chrome/android/java/src/org/chromium/chrome/browser/omaha/OmahaBase.java - chromium/src - Git at Google

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 package org.chromium.chrome.browser.omaha;

 import android.content.Context;
 import android.content.Intent;
 import android.content.SharedPreferences;
 import android.os.Build;
 import android.text.format.DateUtils;

 import androidx.annotation.IntDef;

 import org.chromium.base.ApiCompatibilityUtils;
 import org.chromium.base.ContextUtils;
 import org.chromium.base.Log;
 import org.chromium.base.StreamUtil;
 import org.chromium.base.VisibleForTesting;
 import org.chromium.chrome.browser.ChromeVersionInfo;

 import java.io.BufferedOutputStream;
 import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.InputStreamReader;
 import java.io.OutputStream;
 import java.io.OutputStreamWriter;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.net.HttpURLConnection;
 import java.net.MalformedURLException;
 import java.net.URL;
 import java.util.Date;

 /**
  * Keeps tabs on the current state of Chrome, tracking if and when a request should be sent to the
  * Omaha Server.
  *
  * When Chrome is brought to the foreground, it will trigger a call to
  * {@link OmahaBase#onForegroundSessionStart}, which kicks off a series of scheduled events
  * that allow the class to run.  A single alarm is used to trigger the whole pipeline when needed.
  * - If Chrome isn't running when the alarm is fired, no pings or update checks will be performed.
  * - If Chrome doesn't have a pending request to POST, no POST will be performed.
  *
  * When a fresh install is detected (or the user clears their data), OmahaBase will send an XML
  * request saying that a new install was detected, then follow up with an XML request saying that
  * the user was active and that we need to check for Chrome updates.
  *
  * mevissen suggested being conservative with our timers for sending requests.
  * POST attempts that fail to be acknowledged by the server are re-attempted, with at least
  * one hour between each attempt.
  *
  * Status is saved directly to the the disk after every run of the pipeline.
  *
  * Implementation notes:
  * http://docs.google.com/a/google.com/document/d/1scTCovqASf5ktkOeVj8wFRkWTCeDYw2LrOBNn05CDB0/edit
  */
 public class OmahaBase {
     // Used in various org.chromium.chrome.browser.omaha files.
     static final String TAG = "omaha";

     /** Version config data structure. */
     public static class VersionConfig {
         public final String latestVersion;
         public final String downloadUrl;

         protected VersionConfig(String latestVersion, String downloadUrl) {
             this.latestVersion = latestVersion;
             this.downloadUrl = downloadUrl;
         }
     }

     // Flags for retrieving the OmahaClient's state after it's written to disk.
     // The PREF_PACKAGE doesn't match the current OmahaClient package for historical reasons.
     static final String PREF_PACKAGE = "com.google.android.apps.chrome.omaha";
     static final String PREF_INSTALL_SOURCE = "installSource";
     static final String PREF_LATEST_VERSION = "latestVersion";
     static final String PREF_MARKET_URL = "marketURL";
     static final String PREF_PERSISTED_REQUEST_ID = "persistedRequestID";
     static final String PREF_SEND_INSTALL_EVENT = "sendInstallEvent";
     static final String PREF_TIMESTAMP_FOR_NEW_REQUEST = "timestampForNewRequest";
     static final String PREF_TIMESTAMP_FOR_NEXT_POST_ATTEMPT = "timestampForNextPostAttempt";
     static final String PREF_TIMESTAMP_OF_INSTALL = "timestampOfInstall";
     static final String PREF_TIMESTAMP_OF_REQUEST = "timestampOfRequest";

     static final int MIN_API_JOB_SCHEDULER = Build.VERSION_CODES.M;

     /** Whether or not the Omaha server should really be contacted. */
     private static boolean sIsDisabled;

     // Results of {@link #handlePostRequest()}.
     @IntDef({PostResult.NO_REQUEST, PostResult.SENT, PostResult.FAILED, PostResult.SCHEDULED})
     @Retention(RetentionPolicy.SOURCE)
     @interface PostResult {
         int NO_REQUEST = 0;
         int SENT = 1;
         int FAILED = 2;
         int SCHEDULED = 3;
     }

     /** Deprecated; kept around to cancel alarms set for OmahaClient pre-M58. */
     private static final String ACTION_REGISTER_REQUEST =
             "org.chromium.chrome.browser.omaha.ACTION_REGISTER_REQUEST";

     // Delays between events.
     static final long MS_POST_BASE_DELAY = DateUtils.HOUR_IN_MILLIS;
     static final long MS_POST_MAX_DELAY = DateUtils.HOUR_IN_MILLIS * 5;
     static final long MS_BETWEEN_REQUESTS = DateUtils.HOUR_IN_MILLIS * 5;
     static final int MS_CONNECTION_TIMEOUT = (int) DateUtils.MINUTE_IN_MILLIS;

     // Strings indicating how the Chrome APK arrived on the user's device. These values MUST NOT
     // be changed without updating the corresponding Omaha server strings.
     private static final String INSTALL_SOURCE_SYSTEM = "system_image";
     private static final String INSTALL_SOURCE_ORGANIC = "organic";

     private static final long INVALID_TIMESTAMP = -1;
     private static final String INVALID_REQUEST_ID = "invalid";

     // Member fields not persisted to disk.
     private final OmahaDelegate mDelegate;
     private boolean mStateHasBeenRestored;

     // State saved written to and read from disk.
     private RequestData mCurrentRequest;
     private long mTimestampOfInstall;
     private long mTimestampForNextPostAttempt;
     private long mTimestampForNewRequest;
     private String mInstallSource;
     protected VersionConfig mVersionConfig;
     protected boolean mSendInstallEvent;

     /** See {@link #sIsDisabled}. */
     public static void setIsDisabledForTesting(boolean state) {
         sIsDisabled = state;
     }

     /** See {@link #sIsDisabled}. */
     static boolean isDisabled() {
         return sIsDisabled;
     }

     /**
      * Constructs a new OmahaBase.
      * @param delegate The {@link OmahaDelegate} used to interact with the system.
      */
     OmahaBase(OmahaDelegate delegate) {
         mDelegate = delegate;
     }

     protected void run() {
         if (OmahaBase.isDisabled() || getRequestGenerator() == null) {
             Log.v(TAG, "Disabled.  Ignoring intent.");
             return;
         }

         restoreState(getContext());

         long nextTimestamp = Long.MAX_VALUE;
         if (mDelegate.isChromeBeingUsed()) {
             handleRegisterActiveRequest();
             nextTimestamp = Math.min(nextTimestamp, mTimestampForNewRequest);
         }

         if (hasRequest()) {
             @PostResult
             int result = handlePostRequest();
             if (result == PostResult.FAILED || result == PostResult.SCHEDULED) {
                 nextTimestamp = Math.min(nextTimestamp, mTimestampForNextPostAttempt);
             }
         }

         // TODO(dfalcantara): Prevent Omaha code from repeatedly rescheduling itself immediately in
         //                    case a scheduling error occurs.
         if (nextTimestamp != Long.MAX_VALUE && nextTimestamp >= 0) {
             long currentTimestamp = mDelegate.getScheduler().getCurrentTime();
             Log.i(TAG, "Attempting to schedule next job for: " + new Date(nextTimestamp));
             mDelegate.scheduleService(currentTimestamp, nextTimestamp);
         }

         saveState(getContext());
     }

     /**
      * Determines if a new request should be generated.  New requests are only generated if enough
      * time has passed between now and the last time a request was generated.
      */
     private void handleRegisterActiveRequest() {
         // If the current request is too old, generate a new one.
         long currentTimestamp = getBackoffScheduler().getCurrentTime();
         boolean isTooOld = hasRequest()
                 && mCurrentRequest.getAgeInMilliseconds(currentTimestamp) >= MS_BETWEEN_REQUESTS;
         boolean isOverdue = currentTimestamp >= mTimestampForNewRequest;
         if (isTooOld || isOverdue) {
             registerNewRequest(currentTimestamp);
         }
     }

     /**
      * Sends the request it is holding.
      */
     private @PostResult int handlePostRequest() {
         if (!hasRequest()) {
             mDelegate.onHandlePostRequestDone(PostResult.NO_REQUEST, false);
             return PostResult.NO_REQUEST;
         }

         // If enough time has passed since the last attempt, try sending a request.
         @PostResult
         int result;
         long currentTimestamp = getBackoffScheduler().getCurrentTime();
         boolean installEventWasSent = false;
         if (currentTimestamp >= mTimestampForNextPostAttempt) {
             // All requests made during the same session should have the same ID.
             String sessionID = mDelegate.generateUUID();
             boolean sendingInstallRequest = mSendInstallEvent;
             boolean succeeded = generateAndPostRequest(currentTimestamp, sessionID);

             if (succeeded && sendingInstallRequest) {
                 // Only the first request ever generated should contain an install event.
                 mSendInstallEvent = false;
                 installEventWasSent = true;

                 // Create and immediately send another request for a ping and update check.
                 registerNewRequest(currentTimestamp);
                 succeeded &= generateAndPostRequest(currentTimestamp, sessionID);
             }

             result = succeeded ? PostResult.SENT : PostResult.FAILED;
         } else {
             result = PostResult.SCHEDULED;
         }

         mDelegate.onHandlePostRequestDone(result, installEventWasSent);
         return result;
     }

     protected boolean generateAndPostRequest(long currentTimestamp, String sessionID) {
         boolean succeeded = false;
         try {
             // Generate the XML for the current request.
             long installAgeInDays = RequestGenerator.installAge(
                     currentTimestamp, mTimestampOfInstall, mCurrentRequest.isSendInstallEvent());
             String version =
                     VersionNumberGetter.getInstance().getCurrentlyUsedVersion(getContext());
             String xml = getRequestGenerator().generateXML(
                     sessionID, version, installAgeInDays, mCurrentRequest);

             // Send the request to the server & wait for a response.
             String response = postRequest(currentTimestamp, xml);

             // Parse out the response.
             String appId = getRequestGenerator().getAppId();
             boolean sentPingAndUpdate = !mSendInstallEvent;
             ResponseParser parser = new ResponseParser(
                     appId, mSendInstallEvent, sentPingAndUpdate, sentPingAndUpdate);
             mVersionConfig = parser.parseResponse(response);
             succeeded = true;
         } catch (RequestFailureException e) {
             Log.e(TAG, "Failed to contact server: ", e);
         }
         return onResponseReceived(succeeded);
     }

     protected boolean onResponseReceived(boolean succeeded) {
         ExponentialBackoffScheduler scheduler = getBackoffScheduler();
         if (succeeded) {
             // If we've gotten this far, we've successfully sent a request.
             mCurrentRequest = null;

             scheduler.resetFailedAttempts();
             mTimestampForNewRequest = scheduler.getCurrentTime() + MS_BETWEEN_REQUESTS;
             mTimestampForNextPostAttempt = scheduler.calculateNextTimestamp();
             Log.i(TAG,
                     "Request to Server Successful. Timestamp for next request:"
                             + mTimestampForNextPostAttempt);
         } else {
             // Set the alarm to try again later.  Failures are incremented after setting the timer
             // to allow the first failure to incur the minimum base delay between POSTs.
             mTimestampForNextPostAttempt = scheduler.calculateNextTimestamp();
             scheduler.increaseFailedAttempts();
         }

         mDelegate.onGenerateAndPostRequestDone(succeeded);
         return succeeded;
     }

     /**
      * Registers a new request with the current timestamp.  Internal timestamps are reset to start
      * fresh.
      * @param currentTimestamp Current time.
      */
     private void registerNewRequest(long currentTimestamp) {
         mCurrentRequest = createRequestData(currentTimestamp, null);
         getBackoffScheduler().resetFailedAttempts();
         mTimestampForNextPostAttempt = currentTimestamp;

         // Tentatively set the timestamp for a new request.  This will be updated when the server
         // is successfully contacted.
         mTimestampForNewRequest = currentTimestamp + MS_BETWEEN_REQUESTS;

         mDelegate.onRegisterNewRequestDone(mTimestampForNewRequest, mTimestampForNextPostAttempt);
     }

     private RequestData createRequestData(long currentTimestamp, String persistedID) {
         // If we're sending a persisted event, keep trying to send the same request ID.
         String requestID;
         if (persistedID == null || INVALID_REQUEST_ID.equals(persistedID)) {
             requestID = mDelegate.generateUUID();
         } else {
             requestID = persistedID;
         }
         return new RequestData(mSendInstallEvent, currentTimestamp, requestID, mInstallSource);
     }

     private boolean hasRequest() {
         return mCurrentRequest != null;
     }

     /**
      * Posts the request to the Omaha server.
      * @return the XML response as a String.
      * @throws RequestFailureException if the request fails.
      */
     private String postRequest(long timestamp, String xml) throws RequestFailureException {
         String response = null;

         HttpURLConnection urlConnection = null;
         try {
             urlConnection = createConnection();

             // Prepare the HTTP header.
             urlConnection.setDoOutput(true);
             urlConnection.setFixedLengthStreamingMode(
                     ApiCompatibilityUtils.getBytesUtf8(xml).length);
             if (mSendInstallEvent && getBackoffScheduler().getNumFailedAttempts() > 0) {
                 String age = Long.toString(mCurrentRequest.getAgeInSeconds(timestamp));
                 urlConnection.addRequestProperty("X-RequestAge", age);
             }

             response = OmahaBase.sendRequestToServer(urlConnection, xml);
         } catch (IllegalAccessError e) {
             throw new RequestFailureException("Caught an IllegalAccessError:", e);
         } catch (IllegalArgumentException e) {
             throw new RequestFailureException("Caught an IllegalArgumentException:", e);
         } catch (IllegalStateException e) {
             throw new RequestFailureException("Caught an IllegalStateException:", e);
         } finally {
             if (urlConnection != null) {
                 urlConnection.disconnect();
             }
         }

         return response;
     }

     /**
      * Returns a HttpURLConnection to the server.
      */
     @VisibleForTesting
     protected HttpURLConnection createConnection() throws RequestFailureException {
         try {
             URL url = new URL(getRequestGenerator().getServerUrl());
             HttpURLConnection connection = (HttpURLConnection) url.openConnection();
             connection.setConnectTimeout(MS_CONNECTION_TIMEOUT);
             connection.setReadTimeout(MS_CONNECTION_TIMEOUT);
             return connection;
         } catch (MalformedURLException e) {
             throw new RequestFailureException("Caught a malformed URL exception.", e);
         } catch (IOException e) {
             throw new RequestFailureException("Failed to open connection to URL", e);
         }
     }

     /**
      * Reads the data back from the file it was saved to.  Uses SharedPreferences to handle I/O.
      * Sanity checks are performed on the timestamps to guard against clock changing.
      */
     private void restoreState(Context context) {
         if (mStateHasBeenRestored) return;

         String installSource =
                 mDelegate.isInSystemImage() ? INSTALL_SOURCE_SYSTEM : INSTALL_SOURCE_ORGANIC;
         ExponentialBackoffScheduler scheduler = getBackoffScheduler();
         long currentTime = scheduler.getCurrentTime();

         SharedPreferences preferences = OmahaBase.getSharedPreferences();
         mTimestampForNewRequest =
                 preferences.getLong(OmahaBase.PREF_TIMESTAMP_FOR_NEW_REQUEST, currentTime);
         mTimestampForNextPostAttempt =
                 preferences.getLong(OmahaBase.PREF_TIMESTAMP_FOR_NEXT_POST_ATTEMPT, currentTime);
         mTimestampOfInstall = preferences.getLong(OmahaBase.PREF_TIMESTAMP_OF_INSTALL, currentTime);
         mSendInstallEvent = preferences.getBoolean(OmahaBase.PREF_SEND_INSTALL_EVENT, true);
         mInstallSource = preferences.getString(OmahaBase.PREF_INSTALL_SOURCE, installSource);
         mVersionConfig = getVersionConfig(preferences);

         // If we're not sending an install event, don't bother restoring the request ID:
         // the server does not expect to have persisted request IDs for pings or update checks.
         String persistedRequestId = mSendInstallEvent
                 ? preferences.getString(OmahaBase.PREF_PERSISTED_REQUEST_ID, INVALID_REQUEST_ID)
                 : INVALID_REQUEST_ID;
         long requestTimestamp =
                 preferences.getLong(OmahaBase.PREF_TIMESTAMP_OF_REQUEST, INVALID_TIMESTAMP);
         mCurrentRequest = requestTimestamp == INVALID_TIMESTAMP
                 ? null
                 : createRequestData(requestTimestamp, persistedRequestId);

         // Confirm that the timestamp for the next request is less than the base delay.
         long delayToNewRequest = mTimestampForNewRequest - currentTime;
         if (delayToNewRequest > MS_BETWEEN_REQUESTS) {
             Log.w(TAG,
                     "Delay to next request (" + delayToNewRequest
                             + ") is longer than expected.  Resetting to now.");
             mTimestampForNewRequest = currentTime;
         }

         // Confirm that the timestamp for the next POST is less than the current delay.
         long delayToNextPost = mTimestampForNextPostAttempt - currentTime;
         long lastGeneratedDelay = scheduler.getGeneratedDelay();
         if (delayToNextPost > lastGeneratedDelay) {
             Log.w(TAG,
                     "Delay to next post attempt (" + delayToNextPost
                             + ") is greater than expected (" + lastGeneratedDelay
                             + ").  Resetting to now.");
             mTimestampForNextPostAttempt = currentTime;
         }

         migrateToNewerChromeVersions();
         mStateHasBeenRestored = true;
     }

     /**
      * Writes out the current state to a file.
      */
     private void saveState(Context context) {
         SharedPreferences prefs = OmahaBase.getSharedPreferences();
         SharedPreferences.Editor editor = prefs.edit();
         editor.putBoolean(OmahaBase.PREF_SEND_INSTALL_EVENT, mSendInstallEvent);
         editor.putLong(OmahaBase.PREF_TIMESTAMP_OF_INSTALL, mTimestampOfInstall);
         editor.putLong(
                 OmahaBase.PREF_TIMESTAMP_FOR_NEXT_POST_ATTEMPT, mTimestampForNextPostAttempt);
         editor.putLong(OmahaBase.PREF_TIMESTAMP_FOR_NEW_REQUEST, mTimestampForNewRequest);
         editor.putLong(OmahaBase.PREF_TIMESTAMP_OF_REQUEST,
                 hasRequest() ? mCurrentRequest.getCreationTimestamp() : INVALID_TIMESTAMP);
         editor.putString(OmahaBase.PREF_PERSISTED_REQUEST_ID,
                 hasRequest() ? mCurrentRequest.getRequestID() : INVALID_REQUEST_ID);
         editor.putString(OmahaBase.PREF_INSTALL_SOURCE, mInstallSource);
         setVersionConfig(editor, mVersionConfig);
         editor.apply();

         mDelegate.onSaveStateDone(mTimestampForNewRequest, mTimestampForNextPostAttempt);
     }

     private void migrateToNewerChromeVersions() {
         // Remove any repeating alarms in favor of the new scheduling setup on M58 and up.
         // Seems cheaper to cancel the alarm repeatedly than to store a SharedPreference and never
         // do it again.
         Intent intent = new Intent(getContext(), OmahaClient.class);
         intent.setAction(ACTION_REGISTER_REQUEST);
         getBackoffScheduler().cancelAlarm(intent);
     }

     private Context getContext() {
         return mDelegate.getContext();
     }

     private RequestGenerator getRequestGenerator() {
         return mDelegate.getRequestGenerator();
     }

     private ExponentialBackoffScheduler getBackoffScheduler() {
         return mDelegate.getScheduler();
     }

     /** Begin communicating with the Omaha Update Server. */
     public static void onForegroundSessionStart(Context context) {
         if (!ChromeVersionInfo.isOfficialBuild() || isDisabled()) return;
         OmahaService.startServiceImmediately(context);
     }

     /** Checks whether Chrome has ever tried contacting Omaha before. */
     public static boolean isProbablyFreshInstall(Context context) {
         SharedPreferences prefs = getSharedPreferences();
         return prefs.getLong(PREF_TIMESTAMP_OF_INSTALL, -1) == -1;
     }

     /** Sends the request to the server and returns the response. */
     static String sendRequestToServer(HttpURLConnection urlConnection, String request)
             throws RequestFailureException {
         try {
             OutputStream out = new BufferedOutputStream(urlConnection.getOutputStream());
             OutputStreamWriter writer = new OutputStreamWriter(out);
             writer.write(request, 0, request.length());
             StreamUtil.closeQuietly(writer);
             checkServerResponseCode(urlConnection);
         } catch (IOException | SecurityException | ArrayIndexOutOfBoundsException e) {
             throw new RequestFailureException("Failed to write request to server: ", e);
         }

         try {
             InputStreamReader reader = new InputStreamReader(urlConnection.getInputStream());
             BufferedReader in = new BufferedReader(reader);
             try {
                 StringBuilder response = new StringBuilder();
                 for (String line = in.readLine(); line != null; line = in.readLine()) {
                     response.append(line);
                 }
                 checkServerResponseCode(urlConnection);
                 return response.toString();
             } finally {
                 StreamUtil.closeQuietly(in);
             }
         } catch (IOException e) {
             throw new RequestFailureException("Failed when reading response from server: ", e);
         }
     }

     /** Confirms that the Omaha server sent back an "OK" code. */
     private static void checkServerResponseCode(HttpURLConnection urlConnection)
             throws RequestFailureException {
         try {
             if (urlConnection.getResponseCode() != HttpURLConnection.HTTP_OK) {
                 throw new RequestFailureException("Received " + urlConnection.getResponseCode()
                         + " code instead of 200 (OK) from the server.  Aborting.");
             }
         } catch (IOException e) {
             throw new RequestFailureException("Failed to read response code from server: ", e);
         }
     }

     /** Returns the Omaha SharedPreferences. */
     public static SharedPreferences getSharedPreferences() {
         return ContextUtils.getApplicationContext().getSharedPreferences(
                 PREF_PACKAGE, Context.MODE_PRIVATE);
     }

     static void setVersionConfig(SharedPreferences.Editor editor, VersionConfig versionConfig) {
         editor.putString(OmahaBase.PREF_LATEST_VERSION,
                 versionConfig == null ? "" : versionConfig.latestVersion);
         editor.putString(
                 OmahaBase.PREF_MARKET_URL, versionConfig == null ? "" : versionConfig.downloadUrl);
     }

     static VersionConfig getVersionConfig(SharedPreferences sharedPref) {
         return new VersionConfig(sharedPref.getString(OmahaBase.PREF_LATEST_VERSION, ""),
                 sharedPref.getString(OmahaBase.PREF_MARKET_URL, ""));
     }
 }
	// Copyright 2017 The Chromium Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	package org.chromium.chrome.browser.omaha;

	import android.content.Context;
	import android.content.Intent;
	import android.content.SharedPreferences;
	import android.os.Build;
	import android.text.format.DateUtils;

	import androidx.annotation.IntDef;

	import org.chromium.base.ApiCompatibilityUtils;
	import org.chromium.base.ContextUtils;
	import org.chromium.base.Log;
	import org.chromium.base.StreamUtil;
	import org.chromium.base.VisibleForTesting;
	import org.chromium.chrome.browser.ChromeVersionInfo;

	import java.io.BufferedOutputStream;
	import java.io.BufferedReader;
	import java.io.IOException;
	import java.io.InputStreamReader;
	import java.io.OutputStream;
	import java.io.OutputStreamWriter;
	import java.lang.annotation.Retention;
	import java.lang.annotation.RetentionPolicy;
	import java.net.HttpURLConnection;
	import java.net.MalformedURLException;
	import java.net.URL;
	import java.util.Date;

	/**
	* Keeps tabs on the current state of Chrome, tracking if and when a request should be sent to the
	* Omaha Server.
	*
	* When Chrome is brought to the foreground, it will trigger a call to
	* {@link OmahaBase#onForegroundSessionStart}, which kicks off a series of scheduled events
	* that allow the class to run. A single alarm is used to trigger the whole pipeline when needed.
	* - If Chrome isn't running when the alarm is fired, no pings or update checks will be performed.
	* - If Chrome doesn't have a pending request to POST, no POST will be performed.
	*
	* When a fresh install is detected (or the user clears their data), OmahaBase will send an XML
	* request saying that a new install was detected, then follow up with an XML request saying that
	* the user was active and that we need to check for Chrome updates.
	*
	* mevissen suggested being conservative with our timers for sending requests.
	* POST attempts that fail to be acknowledged by the server are re-attempted, with at least
	* one hour between each attempt.
	*
	* Status is saved directly to the the disk after every run of the pipeline.
	*
	* Implementation notes:
	* http://docs.google.com/a/google.com/document/d/1scTCovqASf5ktkOeVj8wFRkWTCeDYw2LrOBNn05CDB0/edit
	*/
	public class OmahaBase {
	// Used in various org.chromium.chrome.browser.omaha files.
	static final String TAG = "omaha";

	/** Version config data structure. */
	public static class VersionConfig {
	public final String latestVersion;
	public final String downloadUrl;

	protected VersionConfig(String latestVersion, String downloadUrl) {
	this.latestVersion = latestVersion;
	this.downloadUrl = downloadUrl;
	}
	}

	// Flags for retrieving the OmahaClient's state after it's written to disk.
	// The PREF_PACKAGE doesn't match the current OmahaClient package for historical reasons.
	static final String PREF_PACKAGE = "com.google.android.apps.chrome.omaha";
	static final String PREF_INSTALL_SOURCE = "installSource";
	static final String PREF_LATEST_VERSION = "latestVersion";
	static final String PREF_MARKET_URL = "marketURL";
	static final String PREF_PERSISTED_REQUEST_ID = "persistedRequestID";
	static final String PREF_SEND_INSTALL_EVENT = "sendInstallEvent";
	static final String PREF_TIMESTAMP_FOR_NEW_REQUEST = "timestampForNewRequest";
	static final String PREF_TIMESTAMP_FOR_NEXT_POST_ATTEMPT = "timestampForNextPostAttempt";
	static final String PREF_TIMESTAMP_OF_INSTALL = "timestampOfInstall";
	static final String PREF_TIMESTAMP_OF_REQUEST = "timestampOfRequest";

	static final int MIN_API_JOB_SCHEDULER = Build.VERSION_CODES.M;

	/** Whether or not the Omaha server should really be contacted. */
	private static boolean sIsDisabled;

	// Results of {@link #handlePostRequest()}.
	@IntDef({PostResult.NO_REQUEST, PostResult.SENT, PostResult.FAILED, PostResult.SCHEDULED})
	@Retention(RetentionPolicy.SOURCE)
	@interface PostResult {
	int NO_REQUEST = 0;
	int SENT = 1;
	int FAILED = 2;
	int SCHEDULED = 3;
	}

	/** Deprecated; kept around to cancel alarms set for OmahaClient pre-M58. */
	private static final String ACTION_REGISTER_REQUEST =
	"org.chromium.chrome.browser.omaha.ACTION_REGISTER_REQUEST";

	// Delays between events.
	static final long MS_POST_BASE_DELAY = DateUtils.HOUR_IN_MILLIS;
	static final long MS_POST_MAX_DELAY = DateUtils.HOUR_IN_MILLIS * 5;
	static final long MS_BETWEEN_REQUESTS = DateUtils.HOUR_IN_MILLIS * 5;
	static final int MS_CONNECTION_TIMEOUT = (int) DateUtils.MINUTE_IN_MILLIS;

	// Strings indicating how the Chrome APK arrived on the user's device. These values MUST NOT
	// be changed without updating the corresponding Omaha server strings.
	private static final String INSTALL_SOURCE_SYSTEM = "system_image";
	private static final String INSTALL_SOURCE_ORGANIC = "organic";

	private static final long INVALID_TIMESTAMP = -1;
	private static final String INVALID_REQUEST_ID = "invalid";

	// Member fields not persisted to disk.
	private final OmahaDelegate mDelegate;
	private boolean mStateHasBeenRestored;

	// State saved written to and read from disk.
	private RequestData mCurrentRequest;
	private long mTimestampOfInstall;
	private long mTimestampForNextPostAttempt;
	private long mTimestampForNewRequest;
	private String mInstallSource;
	protected VersionConfig mVersionConfig;
	protected boolean mSendInstallEvent;

	/** See {@link #sIsDisabled}. */
	public static void setIsDisabledForTesting(boolean state) {
	sIsDisabled = state;
	}

	/** See {@link #sIsDisabled}. */
	static boolean isDisabled() {
	return sIsDisabled;
	}

	/**
	* Constructs a new OmahaBase.
	* @param delegate The {@link OmahaDelegate} used to interact with the system.
	*/
	OmahaBase(OmahaDelegate delegate) {
	mDelegate = delegate;
	}

	protected void run() {
	if (OmahaBase.isDisabled() \|\| getRequestGenerator() == null) {
	Log.v(TAG, "Disabled. Ignoring intent.");
	return;
	}

	restoreState(getContext());

	long nextTimestamp = Long.MAX_VALUE;
	if (mDelegate.isChromeBeingUsed()) {
	handleRegisterActiveRequest();
	nextTimestamp = Math.min(nextTimestamp, mTimestampForNewRequest);
	}

	if (hasRequest()) {
	@PostResult
	int result = handlePostRequest();
	if (result == PostResult.FAILED \|\| result == PostResult.SCHEDULED) {
	nextTimestamp = Math.min(nextTimestamp, mTimestampForNextPostAttempt);
	}
	}

	// TODO(dfalcantara): Prevent Omaha code from repeatedly rescheduling itself immediately in
	// case a scheduling error occurs.
	if (nextTimestamp != Long.MAX_VALUE && nextTimestamp >= 0) {
	long currentTimestamp = mDelegate.getScheduler().getCurrentTime();
	Log.i(TAG, "Attempting to schedule next job for: " + new Date(nextTimestamp));
	mDelegate.scheduleService(currentTimestamp, nextTimestamp);
	}

	saveState(getContext());
	}

	/**
	* Determines if a new request should be generated. New requests are only generated if enough
	* time has passed between now and the last time a request was generated.
	*/
	private void handleRegisterActiveRequest() {
	// If the current request is too old, generate a new one.
	long currentTimestamp = getBackoffScheduler().getCurrentTime();
	boolean isTooOld = hasRequest()
	&& mCurrentRequest.getAgeInMilliseconds(currentTimestamp) >= MS_BETWEEN_REQUESTS;
	boolean isOverdue = currentTimestamp >= mTimestampForNewRequest;
	if (isTooOld \|\| isOverdue) {
	registerNewRequest(currentTimestamp);
	}
	}

	/**
	* Sends the request it is holding.
	*/
	private @PostResult int handlePostRequest() {
	if (!hasRequest()) {
	mDelegate.onHandlePostRequestDone(PostResult.NO_REQUEST, false);
	return PostResult.NO_REQUEST;
	}

	// If enough time has passed since the last attempt, try sending a request.
	@PostResult
	int result;
	long currentTimestamp = getBackoffScheduler().getCurrentTime();
	boolean installEventWasSent = false;
	if (currentTimestamp >= mTimestampForNextPostAttempt) {
	// All requests made during the same session should have the same ID.
	String sessionID = mDelegate.generateUUID();
	boolean sendingInstallRequest = mSendInstallEvent;
	boolean succeeded = generateAndPostRequest(currentTimestamp, sessionID);

	if (succeeded && sendingInstallRequest) {
	// Only the first request ever generated should contain an install event.
	mSendInstallEvent = false;
	installEventWasSent = true;

	// Create and immediately send another request for a ping and update check.
	registerNewRequest(currentTimestamp);
	succeeded &= generateAndPostRequest(currentTimestamp, sessionID);
	}

	result = succeeded ? PostResult.SENT : PostResult.FAILED;
	} else {
	result = PostResult.SCHEDULED;
	}

	mDelegate.onHandlePostRequestDone(result, installEventWasSent);
	return result;
	}

	protected boolean generateAndPostRequest(long currentTimestamp, String sessionID) {
	boolean succeeded = false;
	try {
	// Generate the XML for the current request.
	long installAgeInDays = RequestGenerator.installAge(
	currentTimestamp, mTimestampOfInstall, mCurrentRequest.isSendInstallEvent());
	String version =
	VersionNumberGetter.getInstance().getCurrentlyUsedVersion(getContext());
	String xml = getRequestGenerator().generateXML(
	sessionID, version, installAgeInDays, mCurrentRequest);

	// Send the request to the server & wait for a response.
	String response = postRequest(currentTimestamp, xml);

	// Parse out the response.
	String appId = getRequestGenerator().getAppId();
	boolean sentPingAndUpdate = !mSendInstallEvent;
	ResponseParser parser = new ResponseParser(
	appId, mSendInstallEvent, sentPingAndUpdate, sentPingAndUpdate);
	mVersionConfig = parser.parseResponse(response);
	succeeded = true;
	} catch (RequestFailureException e) {
	Log.e(TAG, "Failed to contact server: ", e);
	}
	return onResponseReceived(succeeded);
	}

	protected boolean onResponseReceived(boolean succeeded) {
	ExponentialBackoffScheduler scheduler = getBackoffScheduler();
	if (succeeded) {
	// If we've gotten this far, we've successfully sent a request.
	mCurrentRequest = null;

	scheduler.resetFailedAttempts();
	mTimestampForNewRequest = scheduler.getCurrentTime() + MS_BETWEEN_REQUESTS;
	mTimestampForNextPostAttempt = scheduler.calculateNextTimestamp();
	Log.i(TAG,
	"Request to Server Successful. Timestamp for next request:"
	+ mTimestampForNextPostAttempt);
	} else {
	// Set the alarm to try again later. Failures are incremented after setting the timer
	// to allow the first failure to incur the minimum base delay between POSTs.
	mTimestampForNextPostAttempt = scheduler.calculateNextTimestamp();
	scheduler.increaseFailedAttempts();
	}

	mDelegate.onGenerateAndPostRequestDone(succeeded);
	return succeeded;
	}

	/**
	* Registers a new request with the current timestamp. Internal timestamps are reset to start
	* fresh.
	* @param currentTimestamp Current time.
	*/
	private void registerNewRequest(long currentTimestamp) {
	mCurrentRequest = createRequestData(currentTimestamp, null);
	getBackoffScheduler().resetFailedAttempts();
	mTimestampForNextPostAttempt = currentTimestamp;

	// Tentatively set the timestamp for a new request. This will be updated when the server
	// is successfully contacted.
	mTimestampForNewRequest = currentTimestamp + MS_BETWEEN_REQUESTS;

	mDelegate.onRegisterNewRequestDone(mTimestampForNewRequest, mTimestampForNextPostAttempt);
	}

	private RequestData createRequestData(long currentTimestamp, String persistedID) {
	// If we're sending a persisted event, keep trying to send the same request ID.
	String requestID;
	if (persistedID == null \|\| INVALID_REQUEST_ID.equals(persistedID)) {
	requestID = mDelegate.generateUUID();
	} else {
	requestID = persistedID;
	}
	return new RequestData(mSendInstallEvent, currentTimestamp, requestID, mInstallSource);
	}

	private boolean hasRequest() {
	return mCurrentRequest != null;
	}

	/**
	* Posts the request to the Omaha server.
	* @return the XML response as a String.
	* @throws RequestFailureException if the request fails.
	*/
	private String postRequest(long timestamp, String xml) throws RequestFailureException {
	String response = null;

	HttpURLConnection urlConnection = null;
	try {
	urlConnection = createConnection();

	// Prepare the HTTP header.
	urlConnection.setDoOutput(true);
	urlConnection.setFixedLengthStreamingMode(
	ApiCompatibilityUtils.getBytesUtf8(xml).length);
	if (mSendInstallEvent && getBackoffScheduler().getNumFailedAttempts() > 0) {
	String age = Long.toString(mCurrentRequest.getAgeInSeconds(timestamp));
	urlConnection.addRequestProperty("X-RequestAge", age);
	}

	response = OmahaBase.sendRequestToServer(urlConnection, xml);
	} catch (IllegalAccessError e) {
	throw new RequestFailureException("Caught an IllegalAccessError:", e);
	} catch (IllegalArgumentException e) {
	throw new RequestFailureException("Caught an IllegalArgumentException:", e);
	} catch (IllegalStateException e) {
	throw new RequestFailureException("Caught an IllegalStateException:", e);
	} finally {
	if (urlConnection != null) {
	urlConnection.disconnect();
	}
	}

	return response;
	}

	/**
	* Returns a HttpURLConnection to the server.
	*/
	@VisibleForTesting
	protected HttpURLConnection createConnection() throws RequestFailureException {
	try {
	URL url = new URL(getRequestGenerator().getServerUrl());
	HttpURLConnection connection = (HttpURLConnection) url.openConnection();
	connection.setConnectTimeout(MS_CONNECTION_TIMEOUT);
	connection.setReadTimeout(MS_CONNECTION_TIMEOUT);
	return connection;
	} catch (MalformedURLException e) {
	throw new RequestFailureException("Caught a malformed URL exception.", e);
	} catch (IOException e) {
	throw new RequestFailureException("Failed to open connection to URL", e);
	}
	}

	/**
	* Reads the data back from the file it was saved to. Uses SharedPreferences to handle I/O.
	* Sanity checks are performed on the timestamps to guard against clock changing.
	*/
	private void restoreState(Context context) {
	if (mStateHasBeenRestored) return;

	String installSource =
	mDelegate.isInSystemImage() ? INSTALL_SOURCE_SYSTEM : INSTALL_SOURCE_ORGANIC;
	ExponentialBackoffScheduler scheduler = getBackoffScheduler();
	long currentTime = scheduler.getCurrentTime();

	SharedPreferences preferences = OmahaBase.getSharedPreferences();
	mTimestampForNewRequest =
	preferences.getLong(OmahaBase.PREF_TIMESTAMP_FOR_NEW_REQUEST, currentTime);
	mTimestampForNextPostAttempt =
	preferences.getLong(OmahaBase.PREF_TIMESTAMP_FOR_NEXT_POST_ATTEMPT, currentTime);
	mTimestampOfInstall = preferences.getLong(OmahaBase.PREF_TIMESTAMP_OF_INSTALL, currentTime);
	mSendInstallEvent = preferences.getBoolean(OmahaBase.PREF_SEND_INSTALL_EVENT, true);
	mInstallSource = preferences.getString(OmahaBase.PREF_INSTALL_SOURCE, installSource);
	mVersionConfig = getVersionConfig(preferences);

	// If we're not sending an install event, don't bother restoring the request ID:
	// the server does not expect to have persisted request IDs for pings or update checks.
	String persistedRequestId = mSendInstallEvent
	? preferences.getString(OmahaBase.PREF_PERSISTED_REQUEST_ID, INVALID_REQUEST_ID)
	: INVALID_REQUEST_ID;
	long requestTimestamp =
	preferences.getLong(OmahaBase.PREF_TIMESTAMP_OF_REQUEST, INVALID_TIMESTAMP);
	mCurrentRequest = requestTimestamp == INVALID_TIMESTAMP
	? null
	: createRequestData(requestTimestamp, persistedRequestId);

	// Confirm that the timestamp for the next request is less than the base delay.
	long delayToNewRequest = mTimestampForNewRequest - currentTime;
	if (delayToNewRequest > MS_BETWEEN_REQUESTS) {
	Log.w(TAG,
	"Delay to next request (" + delayToNewRequest
	+ ") is longer than expected. Resetting to now.");
	mTimestampForNewRequest = currentTime;
	}

	// Confirm that the timestamp for the next POST is less than the current delay.
	long delayToNextPost = mTimestampForNextPostAttempt - currentTime;
	long lastGeneratedDelay = scheduler.getGeneratedDelay();
	if (delayToNextPost > lastGeneratedDelay) {
	Log.w(TAG,
	"Delay to next post attempt (" + delayToNextPost
	+ ") is greater than expected (" + lastGeneratedDelay
	+ "). Resetting to now.");
	mTimestampForNextPostAttempt = currentTime;
	}

	migrateToNewerChromeVersions();
	mStateHasBeenRestored = true;
	}

	/**
	* Writes out the current state to a file.
	*/
	private void saveState(Context context) {
	SharedPreferences prefs = OmahaBase.getSharedPreferences();
	SharedPreferences.Editor editor = prefs.edit();
	editor.putBoolean(OmahaBase.PREF_SEND_INSTALL_EVENT, mSendInstallEvent);
	editor.putLong(OmahaBase.PREF_TIMESTAMP_OF_INSTALL, mTimestampOfInstall);
	editor.putLong(
	OmahaBase.PREF_TIMESTAMP_FOR_NEXT_POST_ATTEMPT, mTimestampForNextPostAttempt);
	editor.putLong(OmahaBase.PREF_TIMESTAMP_FOR_NEW_REQUEST, mTimestampForNewRequest);
	editor.putLong(OmahaBase.PREF_TIMESTAMP_OF_REQUEST,
	hasRequest() ? mCurrentRequest.getCreationTimestamp() : INVALID_TIMESTAMP);
	editor.putString(OmahaBase.PREF_PERSISTED_REQUEST_ID,
	hasRequest() ? mCurrentRequest.getRequestID() : INVALID_REQUEST_ID);
	editor.putString(OmahaBase.PREF_INSTALL_SOURCE, mInstallSource);
	setVersionConfig(editor, mVersionConfig);
	editor.apply();

	mDelegate.onSaveStateDone(mTimestampForNewRequest, mTimestampForNextPostAttempt);
	}

	private void migrateToNewerChromeVersions() {
	// Remove any repeating alarms in favor of the new scheduling setup on M58 and up.
	// Seems cheaper to cancel the alarm repeatedly than to store a SharedPreference and never
	// do it again.
	Intent intent = new Intent(getContext(), OmahaClient.class);
	intent.setAction(ACTION_REGISTER_REQUEST);
	getBackoffScheduler().cancelAlarm(intent);
	}

	private Context getContext() {
	return mDelegate.getContext();
	}

	private RequestGenerator getRequestGenerator() {
	return mDelegate.getRequestGenerator();
	}

	private ExponentialBackoffScheduler getBackoffScheduler() {
	return mDelegate.getScheduler();
	}

	/** Begin communicating with the Omaha Update Server. */
	public static void onForegroundSessionStart(Context context) {
	if (!ChromeVersionInfo.isOfficialBuild() \|\| isDisabled()) return;
	OmahaService.startServiceImmediately(context);
	}

	/** Checks whether Chrome has ever tried contacting Omaha before. */
	public static boolean isProbablyFreshInstall(Context context) {
	SharedPreferences prefs = getSharedPreferences();
	return prefs.getLong(PREF_TIMESTAMP_OF_INSTALL, -1) == -1;
	}

	/** Sends the request to the server and returns the response. */
	static String sendRequestToServer(HttpURLConnection urlConnection, String request)
	throws RequestFailureException {
	try {
	OutputStream out = new BufferedOutputStream(urlConnection.getOutputStream());
	OutputStreamWriter writer = new OutputStreamWriter(out);
	writer.write(request, 0, request.length());
	StreamUtil.closeQuietly(writer);
	checkServerResponseCode(urlConnection);
	} catch (IOException \| SecurityException \| ArrayIndexOutOfBoundsException e) {
	throw new RequestFailureException("Failed to write request to server: ", e);
	}

	try {
	InputStreamReader reader = new InputStreamReader(urlConnection.getInputStream());
	BufferedReader in = new BufferedReader(reader);
	try {
	StringBuilder response = new StringBuilder();
	for (String line = in.readLine(); line != null; line = in.readLine()) {
	response.append(line);
	}
	checkServerResponseCode(urlConnection);
	return response.toString();
	} finally {
	StreamUtil.closeQuietly(in);
	}
	} catch (IOException e) {
	throw new RequestFailureException("Failed when reading response from server: ", e);
	}
	}

	/** Confirms that the Omaha server sent back an "OK" code. */
	private static void checkServerResponseCode(HttpURLConnection urlConnection)
	throws RequestFailureException {
	try {
	if (urlConnection.getResponseCode() != HttpURLConnection.HTTP_OK) {
	throw new RequestFailureException("Received " + urlConnection.getResponseCode()
	+ " code instead of 200 (OK) from the server. Aborting.");
	}
	} catch (IOException e) {
	throw new RequestFailureException("Failed to read response code from server: ", e);
	}
	}

	/** Returns the Omaha SharedPreferences. */
	public static SharedPreferences getSharedPreferences() {
	return ContextUtils.getApplicationContext().getSharedPreferences(
	PREF_PACKAGE, Context.MODE_PRIVATE);
	}

	static void setVersionConfig(SharedPreferences.Editor editor, VersionConfig versionConfig) {
	editor.putString(OmahaBase.PREF_LATEST_VERSION,
	versionConfig == null ? "" : versionConfig.latestVersion);
	editor.putString(
	OmahaBase.PREF_MARKET_URL, versionConfig == null ? "" : versionConfig.downloadUrl);
	}

	static VersionConfig getVersionConfig(SharedPreferences sharedPref) {
	return new VersionConfig(sharedPref.getString(OmahaBase.PREF_LATEST_VERSION, ""),
	sharedPref.getString(OmahaBase.PREF_MARKET_URL, ""));
	}
	}