fix cmake and doc for pullclient

Author: sy-c

CMakeLists.txt

@@ -248,6 +248,7 @@ foreach (example ${EXAMPLES})
   target_link_libraries(${example_name}
     PRIVATE
       Monitoring Boost::program_options
+      $<$<BOOL:${CURL_FOUND}>:CURL::libcurl>
   )
 endforeach()
 

README.md

@@ -250,15 +250,18 @@ for (;;) {
   auto metrics = client->pull();
   if (!metrics.empty()) {
     /// metric.first => topic name; metric.second => metric itself
+  } else {
+    // wait a bit if no data available
+    std::this_thread::sleep_for(std::chrono::milliseconds(100));
   }
-  std::this_thread::sleep_for(std::chrono::milliseconds(100));
-}
 ```
 
 Run-time parameters:
 - `<topic-to-subscribe>` - List of topics to subscribe
 - `<kafka-server:9092>` - Kafka broker (staging or production)
 - `<client_id>` - unique, self-explainable string describing the client, eg. `dcs-link-status` or `its-link-status`.
 
+Metrics are returned in batch of maximum 100 for each pull() call.
+
 ### Data format
 Native data format is [Influx Line Protocol](https://docs.influxdata.com/influxdb/latest/reference/syntax/line-protocol/) but metrics can be converted into any format listed in here: https://docs.influxdata.com/telegraf/latest/data_formats/output/

examples/13-PullClient.cxx

@@ -9,6 +9,7 @@ using namespace o2::monitoring;
 
 int main()
 {
+  int ix=0;
   /// List of topics to subscribe
   std::vector<std::string> topics = {"cru.link_status"};
   /// Connect to server
@@ -21,7 +22,9 @@ int main()
         /// metric sample: link,serialId=983,endpoint=1,CRU=1,id=11,type=CRU pciAddress="b0:00.0",status=1i 1673940809860009855
         std::cout << metric.second << std::endl;
       }
+    } else {
+      // wait a bit if no data available
+      std::this_thread::sleep_for(std::chrono::milliseconds(100));
     }
-    std::this_thread::sleep_for(std::chrono::milliseconds(100));
   }
 }