We've got this part down { "name": "es_dispatcher_lb", "description": "", "json_class": "Chef::Role", "default_attributes": { }, "override_attributes": { "postfix": { "myhostname": "dispatcher-lb.enstratus.com" } }, "chef_type": "role", "run_list": [ "role[es_loadbalancer]", "recipe[enstratus::dispatcher_lb]", "role[monitored_host]" ], "env_run_lists": { } } Do this Then this Then this
The deep Chefster backends = search(:node, "role:#{node[:enstratus] [:dispatcher_lb][:dispatcher_server_role]} AND chef_environment:#{node.chef_environment}") + <% @backends.each do |be| -%> server <%= be.name %> <%= be.ipaddress %>:2023 check inter 5000 <% end -%> = "recipe[enstratus::dispatcher_lb]"
The deep Chefster backends = search(:node, "role:#{node[:enstratus] [:dispatcher_lb][:dispatcher_server_role]} AND chef_environment:#{node.chef_environment}") + <% @backends.each do |be| -%> server <%= be.name %> <%= be.ipaddress %>:2023 check inter 5000 <% end -%> = "recipe[enstratus::dispatcher_lb]"
You want to... ● Have confguration changes on one system affect change on another system ● Gate confguration changes on one system based on state of another system ● Establish relationships between systems
But... ● Should adding a new backend node cause a chef- client run on the haproxy nodes? ● If the chef-client run on the haproxy node changes a different setting, what node(s) needs to know that? ● What if THOSE nodes change something? NOW who do we tell?
Data comes out... curl -X GET \ http://noahserverhost:5678/applications/fooapp { "id":"0d52d942-4580-f30e-4515-4edda2a2fc3d", "tags":[], "links":[], "name":"fooapp", "created_at":"Thu May 10 02:22:53 UTC 2012", "updated_at":"Thu May 10 02:22:53 UTC 2012", "configurations":{} }
Ephemerals ● Arbitrary paths in the URL scheme namespaced under /ephemerals ● Key is path name /ephemerals/foo/bar/chefconf/ ● Value is...whatever Doesn't have to be JSON. Could be a blob. ● No relation in between keys /foo/bar is unrelated to /foo
Watches ● “Pluggable” callbacks ● Think triggers ● Register against any path in the system ● Changes at that path (or below it) execute the registered callback ● Sends JSON dump of the state of change
Watch Example (part 1) ● Add some data curl -XPUT -d '1' http://localhost:5678/ephemerals/chef/notify/localhost ● Get a response {"action":"create", "result":"success", "id":"7e743edd-a40f-5062-a5a0-70a8b4df7721", "path":"/chef/notify/localhost", "data":"1", "created_at":"Wed May 09 03:56:25 UTC 2012", "updated_at":"Wed May 09 03:56:25 UTC 2012"}
Watch Example (part 2) ● Register a watch curl -XPUT -d '{"pattern":"//noah/ephemerals/chef/notify/localhost", "endpoint":"http://localhost:8080"}' http://localhost:5678/watches/ ● Get a response {"action":"create","result":"success","id":"51828298-ad79-26c3-459b- fd757b85db75","pattern":"//noah/ephemerals/chef/notify/localhost","name" :"Ly9ub2FoL2VwaGVtZXJhbHMvY2hlZi9ub3RpZnkvbG9jYWxob3N0fGh0dHA6Ly9sb2NhbG hvc3Q6ODA4MQ==","endpoint":"http://localhost:8080,"created_at":"Thu May 10 03:02:25 UTC 2012","updated_at":"Thu May 10 03:02:25 UTC 2012"}
Now what? ● Change that data curl -XPUT -d '2' http://localhost:5678/ephemerals/chef/notify/localhost Get a response {"action":"update", "result":"success", "id":"7e743edd-a40f-5062-a5a0-70a8b4df7721", "path":"/chef/notify/localhost", "data":"2", "created_at":"Wed May 09 03:56:25 UTC 2012", "updated_at":"Wed May 09 04:00:00 UTC 2012"}
But something else happened this time... I, [2012-05-09T00:01:00.395491 #36180] INFO -- Noah::Agent: Found new watches D, [2012-05-09T00:01:00.395611 #36180] DEBUG -- Noah::Agent: Current watch count: 0 D, [2012-05-09T00:01:00.396681 #36180] DEBUG -- Noah::Agent: New watch count: 1 I, [2012-05-09T00:01:00.396850 #36180] INFO -- Noah::Agents::HttpAgent: Noah::Agents::HttpAgent worker initiated I, [2012-05-09T23:10:36.438180 #38052] INFO -- Noah::Agents::HttpAgent: Message posted to http://localhost:8080 successfully
And what did localhost:8080 see? { "id"=>"7e743edd-a40f-5062-a5a0-70a8b4df7721", "tags"=>[], "links"=>[], "path"=>"/ephemerals//chef/notify/localhost", "data"=>"1", "created_at"=>"Wed May 09 03:56:25 UTC 2012", "updated_at"=>"Thu May 10 03:10:36 UTC 2012", "action"=>"update", "pubcategory"=>"//noah/ephemerals/chef/notify/localhost" }
What can we do with that? ● Parse the data to effect some change? ● Use it as a signaling mechanism? ● Alert on it? ● More importantly, how can we use it with Chef?
Noah LWRP ● Register any primitive ● noah_application ● noah_service ● noah_configuration ● noah_application ● Dump some data in an ephemeral node ● noah_ephemeral ● Block the chef run until some data shows up in Noah ● noah_block
Triggering Chef Runs ● Use noah_ephemeral at end of the dependency run_list (on the backend node) ● Leverage string interpolation for path name ● Data is unimportant, just the signal
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