file_handle_cache: Add a command to clear all read buffers

This is meant to be called from `rabbitmqctl`:
  rabbitmqctl eval 'file_handle_cache:clear_read_cache().'

The command sends a message to all queues on all vhosts to make them
clear their own read cache. It is asynchronous, so the command will
return before the action is complete.

Fixes #196.

1 files changed, 40 insertions, 2 deletions

diff --git a/src/file_handle_cache.erl b/src/file_handle_cache.erl
index b323842ba0..dfbfa41fa0 100644
--- a/src/file_handle_cache.erl
+++ b/src/file_handle_cache.erl
@@ -148,7 +148,7 @@
          copy/3, set_maximum_since_use/1, delete/1, clear/1]).
 -export([obtain/0, obtain/1, release/0, release/1, transfer/1, transfer/2,
          set_limit/1, get_limit/0, info_keys/0, with_handle/1, with_handle/2,
-         info/0, info/1]).
+         info/0, info/1, clear_read_cache/0]).
 -export([ulimit/0]).
 
 -export([start_link/0, start_link/2, init/1, handle_call/3, handle_cast/2,
@@ -164,6 +164,8 @@
 -define(CLIENT_ETS_TABLE, file_handle_cache_client).
 -define(ELDERS_ETS_TABLE, file_handle_cache_elders).
 
+-include("rabbit.hrl"). % For #amqqueue record definition.
+
 %%----------------------------------------------------------------------------
 
 -record(file,
@@ -581,6 +583,38 @@ info_keys() -> ?INFO_KEYS.
 info() -> info(?INFO_KEYS).
 info(Items) -> gen_server2:call(?SERVER, {info, Items}, infinity).
 
+clear_read_cache() ->
+    gen_server2:cast(?SERVER, clear_read_cache),
+    clear_vhost_read_cache(rabbit_vhost:list()).
+
+clear_vhost_read_cache([]) ->
+    ok;
+clear_vhost_read_cache([VHost | Rest]) ->
+    clear_queue_read_cache(rabbit_amqqueue:list(VHost)),
+    clear_vhost_read_cache(Rest).
+
+clear_queue_read_cache([]) ->
+    ok;
+clear_queue_read_cache([#amqqueue{pid = MPid, slave_pids = SPids} | Rest]) ->
+    Fun = fun(_, State) ->
+        clear_process_read_cache(),
+        State
+    end,
+    rabbit_amqqueue:run_backing_queue(MPid, rabbit_variable_queue, Fun),
+    [rabbit_amqqueue:run_backing_queue(SPid, rabbit_variable_queue, Fun)
+     || SPid <- SPids],
+    clear_queue_read_cache(Rest).
+
+clear_process_read_cache() ->
+    [
+      begin
+          Handle1 = reset_read_buffer(Handle),
+          put({Ref, fhc_handle}, Handle1)
+      end ||
+      {{Ref, fhc_handle}, Handle} <- get(),
+      size(Handle#handle.read_buffer) > 0
+    ].
+
 %%----------------------------------------------------------------------------
 %% Internal functions
 %%----------------------------------------------------------------------------
@@ -1147,7 +1181,11 @@ handle_cast({transfer, N, FromPid, ToPid}, State) ->
     {noreply, process_pending(
                 update_counts({obtain, socket}, ToPid, +N,
                               update_counts({obtain, socket}, FromPid, -N,
-                                            State)))}.
+                                            State)))};
+
+handle_cast(clear_read_cache, State) ->
+    clear_process_read_cache(),
+    {noreply, State}.
 
 handle_info(check_counts, State) ->
     {noreply, maybe_reduce(State #fhc_state { timer_ref = undefined })};