Attributes merged between roles and environments?

Chef Infra (archive)
1

This seems to be the case, but I thought I’d check, just in case I’m making
incorrect assumptions…

Do multi level attributes get ‘merged’ between environments and roles? Ie,
would this environment attribute:

{
“name”: “qa”,
“default_attributes”: {
“mongodb”: {
“cluster_name”: “test1”
}
}

and this role attribute:

{
“name”: “role-mongo-shard1”,
“default_attributes”: {
“mongodb”: {
“shard_name”: “shard1”,
“config”: {
“replSet”: “replset1”
}
}
}
}

be merged into this json?

mongodb": {
“cluster_name”: “test1”,
“shard_name”: “shard1”,
“config”: {
“replSet”: “replset1”
}
}

Or, does one wipe the other?

Thanks,
Doug.

2

On Tuesday, August 12, 2014 at 3:03 PM, Douglas Garstang wrote:

This seems to be the case, but I thought I'd check, just in case I'm making incorrect assumptions...

Do multi level attributes get 'merged' between environments and roles? Ie, would this environment attribute:

{
"name": "qa",
"default_attributes": {
"mongodb": {
"cluster_name": "test1"
}
}

and this role attribute:

{
"name": "role-mongo-shard1",
"default_attributes": {
"mongodb": {
"shard_name": "shard1",
"config": {
"replSet": "replset1"
}
}
}
}

be merged into this json?

mongodb": {
"cluster_name": "test1",
"shard_name": "shard1",
"config": {
"replSet": "replset1"
}
}

Or, does one wipe the other?

Thanks,
Doug.

They’re “deep merged,” which does what you expect as long as everything is a hash (JSON “object” type). With Arrays, it’s tricky because we try to make a compromise that supports two competing use cases (sometimes you want a set union, sometimes you want replacement). The best way to go is just to steer clear of Arrays entirely and it should work as you expect.

--
Daniel DeLeo

3

Thanks Daniel.

On Tue, Aug 12, 2014 at 3:08 PM, Daniel DeLeo dan@kallistec.com wrote:

On Tuesday, August 12, 2014 at 3:03 PM, Douglas Garstang wrote:

This seems to be the case, but I thought I'd check, just in case I'm
making incorrect assumptions...

Do multi level attributes get 'merged' between environments and roles?
Ie, would this environment attribute:

{
"name": "qa",
"default_attributes": {
"mongodb": {
"cluster_name": "test1"
}
}

and this role attribute:

{
"name": "role-mongo-shard1",
"default_attributes": {
"mongodb": {
"shard_name": "shard1",
"config": {
"replSet": "replset1"
}
}
}
}

be merged into this json?

mongodb": {
"cluster_name": "test1",
"shard_name": "shard1",
"config": {
"replSet": "replset1"
}
}

Or, does one wipe the other?

Thanks,
Doug.

They’re “deep merged,” which does what you expect as long as everything is
a hash (JSON “object” type). With Arrays, it’s tricky because we try to
make a compromise that supports two competing use cases (sometimes you want
a set union, sometimes you want replacement). The best way to go is just to
steer clear of Arrays entirely and it should work as you expect.

--
Daniel DeLeo

--
Regards,

Douglas Garstang
http://www.linkedin.com/in/garstang
Email: doug.garstang@gmail.com
Cell: +1-805-340-5627