initial version

.github/dependabot.yml

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+# To get started with Dependabot version updates, you'll need to specify which
+# package ecosystems to update and where the package manifests are located.
+# Please see the documentation for all configuration options:
+# https://help.github.com/github/administering-a-repository/configuration-options-for-dependency-updates
+
+version: 2
+updates:
+  - package-ecosystem: "gomod" # See documentation for possible values
+    directory: "/" # Location of package manifests
+    schedule:
+      interval: "daily"
+
+  - package-ecosystem: github-actions
+    directory: /
+    schedule:
+      interval: daily

.github/workflows/codecov.yml

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+name: Test and coverage
+
+on: [push, pull_request]
+
+permissions:  # added using https://github.com/step-security/secure-workflows
+  contents: read
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Harden Runner
+        uses: step-security/harden-runner@17d0e2bd7d51742c71671bd19fa12bdc9d40a3d6
+        with:
+          egress-policy: audit # TODO: change to 'egress-policy: block' after couple of runs
+
+      - uses: actions/checkout@692973e3d937129bcbf40652eb9f2f61becf3332
+        with:
+          fetch-depth: 2
+      - uses: actions/setup-go@0a12ed9d6a96ab950c8f026ed9f722fe0da7ef32
+        with:
+          go-version: '1.18'
+      - name: Run coverage
+        run: go test ./... -race -coverprofile=coverage.txt -covermode=atomic
+      - name: Upload coverage to Codecov
+        run: bash <(curl -s https://codecov.io/bash)

.github/workflows/codeql-analysis.yml

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+# For most projects, this workflow file will not need changing; you simply need
+# to commit it to your repository.
+#
+# You may wish to alter this file to override the set of languages analyzed,
+# or to provide custom queries or build logic.
+#
+# ******** NOTE ********
+# We have attempted to detect the languages in your repository. Please check
+# the `language` matrix defined below to confirm you have the correct set of
+# supported CodeQL languages.
+#
+name: "CodeQL"
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    # The branches below must be a subset of the branches above
+    branches: [ main ]
+  schedule:
+    - cron: '20 3 * * 4'
+
+permissions:  # added using https://github.com/step-security/secure-workflows
+  contents: read
+
+jobs:
+  analyze:
+    name: Analyze
+    runs-on: ubuntu-latest
+    permissions:
+      actions: read
+      contents: read
+      security-events: write
+
+    strategy:
+      fail-fast: false
+      matrix:
+        language: [ 'go' ]
+        # CodeQL supports [ 'cpp', 'csharp', 'go', 'java', 'javascript', 'python', 'ruby' ]
+        # Learn more about CodeQL language support at https://git.io/codeql-language-support
+
+    steps:
+    - name: Harden Runner
+      uses: step-security/harden-runner@17d0e2bd7d51742c71671bd19fa12bdc9d40a3d6
+      with:
+        egress-policy: audit # TODO: change to 'egress-policy: block' after couple of runs
+
+    - name: Checkout repository
+      uses: actions/checkout@692973e3d937129bcbf40652eb9f2f61becf3332
+
+    # Initializes the CodeQL tools for scanning.
+    - name: Initialize CodeQL
+      uses: github/codeql-action/init@cdcdbb579706841c47f7063dda365e292e5cad7a
+      with:
+        languages: ${{ matrix.language }}
+        # If you wish to specify custom queries, you can do so here or in a config file.
+        # By default, queries listed here will override any specified in a config file.
+        # Prefix the list here with "+" to use these queries and those in the config file.
+        # queries: ./path/to/local/query, your-org/your-repo/queries@main
+
+    # Autobuild attempts to build any compiled languages  (C/C++, C#, or Java).
+    # If this step fails, then you should remove it and run the build manually (see below)
+    - name: Autobuild
+      uses: github/codeql-action/autobuild@cdcdbb579706841c47f7063dda365e292e5cad7a
+
+    # ℹ️ Command-line programs to run using the OS shell.
+    # 📚 https://git.io/JvXDl
+
+    # ✏️ If the Autobuild fails above, remove it and uncomment the following three lines
+    #    and modify them (or add more) to build your code if your project
+    #    uses a compiled language
+
+    #- run: |
+    #   make bootstrap
+    #   make release
+
+    - name: Perform CodeQL Analysis
+      uses: github/codeql-action/analyze@cdcdbb579706841c47f7063dda365e292e5cad7a

.github/workflows/go.yml

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+on: [push, pull_request]
+name: Unit Tests
+permissions:  # added using https://github.com/step-security/secure-workflows
+  contents: read
+
+jobs:
+  test:
+    strategy:
+      matrix:
+        go-version: [1.18.x, 1.19.x, 1.20.x, 1.21.x, 1.22.x]
+        os: [ubuntu-latest, macos-latest, windows-latest]
+    runs-on: ${{ matrix.os }}
+    steps:
+    - name: Harden Runner
+      uses: step-security/harden-runner@17d0e2bd7d51742c71671bd19fa12bdc9d40a3d6
+      with:
+        egress-policy: audit # TODO: change to 'egress-policy: block' after couple of runs
+
+    - name: Install Go
+      uses: actions/setup-go@0a12ed9d6a96ab950c8f026ed9f722fe0da7ef32
+      with:
+        go-version: ${{ matrix.go-version }}
+    - name: Checkout code
+      uses: actions/checkout@692973e3d937129bcbf40652eb9f2f61becf3332
+    - name: Test
+      run: go test ./...

.github/workflows/golangci-lint.yml

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+name: golangci-lint
+on: [push ] 
+permissions:  # added using https://github.com/step-security/secure-workflows
+  contents: read
+
+jobs:
+  golangci:
+    permissions:
+      contents: read  # for actions/checkout to fetch code
+      pull-requests: read  # for golangci/golangci-lint-action to fetch pull requests
+    name: lint
+    runs-on: ubuntu-latest
+    steps:
+      - name: Harden Runner
+        uses: step-security/harden-runner@17d0e2bd7d51742c71671bd19fa12bdc9d40a3d6
+        with:
+          egress-policy: audit # TODO: change to 'egress-policy: block' after couple of runs
+
+      - uses: actions/checkout@692973e3d937129bcbf40652eb9f2f61becf3332
+      - name: golangci-lint
+        uses: golangci/golangci-lint-action@a4f60bb28d35aeee14e6880718e0c85ff1882e64
+        with:
+          # Optional: version of golangci-lint to use in form of v1.2 or v1.2.3 or `latest` to use the latest version
+          version: latest
+
+          # Optional: working directory, useful for monorepos
+          # working-directory: somedir
+          output: checkstyle
+
+          # Optional: golangci-lint command line arguments.
+          # args: --issues-exit-code=0
+          # args: --out-format checkstyle
+
+          # Optional: show only new issues if it's a pull request. The default value is `false`.
+          # only-new-issues: true
+
+          # Optional: if set to true then the action will use pre-installed Go.
+          # skip-go-installation: true
+
+          # Optional: if set to true then the action don't cache or restore ~/go/pkg.
+          # skip-pkg-cache: true
+
+          # Optional: if set to true then the action don't cache or restore ~/.cache/go-build.
+          # skip-build-cache: true

LICENSE

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+The MIT License (MIT)
+
+Copyright (c) 2024 SingleStore, Inc
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+

README.md

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+# keyeddistributor - distribute events to listeners by key
+
+[![GoDoc](https://godoc.org/github.com/memsql/keyeddistributor?status.svg)](https://pkg.go.dev/github.com/memsql/keyeddistributor)
+![unit tests](https://github.com/memsql/keyeddistributor/actions/workflows/go.yml/badge.svg)
+[![report card](https://goreportcard.com/badge/github.com/memsql/keyeddistributor)](https://goreportcard.com/report/github.com/memsql/keyeddistributor)
+[![codecov](https://codecov.io/gh/memsql/keyeddistributor/branch/main/graph/badge.svg)](https://codecov.io/gh/memsql/keyeddistributor)
+
+Install:
+
+	go get github.com/memsql/keyeddistributor
+
+---
+
+Keyeddistributor is an add-on to [eventdistributor](https://github.com/sharnoff/eventdistributor) that
+allows for ad-hoc subscription to events that match a key value.
+
+## An example
+
+```go
+keyed := keyeddistributor.New(func(t Thing) ThingKey) {
+	return t.Key // or whatever is needed to extract a ThingKey from a Thing
+})
+
+reader := keyed.Subscribe("some key value")
+defer reader.Unsubscribe()
+
+<-reader.WaitChan()
+thing := reader.Consume()
+// do stuff with thing
+```

go.mod

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+module github.com/memsql/keyeddistributor
+
+go 1.18
+
+require (
+	github.com/muir/nject v1.7.1
+	github.com/stretchr/testify v1.8.4
+)
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/muir/reflectutils v0.7.0 // indirect
+	github.com/pkg/errors v0.9.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)

keyed.go

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+package keyed
+
+import (
+	"github.com/sharnoff/eventdistributor"
+
+	"singlestore.com/helios/util/refcountmap"
+)
+
+/*
+Package keyeddistributor provides a way to wrap [eventdistributor]
+so that it is efficient to receive notification only for the
+specific events you're interested in: those that have a specific
+value as derived from the underlying event.
+
+[eventdistributor]: https://pkg.go.dev/github.com/sharnoff/eventdistributor
+*/
+
+var closedChannel = func() <-chan struct{} {
+	c := make(chan struct{})
+	close(c)
+	return c
+}()
+
+// Distributor supports subscribing to get a Reader
+type Distributor[E any, K comparable] struct {
+	m   *refcountmap.Map[K, *eventdistributor.Distributor[E]]
+	key func(E) K
+}
+
+// Reader is used by a single subscriber to get events. Select on
+// reader.WaitChan() to know when there is an event ready to consume
+// and then use reader.Consume() to get the event. Use reader.Unsubscribe()
+// when the reader is no longer needed. Reader embeds
+// eventdistributor's Reader.
+type Reader[E any] struct {
+	eventdistributor.Reader[E]
+	release func()
+}
+
+func New[E any, K comparable](key func(E) K) *Distributor[E, K] {
+	return &Distributor[E, K]{
+		m: refcountmap.New[K](func() *eventdistributor.Distributor[E] {
+			return eventdistributor.New[E]()
+		}),
+		key: key,
+	}
+}
+
+// Submit pushes an event into the Distributor. The returned channel is closed
+// when the event has been fully consumed. If there are no subscribers, the
+// event will be considered consumed immediately.
+//
+// Submit is thread-safe
+func (k *Distributor[E, K]) Submit(e E) <-chan struct{} {
+	key := k.key(e)
+	dist, ok := k.m.Load(key)
+	if !ok {
+		return closedChannel
+	}
+	return dist.Submit(e)
+}
+
+// Subscribe creates a Reader that listens for events where the key matches
+// a specific value. It is recommended that immediately after a Subscribe,
+// that you defer the Unsubscribe:
+//
+//	reader := distributor.Subscribe(someValue)
+//	defer reader.Unsubscribe()
+//
+// Subscribe is thread-safe
+func (k *Distributor[E, K]) Subscribe(value K) *Reader[E] {
+	d, release, _ := k.m.Get(value)
+	reader := d.Subscribe()
+	return &Reader[E]{
+		Reader:  reader,
+		release: release,
+	}
+}
+
+// Unsubscribe releases a Reader. After an Unsubscribe, the WaitChan() and
+// Consume() methods should not be used. It is important to Unsubscribe()
+// because otherwise the Distributor will keep buffering events that are
+// meant for the reader.
+func (r *Reader[E]) Unsubscribe() {
+	r.release()
+	r.Reader.Unsubscribe()
+}