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| Warning | ||
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Collections are under heavy development and major parts of the API will change as features are added. |
What are Wrangler Collections?
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Wrangler Collections are a Wrangler provided wrapper around subscriptions that allows a pico to maintain a "collection" of other picos, by using subscription relationships. The owner of the collection accepts subscription requests with a set Tx_role and Rx_role that match the collection parameters. The developer is then able to access the collection members by calling a function from the io.picolabs.collection ruleset.
The following is an example of a collection. The CollectionPico maintains subscriptions with collection members. It can also have subscriptions with picos that are not part of the collection.
Querying the members() function of collections returns the relevant subscription information about each member in the collection:
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/*
[
{
"Rx_role": "collection",
"Tx_role": "member",
"Tx_host": "http://10.37.94.198:8080",
"Id": "cjy922iak0032r4bz8je38al5",
"Tx": "BSQTCB3zp1oaRXXeanJhj8",
"Rx": "FweGnhgVrmYicWog8pfJ1c",
"Tx_verify_key": "6gy2Rn2YKCwzntsW6GVjKE1Yxbi3c6QT6PY3yhqDYqAk",
"Tx_public_key": "4J8agPM9z7Ue31mUsxaBWsVT9pDpdjKQJCEoUDmjCJCk"
},
{
"Rx_role": "collection",
"Tx_role": "member",
"Tx_host": "http://10.37.94.198:8080",
"Id": "cjy922o6p003br4bz82qrhvna",
"Tx": "CM6gsePpn9Ab1SCkRgi8AY",
"Rx": "BfhDCpb8hTaULihx2FAJUM",
"Tx_verify_key": "7Bgn4x5FD8vExdBdvPvXmVGPNRzCz3XMp1CLzzNQEDyt",
"Tx_public_key": "5eAo9Lgx8jccGxGvmF7P5GgCYZJyTy99iHMtNGMhXdxA"
},
{
"Rx_role": "collection",
"Tx_role": "member",
"Tx_host": "http://10.37.94.198:8080",
"Id": "cjy922sa1003ir4bzeafr390e",
"Tx": "NRKkM5QT12HewbsxQYCgXY",
"Rx": "QtshCUNrZa1bP19MErnjW",
"Tx_verify_key": "Cg7HcTmoZjPaBEn1ueHHfiL6zB69T4Xa2sLRUT7WGNn5",
"Tx_public_key": "HFRf82ZBVg9fDouMhY15XoJ3BVXmNi1BnhzNtvkGJFDr"
}
]
*/ |
Creating a Collection
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A collection can be created by installing the io.picolabs.collection ruleset in the desired collection manager and then sending subscription requests with the required Tx_role and Rx_roles. The default Tx_role and Rx_role is "collection" and "member" respectively, but these can (and should) be set to something else to prevent collisions.
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rule addSelfToCollection {
select when example addToCollection
pre {
collectionLoc = event:attr("collectionManager")
}
always {
raise wrangler event "subscription" attributes {
"wellKnown_Tx": collectionLoc,
"Rx_role":"member",
"Tx_role":"collection"
}
}
} |
When the subscription is created and the pico is added to the collection the collection pico will raise event wrangler:new_member that can be selected on.
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rule onNewCollectionMember {
select when collection new_member
pre {
subInfo = event:attr("bus") // Same attributes as given to wrangler subscription_added
}
event:send({"eci":subInfo{"Tx"}, "domain":"example","type":"welcome_to_collection"})
} |
Sending Messages to Collection Members
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Messages can be sent to collection members by using the return value of the members() function to loop through members with a foreach and send an event to each Tx.