Adding ability to disable compression in PrometheusScrapeHandler (#1691)

Resolves #1684

---------

Signed-off-by: Igor Melnichenko <[email protected]>

Author: Myllyenko

prometheus-metrics-config/src/main/java/io/prometheus/metrics/config/ExporterHttpServerProperties.java

@@ -7,18 +7,25 @@
 public class ExporterHttpServerProperties {
 
   private static final String PORT = "port";
+  private static final String PREFER_UNCOMPRESSED_RESPONSE = "preferUncompressedResponse";
   private static final String PREFIX = "io.prometheus.exporter.httpServer";
   @Nullable private final Integer port;
+  private final boolean preferUncompressedResponse;
 
-  private ExporterHttpServerProperties(@Nullable Integer port) {
+  private ExporterHttpServerProperties(@Nullable Integer port, boolean preferUncompressedResponse) {
     this.port = port;
+    this.preferUncompressedResponse = preferUncompressedResponse;
   }
 
   @Nullable
   public Integer getPort() {
     return port;
   }
 
+  public boolean isPreferUncompressedResponse() {
+    return preferUncompressedResponse;
+  }
+
   /**
    * Note that this will remove entries from {@code properties}. This is because we want to know if
    * there are unused properties remaining after all properties have been loaded.
@@ -27,7 +34,12 @@ static ExporterHttpServerProperties load(Map<Object, Object> properties)
       throws PrometheusPropertiesException {
     Integer port = Util.loadInteger(PREFIX + "." + PORT, properties);
     Util.assertValue(port, t -> t > 0, "Expecting value > 0.", PREFIX, PORT);
-    return new ExporterHttpServerProperties(port);
+
+    Boolean preferUncompressedResponse =
+        Util.loadBoolean(PREFIX + "." + PREFER_UNCOMPRESSED_RESPONSE, properties);
+
+    return new ExporterHttpServerProperties(
+        port, preferUncompressedResponse != null && preferUncompressedResponse);
   }
 
   public static Builder builder() {
@@ -37,6 +49,7 @@ public static Builder builder() {
   public static class Builder {
 
     @Nullable private Integer port;
+    private boolean preferUncompressedResponse = false;
 
     private Builder() {}
 
@@ -45,8 +58,13 @@ public Builder port(int port) {
       return this;
     }
 
+    public Builder preferUncompressedResponse(boolean preferUncompressedResponse) {
+      this.preferUncompressedResponse = preferUncompressedResponse;
+      return this;
+    }
+
     public ExporterHttpServerProperties build() {
-      return new ExporterHttpServerProperties(port);
+      return new ExporterHttpServerProperties(port, preferUncompressedResponse);
     }
   }
 }

prometheus-metrics-config/src/test/java/io/prometheus/metrics/config/ExporterHttpServerPropertiesTest.java

@@ -2,6 +2,7 @@
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
+import static org.assertj.core.api.SoftAssertions.assertSoftly;
 
 import java.util.HashMap;
 import java.util.Map;
@@ -13,6 +14,7 @@ void load() {
     ExporterHttpServerProperties properties =
         load(Map.of("io.prometheus.exporter.httpServer.port", "1"));
     assertThat(properties.getPort()).isOne();
+    assertThat(properties.isPreferUncompressedResponse()).isFalse();
 
     assertThatExceptionOfType(PrometheusPropertiesException.class)
         .isThrownBy(() -> load(Map.of("io.prometheus.exporter.httpServer.port", "0")))
@@ -21,7 +23,14 @@ void load() {
 
   @Test
   void builder() {
-    assertThat(ExporterHttpServerProperties.builder().port(1).build().getPort()).isOne();
+    ExporterHttpServerProperties properties =
+        ExporterHttpServerProperties.builder().port(1).build();
+
+    assertSoftly(
+        softly -> {
+          softly.assertThat(properties.getPort()).isOne();
+          softly.assertThat(properties.isPreferUncompressedResponse()).isFalse();
+        });
   }
 
   private static ExporterHttpServerProperties load(Map<String, String> map) {

prometheus-metrics-exporter-common/src/main/java/io/prometheus/metrics/exporter/common/PrometheusScrapeHandler.java

@@ -29,6 +29,7 @@ public class PrometheusScrapeHandler {
   @Nullable private final Predicate<String> nameFilter;
   private final AtomicInteger lastResponseSize = new AtomicInteger(2 << 9); //  0.5 MB
   private final List<String> supportedFormats;
+  private final boolean preferUncompressedResponse;
 
   public PrometheusScrapeHandler() {
     this(PrometheusProperties.get(), PrometheusRegistry.defaultRegistry);
@@ -44,6 +45,8 @@ public PrometheusScrapeHandler(PrometheusProperties config) {
 
   public PrometheusScrapeHandler(PrometheusProperties config, PrometheusRegistry registry) {
     this.expositionFormats = ExpositionFormats.init(config.getExporterProperties());
+    this.preferUncompressedResponse =
+        config.getExporterHttpServerProperties().isPreferUncompressedResponse();
     this.registry = registry;
     this.nameFilter = makeNameFilter(config.getExporterFilterProperties());
     supportedFormats = new ArrayList<>(Arrays.asList("openmetrics", "text"));
@@ -180,6 +183,10 @@ private boolean writeDebugResponse(
   }
 
   private boolean shouldUseCompression(PrometheusHttpRequest request) {
+    if (preferUncompressedResponse) {
+      return false;
+    }
+
     Enumeration<String> encodingHeaders = request.getHeaders("Accept-Encoding");
     if (encodingHeaders == null) {
       return false;