[JENKINS-50669] reflective access shim

jenkinsci · Apr 9, 2018 · 5f42dc4 · 5f42dc4
1 parent 4de3883
commit 5f42dc4
Showing 1 changed file with 32 additions and 6 deletions.
diff --git a/src/main/java/io/jenkins/plugins/essentials/logging/EssentialsLoggingConfigurer.java b/src/main/java/io/jenkins/plugins/essentials/logging/EssentialsLoggingConfigurer.java
@@ -1,12 +1,14 @@
 package io.jenkins.plugins.essentials.logging;
 
 import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
+import hudson.WebAppMain;
 import hudson.init.InitMilestone;
 import hudson.init.Initializer;
 import hudson.triggers.SafeTimerTask;
 import jenkins.model.Jenkins;
 
 import java.io.File;
+import java.lang.reflect.Field;
 import java.util.Collections;
 import java.util.Comparator;
 import java.util.logging.FileHandler;
@@ -27,10 +29,7 @@ public static void configure() throws Exception {
         // Lower Level, debugging hack
         LOGGER.log(Level.SEVERE, "I started!");
 
-        if (Jenkins.logRecords.size() >= getMaxNumberOfLogs()) {
-            LOGGER.severe("The Jenkins logs buffer is full. " +
-                                  "Some logs might have been missed, and so many logs shows something probably very wrong!");
-        }
+        checkNotTooManyLogsAlready();
 
         // FIXME: should I use the no-arg ctor to let usual sysprops be usable?
         FileHandler fileHandler = new FileHandler(getFilePattern(), 10 * 1000 * 1000, 5, false);
@@ -44,6 +43,25 @@ public static void configure() throws Exception {
         Logger.getLogger("").addHandler(fileHandler);
     }
 
+    /**
+     * {@link Jenkins#logRecords} uses an underlying {@link hudson.util.RingBufferLogHandler} with a default size of 256 (at least until 2.114 included).
+     * In our case, we use it only once to access the logs that were generated <strong>before</strong> the current plugin is started.
+     * <p>
+     * If that ring buffer is full, that already means per-se something is most likely unhealthy.
+     * In normal conditions, there should be only like 20 log entries in that buffer when the plugin starts.
+     */
+    private static void checkNotTooManyLogsAlready() {
+        final int logRecordsSize = Jenkins.logRecords.size();
+        LOGGER.log(Level.INFO, "There are {0} log entries that were generated already.", logRecordsSize);
+
+        final int maxNumberOfLogs = getMaxNumberOfLogs();
+        if (logRecordsSize >= maxNumberOfLogs) {
+            LOGGER.log(Level.SEVERE,
+                       "The Jenkins logs buffer is already full. " +
+                               "Some logs might have been missed, and so many logs shows something probably very wrong! (max={0})",
+                       maxNumberOfLogs);
+        }
+    }
 
     @SuppressFBWarnings("RV_RETURN_VALUE_IGNORED_BAD_PRACTICE")
     private static String getFilePattern() {
@@ -55,12 +73,20 @@ private static String getFilePattern() {
     /**
      * Returns the size of the logs buffer used behind .
      * <p>
-     * FIXME: un-hardcode 256 to use the actual value used in {@link hudson.util.RingBufferLogHandler#records.size()}
+     * FIXME: use the new non-reflective access method when JENKINS-50669 is done.
      *
      * @return the size of the {@link Jenkins#logRecords} logs buffer.
      */
     private static int getMaxNumberOfLogs() {
-        return 256;
+        try {
+            final Field default_ring_buffer_size = WebAppMain.class.getDeclaredField("DEFAULT_RING_BUFFER_SIZE");
+            default_ring_buffer_size.setAccessible(true);
+            final int anInt = default_ring_buffer_size.getInt(null);
+            return anInt;
+        } catch (NoSuchFieldException | IllegalAccessException e) {
+            LOGGER.log(Level.SEVERE, "Unable to access WebAppMain.DEFAULT_RING_BUFFER_SIZE. Returning default value.");
+            return 256;
+        }
     }
 
 }