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feat: add ps-cache-kotlin sample for connection-affinity mock matching
Kotlin + Spring Boot + JDBC sample that demonstrates the PS-cache mock mismatch. Uses HikariCP max-pool-size=1, prepareThreshold=1, and a /evict endpoint to force connection cycling. The test records 4 /account requests across 2 connection windows. Without the affinity fix (keploy/integrations#121), test-5 returns Alice's data for Charlie's request. Signed-off-by: slayerjain <shubhamkjain@outlook.com>
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‎ps-cache-kotlin/Dockerfile‎

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FROM maven:3.9-eclipse-temurin-21 AS builder
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WORKDIR /app
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COPY pom.xml .
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RUN mvn dependency:go-offline -q
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COPY src/ src/
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RUN mvn package -DskipTests -q
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FROM eclipse-temurin:21-jre-alpine
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WORKDIR /app
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COPY --from=builder /app/target/kotlin-app-1.0.0.jar app.jar
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EXPOSE 8080
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CMD ["java", "-jar", "app.jar"]

‎ps-cache-kotlin/docker-compose.yml‎

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services:
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db:
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image: postgres:16-alpine
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environment:
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POSTGRES_USER: postgres
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POSTGRES_PASSWORD: postgres
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POSTGRES_DB: testdb
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ports:
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- "5433:5432"
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volumes:
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- pgdata:/var/lib/postgresql/data
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- ./init.sql:/docker-entrypoint-initdb.d/init.sql
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healthcheck:
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test: ["CMD-SHELL", "pg_isready -U postgres"]
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interval: 2s
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timeout: 5s
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retries: 5
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api:
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build: .
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ports:
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- "8080:8080"
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environment:
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DB_HOST: db
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DB_PORT: "5432"
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DB_USER: postgres
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DB_PASSWORD: postgres
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DB_NAME: testdb
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depends_on:
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db:
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condition: service_healthy
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volumes:
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pgdata:

‎ps-cache-kotlin/init.sql‎

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CREATE SCHEMA IF NOT EXISTS travelcard;
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CREATE TABLE IF NOT EXISTS travelcard.travel_account (
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id SERIAL PRIMARY KEY,
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member_id INT NOT NULL UNIQUE,
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name TEXT NOT NULL,
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balance INT NOT NULL DEFAULT 0
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);
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INSERT INTO travelcard.travel_account (member_id, name, balance) VALUES
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(19, 'Alice', 1000),
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(23, 'Bob', 2500),
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(31, 'Charlie', 500),
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(42, 'Diana', 7500)
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ON CONFLICT (member_id) DO NOTHING;

‎ps-cache-kotlin/pom.xml‎

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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns="http://maven.apache.org/POM/4.0.0"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<parent>
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<groupId>org.springframework.boot</groupId>
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<artifactId>spring-boot-starter-parent</artifactId>
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<version>3.4.4</version>
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</parent>
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<groupId>com.demo</groupId>
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<artifactId>kotlin-app</artifactId>
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<version>1.0.0</version>
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<properties>
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<java.version>21</java.version>
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<kotlin.version>1.9.25</kotlin.version>
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</properties>
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<dependencies>
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<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency>
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<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-jdbc</artifactId></dependency>
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<dependency><groupId>org.postgresql</groupId><artifactId>postgresql</artifactId></dependency>
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<dependency><groupId>org.jetbrains.kotlin</groupId><artifactId>kotlin-reflect</artifactId></dependency>
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<dependency><groupId>org.jetbrains.kotlin</groupId><artifactId>kotlin-stdlib</artifactId></dependency>
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</dependencies>
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<build>
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<sourceDirectory>src/main/kotlin</sourceDirectory>
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<plugins>
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<plugin>
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<groupId>org.jetbrains.kotlin</groupId>
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<artifactId>kotlin-maven-plugin</artifactId>
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<version>${kotlin.version}</version>
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<configuration>
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<compilerPlugins><plugin>spring</plugin></compilerPlugins>
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<jvmTarget>${java.version}</jvmTarget>
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</configuration>
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<dependencies>
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<dependency><groupId>org.jetbrains.kotlin</groupId><artifactId>kotlin-maven-allopen</artifactId><version>${kotlin.version}</version></dependency>
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</dependencies>
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<executions><execution><id>compile</id><goals><goal>compile</goal></goals></execution></executions>
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</plugin>
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<plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId></plugin>
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</plugins>
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</build>
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</project>

‎ps-cache-kotlin/src/main/kotlin/com/demo/App.kt‎

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package com.demo
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import org.springframework.boot.autoconfigure.SpringBootApplication
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import org.springframework.boot.runApplication
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import org.springframework.jdbc.core.JdbcTemplate
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import org.springframework.web.bind.annotation.GetMapping
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import org.springframework.web.bind.annotation.RequestParam
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import org.springframework.web.bind.annotation.RestController
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import javax.sql.DataSource
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import com.zaxxer.hikari.HikariDataSource
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@SpringBootApplication
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class App
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fun main(args: Array<String>) {
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runApplication<App>(*args)
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}
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data class Account(
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val id: Int,
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val memberId: Int,
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val name: String,
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val balance: Int
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)
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@RestController
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class AccountController(private val jdbc: JdbcTemplate, private val dataSource: DataSource) {
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@GetMapping("/health")
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fun health() = mapOf("status" to "ok")
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/**
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* /account?member=N queries the travel_account table.
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*
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* JDBC PS caching (prepareThreshold=1):
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* - 1st call on a fresh connection: Parse(query="SELECT ...") + Bind + Describe + Execute
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* - 2nd+ calls on same connection: Bind(ps="S_1") + Execute only (cached PS)
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*
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* The /evict endpoint forces HikariCP to evict all connections, so the
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* NEXT /account call gets a fresh connection with cold PS cache.
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*/
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@GetMapping("/account")
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fun getAccount(@RequestParam("member") memberId: Int): Any {
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return jdbc.execute { conn: java.sql.Connection ->
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conn.autoCommit = false
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try {
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val ps = conn.prepareStatement(
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"""SELECT id, member_id, name, balance
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FROM travelcard.travel_account
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WHERE member_id = ?"""
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)
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ps.setInt(1, memberId)
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val rs = ps.executeQuery()
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val result = if (rs.next()) {
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Account(
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id = rs.getInt("id"),
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memberId = rs.getInt("member_id"),
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name = rs.getString("name"),
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balance = rs.getInt("balance")
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)
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} else {
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mapOf("error" to "not found", "member_id" to memberId)
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}
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rs.close()
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ps.close()
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conn.commit()
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result
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} catch (e: Exception) {
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conn.rollback()
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throw e
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}
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}!!
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}
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/**
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* /evict forces HikariCP to evict all idle connections.
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* Next request gets a FRESH PG connection → cold PS cache.
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* This simulates what happens in production when connections cycle.
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*/
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@GetMapping("/evict")
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fun evict(): Map<String, Any> {
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val hikari = dataSource as HikariDataSource
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hikari.hikariPoolMXBean?.softEvictConnections()
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// Also wait briefly for eviction
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Thread.sleep(200)
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return mapOf("evicted" to true, "active" to (hikari.hikariPoolMXBean?.activeConnections ?: 0),
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"idle" to (hikari.hikariPoolMXBean?.idleConnections ?: 0))
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}
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}

‎ps-cache-kotlin/src/main/resources/application.properties‎

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server.port=8080
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spring.datasource.url=jdbc:postgresql://${DB_HOST:localhost}:${DB_PORT:5432}/${DB_NAME:testdb}?prepareThreshold=1&preparedStatementCacheQueries=256
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spring.datasource.username=${DB_USER:postgres}
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spring.datasource.password=${DB_PASSWORD:postgres}
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spring.datasource.hikari.maximum-pool-size=1
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spring.datasource.hikari.minimum-idle=1
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spring.sql.init.mode=never

‎ps-cache-kotlin/test.sh‎

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#!/usr/bin/env bash
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set -euo pipefail
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BASE_URL="http://localhost:8080"
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echo "=== PS-Cache Mock Mismatch Test (Kotlin/JDBC) ==="
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echo "--- Window 1: Connection A ---"
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echo " /account?member=19:"
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curl -s "$BASE_URL/account?member=19"
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echo ""
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sleep 0.3
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echo " /account?member=23:"
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curl -s "$BASE_URL/account?member=23"
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echo ""
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sleep 0.3
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echo ""
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echo "--- Evict (force new connection) ---"
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echo " /evict:"
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curl -s "$BASE_URL/evict"
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echo ""
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sleep 1
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echo ""
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echo "--- Window 2: Connection B ---"
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echo " /account?member=31:"
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curl -s "$BASE_URL/account?member=31"
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echo ""
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sleep 0.3
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echo " /account?member=42:"
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curl -s "$BASE_URL/account?member=42"
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echo ""
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echo ""
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echo "=== Done ==="

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