fix-1429 maxPoolSize and maxThreadSize should be configurable

documentation/en/user/source/production/index.rst

@@ -102,6 +102,33 @@ Resource Allocation
 
 Also see https://github.com/GeoWebCache/geowebcache/wiki/Estimating-the-number-of-tiles-and-size-on-disk for table that can be used to estimate how much storage you need and how long seeding will take
 
+Seeder thread pool configuration
+++++++++++++++++++++++++++++++
+
+The number of concurrent seed tasks that GeoWebCache can execute is controlled by an internal
+thread pool. You can configure its sizes using environment variables (values shown are
+defaults used when variables are not set):
+
+- ``GWC_SEEDER_CORE_POOL_SIZE``: core pool size, defaults to ``16``
+- ``GWC_SEEDER_MAX_POOL_SIZE``: maximum pool size, defaults to ``32``
+
+Example (Linux/macOS):
+
+.. code-block:: bash
+
+   export GWC_SEEDER_CORE_POOL_SIZE=8
+   export GWC_SEEDER_MAX_POOL_SIZE=16
+   # start your servlet container / GeoWebCache here
+
+On Windows (PowerShell):
+
+.. code-block:: powershell
+
+   $Env:GWC_SEEDER_CORE_POOL_SIZE = "8"
+   $Env:GWC_SEEDER_MAX_POOL_SIZE = "16"
+   # start your servlet container / GeoWebCache here
+
+These settings control the pool used to run seed tasks.
 
 Clustering
 ----------

geowebcache/core/src/test/java/org/geowebcache/seed/SeederThreadPoolExecutorConfigurationTest.java

@@ -0,0 +1,152 @@
+/**
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General
+ * Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any
+ * later version.
+ *
+ * <p>This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+ *
+ * <p>You should have received a copy of the GNU Lesser General Public License along with this program. If not, see
+ * <http://www.gnu.org/licenses/>.
+ */
+package org.geowebcache.seed;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.After;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.contrib.java.lang.system.EnvironmentVariables;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.support.ClassPathXmlApplicationContext;
+
+/**
+ * Test class to verify that the SeederThreadPoolExecutor configuration properly reads environment variables for core
+ * pool size and maximum pool size.
+ */
+public class SeederThreadPoolExecutorConfigurationTest {
+
+    /** Allows to set environment variables for each individual test */
+    @Rule
+    public final EnvironmentVariables environmentVariables = new EnvironmentVariables();
+
+    private ApplicationContext applicationContext;
+
+    @After
+    public void tearDown() {
+        if (applicationContext != null) {
+            ((ClassPathXmlApplicationContext) applicationContext).close();
+        }
+    }
+
+    /** Test that default values are used when environment variables are not set. */
+    @Test
+    public void testDefaultValuesWhenEnvironmentVariablesNotSet() {
+        // Clear any existing environment variables
+        environmentVariables.clear("GWC_SEEDER_CORE_POOL_SIZE");
+        environmentVariables.clear("GWC_SEEDER_MAX_POOL_SIZE");
+
+        // Load the Spring context with test configuration
+        applicationContext = new ClassPathXmlApplicationContext("seeder-thread-pool-test-context.xml");
+
+        // Get the seeder thread pool executor bean
+        SeederThreadPoolExecutor executor =
+                applicationContext.getBean("gwcSeederThreadPoolExec", SeederThreadPoolExecutor.class);
+
+        // Verify default values are used
+        assertEquals("Core pool size should default to 16", 16, executor.getCorePoolSize());
+        assertEquals("Maximum pool size should default to 32", 32, executor.getMaximumPoolSize());
+
+        // Clean up
+        executor.shutdown();
+    }
+
+    /** Test that custom environment variable values are properly loaded. */
+    @Test
+    public void testCustomEnvironmentVariableValues() {
+        // Set custom environment variables
+        environmentVariables.set("GWC_SEEDER_CORE_POOL_SIZE", "8");
+        environmentVariables.set("GWC_SEEDER_MAX_POOL_SIZE", "16");
+
+        // Load the Spring context with test configuration
+        applicationContext = new ClassPathXmlApplicationContext("seeder-thread-pool-test-context.xml");
+
+        // Get the seeder thread pool executor bean
+        SeederThreadPoolExecutor executor =
+                applicationContext.getBean("gwcSeederThreadPoolExec", SeederThreadPoolExecutor.class);
+
+        // Verify custom values are used
+        assertEquals("Core pool size should be set to 8", 8, executor.getCorePoolSize());
+        assertEquals("Maximum pool size should be set to 16", 16, executor.getMaximumPoolSize());
+
+        // Clean up
+        executor.shutdown();
+    }
+
+    /** Test that only one environment variable is set (partial configuration). */
+    @Test
+    public void testPartialEnvironmentVariableConfiguration() {
+        // Set only core pool size environment variable
+        environmentVariables.set("GWC_SEEDER_CORE_POOL_SIZE", "12");
+        environmentVariables.clear("GWC_SEEDER_MAX_POOL_SIZE");
+
+        // Load the Spring context with test configuration
+        applicationContext = new ClassPathXmlApplicationContext("seeder-thread-pool-test-context.xml");
+
+        // Get the seeder thread pool executor bean
+        SeederThreadPoolExecutor executor =
+                applicationContext.getBean("gwcSeederThreadPoolExec", SeederThreadPoolExecutor.class);
+
+        // Verify mixed configuration
+        assertEquals("Core pool size should be set to 12", 12, executor.getCorePoolSize());
+        assertEquals("Maximum pool size should default to 32", 32, executor.getMaximumPoolSize());
+
+        // Clean up
+        executor.shutdown();
+    }
+
+    /** Test that invalid environment variable values fall back to defaults. */
+    @Test
+    public void testInvalidEnvironmentVariableValues() {
+        // Set invalid environment variables
+        environmentVariables.set("GWC_SEEDER_CORE_POOL_SIZE", "invalid");
+        environmentVariables.set("GWC_SEEDER_MAX_POOL_SIZE", "not_a_number");
+
+        // Load the Spring context with test configuration
+        applicationContext = new ClassPathXmlApplicationContext("seeder-thread-pool-test-context.xml");
+
+        // Get the seeder thread pool executor bean
+        SeederThreadPoolExecutor executor =
+                applicationContext.getBean("gwcSeederThreadPoolExec", SeederThreadPoolExecutor.class);
+
+        // Verify default values are used when invalid values are provided
+        assertEquals("Core pool size should default to 16 when invalid value provided", 16, executor.getCorePoolSize());
+        assertEquals(
+                "Maximum pool size should default to 32 when invalid value provided",
+                32,
+                executor.getMaximumPoolSize());
+
+        // Clean up
+        executor.shutdown();
+    }
+
+    /** Test that the SeederThreadPoolExecutor can be created with various configurations. */
+    @Test
+    public void testSeederThreadPoolExecutorCreation() {
+        // Test with different pool sizes
+        SeederThreadPoolExecutor executor1 = new SeederThreadPoolExecutor(4, 8);
+        assertEquals("Core pool size should be 4", 4, executor1.getCorePoolSize());
+        assertEquals("Maximum pool size should be 8", 8, executor1.getMaximumPoolSize());
+        executor1.shutdown();
+
+        SeederThreadPoolExecutor executor2 = new SeederThreadPoolExecutor(1, 1);
+        assertEquals("Core pool size should be 1", 1, executor2.getCorePoolSize());
+        assertEquals("Maximum pool size should be 1", 1, executor2.getMaximumPoolSize());
+        executor2.shutdown();
+
+        SeederThreadPoolExecutor executor3 = new SeederThreadPoolExecutor(64, 128);
+        assertEquals("Core pool size should be 64", 64, executor3.getCorePoolSize());
+        assertEquals("Maximum pool size should be 128", 128, executor3.getMaximumPoolSize());
+        executor3.shutdown();
+    }
+}

geowebcache/core/src/test/resources/seeder-thread-pool-test-context.xml

@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">
+<beans>
+  <description>
+   Test configuration for SeederThreadPoolExecutor with environment variables
+  </description>
+
+  <!-- Property placeholder configurer to resolve environment variables -->
+  <bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
+    <property name="systemPropertiesModeName" value="SYSTEM_PROPERTIES_MODE_OVERRIDE"/>
+    <property name="searchSystemEnvironment" value="true"/>
+  </bean>
+
+  <!-- Thread pool for seeding with environment variable configuration -->
+  <bean id="gwcSeederThreadPoolExec" 
+    class="org.geowebcache.seed.SeederThreadPoolExecutor">
+    <constructor-arg value="${GWC_SEEDER_CORE_POOL_SIZE:16}"/><!-- Size of core pool -->
+    <constructor-arg value="${GWC_SEEDER_MAX_POOL_SIZE:32}"/><!-- Maximum size of pool -->
+  </bean>
+
+</beans>

geowebcache/web/src/main/webapp/WEB-INF/geowebcache-core-context.xml

@@ -183,8 +183,8 @@
   <!-- Thread pool for seeding -->
   <bean id="gwcSeederThreadPoolExec" 
     class="org.geowebcache.seed.SeederThreadPoolExecutor">
-    <constructor-arg value="16"/><!-- Size of core pool -->
-    <constructor-arg value="32"/><!-- Maximum size of pool -->
+    <constructor-arg value="${GWC_SEEDER_CORE_POOL_SIZE:16}"/><!-- Size of core pool -->
+    <constructor-arg value="${GWC_SEEDER_MAX_POOL_SIZE:32}"/><!-- Maximum size of pool -->
   </bean>
 
   <!-- Breeder (the one that seeds) -->