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HTTP Retry Support (#255)
* Basic framework for HTTP retries * Implementing support for retry-after header * Cleaned up the retry-after processing logic * Moved the status code checking logic * Updated tests * Updated class names and tests * Refactored retry impl and tests * Simplified the retry handler * More tests and docs * Further cleaned up the impl and tests * Decoupled retry initializer from credentials * More code cleanup * Cleaning up tests * Not calling any retry code when RetryConfig = null * Added an option to enable/disable retries on IO errors. Added some comments * New test case * Updated some comments; Cleaned up tests * Fixed a typo in a comment * Removing the hard dependency on Apache HTTP Client (#259) * Copied DateUtils source from Apache HC * Updated reference link * Used locks instead of thread locals; Added tests * Added a NOTICE file for third-party code
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‎NOTICE.txt

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Firebase Admin Java SDK
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Copyright 2019 Google Inc.
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This product includes software developed at
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The Apache Software Foundation (http://www.apache.org/).

‎src/main/java/com/google/firebase/internal/DateUtils.java

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/*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.firebase.internal;
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import static com.google.common.base.Preconditions.checkNotNull;
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import java.text.ParsePosition;
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import java.text.SimpleDateFormat;
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import java.util.Calendar;
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import java.util.Date;
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import java.util.TimeZone;
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/**
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* A utility class for parsing and formatting HTTP dates as used in cookies and
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* other headers. This class handles dates as defined by RFC 2616 section
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* 3.3.1 as well as some other common non-standard formats.
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*
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* <p>Most of this class was borrowed from the
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* <a href="http://svn.apache.org/repos/asf/httpcomponents/httpclient/tags/4.3/httpclient/src/main/java/org/apache/http/client/utils/DateUtils.java">
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* Apache HTTP client</a> in order to avoid a direct dependency on it. We currently
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* have a transitive dependency on this library (via Google API client), but the API
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* client team is working towards removing it, so we won't have it in the classpath for long.
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*
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* <p>The original implementation of this class uses
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* thread locals to cache the {@code SimpleDateFormat} instances. Instead, this implementation
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* uses static constants and explicit locking to ensure thread safety. This is probably slower,
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* but also simpler and avoids memory leaks that may result from unreleased thread locals.
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*/
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final class DateUtils {
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/**
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* Date format pattern used to parse HTTP date headers in RFC 1123 format.
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*/
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static final String PATTERN_RFC1123 = "EEE, dd MMM yyyy HH:mm:ss zzz";
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/**
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* Date format pattern used to parse HTTP date headers in RFC 1036 format.
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*/
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static final String PATTERN_RFC1036 = "EEE, dd-MMM-yy HH:mm:ss zzz";
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/**
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* Date format pattern used to parse HTTP date headers in ANSI C
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* {@code asctime()} format.
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*/
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static final String PATTERN_ASCTIME = "EEE MMM d HH:mm:ss yyyy";
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private static final SimpleDateFormat[] DEFAULT_PATTERNS = new SimpleDateFormat[] {
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new SimpleDateFormat(PATTERN_RFC1123),
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new SimpleDateFormat(PATTERN_RFC1036),
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new SimpleDateFormat(PATTERN_ASCTIME)
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};
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static final TimeZone GMT = TimeZone.getTimeZone("GMT");
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static {
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final Calendar calendar = Calendar.getInstance();
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calendar.setTimeZone(GMT);
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calendar.set(2000, Calendar.JANUARY, 1, 0, 0, 0);
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calendar.set(Calendar.MILLISECOND, 0);
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final Date defaultTwoDigitYearStart = calendar.getTime();
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for (final SimpleDateFormat datePattern : DEFAULT_PATTERNS) {
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datePattern.set2DigitYearStart(defaultTwoDigitYearStart);
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}
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}
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/**
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* Parses the date value using the given date formats.
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*
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* @param dateValue the date value to parse
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* @return the parsed date or null if input could not be parsed
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*/
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public static Date parseDate(final String dateValue) {
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String v = checkNotNull(dateValue);
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// trim single quotes around date if present
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// see issue #5279
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if (v.length() > 1 && v.startsWith("'") && v.endsWith("'")) {
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v = v.substring(1, v.length() - 1);
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}
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for (final SimpleDateFormat datePattern : DEFAULT_PATTERNS) {
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final ParsePosition pos = new ParsePosition(0);
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synchronized (datePattern) {
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final Date result = datePattern.parse(v, pos);
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if (pos.getIndex() != 0) {
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return result;
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}
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}
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}
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return null;
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}
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/** This class should not be instantiated. */
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private DateUtils() {
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}
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}

‎src/main/java/com/google/firebase/internal/FirebaseRequestInitializer.java

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import com.google.api.client.http.HttpRequest;
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import com.google.api.client.http.HttpRequestInitializer;
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import com.google.auth.http.HttpCredentialsAdapter;
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import com.google.auth.oauth2.GoogleCredentials;
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import com.google.common.collect.ImmutableList;
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import com.google.firebase.FirebaseApp;
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import com.google.firebase.FirebaseOptions;
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import com.google.firebase.ImplFirebaseTrampolines;
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import java.io.IOException;
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import java.util.List;
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/**
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* {@code HttpRequestInitializer} for configuring outgoing REST calls. Handles OAuth2 authorization
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* and setting timeout values.
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* {@code HttpRequestInitializer} for configuring outgoing REST calls. Initializes requests with
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* OAuth2 credentials, timeout and retry settings.
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*/
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public class FirebaseRequestInitializer implements HttpRequestInitializer {
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public final class FirebaseRequestInitializer implements HttpRequestInitializer {
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private final HttpCredentialsAdapter credentialsAdapter;
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private final int connectTimeout;
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private final int readTimeout;
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private final List<HttpRequestInitializer> initializers;
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public FirebaseRequestInitializer(FirebaseApp app) {
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GoogleCredentials credentials = ImplFirebaseTrampolines.getCredentials(app);
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this.credentialsAdapter = new HttpCredentialsAdapter(credentials);
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this.connectTimeout = app.getOptions().getConnectTimeout();
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this.readTimeout = app.getOptions().getReadTimeout();
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this(app, null);
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}
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public FirebaseRequestInitializer(FirebaseApp app, @Nullable RetryConfig retryConfig) {
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ImmutableList.Builder<HttpRequestInitializer> initializers =
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ImmutableList.<HttpRequestInitializer>builder()
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.add(new HttpCredentialsAdapter(ImplFirebaseTrampolines.getCredentials(app)))
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.add(new TimeoutInitializer(app.getOptions()));
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if (retryConfig != null) {
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initializers.add(new RetryInitializer(retryConfig));
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}
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this.initializers = initializers.build();
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}
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@Override
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public void initialize(HttpRequest httpRequest) throws IOException {
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credentialsAdapter.initialize(httpRequest);
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httpRequest.setConnectTimeout(connectTimeout);
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httpRequest.setReadTimeout(readTimeout);
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public void initialize(HttpRequest request) throws IOException {
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for (HttpRequestInitializer initializer : initializers) {
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initializer.initialize(request);
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}
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}
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private static class TimeoutInitializer implements HttpRequestInitializer {
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private final int connectTimeoutMillis;
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private final int readTimeoutMillis;
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TimeoutInitializer(FirebaseOptions options) {
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this.connectTimeoutMillis = options.getConnectTimeout();
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this.readTimeoutMillis = options.getReadTimeout();
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}
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@Override
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public void initialize(HttpRequest request) {
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request.setConnectTimeout(connectTimeoutMillis);
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request.setReadTimeout(readTimeoutMillis);
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}
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}
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}

‎src/main/java/com/google/firebase/internal/RetryConfig.java

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/*
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* Copyright 2019 Google Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.firebase.internal;
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import static com.google.common.base.Preconditions.checkArgument;
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import static com.google.common.base.Preconditions.checkNotNull;
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import com.google.api.client.util.BackOff;
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import com.google.api.client.util.ExponentialBackOff;
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import com.google.api.client.util.Sleeper;
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import com.google.common.annotations.VisibleForTesting;
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import com.google.common.collect.ImmutableList;
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import java.util.List;
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import java.util.concurrent.TimeUnit;
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/**
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* Configures when and how HTTP requests should be retried.
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*/
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public final class RetryConfig {
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private static final int INITIAL_INTERVAL_MILLIS = 500;
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private final List<Integer> retryStatusCodes;
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private final boolean retryOnIOExceptions;
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private final int maxRetries;
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private final Sleeper sleeper;
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private final ExponentialBackOff.Builder backOffBuilder;
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private RetryConfig(Builder builder) {
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if (builder.retryStatusCodes != null) {
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this.retryStatusCodes = ImmutableList.copyOf(builder.retryStatusCodes);
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} else {
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this.retryStatusCodes = ImmutableList.of();
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}
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this.retryOnIOExceptions = builder.retryOnIOExceptions;
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checkArgument(builder.maxRetries >= 0, "maxRetries must not be negative");
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this.maxRetries = builder.maxRetries;
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this.sleeper = checkNotNull(builder.sleeper);
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this.backOffBuilder = new ExponentialBackOff.Builder()
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.setInitialIntervalMillis(INITIAL_INTERVAL_MILLIS)
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.setMaxIntervalMillis(builder.maxIntervalMillis)
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.setMultiplier(builder.backOffMultiplier)
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.setRandomizationFactor(0);
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// Force validation of arguments by building the BackOff object
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this.backOffBuilder.build();
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}
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List<Integer> getRetryStatusCodes() {
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return retryStatusCodes;
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}
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boolean isRetryOnIOExceptions() {
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return retryOnIOExceptions;
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}
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int getMaxRetries() {
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return maxRetries;
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}
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int getMaxIntervalMillis() {
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return backOffBuilder.getMaxIntervalMillis();
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}
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double getBackOffMultiplier() {
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return backOffBuilder.getMultiplier();
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}
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Sleeper getSleeper() {
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return sleeper;
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}
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BackOff newBackOff() {
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return backOffBuilder.build();
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}
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public static Builder builder() {
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return new Builder();
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}
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public static final class Builder {
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private List<Integer> retryStatusCodes;
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private boolean retryOnIOExceptions;
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private int maxRetries;
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private int maxIntervalMillis = (int) TimeUnit.MINUTES.toMillis(2);
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private double backOffMultiplier = 2.0;
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private Sleeper sleeper = Sleeper.DEFAULT;
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private Builder() { }
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/**
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* Sets a list of HTTP status codes that should be retried. If null or empty, HTTP requests
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* will not be retried as long as they result in some HTTP response message.
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*
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* @param retryStatusCodes A list of status codes.
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* @return This builder.
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*/
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public Builder setRetryStatusCodes(List<Integer> retryStatusCodes) {
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this.retryStatusCodes = retryStatusCodes;
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return this;
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}
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/**
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* Sets whether requests should be retried on IOExceptions.
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*
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* @param retryOnIOExceptions A boolean indicating whether to retry on IOExceptions.
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* @return This builder.
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*/
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public Builder setRetryOnIOExceptions(boolean retryOnIOExceptions) {
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this.retryOnIOExceptions = retryOnIOExceptions;
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return this;
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}
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/**
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* Maximum number of retry attempts for a request. This is the cumulative total for all retries
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* regardless of their cause (I/O errors and HTTP error responses).
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*
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* @param maxRetries A non-negative integer.
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* @return This builder.
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*/
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public Builder setMaxRetries(int maxRetries) {
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this.maxRetries = maxRetries;
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return this;
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}
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/**
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* Maximum interval to wait before a request should be retried. Must be at least 500
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* milliseconds. Defaults to 2 minutes.
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*
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* @param maxIntervalMillis Interval in milliseconds.
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* @return This builder.
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*/
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public Builder setMaxIntervalMillis(int maxIntervalMillis) {
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this.maxIntervalMillis = maxIntervalMillis;
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return this;
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}
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/**
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* Factor by which the retry interval is multiplied when employing exponential back
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* off to delay consecutive retries of the same request. Must be at least 1. Defaults
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* to 2.
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*
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* @param backOffMultiplier Multiplication factor for exponential back off.
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* @return This builder.
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*/
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public Builder setBackOffMultiplier(double backOffMultiplier) {
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this.backOffMultiplier = backOffMultiplier;
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return this;
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}
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@VisibleForTesting
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Builder setSleeper(Sleeper sleeper) {
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this.sleeper = sleeper;
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return this;
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}
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public RetryConfig build() {
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return new RetryConfig(this);
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}
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}
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}

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