refactor broker overlay for topology flexibility

doc/man7/flux-broker-attributes.rst

@@ -146,7 +146,9 @@ TREE BASED OVERLAY NETWORK
 ==========================
 
 tbon.fanout [Updates: C]
-   Branching factor of the tree based overlay network.  Default: ``2``.
+   Branching factor of the tree based overlay network.  A value of ``0``
+   means the topology is "flat" (rank 0 is the parent of all other ranks).
+   Default: ``2``.
 
 tbon.descendants
    Number of descendants "below" this node of the tree based

etc/flux.service.in

@@ -11,7 +11,6 @@ ExecStart=/bin/bash -c '\
   @X_BINDIR@/flux broker \
   --config-path=@X_SYSCONFDIR@/flux/system/conf.d \
   -Scron.directory=@X_SYSCONFDIR@/flux/system/cron.d \
-  -Stbon.fanout=256 \
   -Srundir=@X_RUNSTATEDIR@/flux \
   -Sstatedir=${STATE_DIRECTORY:-/var/lib/flux} \
   -Slocal-uri=local://@X_RUNSTATEDIR@/flux/local \

src/broker/Makefile.am

@@ -65,7 +65,9 @@ libbroker_la_SOURCES = \
 	groups.h \
 	groups.c \
 	shutdown.h \
-	shutdown.c
+	shutdown.c \
+	topology.h \
+	topology.c
 
 flux_broker_LDADD = \
 	$(builddir)/libbroker.la \
@@ -88,7 +90,8 @@ TESTS = test_attr.t \
 	test_pmiutil.t \
 	test_boot_config.t \
 	test_runat.t \
-	test_overlay.t
+	test_overlay.t \
+	test_topology.t
 
 test_ldadd = \
 	$(builddir)/libbroker.la \
@@ -150,3 +153,8 @@ test_overlay_t_SOURCES = test/overlay.c
 test_overlay_t_CPPFLAGS = $(test_cppflags)
 test_overlay_t_LDADD = $(test_ldadd)
 test_overlay_t_LDFLAGS = $(test_ldflags)
+
+test_topology_t_SOURCES = test/topology.c
+test_topology_t_CPPFLAGS = $(test_cppflags)
+test_topology_t_LDADD = $(test_ldadd)
+test_topology_t_LDFLAGS = $(test_ldflags)

src/broker/attr.c

@@ -242,13 +242,14 @@ static int set_int (const char *name, const char *val, void *arg)
         errno = EINVAL;
         return -1;
     }
+    errno = 0;
     n = strtol (val, &endptr, 0);
-    if (n <= INT_MIN || n >= INT_MAX) {
-        errno = ERANGE;
+    if (errno != 0 || *endptr != '\0') {
+        errno = EINVAL;
         return -1;
     }
-    if (*endptr != '\0') {
-        errno = EINVAL;
+    if (n <= INT_MIN || n >= INT_MAX) {
+        errno = ERANGE;
         return -1;
     }
     *i = (int)n;
@@ -288,10 +289,9 @@ static int set_uint32 (const char *name, const char *val, void *arg)
     char *endptr;
     unsigned long n;
 
+    errno = 0;
     n = strtoul (val, &endptr, 0);
-    if (n == ULONG_MAX) /* ERANGE set by strtol */
-        return -1;
-    if (endptr == val || *endptr != '\0') {
+    if (errno != 0 || *endptr != '\0') {
         errno = EINVAL;
         return -1;
     }
@@ -314,6 +314,25 @@ int attr_add_active_uint32 (attr_t *attrs, const char *name, uint32_t *val,
     return attr_add_active (attrs, name, flags, get_uint32, set_uint32, val);
 }
 
+int attr_get_uint32 (attr_t *attrs, const char *name, uint32_t *value)
+{
+    const char *s;
+    uint32_t i;
+    char *endptr;
+
+    if (attr_get (attrs, name, &s, NULL) < 0)
+        return -1;
+
+    errno = 0;
+    i = strtoul (s, &endptr, 10);
+    if (errno != 0 || *endptr != '\0') {
+        errno = EINVAL;
+        return -1;
+    }
+    *value = i;
+    return 0;
+}
+
 const char *attr_first (attr_t *attrs)
 {
     struct entry *e = zhash_first (attrs->hash);

src/broker/attr.h

@@ -75,6 +75,10 @@ int attr_add_active_int (attr_t *attrs, const char *name, int *val,
 int attr_add_active_uint32 (attr_t *attrs, const char *name, uint32_t *val,
                             int flags);
 
+/* Get an attribute and parse it as an integer value.
+ */
+int attr_get_uint32 (attr_t *attrs, const char *name, uint32_t *value);
+
 /* Iterate over attribute names with internal cursor.
  */
 const char *attr_first (attr_t *attrs);

src/broker/boot_config.c

@@ -22,14 +22,16 @@
 #include <flux/hostlist.h>
 
 #include "src/common/libutil/log.h"
-#include "src/common/libutil/kary.h"
 #include "src/common/libutil/errno_safe.h"
 #include "src/common/libpmi/clique.h"
 
 #include "attr.h"
 #include "overlay.h"
+#include "topology.h"
 #include "boot_config.h"
 
+#define DEFAULT_FANOUT 0
+
 
 /* Copy 'fmt' into 'buf', substituting the following tokens:
  * - %h  host
@@ -456,8 +458,21 @@ int boot_config (flux_t *h, struct overlay *overlay, attr_t *attrs)
     struct boot_conf conf;
     uint32_t rank;
     uint32_t size;
-    int fanout = overlay_get_fanout (overlay);
+    uint32_t fanout;
     json_t *hosts = NULL;
+    struct topology *topo = NULL;
+
+    /* Fetch the tbon.fanout attribute and supply a default value if unset.
+     */
+    if (attr_get_uint32 (attrs, "tbon.fanout", &fanout) < 0)
+        fanout = DEFAULT_FANOUT;
+    else
+        (void)attr_delete (attrs, "tbon.fanout", true);
+    if (attr_add_uint32 (attrs,
+                         "tbon.fanout",
+                         fanout,
+                         FLUX_ATTRFLAG_IMMUTABLE) < 0)
+        return -1;
 
     /* Ingest the [bootstrap] stanza.
      */
@@ -492,7 +507,10 @@ int boot_config (flux_t *h, struct overlay *overlay, attr_t *attrs)
     /* Tell overlay network this broker's rank and size.
      * If a curve certificate was provided, load it.
      */
-    if (overlay_set_geometry (overlay, size, rank) < 0)
+    if (!(topo = topology_create (size))
+        || topology_set_kary (topo, fanout) < 0
+        || topology_set_rank (topo, rank) < 0
+        || overlay_set_topology (overlay, topo) < 0)
         goto error;
     if (conf.curve_cert) {
         if (overlay_cert_load (overlay, conf.curve_cert) < 0)
@@ -509,7 +527,7 @@ int boot_config (flux_t *h, struct overlay *overlay, attr_t *attrs)
      * attribute to the URI peers will connect to.  If broker has no
      * downstream peers, set tbon.endpoint to NULL.
      */
-    if (kary_childof (fanout, size, rank, 0) != KARY_NONE) {
+    if (topology_get_child_ranks (topo, NULL, 0) > 0) {
         char bind_uri[MAX_URI + 1];
         char my_uri[MAX_URI + 1];
 
@@ -559,7 +577,7 @@ int boot_config (flux_t *h, struct overlay *overlay, attr_t *attrs)
         char parent_uri[MAX_URI + 1];
         if (boot_config_geturibyrank (hosts,
                                       &conf,
-                                      kary_parentof (fanout, rank),
+                                      topology_get_parent (topo),
                                       parent_uri,
                                       sizeof (parent_uri)) < 0)
             goto error;
@@ -584,9 +602,11 @@ int boot_config (flux_t *h, struct overlay *overlay, attr_t *attrs)
         goto error;
     }
     json_decref (hosts);
+    topology_decref (topo);
     return 0;
 error:
     ERRNO_SAFE_WRAP (json_decref, hosts);
+    ERRNO_SAFE_WRAP (topology_decref, topo);
     return -1;
 }
 

src/broker/boot_pmi.c

@@ -20,17 +20,19 @@
 #include "src/common/libutil/log.h"
 #include "src/common/libutil/cleanup.h"
 #include "src/common/libutil/ipaddr.h"
-#include "src/common/libutil/kary.h"
 #include "src/common/libutil/errno_safe.h"
 #include "src/common/libpmi/pmi.h"
 #include "src/common/libpmi/pmi_strerror.h"
 #include "src/common/libpmi/clique.h"
 
 #include "attr.h"
 #include "overlay.h"
+#include "topology.h"
 #include "boot_pmi.h"
 #include "pmiutil.h"
 
+#define DEFAULT_FANOUT 2
+
 
 /*  If the broker is launched via flux-shell, then the shell may opt
  *  to set a "flux.instance-level" parameter in the PMI kvs to tell
@@ -178,8 +180,7 @@ static int set_hostlist_attr (attr_t *attrs, struct hostlist *hl)
 
 int boot_pmi (struct overlay *overlay, attr_t *attrs)
 {
-    int fanout = overlay_get_fanout (overlay);
-    int rank;
+    uint32_t fanout;
     char key[64];
     char val[1024];
     char hostname[MAXHOSTNAMELEN + 1];
@@ -188,10 +189,26 @@ int boot_pmi (struct overlay *overlay, attr_t *attrs)
     json_t *o;
     struct pmi_handle *pmi;
     struct pmi_params pmi_params;
+    struct topology *topo = NULL;
+    int child_count;
+    int *child_ranks = NULL;
     int result;
     const char *uri;
     int i;
 
+    /* Fetch the tbon.fanout attribute and supply a default value if unset.
+     */
+    if (attr_get_uint32 (attrs, "tbon.fanout", &fanout) < 0)
+        fanout = DEFAULT_FANOUT;
+    else
+        (void)attr_delete (attrs, "tbon.fanout", true);
+    if (attr_add_uint32 (attrs,
+                         "tbon.fanout",
+                         fanout,
+                         FLUX_ATTRFLAG_IMMUTABLE) < 0)
+        return -1;
+
+
     memset (&pmi_params, 0, sizeof (pmi_params));
     if (!(pmi = broker_pmi_create ())) {
         log_err ("broker_pmi_create");
@@ -215,9 +232,10 @@ int boot_pmi (struct overlay *overlay, attr_t *attrs)
         log_err ("error setting broker.mapping attribute");
         goto error;
     }
-    if (overlay_set_geometry (overlay,
-                              pmi_params.size,
-                              pmi_params.rank) < 0)
+    if (!(topo = topology_create (pmi_params.size))
+        || topology_set_kary (topo, fanout) < 0
+        || topology_set_rank (topo, pmi_params.rank) < 0
+        || overlay_set_topology (overlay, topo) < 0)
         goto error;
     if (gethostname (hostname, sizeof (hostname)) < 0) {
         log_err ("gethostname");
@@ -242,15 +260,17 @@ int boot_pmi (struct overlay *overlay, attr_t *attrs)
      */
     overlay_set_ipv6 (overlay, 1);
 
+    child_count = topology_get_child_ranks (topo, NULL, 0);
+    if (child_count > 0) {
+        if (!(child_ranks = calloc (child_count, sizeof (child_ranks[0])))
+            || topology_get_child_ranks (topo, child_ranks, child_count) < 0)
+            goto error;
+    }
+
     /* If there are to be downstream peers, then bind to socket and extract
      * the concretized URI for sharing with other ranks.
-     * N.B. there are no downstream peers if the 0th child of this rank
-     * in k-ary tree does not exist.
      */
-    if (kary_childof (fanout,
-                      pmi_params.size,
-                      pmi_params.rank,
-                      0) != KARY_NONE) {
+    if (child_count > 0) {
         char buf[1024];
 
         if (format_bind_uri (buf, sizeof (buf), attrs, pmi_params.rank) < 0)
@@ -306,8 +326,8 @@ int boot_pmi (struct overlay *overlay, attr_t *attrs)
     if (pmi_params.rank > 0) {
         const char *peer_pubkey;
         const char *peer_uri;
+        int rank = topology_get_parent (topo);
 
-        rank = kary_parentof (fanout, pmi_params.rank);
         if (snprintf (key, sizeof (key), "%d", rank) >= sizeof (key)) {
             log_msg ("pmi key string overflow");
             goto error;
@@ -343,12 +363,10 @@ int boot_pmi (struct overlay *overlay, attr_t *attrs)
 
     /* Fetch the business card of children and inform overlay of public keys.
      */
-    for (i = 0; i < fanout; i++) {
+    for (i = 0; i < child_count; i++) {
         const char *peer_pubkey;
+        int rank = child_ranks[i];
 
-        rank = kary_childof (fanout, pmi_params.size, pmi_params.rank, i);
-        if (rank == KARY_NONE)
-            break;
         if (snprintf (key, sizeof (key), "%d", rank) >= sizeof (key)) {
             log_msg ("pmi key string overflow");
             goto error;
@@ -427,11 +445,15 @@ int boot_pmi (struct overlay *overlay, attr_t *attrs)
     free (bizcard);
     broker_pmi_destroy (pmi);
     hostlist_destroy (hl);
+    free (child_ranks);
+    topology_decref (topo);
     return 0;
 error:
     free (bizcard);
     broker_pmi_destroy (pmi);
     hostlist_destroy (hl);
+    free (child_ranks);
+    topology_decref (topo);
     return -1;
 }
 

src/broker/broker.c

@@ -37,7 +37,6 @@
 #include "src/common/libutil/cleanup.h"
 #include "src/common/libidset/idset.h"
 #include "src/common/libutil/ipaddr.h"
-#include "src/common/libutil/kary.h"
 #include "src/common/libpmi/pmi.h"
 #include "src/common/libpmi/pmi_strerror.h"
 #include "src/common/libutil/fsd.h"