[apex] Same-instance callouts provide separate transactions

[Anonymous Apex]

System.debug(
    JSON.serializePretty(
        JSON.deserializeUntyped(
            LimitProfilingCallout.call()
        )
    )
);

[Log]

33.0 APEX_CODE,DEBUG;APEX_PROFILING,INFO;CALLOUT,INFO;DB,INFO;SYSTEM,DEBUG;VALIDATION,INFO;VISUALFORCE,DEBUG;WORKFLOW,INFO
Execute Anonymous: System.debug(
Execute Anonymous:     JSON.serializePretty(
Execute Anonymous:         JSON.deserializeUntyped(
Execute Anonymous:             LimitProfilingCallout.call()
Execute Anonymous:         )
Execute Anonymous:     )
Execute Anonymous: );
17:06:11.6 (6084087)|USER_INFO|[EXTERNAL]|00537000000IQNR|[email protected]|Pacific Standard Time|GMT-07:00
17:06:11.6 (6106185)|EXECUTION_STARTED
17:06:11.6 (6113334)|CODE_UNIT_STARTED|[EXTERNAL]|execute_anonymous_apex
17:06:11.6 (6502538)|SYSTEM_MODE_ENTER|false
17:06:11.6 (12000031)|CALLOUT_REQUEST|[41]|System.HttpRequest[Endpoint=https://na31.salesforce.com/services/apexrest/LimitProfiling, Method=POST]
17:06:11.6 (615485199)|CALLOUT_RESPONSE|[41]|System.HttpResponse[Status=OK, StatusCode=200]
17:06:11.6 (618255215)|CALLOUT_REQUEST|[44]|System.HttpRequest[Endpoint=https://na31.salesforce.com/services/apexrest/LimitProfiling, Method=POST]
17:06:12.135 (1135171319)|CALLOUT_RESPONSE|[44]|System.HttpResponse[Status=OK, StatusCode=200]
17:06:12.135 (1137783862)|CALLOUT_REQUEST|[49]|System.HttpRequest[Endpoint=https://na31.salesforce.com/services/apexrest/LimitProfiling, Method=POST]
17:06:12.135 (1378151799)|CALLOUT_RESPONSE|[49]|System.HttpResponse[Status=OK, StatusCode=200]
17:06:12.135 (1380913692)|CALLOUT_REQUEST|[52]|System.HttpRequest[Endpoint=https://na31.salesforce.com/services/apexrest/LimitProfiling, Method=POST]
17:06:12.135 (1635225210)|CALLOUT_RESPONSE|[52]|System.HttpResponse[Status=OK, StatusCode=200]
17:06:12.135 (1637869845)|CALLOUT_REQUEST|[57]|System.HttpRequest[Endpoint=https://na31.salesforce.com/services/apexrest/LimitProfiling, Method=POST]
17:06:13.314 (2314211352)|CALLOUT_RESPONSE|[57]|System.HttpResponse[Status=OK, StatusCode=200]
17:06:13.314 (2316166883)|SYSTEM_MODE_EXIT|false
17:06:13.314 (2316226547)|SYSTEM_MODE_ENTER|false
17:06:13.314 (2317109946)|SYSTEM_MODE_EXIT|false
17:06:13.314 (2317139631)|SYSTEM_MODE_ENTER|false
17:06:13.314 (2318126765)|SYSTEM_MODE_EXIT|false
17:06:13.314 (2318168979)|USER_DEBUG|[1]|DEBUG|[ {
  "soql_query_limit" : 100,
  "soql_queries" : 0,
  "cpu_limit" : 10000,
  "cpu" : 460
}, {
  "soql_query_limit" : 100,
  "soql_queries" : 0,
  "cpu_limit" : 10000,
  "cpu" : 459
}, {
  "soql_query_limit" : 100,
  "soql_queries" : 100,
  "cpu_limit" : 10000,
  "cpu" : 118
}, {
  "soql_query_limit" : 100,
  "soql_queries" : 100,
  "cpu_limit" : 10000,
  "cpu" : 125
}, {
  "soql_query_limit" : 100,
  "soql_queries" : 100,
  "cpu_limit" : 10000,
  "cpu" : 540
} ]
17:06:13.320 (2320105676)|CUMULATIVE_LIMIT_USAGE
17:06:13.320 (2320105676)|LIMIT_USAGE_FOR_NS|(default)|
  Number of SOQL queries: 0 out of 100
  Number of query rows: 0 out of 50000
  Number of SOSL queries: 0 out of 20
  Number of DML statements: 0 out of 150
  Number of DML rows: 0 out of 10000
  Maximum CPU time: 0 out of 10000
  Maximum heap size: 0 out of 6000000
  Number of callouts: 5 out of 100
  Number of Email Invocations: 0 out of 10
  Number of future calls: 0 out of 50
  Number of queueable jobs added to the queue: 0 out of 50
  Number of Mobile Apex push calls: 0 out of 10

17:06:13.320 (2320105676)|CUMULATIVE_LIMIT_USAGE_END

17:06:13.314 (2320173460)|CODE_UNIT_FINISHED|execute_anonymous_apex
17:06:13.314 (2321394517)|EXECUTION_FINISHED

LimitProfilingCallout.cls

@RestResource(urlMapping = '/LimitProfiling/*')
global with sharing class LimitProfilingCallout {

	@HttpPost
	global static void callMeMaybe() {
		RestRequest req = RestContext.request;
		RestResponse res = RestContext.response;
		
		Map<String, Object> data = (Map<String, Object>) JSON.deserializeUntyped(req.requestBody.toString());
		
		if (data.get('cpu') == true) {
			stressTestCPU();
		}
		if (data.get('soql_statements') == true) {
			stressTestSoqlStatements();
		}
		
		Map<String, Integer> limitData = new Map<String, Integer>();
		limitData.put('cpu', Limits.getCpuTime());
		limitData.put('soql_statements', Limits.getQueries());
		
		res.responseBody = Blob.valueOf(JSON.serialize(limitData));
	}
	
	public static String call() {
		Http http = new Http();
		HttpRequest req = new HttpRequest();
		req.setEndpoint('https://na31.salesforce.com/services/apexrest/LimitProfiling');
		req.setMethod('POST');
		req.setHeader('Authorization', 'OAuth ' + UserInfo.getSessionId());
		req.setHeader('Content-Type', 'application/json');
		req.setHeader('Content-Length', '0');
		
		List<Object> responses = new List<Object>();
		
		HttpResponse res;
		// testing cpu
		req.setBody('{"cpu":true}');
		res = http.send(req);
		responses.add(JSON.deserializeUntyped(res.getBody()));

		res = http.send(req);
		responses.add(JSON.deserializeUntyped(res.getBody()));
		
		// testing soql statements
		req.setBody('{"soql_statements":true}');
		res = http.send(req);
		responses.add(JSON.deserializeUntyped(res.getBody()));

		res = http.send(req);
		responses.add(JSON.deserializeUntyped(res.getBody()));

		// testing both
		req.setBody('{"cpu":true,"soql_statements":true}');
		res = http.send(req);
		responses.add(JSON.deserializeUntyped(res.getBody()));
		
		return JSON.serialize(responses);
	}
	
	public static void stressTestCPU() {
		Integer n = 0;
		for (Integer i = 0; i < 100; i++) {
			for (Integer j = 0; j < 100; j++) {
				for (Integer k = 0; k < 100; k++) {
					n = i + j + k;
				}
			}
		}
	}
	
	public static void stressTestSoqlStatements() {
		for (Integer i = 0; i < 100; i++) {
			User u = [ SELECT Id FROM User LIMIT 1 ];
		}
	}
}