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https://issues.apache.org/jira/browse/YARN-2678?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14173945#comment-14173945
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Steve Loughran commented on YARN-2678:
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Gour: I'll do these, as they seem goood and they need to be done before the
registry ships with hadoop.
w.r.t the header in the ZK nodes, it's to deal with the problems
* znodes with 0 bytes of data still have a stated size of 12 bytes. Requiring
16 bytes of header makes it trivial to decide whether or not it has data (makes
enuming child records faster)
* allows for future expansion to have different record types.
Here's what I propose
# drop the header
# add a {{type}} field to the json
# mandate a service record type declaration
{code}
"type":"ServiceRecord-1.0.0"
{code}
# declare that the presence of the byte sequence {{"ServiceRecord-1.0.0"}}
implies the entry is a sevice record. JSON is UTF-8 encoded, so this matches
the value of the {{type}} field.
# if the string is present, the entry MUST be parseable as a service record
# declare that the absence of the sequence implies that there is no service
record there.
{code}
Parsing/validating becomes one of
{code}
if len(data)<len("ServiceRecord-1.0.0"): raise NotFound
if not contains(data,"ServiceRecord-1.0.0"): raise NotFound
if not parse(data) raise InvalidRecord
if not valid(parse(data)) raise InvalidRecord
{code}
That is, if there isn't the string, it is not a parse error, it is simply "not
a record"
Validation becomes
# assert presence of {{"type":"ServiceRecord-1.0.0"}}
# forall endpoints, {{valid(endpoint)}}
# endpoints are valid if they follow the structure, al elements in the
dictionary of an address are simple strings, etc.
that's it: all other fields are optional
I'll update the .tla file and the code to match
> Recommended improvements to Yarn Registry
> -----------------------------------------
>
> Key: YARN-2678
> URL: https://issues.apache.org/jira/browse/YARN-2678
> Project: Hadoop YARN
> Issue Type: Sub-task
> Components: api, resourcemanager
> Reporter: Gour Saha
> Assignee: Steve Loughran
>
> In the process of binding to Slider AM from Slider agent python code here are
> some of the items I stumbled upon and would recommend as improvements.
> This is how the Slider's registry looks today -
> {noformat}
> jsonservicerec{
> "description" : "Slider Application Master",
> "external" : [ {
> "api" : "org.apache.slider.appmaster",
> "addressType" : "host/port",
> "protocolType" : "hadoop/protobuf",
> "addresses" : [ [ "c6408.ambari.apache.org", "34837" ] ]
> }, {
> "api" : "org.apache.http.UI",
> "addressType" : "uri",
> "protocolType" : "webui",
> "addresses" : [ [ "http://c6408.ambari.apache.org:43314"; ] ]
> }, {
> "api" : "org.apache.slider.management",
> "addressType" : "uri",
> "protocolType" : "REST",
> "addresses" : [ [
> "http://c6408.ambari.apache.org:43314/ws/v1/slider/mgmt"; ] ]
> }, {
> "api" : "org.apache.slider.publisher",
> "addressType" : "uri",
> "protocolType" : "REST",
> "addresses" : [ [
> "http://c6408.ambari.apache.org:43314/ws/v1/slider/publisher"; ] ]
> }, {
> "api" : "org.apache.slider.registry",
> "addressType" : "uri",
> "protocolType" : "REST",
> "addresses" : [ [
> "http://c6408.ambari.apache.org:43314/ws/v1/slider/registry"; ] ]
> }, {
> "api" : "org.apache.slider.publisher.configurations",
> "addressType" : "uri",
> "protocolType" : "REST",
> "addresses" : [ [
> "http://c6408.ambari.apache.org:43314/ws/v1/slider/publisher/slider"; ] ]
> } ],
> "internal" : [ {
> "api" : "org.apache.slider.agents.secure",
> "addressType" : "uri",
> "protocolType" : "REST",
> "addresses" : [ [
> "https://c6408.ambari.apache.org:46958/ws/v1/slider/agents"; ] ]
> }, {
> "api" : "org.apache.slider.agents.oneway",
> "addressType" : "uri",
> "protocolType" : "REST",
> "addresses" : [ [
> "https://c6408.ambari.apache.org:57513/ws/v1/slider/agents"; ] ]
> } ],
> "yarn:persistence" : "application",
> "yarn:id" : "application_1412974695267_0015"
> }
> {noformat}
> Recommendations:
> 1. I would suggest to either remove the string
> {color:red}jsonservicerec{color} or if it is desirable to have a non-null
> data at all times then loop the string into the json structure as a top-level
> attribute to ensure that the registry data is always a valid json document.
> 2. The {color:red}addresses{color} attribute is currently a list of list. I
> would recommend to convert it to a list of dictionary objects. In the
> dictionary object it would be nice to have the host and port portions of
> objects of addressType "uri" as separate key-value pairs to avoid parsing on
> the client side. The URI should also be retained as a key say "uri" to avoid
> clients trying to generate it by concatenating host, port, resource-path,
> etc. Here is a proposed structure -
> {noformat}
> {
> ...
> "internal" : [ {
> "api" : "org.apache.slider.agents.secure",
> "addressType" : "uri",
> "protocolType" : "REST",
> "addresses" : [
> { "uri" : "https://c6408.ambari.apache.org:46958/ws/v1/slider/agents";,
> "host" : "c6408.ambari.apache.org",
> "port": "46958"
> }
> ]
> }
> ],
> }
> {noformat}
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