Introduce new printing queue threshold

core/src/main/java/org/mapfish/print/metrics/ApplicationStatus.java

@@ -10,46 +10,50 @@
 import org.springframework.beans.factory.annotation.Value;
 
 class ApplicationStatus extends HealthCheck {
-  @Value("${expectedMaxTime.sinceLastPrint.InSeconds}")
+  @Value("${healthStatus.expectedMaxTime.sinceLastPrint.InSeconds}")
   private int secondsInFloatingWindow;
 
+  @Value("${healthStatus.unhealthyThreshold.maxNbrPrintJobQueued}")
+  private int maxNbrPrintJobQueued;
+
   @Autowired private JobQueue jobQueue;
   @Autowired private ThreadPoolJobManager jobManager;
 
-  private long previousNumberOfWaitingJobs = 0L;
-
+  /**
+   * When a Result is returned it can be healthy or unhealthy. In both cases it is associated to a
+   * Http 200 status. When an exception is thrown it means the server is no longer working at all,
+   * it is associated to a Http 500 status.
+   */
   @Override
   protected Result check() throws Exception {
     long waitingJobsCount = jobQueue.getWaitingJobsCount();
     if (waitingJobsCount == 0) {
-      previousNumberOfWaitingJobs = waitingJobsCount;
       return Result.healthy("No print job is waiting in the queue.");
     }
 
-    String health = "Number of print jobs waiting is " + waitingJobsCount;
+    String health = " Number of print jobs waiting is " + waitingJobsCount;
 
     if (jobManager.getLastExecutedJobTimestamp() == null) {
-      return Result.unhealthy("No print job was ever processed by this server. " + health);
-    } else if (hasJobExecutedRecently()) {
-      if (waitingJobsCount > previousNumberOfWaitingJobs) {
-        previousNumberOfWaitingJobs = waitingJobsCount;
+      return Result.unhealthy("No print job was ever processed by this server." + health);
+    } else if (hasThisServerPrintedRecently()) {
+      if (waitingJobsCount > maxNbrPrintJobQueued) {
         return Result.unhealthy(
-            "Number of print jobs queued is increasing. But this server is processing them. "
-                + health);
+            "Number of print jobs queued is above threshold: " + maxNbrPrintJobQueued + health);
       } else {
-        previousNumberOfWaitingJobs = waitingJobsCount;
-        return Result.healthy(
-            "Print jobs are being dequeued. Number of print jobs waiting is " + waitingJobsCount);
+        return Result.healthy("This server instance is printing." + health);
       }
     } else {
-      previousNumberOfWaitingJobs = waitingJobsCount;
-      throw new RuntimeException(
-          "No print job was processed by this server, in the last (seconds): "
-              + secondsInFloatingWindow);
+      throw notificationForBrokenServer();
     }
   }
 
-  private boolean hasJobExecutedRecently() {
+  private RuntimeException notificationForBrokenServer() {
+    return new RuntimeException(
+        "None of the print job queued was processed by this server, in the last (seconds): "
+            + secondsInFloatingWindow);
+  }
+
+  private boolean hasThisServerPrintedRecently() {
     final Instant lastExecutedJobTime = jobManager.getLastExecutedJobTimestamp().toInstant();
     final Instant beginningOfTimeWindow = getBeginningOfTimeWindow();
     return lastExecutedJobTime.isAfter(beginningOfTimeWindow);

core/src/main/resources/mapfish-spring.properties

@@ -54,4 +54,7 @@ httpRequest.fetchRetry.maxNumber=3
 httpRequest.fetchRetry.intervalMillis=100
 
 # Amount of time in the past where we check if a print job was executed by this server
-expectedMaxTime.sinceLastPrint.InSeconds=300
+healthStatus.expectedMaxTime.sinceLastPrint.InSeconds=300
+
+# Maximum number of Print Jobs queued before raising it i
+healthStatus.unhealthyThreshold.maxNbrPrintJobQueued=4

core/src/test/java/org/mapfish/print/metrics/ApplicationStatusTest.java

@@ -52,33 +52,34 @@ public void testCheck_Failed_NoPrintJobs() throws Exception {
       fail("Expected exception not thrown");
     } catch (RuntimeException e) {
       assertEquals(
-          "No print job was processed by this server, in the last (seconds): 300", e.getMessage());
+          "None of the print job queued was processed by this server, in the last (seconds): 300",
+          e.getMessage());
     } catch (Exception e) {
       fail("Incorrect Exception thrown: " + e);
     }
   }
 
   @Test
   public void testCheck_Success_PrintJobs() throws Exception {
-    when(jobQueue.getWaitingJobsCount()).thenReturn(10L, 9L);
+    when(jobQueue.getWaitingJobsCount()).thenReturn(5L, 4L);
     when(jobManager.getLastExecutedJobTimestamp()).thenReturn(new Date());
 
     applicationStatus.check();
     HealthCheck.Result result = applicationStatus.check();
 
     assertTrue(result.isHealthy());
-    assertTrue(result.getMessage().contains("Print jobs are being dequeued"));
+    assertTrue(result.getMessage().contains("This server instance is printing."));
   }
 
   @Test
-  public void testCheck_Fail_PrintJobsButIncreasing() throws Exception {
-    when(jobQueue.getWaitingJobsCount()).thenReturn(0L, 1L);
+  public void testCheck_Fail_TooManyJobsAreQueued() throws Exception {
+    when(jobQueue.getWaitingJobsCount()).thenReturn(4L, 5L);
     when(jobManager.getLastExecutedJobTimestamp()).thenReturn(new Date());
 
     applicationStatus.check();
     HealthCheck.Result result = applicationStatus.check();
 
     assertFalse(result.isHealthy());
-    assertTrue(result.getMessage().contains("Number of print jobs queued is increasing."));
+    assertTrue(result.getMessage().contains("Number of print jobs queued is above threshold: "));
   }
 }