Logger.h

//
//  Created by Pavel Alexeev on 03.09.14.
//

#import <Foundation/Foundation.h>


@interface Logger : NSObject

+ (void)logString:(NSString *)string;
+ (void)log:(NSString *)format, ... NS_REQUIRES_NIL_TERMINATION;

@end

Logger.m

//
//  Created by Pavel Alexeev on 03.09.14.
//

#import "Logger.h"
#import "AFHTTPRequestOperation.h"
#import "Session.h"
#import "NSString+PhoneNumberFormat.h"
#import "NSDate+Formatter.h"


@implementation Logger

static NSMutableString *messagesToSend;
static NSURL *logglyURL;
static NSString *bundleId;
static NSString *deviceId;
static NSString *version;

+ (void)logString:(NSString *)string
{
	NSLog(@"%@", string);

	if (!messagesToSend) {
		messagesToSend = [NSMutableString string];

		[messagesToSend appendString:@".\n"];
		[messagesToSend appendString:@".\n"];
		[messagesToSend appendString:@".\n"];
		[messagesToSend appendString:@"----------------------------------------------\n"];
		[messagesToSend appendFormat:@"Starting session at %@\n", [[NSDate date] isoString]];
		[messagesToSend appendString:@"----------------------------------------------\n"];
		[messagesToSend appendString:@".\n"];

		[[NSNotificationCenter defaultCenter] addObserver: [self class]
		                                         selector: @selector(applicationDidEnterBackground:)
				                                     name: UIApplicationDidEnterBackgroundNotification
					                               object: nil];
	}

	[messagesToSend appendFormat:@"%@\n", string];

	if ([string containsString:@"error"] || messagesToSend.length > 1000) {
		[self sendLogs];
	}
}

+ (void)applicationDidEnterBackground:(NSNotification *)notification
{
	[self sendLogs];
}

+ (void)log:(NSString *)format, ...
{
	va_list args;
	va_start(args, format);

	NSString *string = [[NSString alloc] initWithFormat:format arguments:args];

	va_end(args);

	[self logString:string];
}

+ (void)sendLogs
{
	NSMutableString *sendingMessages = messagesToSend;
	messagesToSend = [NSMutableString string];

	if (!logglyURL) {
		logglyURL = [NSURL URLWithString:[NSString stringWithFormat:@"https://logs-01.loggly.com/bulk/%@/tag/%@/",
		                                           [Logger logglyKey],
		                                           [Logger logglyTags]]];
	}

	NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:logglyURL];
	[request setHTTPMethod:@"POST"];
	[request setValue:@"text/plain;charset=UTF-8" forHTTPHeaderField:@"content-type"];
	[request setHTTPBody:[sendingMessages dataUsingEncoding:NSUTF8StringEncoding]];

	AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
	// Make sure the post request can finish in background
	[operation setShouldExecuteAsBackgroundTaskWithExpirationHandler:^{
	    // Handle what to do when the background time has been consumed and iOS will shut us down
	    // So, let's do... nothing at all
	}];

	[operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *op, id responseObject) {

	} failure:^(AFHTTPRequestOperation *op, NSError *error) {
		NSLog(@"Loggly post error: %@", error);

	    [messagesToSend insertString:@"\n" atIndex:0];
	    [messagesToSend insertString:sendingMessages atIndex:0];
	}];

	[operation start];
}

+ (NSString *)logglyKey
{
	return @"YOUR-LOGGLY-API-KEY";
}

+ (NSString *)logglyTags
{
	if (!bundleId) {
		bundleId = [NSBundle mainBundle].infoDictionary[@"CFBundleIdentifier"];
	}
	if (!version) {
		version = [NSBundle mainBundle].infoDictionary[@"CFBundleVersion"];
	}
	if (!deviceId) {
		deviceId = [[UIDevice currentDevice] identifierForVendor].UUIDString;
	}

	return [NSString stringWithFormat:@"%@,%@,%@,%@,", bundleId, version, deviceId, [[Session currentSession].phoneNumber rawPhoneNumberWithoutPlus]];
}


@end

Macros.h

#define Log(format, ...) [Logger logString:[NSString stringWithFormat:@"%s:%d " format, __func__, __LINE__, ## __VA_ARGS__]]