Prevent hangs of child processes when writing to piped loggers at

the time of graceful restart.

PR:          26467
Reviewed by: Joe Orton

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@170281 13f79535-47bb-0310-9956-ffa450edef68

diff --git a/CHANGES b/CHANGES
index 4edebf661dc5eaeb61d21d4fa25f463156fb83b8..660b7484b8304402d226d66461df20954ab793af 100644 (file)
--- a/CHANGES
+++ b/CHANGES
@@ -1,6 +1,9 @@
 Changes with Apache 2.1.5
 
   [Remove entries to the current 2.0 section below, when backported]
+
+  *) Prevent hangs of child processes when writing to piped loggers at
+     the time of graceful restart.  PR 26467.  [Jeff Trawick]
   
   *) mod_info: Show the Quick Handler [Paul Querna]
 

diff --git a/include/http_log.h b/include/http_log.h
index 1e96f97b8548530000669c0737297bf609afebe7..b6b5a7affb46c42016960e34545932eaa1029076 100644 (file)
--- a/include/http_log.h
+++ b/include/http_log.h
@@ -116,6 +116,16 @@ AP_DECLARE(apr_status_t) ap_replace_stderr_log(apr_pool_t *p,
 int ap_open_logs(apr_pool_t *pconf, apr_pool_t *plog, 
                  apr_pool_t *ptemp, server_rec *s_main);
 
+/**
+ * Perform special processing for piped loggers in MPM child
+ * processes.
+ * @param p Not used
+ * @param s Not used
+ * @tip ap_logs_child_init is not for use by modules; it is an
+ * internal core function
+ */
+void ap_logs_child_init(apr_pool_t *p, server_rec *s);
+
 /* 
  * The primary logging functions, ap_log_error, ap_log_rerror, ap_log_cerror,
  * and ap_log_perror use a printf style format string to build the log message.  

diff --git a/server/core.c b/server/core.c
index b0e14c4224b6f5eb8ed28f4cd44fa2931bd9a2b0..391b09077d3b827fe3df7510d39920f023f48a70 100644 (file)
--- a/server/core.c
+++ b/server/core.c
@@ -3755,6 +3755,7 @@ static void register_hooks(apr_pool_t *p)
     ap_hook_translate_name(ap_core_translate,NULL,NULL,APR_HOOK_REALLY_LAST);
     ap_hook_map_to_storage(core_map_to_storage,NULL,NULL,APR_HOOK_REALLY_LAST);
     ap_hook_open_logs(ap_open_logs,NULL,NULL,APR_HOOK_REALLY_FIRST);
+    ap_hook_child_init(ap_logs_child_init,NULL,NULL,APR_HOOK_MIDDLE);
     ap_hook_handler(default_handler,NULL,NULL,APR_HOOK_REALLY_LAST);
     /* FIXME: I suspect we can eliminate the need for these do_nothings - Ben */
     ap_hook_type_checker(do_nothing,NULL,NULL,APR_HOOK_REALLY_LAST);

diff --git a/server/log.c b/server/log.c
index da5ecbc230eefcd937dfa3f4a7c481daabb1ad90..6bcc202e76a769a76532c4e62f13fda43441a8a4 100644 (file)
--- a/server/log.c
+++ b/server/log.c
@@ -141,6 +141,45 @@ static const TRANS priorities[] = {
 
 static apr_file_t *stderr_log = NULL;
 
+/* track pipe handles to close in child process */
+typedef struct read_handle_t {
+    struct read_handle_t *next;
+    apr_file_t *handle;
+} read_handle_t;
+
+static read_handle_t *read_handles;
+
+/* clear_handle_list() is called when plog is cleared; at that
+ * point we need to forget about our old list of pipe read
+ * handles
+ */
+static apr_status_t clear_handle_list(void *v)
+{
+    read_handles = NULL;
+    return APR_SUCCESS;
+}
+
+/* remember to close this handle in the child process */
+static void close_handle_in_child(apr_pool_t *p, apr_file_t *f)
+{
+    read_handle_t *new_handle;
+
+    new_handle = apr_pcalloc(p, sizeof(read_handle_t));
+    new_handle->next = read_handles;
+    new_handle->handle = f;
+    read_handles = new_handle;
+}
+
+void ap_logs_child_init(apr_pool_t *p, server_rec *s)
+{
+    read_handle_t *cur = read_handles;
+
+    while (cur) {
+        apr_file_close(cur->handle);
+        cur = cur->next;
+    }
+}
+
 AP_DECLARE(void) ap_open_stderr_log(apr_pool_t *p)
 {
     apr_file_open_stderr(&stderr_log, p);
@@ -218,6 +257,9 @@ static int log_child(apr_pool_t *p, const char *progname,
         if (rc == APR_SUCCESS) {
             apr_pool_note_subprocess(p, procnew, APR_KILL_AFTER_TIMEOUT);
             (*fpin) = procnew->in;
+            /* read handle to pipe not kept open, so no need to call
+             * close_handle_in_child()
+             */
         }
     }
 
@@ -294,6 +336,8 @@ int ap_open_logs(apr_pool_t *pconf, apr_pool_t *p /* plog */,
     int replace_stderr;
     apr_file_t *errfile = NULL;
 
+    apr_pool_cleanup_register(p, NULL, clear_handle_list,
+                              apr_pool_cleanup_null);
     if (open_error_log(s_main, p) != OK) {
         return DONE;
     }
@@ -780,6 +824,7 @@ static int piped_log_spawn(piped_log *pl)
             ap_piped_log_write_fd(pl) = procnew->in;
             apr_proc_other_child_register(procnew, piped_log_maintenance, pl,
                                           ap_piped_log_write_fd(pl), pl->p);
+            close_handle_in_child(pl->p, ap_piped_log_read_fd(pl));
         }
         else {
             char buf[120];