fix: fix the bug of deadlock in info collector in onebox environment (#404)

src/server/config.ini

@@ -86,6 +86,12 @@
   name = default
   partitioned = false
   worker_priority = THREAD_xPRIORITY_NORMAL
+  # The worker count in THREAD_POOL_DEFAULT must be >= 5.
+  # Because in info collector server, there are four timer tasks(LPC_PEGASUS_APP_STAT_TIMER, LPC_PEGASUS_STORAGE_SIZE_STAT_TIMER,
+  # LPC_DETECT_AVAILABLE and LPC_PEGASUS_CAPACITY_UNIT_STAT_TIMER). Each of these timer tasks occupies a thread in THREAD_POOL_DEFAULT.
+  # Each of these timer tasks calls remote procedure to meta server(which produce a callback), and waits for the rpc's callback to execute.
+  # If the worker_count <= 4, all of these threads are occupied by these timer tasks. so their rpc's callbacks can't get a thread to run.
+  # it comes to be a deadlock(timer task wait for rpc's callback to execute, and rpc's callback wait for the timer task to release the thread).
   worker_count = 8
 
 [threadpool.THREAD_POOL_REPLICATION]

src/server/config.min.ini

@@ -40,7 +40,13 @@
 
 [threadpool.THREAD_POOL_DEFAULT]
   name = default
-  worker_count = 2
+  # The worker count in THREAD_POOL_DEFAULT must be >= 5.
+  # Because in info collector server, there are four timer tasks(LPC_PEGASUS_APP_STAT_TIMER, LPC_PEGASUS_STORAGE_SIZE_STAT_TIMER,
+  # LPC_DETECT_AVAILABLE and LPC_PEGASUS_CAPACITY_UNIT_STAT_TIMER). Each of these timer tasks occupies a thread in THREAD_POOL_DEFAULT.
+  # Each of these timer tasks calls remote procedure to meta server(which produce a callback), and waits for the rpc's callback to execute.
+  # If the worker_count <= 4, all of these threads are occupied by these timer tasks. so their rpc's callbacks can't get a thread to run.
+  # it comes to be a deadlock(timer task wait for rpc's callback to execute, and rpc's callback wait for the timer task to release the thread).
+  worker_count = 5
 
 [threadpool.THREAD_POOL_REPLICATION]
   name = replica

src/server/info_collector_app.h

@@ -11,8 +11,6 @@
 namespace pegasus {
 namespace server {
 
-DEFINE_TASK_CODE(LPC_PEGASUS_COLLECTOR_TIMER, TASK_PRIORITY_COMMON, ::dsn::THREAD_POOL_DEFAULT)
-
 class info_collector_app : public ::dsn::service_app
 {
 public: