pacemaker/SOURCES/005-glib-priorities.patch

From 65170ffd5fa10cbda176b3f88e817d534b6331d6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jan=20Pokorn=C3=BD?= <jpokorny@redhat.com>
Date: Wed, 29 Aug 2018 15:49:58 +0200
Subject: [PATCH 1/2] Low: mainloop: make it possible to specify server's
 priority in mainloop

---
 include/crm/common/mainloop.h | 24 +++++++++++++
 lib/common/mainloop.c         | 82 +++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 103 insertions(+), 3 deletions(-)

diff --git a/include/crm/common/mainloop.h b/include/crm/common/mainloop.h
index 85da1cd..2cfb63e 100644
--- a/include/crm/common/mainloop.h
+++ b/include/crm/common/mainloop.h
@@ -79,6 +79,30 @@ struct ipc_client_callbacks {
 qb_ipcs_service_t *mainloop_add_ipc_server(const char *name, enum qb_ipc_type type,
                                            struct qb_ipcs_service_handlers *callbacks);
 
+/*!
+ * \brief Start server-side API end-point, hooked into the internal event loop
+ *
+ * \param[in] name    name of the IPC end-point ("address" for the client)
+ * \param[in] type    selects libqb's IPC back-end (or use #QB_IPC_NATIVE)
+ * \param[in] callbacks  defines libqb's IPC service-level handlers
+ * \param[in] priority  priority relative to other events handled in the
+ *                      abstract handling loop, use #QB_LOOP_MED when unsure
+ *
+ * \return libqb's opaque handle to the created service abstraction
+ *
+ * \note For portability concerns, do not use this function if you keep
+ *       \p priority as #QB_LOOP_MED, stick with #mainloop_add_ipc_server
+ *       (with exactly such semantics) instead (once you link with this new
+ *       symbol employed, you can't downgrade the library freely anymore).
+ *
+ * \note The intended effect will only get fully reflected when run-time
+ *       linked to patched libqb: https://github.com/ClusterLabs/libqb/pull/352
+ */
+qb_ipcs_service_t *mainloop_add_ipc_server_with_prio(const char *name,
+                                                    enum qb_ipc_type type,
+                                                    struct qb_ipcs_service_handlers *callbacks,
+                                                    enum qb_loop_priority prio);
+
 void mainloop_del_ipc_server(qb_ipcs_service_t * server);
 
 mainloop_io_t *mainloop_add_ipc_client(const char *name, int priority, size_t max_size,
diff --git a/lib/common/mainloop.c b/lib/common/mainloop.c
index 18f7014..17e69f0 100644
--- a/lib/common/mainloop.c
+++ b/lib/common/mainloop.c
@@ -509,6 +509,65 @@ gio_poll_destroy(gpointer data)
     }
 }
 
+/*!
+ * \internal
+ * \brief Convert libqb's poll priority into GLib's one
+ *
+ * \param[in] prio  libqb's poll priority (#QB_LOOP_MED assumed as fallback)
+ *
+ * \return  best matching GLib's priority
+ */
+static gint
+conv_prio_libqb2glib(enum qb_loop_priority prio)
+{
+    gint ret = G_PRIORITY_DEFAULT;
+    switch (prio) {
+        case QB_LOOP_LOW:
+            ret = G_PRIORITY_LOW;
+            break;
+        case QB_LOOP_HIGH:
+            ret = G_PRIORITY_HIGH;
+            break;
+        default:
+            crm_trace("Invalid libqb's loop priority %d, assuming QB_LOOP_MED",
+                      prio);
+            /* fall-through */
+        case QB_LOOP_MED:
+            break;
+    }
+    return ret;
+}
+
+/*!
+ * \internal
+ * \brief Convert libqb's poll priority to rate limiting spec
+ *
+ * \param[in] prio  libqb's poll priority (#QB_LOOP_MED assumed as fallback)
+ *
+ * \return  best matching rate limiting spec
+ */
+static enum qb_ipcs_rate_limit
+conv_libqb_prio2ratelimit(enum qb_loop_priority prio)
+{
+    /* this is an inversion of what libqb's qb_ipcs_request_rate_limit does */
+    enum qb_ipcs_rate_limit ret = QB_IPCS_RATE_NORMAL;
+    switch (prio) {
+        case QB_LOOP_LOW:
+            ret = QB_IPCS_RATE_SLOW;
+            break;
+        case QB_LOOP_HIGH:
+            ret = QB_IPCS_RATE_FAST;
+            break;
+        default:
+            crm_trace("Invalid libqb's loop priority %d, assuming QB_LOOP_MED",
+                      prio);
+            /* fall-through */
+        case QB_LOOP_MED:
+            break;
+    }
+    return ret;
+}
+
 static int32_t
 gio_poll_dispatch_update(enum qb_loop_priority p, int32_t fd, int32_t evts,
                          void *data, qb_ipcs_dispatch_fn_t fn, int32_t add)
@@ -555,8 +614,8 @@ gio_poll_dispatch_update(enum qb_loop_priority p, int32_t fd, int32_t evts,
     adaptor->p = p;
     adaptor->is_used++;
     adaptor->source =
-        g_io_add_watch_full(channel, G_PRIORITY_DEFAULT, evts, gio_read_socket, adaptor,
-                            gio_poll_destroy);
+        g_io_add_watch_full(channel, conv_prio_libqb2glib(p), evts,
+                            gio_read_socket, adaptor, gio_poll_destroy);
 
     /* Now that mainloop now holds a reference to channel,
      * thanks to g_io_add_watch_full(), drop ours from g_io_channel_unix_new().
@@ -640,7 +699,15 @@ pick_ipc_type(enum qb_ipc_type requested)
 
 qb_ipcs_service_t *
 mainloop_add_ipc_server(const char *name, enum qb_ipc_type type,
-                        struct qb_ipcs_service_handlers * callbacks)
+                        struct qb_ipcs_service_handlers *callbacks)
+{
+    return mainloop_add_ipc_server_with_prio(name, type, callbacks, QB_LOOP_MED);
+}
+
+qb_ipcs_service_t *
+mainloop_add_ipc_server_with_prio(const char *name, enum qb_ipc_type type,
+                                  struct qb_ipcs_service_handlers *callbacks,
+                                  enum qb_loop_priority prio)
 {
     int rc = 0;
     qb_ipcs_service_t *server = NULL;
@@ -652,6 +719,15 @@ mainloop_add_ipc_server(const char *name, enum qb_ipc_type type,
     crm_client_init();
     server = qb_ipcs_create(name, 0, pick_ipc_type(type), callbacks);
 
+    if (server == NULL) {
+        crm_err("Could not create %s IPC server: %s (%d)", name, pcmk_strerror(rc), rc);
+        return NULL;
+    }
+
+    if (prio != QB_LOOP_MED) {
+        qb_ipcs_request_rate_limit(server, conv_libqb_prio2ratelimit(prio));
+    }
+
 #ifdef HAVE_IPCS_GET_BUFFER_SIZE
     /* All clients should use at least ipc_buffer_max as their buffer size */
     qb_ipcs_enforce_buffer_size(server, crm_ipc_default_buffer_size());
-- 
1.8.3.1


From 3401f25994e8cc059898550082f9b75f2d07f103 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jan=20Pokorn=C3=BD?= <jpokorny@redhat.com>
Date: Wed, 29 Aug 2018 15:50:57 +0200
Subject: [PATCH 2/2] High: stonith-ng's function cannot be blocked with CIB
 updates forever

In the high-load (or high-rate-config-change) scenarios,
pacemaker-fenced would be unable to provide service when basically DoS'd
with CIB update notifications.  Try to reconcile that with elevated
priority of the server's proper listening interface in the mainloop, at
worst, it will try to fence with slightly outdated config, but appears
to be less bad than not carrying the execution at all, for instance.
Other daemons might be considered as well.

Prerequisites:
- https://github.com/ClusterLabs/libqb/pull/352
  (libqb used to contain a bug due to which one particular step in the
  initial-client-connection-accepting-at-the-server procedure that would
  be carried out with hard-coded (and hence possibly lower than competing
  events') priority, which backfires exactly in this case (once the
  pacemaker part is fixed -- by the means of elevating priority for
  the API end-point of fenced so that it won't get consistently
  overridden with a non-socket-based event source/trigger)

How to verify:
- mocked/based -N (see commit adding that module to mocked based daemon)
---
 lib/common/utils.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/common/utils.c b/lib/common/utils.c
index 758eb1b..d1c3e26 100644
--- a/lib/common/utils.c
+++ b/lib/common/utils.c
@@ -1031,7 +1031,8 @@ attrd_ipc_server_init(qb_ipcs_service_t **ipcs, struct qb_ipcs_service_handlers
 void
 stonith_ipc_server_init(qb_ipcs_service_t **ipcs, struct qb_ipcs_service_handlers *cb)
 {
-    *ipcs = mainloop_add_ipc_server("stonith-ng", QB_IPC_NATIVE, cb);
+    *ipcs = mainloop_add_ipc_server_with_prio("stonith-ng", QB_IPC_NATIVE, cb,
+                                              QB_LOOP_HIGH);
 
     if (*ipcs == NULL) {
         crm_err("Failed to create fencer: exiting and inhibiting respawn.");
-- 
1.8.3.1