mpm_event,core: Handle async POLLIN/POLLOUT in CONN_STATE_PROCESS state.

* include/httpd.h:
  Rename CONN_STATE_CHECK_REQUEST_LINE_READABLE to CONN_STATE_KEEPALIVE
  and CONN_STATE_READ_REQUEST_LINE to CONN_STATE_PROCESS, keeping the
  old enums as aliases. Rework comments about each state.

* server/mpm/event/event.c:
  Use the new states names.
  Let the process_connection hooks return CONN_STATE_PROCESS for mpm_event
  to POLLIN or POLLOUT depending on c->cs->sense being CONN_SENSE_WANT_READ
  or CONN_SENSE_WANT_WRITE respectively.
  Remove (ab)use of CONN_STATE_WRITE_COMPLETION with CONN_SENSE_WANT_READ to
  mean poll() for read (and the need for the obscure c->clogging_input_filters
  to make it work as expected). This is what CONN_STATE_PROCESS is for now.
  Update the comment about the states that can be returned by process_connection
  hooks (and their usage).
  Use the same queue (process_q renamed from write_completion_q) for polling
  connections in both CONN_STATE_PROCESS and CONN_STATE_WRITE_COMPLETION
  states since they both use the same (server_rec's) Timeout. This implies
  that both states are accounted as "write-completion" in mod_status for now.

* server/mpm/motorz/motorz.c, server/mpm/simple/simple_io.c, modules/http/http_core.c:
  Use the new states names (only).

* include/scoreboard.h:
  Change comment about process_score->write_completion to note that the
  counter refers to CONN_STATE_PROCESS connections returned to the MPM
  too.

* modules/http2/h2_c1.c:
  Return the c1 connection with the CONN_STATE_PROCESS state rather than
  CONN_STATE_WRITE_COMPLETION when waiting for a window update (i.e. ask
  the MPM to poll for read directly). This avoids the transition to
  CONN_STATE_KEEPALIVE which could kill the connection under high load.


Github: closes #448



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1918022 13f79535-47bb-0310-9956-ffa450edef68

2 files changed, 16 insertions, 11 deletions

diff --git a/include/httpd.h b/include/httpd.h
index ccbe417328..c547c30ea4 100644
--- a/include/httpd.h
+++ b/include/httpd.h
@@ -1318,16 +1318,21 @@ struct conn_slave_rec {
  * only be set by the MPM. Use CONN_STATE_LINGER outside of the MPM.
  */
 typedef enum  {
-    CONN_STATE_CHECK_REQUEST_LINE_READABLE,
-    CONN_STATE_READ_REQUEST_LINE,
-    CONN_STATE_HANDLER,
-    CONN_STATE_WRITE_COMPLETION,
-    CONN_STATE_SUSPENDED,
-    CONN_STATE_LINGER,          /* connection may be closed with lingering */
-    CONN_STATE_LINGER_NORMAL,   /* MPM has started lingering close with normal timeout */
-    CONN_STATE_LINGER_SHORT,    /* MPM has started lingering close with short timeout */
-
-    CONN_STATE_NUM              /* Number of states (keep/kept last) */
+    CONN_STATE_KEEPALIVE,           /* Kept alive in the MPM (using KeepAliveTimeout) */
+    CONN_STATE_PROCESS,             /* Handled by process_connection() hooks, may be returned
+                                       to the MPM for POLLIN/POLLOUT (using Timeout) */
+    CONN_STATE_HANDLER,             /* Processed by the modules handlers */
+    CONN_STATE_WRITE_COMPLETION,    /* Flushed by the MPM before entering CONN_STATE_KEEPALIVE */
+    CONN_STATE_SUSPENDED,           /* Suspended in the MPM until ap_run_resume_suspended() */
+    CONN_STATE_LINGER,              /* MPM flushes then closes the connection with lingering */
+    CONN_STATE_LINGER_NORMAL,       /* MPM has started lingering close with normal timeout */
+    CONN_STATE_LINGER_SHORT,        /* MPM has started lingering close with short timeout */
+
+    CONN_STATE_NUM,                 /* Number of states (keep here before aliases) */
+
+    /* Aliases (legacy) */
+    CONN_STATE_CHECK_REQUEST_LINE_READABLE  = CONN_STATE_KEEPALIVE,
+    CONN_STATE_READ_REQUEST_LINE            = CONN_STATE_PROCESS,
 } conn_state_e;
 
 typedef enum  {
diff --git a/include/scoreboard.h b/include/scoreboard.h
index 7cf92e405a..7542999b83 100644
--- a/include/scoreboard.h
+++ b/include/scoreboard.h
@@ -144,7 +144,7 @@ struct process_score {
                              * connections (for async MPMs)
                              */
     apr_uint32_t connections;       /* total connections (for async MPMs) */
-    apr_uint32_t write_completion;  /* async connections doing write completion */
+    apr_uint32_t write_completion;  /* async connections in write completion or POLLIN/POLLOUT */
     apr_uint32_t lingering_close;   /* async connections in lingering close */
     apr_uint32_t keep_alive;        /* async connections in keep alive */
     apr_uint32_t suspended;         /* connections suspended by some module */