flink-udf

flink-udf is a skill for Claude Code from confluentinc/agent-skills. It costs 189 tokens per session (811 once invoked), scanned A, original, Apache-2.0.

A skill for building Java user-defined functions for Apache Flink, a system that processes data streams, including streams from Kafka. These functions add custom logic to Flink SQL or its Table API.

In plain words
What is it for?
Creating functions that return one value, multiple table rows, or stateful results such as windows, deduplication, and state machines.
Why use it?
It provides an implementation path for logic that built-in Flink functions cannot express, along with deployment options for Confluent Cloud or local Docker.

Skill for Claude Code ✓ vendor

Written for Claude Code: shipped in a Claude Code plugin.

Part of the streaming-skills-plugin plugin — 16 skills shipped together

Good fit Creating functions that return one value, multiple table rows, or stateful results such as windows, deduplication, and state machines.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/confluentinc/agent-skills/flink-udf
About the project

AI Agent Skills by Confluent is a collection of skills for building Kafka producers, Flink applications, and real-time data-streaming pipelines. Developers use it with coding assistants when creating applications and pipelines on Confluent. The catalogue entries are its skills, plugin, and instruction.

confluentinc/agent-skills · 56 stars · on GitHub

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add confluentinc/agent-skills --skill flink-udf
Clone the repo
git clone --depth 1 https://github.com/confluentinc/agent-skills

Made for: Claude Code.

Or install streaming-skills-plugin, the plugin that ships this one along with the rest of its 16 skills.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for flink-udf

README.md
[![agentmods](https://agentmods.dev/badge/skills/confluentinc/agent-skills/flink-udf/github.svg)](https://agentmods.dev/skills/confluentinc/agent-skills/flink-udf)
Your own site
<a href="https://agentmods.dev/skills/confluentinc/agent-skills/flink-udf"><img src="https://agentmods.dev/badge/skills/confluentinc/agent-skills/flink-udf/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for flink-udf

Your own site · 80×15
<a href="https://agentmods.dev/skills/confluentinc/agent-skills/flink-udf"><img src="https://agentmods.dev/badge/skills/confluentinc/agent-skills/flink-udf.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 189 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 811 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector pass 7 Sept 2026
How audits are shown
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00189 $0.00811
Opus 5 $0.00095 $0.00405
Sonnet 5 $0.00038 $0.00162
Haiku 4.5 $0.00019 $0.00081

Measured 10d ago against content hash faa794eca039, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

flink-udf scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 10d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/flink-udf/SKILL.md · 66 lines

How it starts

The opening of the file, as written. The whole thing — 66 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Build and deploy custom functions in Java for Apache Flink to extend SQL and Table API capabilities with custom logic.

Function Types

Before proceeding, identify which type of function the user needs:

  • Scalar UDF: Maps input values to a single output value (e.g., custom hash, string manipulation, calculations)
  • User-Defined Table Function (UDTF): Maps input to multiple output rows (e.g., split strings, explode arrays)
  • Process Table Function (PTF): Advanced stateful processing with N-to-M semantics, managed state, and timers (e.g., windowing, deduplication, state machines)

Gather Requirements

Ask the user these questions to determine the implementation path (if not already clear from context):

  1. Deployment target: Confluent Cloud or local Docker?
  2. Infrastructure: Deploy new infrastructure (Kafka + Flink) or use existing?
  3. Invocation method: Flink SQL or Table API?

Route to Implementation Guide

Based on the answers above, read the appropriate reference file:

Confluent Cloud Deployment

  • Scalar UDF or UDTF → Read references/udf-udtf-java-confluent-cloud.md
  • Process Table Function (PTF) → Read references/ptf-java-confluent-cloud.md

If infrastructure setup is needed, also read references/confluent-cloud-setup.md first.

Local Docker Deployment

  • Scalar UDF or UDTF → Read references/udf-udtf-java-local.md
  • Process Table Function (PTF) → Read references/ptf-java-local.md

If infrastructure setup is needed, also read references/local-docker-setup.md first.

Implementation Workflow

After reading the appropriate reference:

  1. Set up infrastructure (if needed)
  2. Generate boilerplate code for the function
  3. Implement the business logic
  4. Build and package the JAR
  5. Confirm the deployment plan with the user. Before any resource-modifying call (confluent flink artifact create, docker cp into a running container, CREATE FUNCTION, etc.), present the plan and wait for explicit approval. Show:
    • Artifact name and JAR path
    • Function name to register
    • Target environment (Confluent Cloud env + compute pool ID, or local Docker container name)
    • The exact commands and SQL that will run Do not proceed to steps 6–7 until the user confirms.
  6. Deploy the artifact
  7. Register the function in Flink
  8. Test the function with sample data
  9. Provide usage examples (SQL or Table API)

Read the full file on GitHub · 66 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 10d ago First seen · 66 lines · 189 tokens per session scan A faa794eca039

Subscribe to this mod's changes

flink-udf is a skill published in the GitHub repository confluentinc/agent-skills (56 stars, last pushed 6d ago), licensed Apache-2.0. It adds 189 tokens to every session and 811 once invoked, about $0.0009 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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