This section covers the option involving the caching of SSH host lookups
(knownhosts) on each nova-compute unit. Caching of SSH host lookups speeds up
deployment of nova-compute units when first deploying a cloud, and when adding
a new unit.
There is a new Boolean configuration key `cache-known-hosts` that ensures
that any given host lookup to be performed just once. The default is
`false` which effectively means that caching is not performed.
There is a Boolean configuration key `cache-known-hosts` that ensures that any
given host lookup to be performed just once. The default is `true` which means
that caching is performed.
**Note**: A cloud can be deployed with the `cache-known-hosts` key set to
`false`, and be set to `true` post-deployment. At that point the hosts

26
config.yaml
View File

@ -145,29 +145,27 @@ options:
* identity-service
cache-known-hosts:
type: boolean
default: false
default: true
description: |
EXPERIMENTAL - If true then the charm will cache host and ip lookups for
a unit when populating the knownhosts file for nova-compute service.
This is a known performance issue around maintaining the knownhosts files
for each nova-compute service, and caching is a strategy to reduce the
hook execution time when the 'cloud-compute' relation changes. If false,
then no caching is performed. Changing from true to false will NOT cause
new lookups to be performed.
If true then the charm will cache host and ip lookups for a unit when
populating the knownhosts file for nova-compute service. This is a known
performance issue around maintaining the knownhosts files for each
nova-compute service, and caching is a strategy to reduce the hook
execution time when the 'cloud-compute' relation changes. If false, then
no caching is performed. Changing from true to false will NOT cause new
lookups to be performed.
.
To clear the caches and force new lookups to be performed, the action
'clear-unit-knownhost-cache' should be used.
.
This config flag is experimental as it's very hard to determine if there
will be any DNS issues during the deployment onto different platforms.
Thus it may be preferred to keep the flag false during deployment and
then switch to true after deployment.
This config flag is new. If there are any DNS issues during the
deployment onto different platforms then the knownhost lookups may be
inconsistent. Thus it may be preferred to keep the flag false during
deployment and then switch to true after deployment.
.
Note that the charm keeps a record of the lookups for each unit
regardless of the setting of this flag. The cache is only used if the
flag is true.
.
At a future release the default will be true.
console-access-protocol:
type: string
default: