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/*
* Copyright 2019 Google
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#import "FirebaseRemoteConfig/Sources/Private/RCNConfigFetch.h"
#import <GoogleUtilities/GULNSData+zlib.h>
#import "FirebaseCore/Sources/Private/FirebaseCoreInternal.h"
#import "FirebaseInstallations/Source/Library/Private/FirebaseInstallationsInternal.h"
#import "FirebaseRemoteConfig/Sources/Private/RCNConfigSettings.h"
#import "FirebaseRemoteConfig/Sources/RCNConfigConstants.h"
#import "FirebaseRemoteConfig/Sources/RCNConfigContent.h"
#import "FirebaseRemoteConfig/Sources/RCNConfigExperiment.h"
#import "FirebaseRemoteConfig/Sources/RCNDevice.h"
#ifdef RCN_STAGING_SERVER
static NSString *const kServerURLDomain =
@"https://staging-firebaseremoteconfig.sandbox.googleapis.com";
#else
static NSString *const kServerURLDomain = @"https://firebaseremoteconfig.googleapis.com";
#endif
static NSString *const kServerURLVersion = @"/v1";
static NSString *const kServerURLProjects = @"/projects/";
static NSString *const kServerURLNamespaces = @"/namespaces/";
static NSString *const kServerURLQuery = @":fetch?";
static NSString *const kServerURLKey = @"key=";
static NSString *const kRequestJSONKeyAppID = @"app_id";
static NSString *const kHTTPMethodPost = @"POST"; ///< HTTP request method config fetch using
static NSString *const kContentTypeHeaderName = @"Content-Type"; ///< HTTP Header Field Name
static NSString *const kContentEncodingHeaderName =
@"Content-Encoding"; ///< HTTP Header Field Name
static NSString *const kAcceptEncodingHeaderName = @"Accept-Encoding"; ///< HTTP Header Field Name
static NSString *const kETagHeaderName = @"etag"; ///< HTTP Header Field Name
static NSString *const kIfNoneMatchETagHeaderName = @"if-none-match"; ///< HTTP Header Field Name
static NSString *const kInstallationsAuthTokenHeaderName = @"x-goog-firebase-installations-auth";
// Sends the bundle ID. Refer to b/130301479 for details.
static NSString *const kiOSBundleIdentifierHeaderName =
@"X-Ios-Bundle-Identifier"; ///< HTTP Header Field Name
/// Config HTTP request content type proto buffer
static NSString *const kContentTypeValueJSON = @"application/json";
/// HTTP status codes. Ref: https://cloud.google.com/apis/design/errors#error_retries
static NSInteger const kRCNFetchResponseHTTPStatusCodeOK = 200;
static NSInteger const kRCNFetchResponseHTTPStatusTooManyRequests = 429;
static NSInteger const kRCNFetchResponseHTTPStatusCodeInternalError = 500;
static NSInteger const kRCNFetchResponseHTTPStatusCodeServiceUnavailable = 503;
static NSInteger const kRCNFetchResponseHTTPStatusCodeGatewayTimeout = 504;
// Deprecated error code previously from FirebaseCore
static const NSInteger sFIRErrorCodeConfigFailed = -114;
#pragma mark - RCNConfig
@implementation RCNConfigFetch {
RCNConfigContent *_content;
RCNConfigSettings *_settings;
id<FIRAnalyticsInterop> _analytics;
RCNConfigExperiment *_experiment;
dispatch_queue_t _lockQueue; /// Guard the read/write operation.
NSURLSession *_fetchSession; /// Managed internally by the fetch instance.
NSString *_FIRNamespace;
FIROptions *_options;
}
- (instancetype)init {
NSAssert(NO, @"Invalid initializer.");
return nil;
}
/// Designated initializer
- (instancetype)initWithContent:(RCNConfigContent *)content
DBManager:(RCNConfigDBManager *)DBManager
settings:(RCNConfigSettings *)settings
analytics:(nullable id<FIRAnalyticsInterop>)analytics
experiment:(RCNConfigExperiment *)experiment
queue:(dispatch_queue_t)queue
namespace:(NSString *)FIRNamespace
options:(FIROptions *)options {
self = [super init];
if (self) {
_FIRNamespace = FIRNamespace;
_settings = settings;
_analytics = analytics;
_experiment = experiment;
_lockQueue = queue;
_content = content;
_fetchSession = [self newFetchSession];
_options = options;
}
return self;
}
/// Force a new NSURLSession creation for updated config.
- (void)recreateNetworkSession {
if (_fetchSession) {
[_fetchSession invalidateAndCancel];
}
_fetchSession = [self newFetchSession];
}
/// Return the current session. (Tests).
- (NSURLSession *)currentNetworkSession {
return _fetchSession;
}
- (void)dealloc {
[_fetchSession invalidateAndCancel];
}
#pragma mark - Fetch Config API
- (void)fetchConfigWithExpirationDuration:(NSTimeInterval)expirationDuration
completionHandler:(FIRRemoteConfigFetchCompletion)completionHandler {
// Note: We expect the googleAppID to always be available.
BOOL hasDeviceContextChanged =
FIRRemoteConfigHasDeviceContextChanged(_settings.deviceContext, _options.googleAppID);
__weak RCNConfigFetch *weakSelf = self;
dispatch_async(_lockQueue, ^{
RCNConfigFetch *strongSelf = weakSelf;
if (strongSelf == nil) {
return;
}
// Check whether we are outside of the minimum fetch interval.
if (![strongSelf->_settings hasMinimumFetchIntervalElapsed:expirationDuration] &&
!hasDeviceContextChanged) {
FIRLogDebug(kFIRLoggerRemoteConfig, @"I-RCN000051", @"Returning cached data.");
return [strongSelf reportCompletionOnHandler:completionHandler
withStatus:FIRRemoteConfigFetchStatusSuccess
withError:nil];
}
// Check if a fetch is already in progress.
if (strongSelf->_settings.isFetchInProgress) {
// Check if we have some fetched data.
if (strongSelf->_settings.lastFetchTimeInterval > 0) {
FIRLogDebug(kFIRLoggerRemoteConfig, @"I-RCN000052",
@"A fetch is already in progress. Using previous fetch results.");
return [strongSelf reportCompletionOnHandler:completionHandler
withStatus:strongSelf->_settings.lastFetchStatus
withError:nil];
} else {
FIRLogError(kFIRLoggerRemoteConfig, @"I-RCN000053",
@"A fetch is already in progress. Ignoring duplicate request.");
NSError *error =
[NSError errorWithDomain:FIRRemoteConfigErrorDomain
code:sFIRErrorCodeConfigFailed
userInfo:@{
NSLocalizedDescriptionKey :
@"FetchError: Duplicate request while the previous one is pending"
}];
return [strongSelf reportCompletionOnHandler:completionHandler
withStatus:FIRRemoteConfigFetchStatusFailure
withError:error];
}
}
// Check whether cache data is within throttle limit.
if ([strongSelf->_settings shouldThrottle] && !hasDeviceContextChanged) {
// Must set lastFetchStatus before FailReason.
strongSelf->_settings.lastFetchStatus = FIRRemoteConfigFetchStatusThrottled;
strongSelf->_settings.lastFetchError = FIRRemoteConfigErrorThrottled;
NSTimeInterval throttledEndTime = strongSelf->_settings.exponentialBackoffThrottleEndTime;
NSError *error =
[NSError errorWithDomain:FIRRemoteConfigErrorDomain
code:FIRRemoteConfigErrorThrottled
userInfo:@{
FIRRemoteConfigThrottledEndTimeInSecondsKey : @(throttledEndTime)
}];
return [strongSelf reportCompletionOnHandler:completionHandler
withStatus:strongSelf->_settings.lastFetchStatus
withError:error];
}
strongSelf->_settings.isFetchInProgress = YES;
[strongSelf refreshInstallationsTokenWithCompletionHandler:completionHandler];
});
}
#pragma mark - Fetch helpers
- (NSString *)FIRAppNameFromFullyQualifiedNamespace {
return [[_FIRNamespace componentsSeparatedByString:@":"] lastObject];
}
/// Refresh installation ID token before fetching config. installation ID is now mandatory for fetch
/// requests to work.(b/14751422).
- (void)refreshInstallationsTokenWithCompletionHandler:
(FIRRemoteConfigFetchCompletion)completionHandler {
FIRInstallations *installations = [FIRInstallations
installationsWithApp:[FIRApp appNamed:[self FIRAppNameFromFullyQualifiedNamespace]]];
if (!installations || !_options.GCMSenderID) {
NSString *errorDescription = @"Failed to get GCMSenderID";
FIRLogError(kFIRLoggerRemoteConfig, @"I-RCN000074", @"%@",
[NSString stringWithFormat:@"%@", errorDescription]);
self->_settings.isFetchInProgress = NO;
return [self
reportCompletionOnHandler:completionHandler
withStatus:FIRRemoteConfigFetchStatusFailure
withError:[NSError errorWithDomain:FIRRemoteConfigErrorDomain
code:FIRRemoteConfigErrorInternalError
userInfo:@{
NSLocalizedDescriptionKey : errorDescription
}]];
}
__weak RCNConfigFetch *weakSelf = self;
FIRInstallationsTokenHandler installationsTokenHandler = ^(
FIRInstallationsAuthTokenResult *tokenResult, NSError *error) {
RCNConfigFetch *strongSelf = weakSelf;
if (strongSelf == nil) {
return;
}
if (!tokenResult || !tokenResult.authToken || error) {
NSString *errorDescription =
[NSString stringWithFormat:@"Failed to get installations token. Error : %@.", error];
FIRLogError(kFIRLoggerRemoteConfig, @"I-RCN000073", @"%@",
[NSString stringWithFormat:@"%@", errorDescription]);
strongSelf->_settings.isFetchInProgress = NO;
return [strongSelf
reportCompletionOnHandler:completionHandler
withStatus:FIRRemoteConfigFetchStatusFailure
withError:[NSError errorWithDomain:FIRRemoteConfigErrorDomain
code:FIRRemoteConfigErrorInternalError
userInfo:@{
NSLocalizedDescriptionKey : errorDescription
}]];
}
// We have a valid token. Get the backing installationID.
[installations installationIDWithCompletion:^(NSString *_Nullable identifier,
NSError *_Nullable error) {
RCNConfigFetch *strongSelf = weakSelf;
if (strongSelf == nil) {
return;
}
// Dispatch to the RC serial queue to update settings on the queue.
dispatch_async(strongSelf->_lockQueue, ^{
RCNConfigFetch *strongSelfQueue = weakSelf;
if (strongSelfQueue == nil) {
return;
}
// Update config settings with the IID and token.
strongSelfQueue->_settings.configInstallationsToken = tokenResult.authToken;
strongSelfQueue->_settings.configInstallationsIdentifier = identifier;
if (!identifier || error) {
NSString *errorDescription =
[NSString stringWithFormat:@"Error getting iid : %@.", error];
FIRLogError(kFIRLoggerRemoteConfig, @"I-RCN000055", @"%@",
[NSString stringWithFormat:@"%@", errorDescription]);
strongSelfQueue->_settings.isFetchInProgress = NO;
return [strongSelfQueue
reportCompletionOnHandler:completionHandler
withStatus:FIRRemoteConfigFetchStatusFailure
withError:[NSError
errorWithDomain:FIRRemoteConfigErrorDomain
code:FIRRemoteConfigErrorInternalError
userInfo:@{
NSLocalizedDescriptionKey : errorDescription
}]];
}
FIRLogInfo(kFIRLoggerRemoteConfig, @"I-RCN000022", @"Success to get iid : %@.",
strongSelfQueue->_settings.configInstallationsIdentifier);
[strongSelf doFetchCall:completionHandler];
});
}];
};
FIRLogDebug(kFIRLoggerRemoteConfig, @"I-RCN000039", @"Starting requesting token.");
[installations authTokenWithCompletion:installationsTokenHandler];
}
- (void)doFetchCall:(FIRRemoteConfigFetchCompletion)completionHandler {
[self getAnalyticsUserPropertiesWithCompletionHandler:^(NSDictionary *userProperties) {
dispatch_async(self->_lockQueue, ^{
[self fetchWithUserProperties:userProperties completionHandler:completionHandler];
});
}];
}
- (void)getAnalyticsUserPropertiesWithCompletionHandler:
(FIRAInteropUserPropertiesCallback)completionHandler {
FIRLogDebug(kFIRLoggerRemoteConfig, @"I-RCN000060", @"Fetch with user properties completed.");
id<FIRAnalyticsInterop> analytics = self->_analytics;
if (analytics == nil) {
completionHandler(@{});
} else {
[analytics getUserPropertiesWithCallback:completionHandler];
}
}
- (void)reportCompletionOnHandler:(FIRRemoteConfigFetchCompletion)completionHandler
withStatus:(FIRRemoteConfigFetchStatus)status
withError:(NSError *)error {
if (completionHandler) {
dispatch_async(dispatch_get_main_queue(), ^{
completionHandler(status, error);
});
}
}
- (void)fetchWithUserProperties:(NSDictionary *)userProperties
completionHandler:(FIRRemoteConfigFetchCompletion)completionHandler {
FIRLogDebug(kFIRLoggerRemoteConfig, @"I-RCN000061", @"Fetch with user properties initiated.");
NSString *postRequestString = [_settings nextRequestWithUserProperties:userProperties];
// Get POST request content.
NSData *content = [postRequestString dataUsingEncoding:NSUTF8StringEncoding];
NSError *compressionError;
NSData *compressedContent = [NSData gul_dataByGzippingData:content error:&compressionError];
if (compressionError) {
NSString *errString = [NSString stringWithFormat:@"Failed to compress the config request."];
FIRLogWarning(kFIRLoggerRemoteConfig, @"I-RCN000033", @"%@", errString);
self->_settings.isFetchInProgress = NO;
return [self
reportCompletionOnHandler:completionHandler
withStatus:FIRRemoteConfigFetchStatusFailure
withError:[NSError
errorWithDomain:FIRRemoteConfigErrorDomain
code:FIRRemoteConfigErrorInternalError
userInfo:@{NSLocalizedDescriptionKey : errString}]];
}
FIRLogDebug(kFIRLoggerRemoteConfig, @"I-RCN000040", @"Start config fetch.");
__weak RCNConfigFetch *weakSelf = self;
RCNConfigFetcherCompletion fetcherCompletion = ^(NSData *data, NSURLResponse *response,
NSError *error) {
FIRLogDebug(kFIRLoggerRemoteConfig, @"I-RCN000050",
@"config fetch completed. Error: %@ StatusCode: %ld", (error ? error : @"nil"),
(long)[((NSHTTPURLResponse *)response) statusCode]);
RCNConfigFetch *fetcherCompletionSelf = weakSelf;
if (fetcherCompletionSelf == nil) {
return;
}
// The fetch has completed.
fetcherCompletionSelf->_settings.isFetchInProgress = NO;
dispatch_async(fetcherCompletionSelf->_lockQueue, ^{
RCNConfigFetch *strongSelf = weakSelf;
if (strongSelf == nil) {
return;
}
NSInteger statusCode = [((NSHTTPURLResponse *)response) statusCode];
if (error || (statusCode != kRCNFetchResponseHTTPStatusCodeOK)) {
// Update metadata about fetch failure.
[strongSelf->_settings updateMetadataWithFetchSuccessStatus:NO];
if (error) {
if (strongSelf->_settings.lastFetchStatus == FIRRemoteConfigFetchStatusSuccess) {
FIRLogError(kFIRLoggerRemoteConfig, @"I-RCN000025",
@"RCN Fetch failure: %@. Using cached config result.", error);
} else {
FIRLogError(kFIRLoggerRemoteConfig, @"I-RCN000026",
@"RCN Fetch failure: %@. No cached config result.", error);
}
}
if (statusCode != kRCNFetchResponseHTTPStatusCodeOK) {
FIRLogError(kFIRLoggerRemoteConfig, @"I-RCN000026",
@"RCN Fetch failure. Response http error code: %ld", (long)statusCode);
// Response error code 429, 500, 503 will trigger exponential backoff mode.
if (statusCode == kRCNFetchResponseHTTPStatusTooManyRequests ||
statusCode == kRCNFetchResponseHTTPStatusCodeInternalError ||
statusCode == kRCNFetchResponseHTTPStatusCodeServiceUnavailable ||
statusCode == kRCNFetchResponseHTTPStatusCodeGatewayTimeout) {
[strongSelf->_settings updateExponentialBackoffTime];
if ([strongSelf->_settings shouldThrottle]) {
// Must set lastFetchStatus before FailReason.
strongSelf->_settings.lastFetchStatus = FIRRemoteConfigFetchStatusThrottled;
strongSelf->_settings.lastFetchError = FIRRemoteConfigErrorThrottled;
NSTimeInterval throttledEndTime =
strongSelf->_settings.exponentialBackoffThrottleEndTime;
NSError *error = [NSError
errorWithDomain:FIRRemoteConfigErrorDomain
code:FIRRemoteConfigErrorThrottled
userInfo:@{
FIRRemoteConfigThrottledEndTimeInSecondsKey : @(throttledEndTime)
}];
return [strongSelf reportCompletionOnHandler:completionHandler
withStatus:strongSelf->_settings.lastFetchStatus
withError:error];
}
}
}
// Return back the received error.
// Must set lastFetchStatus before setting Fetch Error.
strongSelf->_settings.lastFetchStatus = FIRRemoteConfigFetchStatusFailure;
strongSelf->_settings.lastFetchError = FIRRemoteConfigErrorInternalError;
NSDictionary<NSErrorUserInfoKey, id> *userInfo = @{
NSLocalizedDescriptionKey :
([error localizedDescription]
?: [NSString
stringWithFormat:@"Internal Error. Status code: %ld", (long)statusCode])
};
return [strongSelf
reportCompletionOnHandler:completionHandler
withStatus:FIRRemoteConfigFetchStatusFailure
withError:[NSError errorWithDomain:FIRRemoteConfigErrorDomain
code:FIRRemoteConfigErrorInternalError
userInfo:userInfo]];
}
// Fetch was successful. Check if we have data.
NSError *retError;
if (!data) {
FIRLogInfo(kFIRLoggerRemoteConfig, @"I-RCN000043", @"RCN Fetch: No data in fetch response");
return [strongSelf reportCompletionOnHandler:completionHandler
withStatus:FIRRemoteConfigFetchStatusSuccess
withError:nil];
}
// Config fetch succeeded.
// JSONObjectWithData is always expected to return an NSDictionary in our case
NSMutableDictionary *fetchedConfig =
[NSJSONSerialization JSONObjectWithData:data
options:NSJSONReadingMutableContainers
error:&retError];
if (retError) {
FIRLogError(kFIRLoggerRemoteConfig, @"I-RCN000042",
@"RCN Fetch failure: %@. Could not parse response data as JSON", error);
}
// Check and log if we received an error from the server
if (fetchedConfig && fetchedConfig.count == 1 && fetchedConfig[RCNFetchResponseKeyError]) {
NSString *errStr = [NSString stringWithFormat:@"RCN Fetch Failure: Server returned error:"];
NSDictionary *errDict = fetchedConfig[RCNFetchResponseKeyError];
if (errDict[RCNFetchResponseKeyErrorCode]) {
errStr = [errStr
stringByAppendingString:[NSString
stringWithFormat:@"code: %@",
errDict[RCNFetchResponseKeyErrorCode]]];
}
if (errDict[RCNFetchResponseKeyErrorStatus]) {
errStr = [errStr stringByAppendingString:
[NSString stringWithFormat:@". Status: %@",
errDict[RCNFetchResponseKeyErrorStatus]]];
}
if (errDict[RCNFetchResponseKeyErrorMessage]) {
errStr =
[errStr stringByAppendingString:
[NSString stringWithFormat:@". Message: %@",
errDict[RCNFetchResponseKeyErrorMessage]]];
}
FIRLogError(kFIRLoggerRemoteConfig, @"I-RCN000044", @"%@.", errStr);
return [strongSelf
reportCompletionOnHandler:completionHandler
withStatus:FIRRemoteConfigFetchStatusFailure
withError:[NSError
errorWithDomain:FIRRemoteConfigErrorDomain
code:FIRRemoteConfigErrorInternalError
userInfo:@{NSLocalizedDescriptionKey : errStr}]];
}
// Add the fetched config to the database.
if (fetchedConfig) {
// Update config content to cache and DB.
[strongSelf->_content updateConfigContentWithResponse:fetchedConfig
forNamespace:strongSelf->_FIRNamespace];
// Update experiments only for 3p namespace
NSString *namespace = [strongSelf->_FIRNamespace
substringToIndex:[strongSelf->_FIRNamespace rangeOfString:@":"].location];
if ([namespace isEqualToString:FIRNamespaceGoogleMobilePlatform]) {
[strongSelf->_experiment updateExperimentsWithResponse:
fetchedConfig[RCNFetchResponseKeyExperimentDescriptions]];
}
} else {
FIRLogDebug(kFIRLoggerRemoteConfig, @"I-RCN000063",
@"Empty response with no fetched config.");
}
// We had a successful fetch. Update the current eTag in settings if different.
NSString *latestETag = ((NSHTTPURLResponse *)response).allHeaderFields[kETagHeaderName];
if (!strongSelf->_settings.lastETag ||
!([strongSelf->_settings.lastETag isEqualToString:latestETag])) {
strongSelf->_settings.lastETag = latestETag;
}
[strongSelf->_settings updateMetadataWithFetchSuccessStatus:YES];
return [strongSelf reportCompletionOnHandler:completionHandler
withStatus:FIRRemoteConfigFetchStatusSuccess
withError:nil];
});
};
FIRLogDebug(kFIRLoggerRemoteConfig, @"I-RCN000061", @"Making remote config fetch.");
NSURLSessionDataTask *dataTask = [self URLSessionDataTaskWithContent:compressedContent
completionHandler:fetcherCompletion];
[dataTask resume];
}
- (NSString *)constructServerURL {
NSString *serverURLStr = [[NSString alloc] initWithString:kServerURLDomain];
serverURLStr = [serverURLStr stringByAppendingString:kServerURLVersion];
serverURLStr = [serverURLStr stringByAppendingString:kServerURLProjects];
serverURLStr = [serverURLStr stringByAppendingString:_options.projectID];
serverURLStr = [serverURLStr stringByAppendingString:kServerURLNamespaces];
// Get the namespace from the fully qualified namespace string of "namespace:FIRAppName".
NSString *namespace =
[_FIRNamespace substringToIndex:[_FIRNamespace rangeOfString:@":"].location];
serverURLStr = [serverURLStr stringByAppendingString:namespace];
serverURLStr = [serverURLStr stringByAppendingString:kServerURLQuery];
if (_options.APIKey) {
serverURLStr = [serverURLStr stringByAppendingString:kServerURLKey];
serverURLStr = [serverURLStr stringByAppendingString:_options.APIKey];
} else {
FIRLogError(kFIRLoggerRemoteConfig, @"I-RCN000071",
@"Missing `APIKey` from `FirebaseOptions`, please ensure the configured "
@"`FirebaseApp` is configured with `FirebaseOptions` that contains an `APIKey`.");
}
return serverURLStr;
}
- (NSURLSession *)newFetchSession {
NSURLSessionConfiguration *config =
[[NSURLSessionConfiguration defaultSessionConfiguration] copy];
config.timeoutIntervalForRequest = _settings.fetchTimeout;
config.timeoutIntervalForResource = _settings.fetchTimeout;
NSURLSession *session = [NSURLSession sessionWithConfiguration:config];
return session;
}
- (NSURLSessionDataTask *)URLSessionDataTaskWithContent:(NSData *)content
completionHandler:
(RCNConfigFetcherCompletion)fetcherCompletion {
NSURL *URL = [NSURL URLWithString:[self constructServerURL]];
FIRLogDebug(kFIRLoggerRemoteConfig, @"I-RCN000046", @"%@",
[NSString stringWithFormat:@"Making config request: %@", [URL absoluteString]]);
NSTimeInterval timeoutInterval = _fetchSession.configuration.timeoutIntervalForResource;
NSMutableURLRequest *URLRequest =
[[NSMutableURLRequest alloc] initWithURL:URL
cachePolicy:NSURLRequestReloadIgnoringLocalCacheData
timeoutInterval:timeoutInterval];
URLRequest.HTTPMethod = kHTTPMethodPost;
[URLRequest setValue:kContentTypeValueJSON forHTTPHeaderField:kContentTypeHeaderName];
[URLRequest setValue:_settings.configInstallationsToken
forHTTPHeaderField:kInstallationsAuthTokenHeaderName];
[URLRequest setValue:[[NSBundle mainBundle] bundleIdentifier]
forHTTPHeaderField:kiOSBundleIdentifierHeaderName];
[URLRequest setValue:@"gzip" forHTTPHeaderField:kContentEncodingHeaderName];
[URLRequest setValue:@"gzip" forHTTPHeaderField:kAcceptEncodingHeaderName];
// Set the eTag from the last successful fetch, if available.
if (_settings.lastETag) {
[URLRequest setValue:_settings.lastETag forHTTPHeaderField:kIfNoneMatchETagHeaderName];
}
[URLRequest setHTTPBody:content];
return [_fetchSession dataTaskWithRequest:URLRequest completionHandler:fetcherCompletion];
}
@end