feat: Enable GZIP compression for request payloads

src/androidTest/java/com/mixpanel/android/mpmetrics/MPConfigTest.java

@@ -195,6 +195,32 @@ public void testSetMaximumDatabaseLimit2() {
         assertEquals(100000000, mixpanelAPI.getMaximumDatabaseLimit());
     }
 
+    @Test
+    public void testShouldGzipRequestPayload() {
+        final Bundle metaData = new Bundle();
+        metaData.putBoolean("com.mixpanel.android.MPConfig.GzipRequestPayload", true);
+        MPConfig mpConfig = mpConfig(metaData);
+        assertTrue(mpConfig.shouldGzipRequestPayload());
+
+        mpConfig.setShouldGzipRequestPayload(false);
+        assertFalse(mpConfig.shouldGzipRequestPayload());
+
+        mpConfig.setShouldGzipRequestPayload(true);
+        assertTrue(mpConfig.shouldGzipRequestPayload());
+
+        // assert false by default
+        MPConfig mpConfig2 = mpConfig(new Bundle());
+        assertFalse(mpConfig2.shouldGzipRequestPayload());
+
+        MixpanelAPI mixpanelAPI = mixpanelApi(mpConfig);
+
+        assertTrue(mixpanelAPI.shouldGzipRequestPayload());
+
+        mixpanelAPI.setShouldGzipRequestPayload(false);
+        assertFalse(mixpanelAPI.shouldGzipRequestPayload());
+
+    }
+
     private MPConfig mpConfig(final Bundle metaData) {
         return new MPConfig(metaData, InstrumentationRegistry.getInstrumentation().getContext(), null);
     }

src/main/java/com/mixpanel/android/mpmetrics/AnalyticsMessages.java

@@ -171,7 +171,7 @@ protected MPDbAdapter makeDbAdapter(Context context) {
     }
 
     protected RemoteService getPoster() {
-        return new HttpService();
+        return new HttpService(mConfig.shouldGzipRequestPayload());
     }
 
     ////////////////////////////////////////////////////

src/main/java/com/mixpanel/android/mpmetrics/MPConfig.java

@@ -200,6 +200,7 @@ public synchronized void setOfflineMode(OfflineMode offlineMode) {
         mBulkUploadLimit = metaData.getInt("com.mixpanel.android.MPConfig.BulkUploadLimit", 40); // 40 records default
         mFlushInterval = metaData.getInt("com.mixpanel.android.MPConfig.FlushInterval", 60 * 1000); // one minute default
         mFlushBatchSize = metaData.getInt("com.mixpanel.android.MPConfig.FlushBatchSize", 50); // flush 50 events at a time by default
+        shouldGzipRequestPayload = metaData.getBoolean("com.mixpanel.android.MPConfig.GzipRequestPayload", false);
         mFlushOnBackground = metaData.getBoolean("com.mixpanel.android.MPConfig.FlushOnBackground", true);
         mMinimumDatabaseLimit = metaData.getInt("com.mixpanel.android.MPConfig.MinimumDatabaseLimit", 20 * 1024 * 1024); // 20 Mb
         mMaximumDatabaseLimit = metaData.getInt("com.mixpanel.android.MPConfig.MaximumDatabaseLimit", Integer.MAX_VALUE); // 2 Gb
@@ -277,6 +278,10 @@ public int getFlushBatchSize() {
     public void setFlushBatchSize(int flushBatchSize) {
         mFlushBatchSize = flushBatchSize;
     }
+    public boolean shouldGzipRequestPayload() { return shouldGzipRequestPayload; }
+
+    public void setShouldGzipRequestPayload(Boolean shouldGzip) { shouldGzipRequestPayload = shouldGzip; }
+
 
     // Throw away records that are older than this in milliseconds. Should be below the server side age limit for events.
     public long getDataExpiration() {
@@ -476,6 +481,7 @@ public String toString() {
     private String mPeopleEndpoint;
     private String mGroupsEndpoint;
     private int mFlushBatchSize;
+    private boolean shouldGzipRequestPayload;
 
     private final String mResourcePackageName;
     private final int mMinSessionDuration;

src/main/java/com/mixpanel/android/mpmetrics/MixpanelAPI.java

@@ -513,6 +513,24 @@ public int getFlushBatchSize() {
         return mConfig.getFlushBatchSize();
     }
 
+    /**
+     * Set whether the request payload should be GZIP-compressed before being sent.
+     *
+     * @param shouldGzipRequestPayload boolean, true to enable GZIP compression, false otherwise.
+     */
+    public void setShouldGzipRequestPayload(boolean shouldGzipRequestPayload) {
+        mConfig.setShouldGzipRequestPayload(shouldGzipRequestPayload);
+    }
+
+    /**
+     * Get whether the request payload is currently set to be GZIP-compressed.
+     *
+     * @return boolean, whether GZIP compression is enabled
+     */
+    public boolean shouldGzipRequestPayload() {
+        return mConfig.shouldGzipRequestPayload();
+    }
+
     /**
      * Set an integer number of bytes, the maximum size limit to the Mixpanel database.
      *

src/main/java/com/mixpanel/android/util/HttpService.java

@@ -18,6 +18,7 @@
 import java.net.InetAddress;
 import java.net.URL;
 import java.util.Map;
+import java.util.zip.GZIPOutputStream;
 
 import javax.net.ssl.HttpsURLConnection;
 import javax.net.ssl.SSLSocketFactory;
@@ -27,10 +28,20 @@
  */
 public class HttpService implements RemoteService {
 
+
+    private final boolean shouldGzipRequestPayload;
+
     private static boolean sIsMixpanelBlocked;
     private static final int MIN_UNAVAILABLE_HTTP_RESPONSE_CODE = HttpURLConnection.HTTP_INTERNAL_ERROR;
     private static final int MAX_UNAVAILABLE_HTTP_RESPONSE_CODE = 599;
 
+    public HttpService(boolean shouldGzipRequestPayload) {
+        this.shouldGzipRequestPayload = shouldGzipRequestPayload;
+    }
+
+    public HttpService() {
+        this(false);
+    }
     @Override
     public void checkIsMixpanelBlocked() {
         Thread t = new Thread(new Runnable() {
@@ -104,7 +115,7 @@ public byte[] performRequest(String endpointUrl, ProxyServerInteractor interacto
         while (retries < 3 && !succeeded) {
             InputStream in = null;
             OutputStream out = null;
-            BufferedOutputStream bout = null;
+            OutputStream bout = null;
             HttpURLConnection connection = null;
 
             try {
@@ -131,12 +142,15 @@ public byte[] performRequest(String endpointUrl, ProxyServerInteractor interacto
                         builder.appendQueryParameter(param.getKey(), param.getValue().toString());
                     }
                     String query = builder.build().getEncodedQuery();
-
-                    connection.setFixedLengthStreamingMode(query.getBytes().length);
+                    if (shouldGzipRequestPayload) {
+                        connection.setRequestProperty(CONTENT_ENCODING_HEADER, GZIP_CONTENT_TYPE_HEADER);
+                    } else {
+                        connection.setFixedLengthStreamingMode(query.getBytes().length);
+                    }
                     connection.setDoOutput(true);
                     connection.setRequestMethod("POST");
                     out = connection.getOutputStream();
-                    bout = new BufferedOutputStream(out);
+                    bout = getBufferedOutputStream(out);
                     bout.write(query.getBytes("UTF-8"));
                     bout.flush();
                     bout.close();
@@ -179,6 +193,14 @@ public byte[] performRequest(String endpointUrl, ProxyServerInteractor interacto
         return response;
     }
 
+    private OutputStream getBufferedOutputStream(OutputStream out) throws IOException {
+        if(shouldGzipRequestPayload) {
+          return new GZIPOutputStream(new BufferedOutputStream(out), HTTP_OUTPUT_STREAM_BUFFER_SIZE);
+        } else {
+            return new BufferedOutputStream(out);
+        }
+    }
+
     private static boolean isProxyRequest(String endpointUrl) {
         return !endpointUrl.toLowerCase().contains(MIXPANEL_API.toLowerCase());
     }
@@ -199,4 +221,7 @@ private static byte[] slurp(final InputStream inputStream)
     }
 
     private static final String LOGTAG = "MixpanelAPI.Message";
+    private static final int HTTP_OUTPUT_STREAM_BUFFER_SIZE = 8192;
+    private static final String CONTENT_ENCODING_HEADER = "Content-Encoding";
+    private static final String GZIP_CONTENT_TYPE_HEADER = "gzip";
 }