Refactor to use StringBuilder

dhis-2/dhis-web-api/src/main/java/org/hisp/dhis/webapi/controller/datasummary/DataSummaryController.java

@@ -31,24 +31,18 @@
 import static org.springframework.http.MediaType.APPLICATION_JSON_VALUE;
 import static org.springframework.http.MediaType.TEXT_PLAIN_VALUE;
 
-import io.prometheus.client.CollectorRegistry;
-import io.prometheus.client.exporter.common.TextFormat;
-import java.io.IOException;
-import java.io.StringWriter;
-import java.io.Writer;
 import org.hisp.dhis.common.DhisApiVersion;
 import org.hisp.dhis.common.OpenApi;
 import org.hisp.dhis.datastatistics.DataStatisticsService;
 import org.hisp.dhis.datasummary.DataSummary;
 import org.hisp.dhis.security.RequiresAuthority;
 import org.hisp.dhis.webapi.mvc.annotation.ApiVersion;
+import org.hisp.dhis.webapi.utils.PrometheusTextBuilder;
 import org.springframework.beans.factory.annotation.Autowired;
-import org.springframework.http.HttpStatus;
 import org.springframework.stereotype.Controller;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.ResponseBody;
-import org.springframework.web.server.ResponseStatusException;
 
 /**
  * dataSummary endpoint to access System Statistics
@@ -74,15 +68,57 @@ public class DataSummaryController {
   @GetMapping(value = "/metrics", produces = TEXT_PLAIN_VALUE)
   @RequiresAuthority(anyOf = F_PERFORM_MAINTENANCE)
   public @ResponseBody String getPrometheusMetrics() {
-    try {
-      DataSummary summary = dataStatisticsService.getSystemStatisticsSummary();
-      DataSummaryPrometheusMetrics.updateMetrics(summary);
-      Writer writer = new StringWriter();
-      TextFormat.write004(writer, CollectorRegistry.defaultRegistry.metricFamilySamples());
-      return writer.toString();
-    } catch (IOException e) {
-      throw new ResponseStatusException(
-          HttpStatus.INTERNAL_SERVER_ERROR, "Unable to produce metrics", e);
+    DataSummary summary = dataStatisticsService.getSystemStatisticsSummary();
+    final String PROMETHEUS_GAUGE_NAME = "gauge";
+    PrometheusTextBuilder metrics = new PrometheusTextBuilder();
+
+    metrics.updateMetricsFromMap(
+        summary.getObjectCounts(),
+        "data_summary_object_counts",
+        "type",
+        "Count of metadata objects",
+        PROMETHEUS_GAUGE_NAME);
+
+    metrics.updateMetricsFromMap(
+        summary.getActiveUsers(),
+        "data_summary_active_users",
+        "days",
+        "Count of active users",
+        PROMETHEUS_GAUGE_NAME);
+
+    metrics.updateMetricsFromMap(
+        summary.getUserInvitations(),
+        "data_summary_user_invitations",
+        "type",
+        "Count of user invitations",
+        PROMETHEUS_GAUGE_NAME);
+
+    metrics.updateMetricsFromMap(
+        summary.getDataValueCount(),
+        "data_summary_data_value_count",
+        "days",
+        "Count of updated data values by day",
+        PROMETHEUS_GAUGE_NAME);
+
+    metrics.updateMetricsFromMap(
+        summary.getEventCount(),
+        "data_summary_event_count",
+        "days",
+        "Count of updated events by day",
+        PROMETHEUS_GAUGE_NAME);
+
+    // The system information is presented just as a static gauge with value 1.0
+    // The key is the field name and the value is the field value
+    metrics.createPrometheusHelpLine("data_summary_system_info", "System information");
+    metrics.createPrometheusTypeLine("data_summary_system_info", "gauge");
+    if (summary.getSystem() != null) {
+      metrics.appendSystemInfo("version", summary.getSystem().getVersion());
+      metrics.appendSystemInfo("revision", summary.getSystem().getRevision());
+      metrics.appendSystemInfo("build_time", summary.getSystem().getBuildTime().toString());
+      metrics.appendSystemInfo("system_id", summary.getSystem().getSystemId());
+      metrics.appendSystemInfo("server_date", summary.getSystem().getServerDate().toString());
     }
+
+    return metrics.getMetrics();
   }
 }

dhis-2/dhis-web-api/src/main/java/org/hisp/dhis/webapi/utils/PrometheusTextBuilder.java

@@ -0,0 +1,67 @@
+/*
+ * Copyright (c) 2004-2025, University of Oslo
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ * Redistributions of source code must retain the above copyright notice, this
+ * list of conditions and the following disclaimer.
+ *
+ * Redistributions in binary form must reproduce the above copyright notice,
+ * this list of conditions and the following disclaimer in the documentation
+ * and/or other materials provided with the distribution.
+ * Neither the name of the HISP project nor the names of its contributors may
+ * be used to endorse or promote products derived from this software without
+ * specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
+ * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+package org.hisp.dhis.webapi.utils;
+
+import java.util.Map;
+
+public class PrometheusTextBuilder {
+
+  private StringBuilder metrics = new StringBuilder();
+
+  public void createPrometheusHelpLine(String metricName, String help) {
+    metrics.append("# HELP ").append(metricName).append(" ").append(help).append("\n");
+  }
+
+  public void createPrometheusTypeLine(String metricName, String type) {
+    metrics.append("# TYPE ").append(metricName).append(" ").append(type).append("\n");
+  }
+
+  public void updateMetricsFromMap(
+      Map<?, ?> map, String metricName, String keyName, String help, String type) {
+    createPrometheusHelpLine(metricName, help);
+    createPrometheusTypeLine(metricName, type);
+    map.forEach(
+        (key, value) ->
+            metrics.append("%s{%s=\"%s\", } %s.0 \n".formatted(metricName, keyName, key, value)));
+  }
+
+  public void appendSystemInfo(String key, String value) {
+    if (value != null) {
+      metrics
+          .append("data_summary_system_info{key=\"")
+          .append(key)
+          .append("\", value=\"")
+          .append(value)
+          .append("\"} 1.0\n");
+    }
+  }
+
+  public String getMetrics() {
+    return metrics.toString();
+  }
+}