Add threads limit to router config (#97)

Signed-off-by: Yadunund <[email protected]>

rmw_zenoh_cpp/config/DEFAULT_RMW_ZENOH_ROUTER_CONFIG.json5

@@ -185,6 +185,16 @@
           /// Higher values lead to a more aggressive batching but it will introduce additional latency.
           backoff: 100,
         },
+        // Number of threads dedicated to transmission
+        // By default, the number of threads is calculated as follows: 1 + ((#cores - 1) / 4)
+        // We limit the number of threads that the zenoh session can spin to 1.
+        // Without this limit, applications with multiple zenoh sessions can
+        // encounter system resource errors when trying to create new threads.
+        // Once zenoh migrates to relying on tokio for its async runtime,
+        // see https://github.com/eclipse-zenoh/zenoh/pull/566, we can consider
+        // removing these flags since with tokio, zenoh can better manage the threads it spins
+        // with the help of thread pools.
+        threads: 1,
       },
       /// Configure the zenoh RX parameters of a link
       rx: {