Re: Proposal: feature flag implementation for Juju
So, having spoken to Tim about this, and coming to understand the
motivations a bit more, I think the env var propagated everywhere, no
exceptions approach is the winner.
The deciding factor is that environ-config requires an API connection,
and that (one of) the motivating use case(s) involves exposing
incomplete CLI commands via feature flag (and I'm not aware of ones
that can't be fulfilled by env vars). I understand that environ-config
is superior in some other respects, but it's also more complex; and
furthermore I'd like to avoid having multiple mechanisms for the same
thing.
The biggest risk is that people will start to use and depend upon
feature flag behaviour, so I require that anyone using a feature flag
make it abundantly clear that it's unsupported behaviour, by (1)
including something like DEV in the var name and (2) logging its
usage promiscuously, and making clear in those messages that the
behaviour is not supported.
Cheers
William
On Wed, Nov 26, 2014 at 4:50 PM, Casey Marshall
casey.marsh...@canonical.com wrote:
+1 for feature flags in general and +1 for using environment variables
in upstart to get them to the servers agents.
I think it'd be nice to have an environment variable per flag, with a
common prefix JUJU_FEATURE_. That way, if you need to check one in a
package init(), you don't have to parse the whole list of flags to find
the one you care about -- or depend on a globally initialized parsing of
that list.
env config seems reasonable, but dealing with parsing, errors and then
making that config globally available at init seems complex and not
always feasible.
How about defining them free form in an env config field, which is
then used to emit the env vars as described above to the upstart config
during bootstrap?
-Casey
On 11/25/2014 10:16 PM, Ian Booth wrote:
I like feature flags so am +1 to the overall proposal. I also agree with the
approach to keep them immutable, given the stated goals and complexity
associated with making them not so.
I think the env variable implementation is ok too - this keeps everything
very
loosely coupled and avoids polluting a juju environment with an extra config
attribute.
On 26/11/14 08:47, Tim Penhey wrote:
Hi all,
There are often times when we want to hook up features for testing that
we don't want exposed to the general user community.
In the past we have hooked things up in master, then when the release
branch is made, we have had to go and change things there. This is a
terrible way to do it.
Here is my proposal:
http://reviews.vapour.ws/r/531/diff/#
We have an environment variable called JUJU_FEATURE_FLAGS. It contains
comma delimited strings that are used as flags.
The value is read when the program initializes and is not mutable.
Simple checks can be used in the code:
if featureflag.Enabled(foo) {
// do foo like things
}
Thoughts and suggestions appreciated, but I don't want to have the
bike-shedding go on too long.
Tim
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Re: Proposal: feature flag implementation for Juju
Yes, that is exactly what the code that came with the proposal did :-)
Tim
On 27/11/14 23:40, John Meinel wrote:
It sounded like we needed the env set in agents as well. What gets them
set there? Just a change to the upstart job that runs them?
John
=:-
On Nov 27, 2014 12:52 PM, William Reade william.re...@canonical.com
mailto:william.re...@canonical.com wrote:
So, having spoken to Tim about this, and coming to understand the
motivations a bit more, I think the env var propagated everywhere, no
exceptions approach is the winner.
The deciding factor is that environ-config requires an API connection,
and that (one of) the motivating use case(s) involves exposing
incomplete CLI commands via feature flag (and I'm not aware of ones
that can't be fulfilled by env vars). I understand that environ-config
is superior in some other respects, but it's also more complex; and
furthermore I'd like to avoid having multiple mechanisms for the same
thing.
The biggest risk is that people will start to use and depend upon
feature flag behaviour, so I require that anyone using a feature flag
make it abundantly clear that it's unsupported behaviour, by (1)
including something like DEV in the var name and (2) logging its
usage promiscuously, and making clear in those messages that the
behaviour is not supported.
Cheers
William
On Wed, Nov 26, 2014 at 4:50 PM, Casey Marshall
casey.marsh...@canonical.com mailto:casey.marsh...@canonical.com
wrote:
+1 for feature flags in general and +1 for using environment variables
in upstart to get them to the servers agents.
I think it'd be nice to have an environment variable per flag, with a
common prefix JUJU_FEATURE_. That way, if you need to check one in a
package init(), you don't have to parse the whole list of flags to
find
the one you care about -- or depend on a globally initialized
parsing of
that list.
env config seems reasonable, but dealing with parsing, errors and then
making that config globally available at init seems complex and not
always feasible.
How about defining them free form in an env config field, which is
then used to emit the env vars as described above to the upstart
config
during bootstrap?
-Casey
On 11/25/2014 10:16 PM, Ian Booth wrote:
I like feature flags so am +1 to the overall proposal. I also
agree with the
approach to keep them immutable, given the stated goals and
complexity
associated with making them not so.
I think the env variable implementation is ok too - this keeps
everything very
loosely coupled and avoids polluting a juju environment with an
extra config
attribute.
On 26/11/14 08:47, Tim Penhey wrote:
Hi all,
There are often times when we want to hook up features for
testing that
we don't want exposed to the general user community.
In the past we have hooked things up in master, then when the
release
branch is made, we have had to go and change things there. This
is a
terrible way to do it.
Here is my proposal:
http://reviews.vapour.ws/r/531/diff/#
We have an environment variable called JUJU_FEATURE_FLAGS. It
contains
comma delimited strings that are used as flags.
The value is read when the program initializes and is not mutable.
Simple checks can be used in the code:
if featureflag.Enabled(foo) {
// do foo like things
}
Thoughts and suggestions appreciated, but I don't want to have the
bike-shedding go on too long.
Tim
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Re: Proposal: feature flag implementation for Juju
+1 for feature flags in general and +1 for using environment variables
in upstart to get them to the servers agents.
I think it'd be nice to have an environment variable per flag, with a
common prefix JUJU_FEATURE_. That way, if you need to check one in a
package init(), you don't have to parse the whole list of flags to find
the one you care about -- or depend on a globally initialized parsing of
that list.
env config seems reasonable, but dealing with parsing, errors and then
making that config globally available at init seems complex and not
always feasible.
How about defining them free form in an env config field, which is
then used to emit the env vars as described above to the upstart config
during bootstrap?
-Casey
On 11/25/2014 10:16 PM, Ian Booth wrote:
I like feature flags so am +1 to the overall proposal. I also agree with the
approach to keep them immutable, given the stated goals and complexity
associated with making them not so.
I think the env variable implementation is ok too - this keeps everything very
loosely coupled and avoids polluting a juju environment with an extra config
attribute.
On 26/11/14 08:47, Tim Penhey wrote:
Hi all,
There are often times when we want to hook up features for testing that
we don't want exposed to the general user community.
In the past we have hooked things up in master, then when the release
branch is made, we have had to go and change things there. This is a
terrible way to do it.
Here is my proposal:
http://reviews.vapour.ws/r/531/diff/#
We have an environment variable called JUJU_FEATURE_FLAGS. It contains
comma delimited strings that are used as flags.
The value is read when the program initializes and is not mutable.
Simple checks can be used in the code:
if featureflag.Enabled(foo) {
// do foo like things
}
Thoughts and suggestions appreciated, but I don't want to have the
bike-shedding go on too long.
Tim
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Re: Proposal: feature flag implementation for Juju
I like the idea. Thinking out loud: do we want to combine this with the
wrench so that we have 1 consistent way to fiddle with Juju behavior?
On Tue, Nov 25, 2014 at 4:47 PM, Tim Penhey tim.pen...@canonical.com
wrote:
Hi all,
There are often times when we want to hook up features for testing that
we don't want exposed to the general user community.
In the past we have hooked things up in master, then when the release
branch is made, we have had to go and change things there. This is a
terrible way to do it.
Here is my proposal:
http://reviews.vapour.ws/r/531/diff/#
We have an environment variable called JUJU_FEATURE_FLAGS. It contains
comma delimited strings that are used as flags.
The value is read when the program initializes and is not mutable.
Simple checks can be used in the code:
if featureflag.Enabled(foo) {
// do foo like things
}
Thoughts and suggestions appreciated, but I don't want to have the
bike-shedding go on too long.
Tim
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Re: Proposal: feature flag implementation for Juju
On Wed, Nov 26, 2014 at 6:47 AM, Tim Penhey tim.pen...@canonical.com
wrote:
Hi all,
There are often times when we want to hook up features for testing that
we don't want exposed to the general user community.
In the past we have hooked things up in master, then when the release
branch is made, we have had to go and change things there. This is a
terrible way to do it.
Here is my proposal:
http://reviews.vapour.ws/r/531/diff/#
We have an environment variable called JUJU_FEATURE_FLAGS. It contains
comma delimited strings that are used as flags.
The value is read when the program initializes and is not mutable.
Simple checks can be used in the code:
if featureflag.Enabled(foo) {
// do foo like things
}
Thoughts and suggestions appreciated, but I don't want to have the
bike-shedding go on too long.
I like the idea of having flags.
I'm not sure about setting it at bootstrap and it being global. How would
we test upgrade scenarios where some agents have the feature, and others
don't?
Cheers,
Andrew
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Re: Proposal: feature flag implementation for Juju
On 26/11/14 14:18, Andrew Wilkins wrote:
On Wed, Nov 26, 2014 at 6:47 AM, Tim Penhey tim.pen...@canonical.com
mailto:tim.pen...@canonical.com wrote:
Hi all,
There are often times when we want to hook up features for testing that
we don't want exposed to the general user community.
In the past we have hooked things up in master, then when the release
branch is made, we have had to go and change things there. This is a
terrible way to do it.
Here is my proposal:
http://reviews.vapour.ws/r/531/diff/#
We have an environment variable called JUJU_FEATURE_FLAGS. It contains
comma delimited strings that are used as flags.
The value is read when the program initializes and is not mutable.
Simple checks can be used in the code:
if featureflag.Enabled(foo) {
// do foo like things
}
Thoughts and suggestions appreciated, but I don't want to have the
bike-shedding go on too long.
I like the idea of having flags.
I'm not sure about setting it at bootstrap and it being global. How
would we test upgrade scenarios where some agents have the feature, and
others don't?
The idea is that the machines get the flags when they are deployed using
environment variables in the upstart script (or other service starting
thingimy-widget).
All agents in a given environment would have the same flags.
I'm in two minds about whether feature flags should be able to be turned
on and off on the fly.
I'm mostly against it as we may have different workers for feature
flags, and this would mean that we'd then have to code watchers for the
flags in order to start and stop workers based on flag changes.
I think simple is better here.
Tim
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Re: Proposal: feature flag implementation for Juju
Given the constraints you just listed (globally set in the environment,
etc), why not just make it environment config, rather than yet-another-way
to set env config?
John
=:-
On Wed, Nov 26, 2014 at 5:22 AM, Tim Penhey tim.pen...@canonical.com
wrote:
On 26/11/14 14:18, Andrew Wilkins wrote:
On Wed, Nov 26, 2014 at 6:47 AM, Tim Penhey tim.pen...@canonical.com
mailto:tim.pen...@canonical.com wrote:
Hi all,
There are often times when we want to hook up features for testing
that
we don't want exposed to the general user community.
In the past we have hooked things up in master, then when the release
branch is made, we have had to go and change things there. This is a
terrible way to do it.
Here is my proposal:
http://reviews.vapour.ws/r/531/diff/#
We have an environment variable called JUJU_FEATURE_FLAGS. It
contains
comma delimited strings that are used as flags.
The value is read when the program initializes and is not mutable.
Simple checks can be used in the code:
if featureflag.Enabled(foo) {
// do foo like things
}
Thoughts and suggestions appreciated, but I don't want to have the
bike-shedding go on too long.
I like the idea of having flags.
I'm not sure about setting it at bootstrap and it being global. How
would we test upgrade scenarios where some agents have the feature, and
others don't?
The idea is that the machines get the flags when they are deployed using
environment variables in the upstart script (or other service starting
thingimy-widget).
All agents in a given environment would have the same flags.
I'm in two minds about whether feature flags should be able to be turned
on and off on the fly.
I'm mostly against it as we may have different workers for feature
flags, and this would mean that we'd then have to code watchers for the
flags in order to start and stop workers based on flag changes.
I think simple is better here.
Tim
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Re: Proposal: feature flag implementation for Juju
I like feature flags so am +1 to the overall proposal. I also agree with the
approach to keep them immutable, given the stated goals and complexity
associated with making them not so.
I think the env variable implementation is ok too - this keeps everything very
loosely coupled and avoids polluting a juju environment with an extra config
attribute.
On 26/11/14 08:47, Tim Penhey wrote:
Hi all,
There are often times when we want to hook up features for testing that
we don't want exposed to the general user community.
In the past we have hooked things up in master, then when the release
branch is made, we have had to go and change things there. This is a
terrible way to do it.
Here is my proposal:
http://reviews.vapour.ws/r/531/diff/#
We have an environment variable called JUJU_FEATURE_FLAGS. It contains
comma delimited strings that are used as flags.
The value is read when the program initializes and is not mutable.
Simple checks can be used in the code:
if featureflag.Enabled(foo) {
// do foo like things
}
Thoughts and suggestions appreciated, but I don't want to have the
bike-shedding go on too long.
Tim
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Re: Proposal: feature flag implementation for Juju
Because I explicitly wanted to avoid touching config.
We want a simple method for checking flags that can't fail. Dealing with
config doesn't give us that.
I don't think that using an environment variable to define feature flags
is too terrible. We don't want to make it too easy ;-)
Tim
On 26/11/14 17:10, John Meinel wrote:
Given the constraints you just listed (globally set in the environment,
etc), why not just make it environment config, rather than
yet-another-way to set env config?
John
=:-
On Wed, Nov 26, 2014 at 5:22 AM, Tim Penhey tim.pen...@canonical.com
mailto:tim.pen...@canonical.com wrote:
On 26/11/14 14:18, Andrew Wilkins wrote:
On Wed, Nov 26, 2014 at 6:47 AM, Tim Penhey tim.pen...@canonical.com
mailto:tim.pen...@canonical.com
mailto:tim.pen...@canonical.com
mailto:tim.pen...@canonical.com wrote:
Hi all,
There are often times when we want to hook up features for
testing that
we don't want exposed to the general user community.
In the past we have hooked things up in master, then when the
release
branch is made, we have had to go and change things there.
This is a
terrible way to do it.
Here is my proposal:
http://reviews.vapour.ws/r/531/diff/#
We have an environment variable called JUJU_FEATURE_FLAGS. It
contains
comma delimited strings that are used as flags.
The value is read when the program initializes and is not mutable.
Simple checks can be used in the code:
if featureflag.Enabled(foo) {
// do foo like things
}
Thoughts and suggestions appreciated, but I don't want to have the
bike-shedding go on too long.
I like the idea of having flags.
I'm not sure about setting it at bootstrap and it being global. How
would we test upgrade scenarios where some agents have the
feature, and
others don't?
The idea is that the machines get the flags when they are deployed using
environment variables in the upstart script (or other service starting
thingimy-widget).
All agents in a given environment would have the same flags.
I'm in two minds about whether feature flags should be able to be turned
on and off on the fly.
I'm mostly against it as we may have different workers for feature
flags, and this would mean that we'd then have to code watchers for the
flags in order to start and stop workers based on flag changes.
I think simple is better here.
Tim
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