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45 lines
2.2 KiB
Markdown
45 lines
2.2 KiB
Markdown
# Pushservice
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Pushservice is the main push recommendation service at Twitter used to generate recommendation-based notifications for users. It currently powers two functionalities:
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- RefreshForPushHandler: This handler determines whether to send a recommendation push to a user based on their ID. It generates the best push recommendation item and coordinates with downstream services to deliver it
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- SendHandler: This handler determines and manage whether send the push to users based on the given target user details and the provided push recommendation item
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## Overview
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### RefreshForPushHandler
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RefreshForPushHandler follows these steps:
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- Building Target and checking eligibility
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- Builds a target user object based on the given user ID
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- Performs target-level filterings to determine if the target is eligible for a recommendation push
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- Fetch Candidates
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- Retrieves a list of potential candidates for the push by querying various candidate sources using the target
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- Candidate Hydration
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- Hydrates the candidate details with batch calls to different downstream services
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- Pre-rank Filtering, also called Light Filtering
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- Filters the hydrated candidates with lightweight RPC calls
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- Rank
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- Perform feature hydration for candidates and target user
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- Performs light ranking on candidates
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- Performs heavy ranking on candidates
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- Take Step, also called Heavy Filtering
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- Takes the top-ranked candidates one by one and applies heavy filtering until one candidate passes all filter steps
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- Send
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- Calls the appropriate downstream service to deliver the eligible candidate as a push and in-app notification to the target user
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### SendHandler
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SendHandler follows these steps:
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- Building Target
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- Builds a target user object based on the given user ID
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- Candidate Hydration
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- Hydrates the candidate details with batch calls to different downstream services
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- Feature Hydration
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- Perform feature hydration for candidates and target user
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- Take Step, also called Heavy Filtering
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- Perform filterings and validation checking for the given candidate
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- Send
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- Calls the appropriate downstream service to deliver the given candidate as a push and/or in-app notification to the target user |