broker: use enclosing instance tbon.interface-hint unless overridden

doc/man5/flux-config-tbon.rst

@@ -89,6 +89,11 @@ interface-hint
      network address in CIDR form, e.g. ``10.0.2.0/24``.  NOTE: IPv6
      network addresses are not supported at this time.
 
+   This configured value may be overridden by setting the
+   ``tbon.interface-hint`` broker attribute on the command line.
+   It is inherited by sub-instances spawned for batch jobs and allocations.
+   Refer to :man7:`flux-broker-attributes` for more information.
+
 
 EXAMPLE
 =======

doc/man7/flux-broker-attributes.rst

@@ -188,12 +188,12 @@ tbon.prefertcp [Updates: C]
    with PMI, tcp:// endpoints will be used instead of ipc://, even if all
    brokers are on a single node.  Default: ``0``.
 
-tbon.interface-hint
-   When bootstrapping with PMI, tcp:// endpoints are chosen heuristically
+tbon.interface-hint [Updates: C, R]
+   When bootstrapping with PMI, tcp endpoints are chosen heuristically
    using one of the following methods:
 
    default-route
-      The address associated with the default route (the default hint).
+      The address associated with the default route (default, but see below).
    hostname
       The address associated with the system hostname.
    *interface*
@@ -203,6 +203,15 @@ tbon.interface-hint
      network address in CIDR form, e.g. ``10.0.2.0/24``.  NOTE: IPv6
      network addresses are not supported at this time.
 
+   If the attribute is not explicitly set, its value is assigned from
+   (in descending precedence):
+
+   1. the TOML configuration key of the same name
+   2. the :envvar:`FLUX_IPADDR_INTERFACE` or :envvar:`FLUX_IPADDR_HOSTNAME`
+      environment variables (these should be considered deprecated)
+   3. the enclosing Flux instance's value (via the PMI KVS)
+   4. the compiled-in default of default-route
+
 tbon.torpid_min [Updates: C, R]
    The amount of time (in RFC 23 Flux Standard Duration format) that a broker
    will allow the connection to its TBON parent to remain idle before sending a

src/broker/boot_config.c

@@ -599,6 +599,13 @@
      */
     overlay_set_ipv6 (overlay, conf.enable_ipv6);
 
+    /* Ensure that tbon.interface-hint is set.
+     */
+    if (overlay_set_tbon_interface_hint (overlay, NULL) < 0) {
+        log_err ("error setting tbon.interface-hint attribute");
+        goto error;
+    }
+
     /* If broker has "downstream" peers, determine the URI to bind to
      * from the config and tell overlay.  Also, set the tbon.endpoint
      * attribute to the URI peers will connect to.  If broker has no

src/broker/boot_pmi.c

@@ -36,27 +36,46 @@
  *  the booting instance at what "level" it will be running, i.e. the
  *  number of parents. If the PMI key is missing, this is not an error,
  *  instead the level of this instance is considered to be zero.
- *  Additionally, if level > 0, the shell will have put the instance's
- *  jobid in the PMI kvsname for us as well, so populate the 'jobid' attr.
  */
 static int set_instance_level_attr (struct upmi *upmi,
-                                    const char *name,
-                                    attr_t *attrs)
+                                    attr_t *attrs,
+                                    bool *under_flux)
 {
-    int rc;
     char *val = NULL;
-    const char *level = "0";
-    const char *jobid = NULL;
+    int rc = -1;
 
-    if (upmi_get (upmi, "flux.instance-level", -1, &val, NULL) == 0) {
-        level = val;
-        jobid = name;
-    }
-    rc = attr_add (attrs, "instance-level", level, ATTR_IMMUTABLE);
-    free (val);
-    if (rc < 0 || attr_add (attrs, "jobid", jobid, ATTR_IMMUTABLE) < 0)
-        return -1;
-    return 0;
+    (void)upmi_get (upmi, "flux.instance-level", -1, &val, NULL);
+    if (attr_add (attrs, "instance-level", val ? val : "0", ATTR_IMMUTABLE) < 0)
+        goto error;
+    *under_flux = val ? true : false;
+    rc = 0;
+error:
+    ERRNO_SAFE_WRAP (free, val);
+    return rc;
+}
+
+/* If the tbon.interface-hint broker attr is not already set, set it.
+ * If running under Flux, use the value, if any, placed in PMI KVS by
+ * the enclsoing instance.  Otherwise, set a default value.
+ */
+static int set_tbon_interface_hint_attr (struct upmi *upmi,
+                                         attr_t *attrs,
+                                         struct overlay *ov,
+                                         bool under_flux)
+{
+    char *val = NULL;
+    int rc = -1;
+
+    if (attr_get (attrs, "tbon.interface-hint", NULL, NULL) == 0)
+        return 0;
+    if (under_flux)
+        (void)upmi_get (upmi, "flux.tbon-interface-hint", -1, &val, NULL);
+    if (overlay_set_tbon_interface_hint (ov, val) < 0)
+        goto error;
+    rc = 0;
+error:
+    ERRNO_SAFE_WRAP (free, val);
+    return rc;
 }
 
 static char *pmi_mapping_to_taskmap (const char *s)
@@ -241,6 +260,7 @@
     int i;
     int upmi_flags = UPMI_LIBPMI_NOFLUX;
     const char *upmi_method;
+    bool under_flux;
 
     // N.B. overlay_create() sets the tbon.topo attribute
     if (attr_get (attrs, "tbon.topo", &topo_uri, NULL) < 0) {
@@ -264,10 +284,20 @@
         upmi_destroy (upmi);
         return -1;
     }
-    if (set_instance_level_attr (upmi, info.name, attrs) < 0) {
+    if (set_instance_level_attr (upmi, attrs, &under_flux) < 0) {
         log_err ("set_instance_level_attr");
         goto error;
     }
+    if (under_flux) {
+        if (attr_add (attrs, "jobid", info.name, ATTR_IMMUTABLE) < 0) {
+            log_err ("error setting jobid attribute");
+            goto error;
+        }
+    }
+    if (set_tbon_interface_hint_attr (upmi, attrs, overlay, under_flux) < 0) {
+        log_err ("error setting tbon.interface-hint attribute");
+        goto error;
+    }
     if (set_broker_mapping_attr (upmi, info.size, attrs) < 0) {
         log_err ("error setting broker.mapping attribute");
         goto error;

src/broker/overlay.c

@@ -2134,51 +2134,64 @@
     return -1;
 }
 
+/* This is called from boot_*.c with a default value to set if the attribute
+ * is not set already.
+ */
+int overlay_set_tbon_interface_hint (struct overlay *ov, const char *val)
+{
+    if (attr_get (ov->attrs, "tbon.interface-hint", NULL, NULL) == 0)
+        return 0;
+    if (!val)
+        val = default_interface_hint;
+    return attr_add (ov->attrs, "tbon.interface-hint", val, 0);
+}
+
+/* Set attribute with the following precedence:
+ * 1. broker attribute
+ * 2. TOML config
+ * 3. legacy environment variables
+ * Leave it unset if none of those are available.
+ * The bootstrap methods set it later, but only if not already set.
+ */
 static int overlay_configure_interface_hint (struct overlay *ov,
                                              const char *table,
-                                             const char *name,
-                                             const char *default_value)
+                                             const char *name)
 {
     char long_name[128];
-    const char *val;
-    const char *s;
+    const char *val = NULL;
+    const char *config_val = NULL;
+    const char *attr_val = NULL;
+    int flags;
     const flux_conf_t *cf;
+    flux_error_t error;
 
-    (void)snprintf (long_name, sizeof (long_name), "%s.%s", table, name);
-
-    /* Take initial value from compiled-in default or legacy
-     * environment variable settings.
-     */
-    if ((s = getenv ("FLUX_IPADDR_INTERFACE")))
-        val = s;
-    else if (getenv ("FLUX_IPADDR_HOSTNAME"))
-        val = "hostname";
-    else
-        val = default_value;
-
-    /* Override with config file settings, if any.
-     */
     if ((cf = flux_get_conf (ov->h))) {
-        flux_error_t error;
-
-        s = NULL;
-        if (flux_conf_unpack (flux_get_conf (ov->h),
+        if (flux_conf_unpack (cf,
                               &error,
                               "{s?{s?s}}",
                               table,
-                                name, &s) < 0) {
+                                name, &config_val) < 0) {
             log_msg ("Config file error [%s]: %s", table, error.text);
             return -1;
         }
-        if (s)
-            val = s;
     }
-    /* Override with broker attribute, if any.
-     * Then set broker attribute to reflect current value.
-     */
-    if (overlay_configure_attr (ov->attrs, long_name, val, NULL) < 0) {
-        log_err ("Error setting %s attribute", long_name);
-        return -1;
+    (void)snprintf (long_name, sizeof (long_name), "%s.%s", table, name);
+    (void)attr_get (ov->attrs, long_name, &attr_val, &flags);
+
+    if (attr_val)
+        val = attr_val;
+    else if (config_val)
+        val = config_val;
+    else if ((val = getenv ("FLUX_IPADDR_INTERFACE")))
+        ;
+    else if (getenv ("FLUX_IPADDR_HOSTNAME"))
+        val = "hostname";
+
+    if (val && !attr_val) {
+         if (attr_add (ov->attrs, long_name, val, 0) < 0) {
+            log_err ("Error setting %s attribute value", long_name);
+            return -1;
+         }
     }
     return 0;
 }
@@ -2502,10 +2515,7 @@
         goto nomem;
     if (overlay_configure_attr_int (ov->attrs, "tbon.prefertcp", 0, NULL) < 0)
         goto error;
-    if (overlay_configure_interface_hint (ov,
-                                          "tbon",
-                                          "interface-hint",
-                                          default_interface_hint) < 0)
+    if (overlay_configure_interface_hint (ov, "tbon", "interface-hint") < 0)
         goto error;
     if (overlay_configure_torpid (ov) < 0)
         goto error;
@@ -2567,7 +2577,6 @@
     return NULL;
 }
 
-
 /*
  * vi:tabstop=4 shiftwidth=4 expandtab
  */

src/broker/overlay.h

@@ -95,6 +95,7 @@ const char *overlay_get_uuid (struct overlay *ov);
 bool overlay_uuid_is_parent (struct overlay *ov, const char *uuid);
 bool overlay_uuid_is_child (struct overlay *ov, const char *uuid);
 void overlay_set_ipv6 (struct overlay *ov, int enable);
+int overlay_set_tbon_interface_hint (struct overlay *ov, const char *val);
 
 /* Return an idset of critical ranks, i.e. non-leaf brokers
  */

src/shell/pmi/pmi.c

@@ -423,6 +423,16 @@
     return 0;
 }
 
+static int set_flux_tbon_interface_hint (struct shell_pmi *pmi)
+{
+    const char *hint;
+
+    if (!(hint = flux_attr_get (pmi->shell->h, "tbon.interface-hint")))
+        return 0;
+    put_dict (pmi->locals, "flux.tbon-interface-hint", hint);
+    return 0;
+}
+
 static int set_flux_instance_level (struct shell_pmi *pmi)
 {
     char *p;
@@ -575,6 +585,7 @@
     if (!nomap && init_clique (pmi) < 0)
         goto error;
     if (set_flux_instance_level (pmi) < 0
+        || set_flux_tbon_interface_hint (pmi) < 0
         || (!nomap && set_flux_taskmap (pmi) < 0))
         goto error;
     return pmi;

t/Makefile.am

@@ -90,6 +90,7 @@ TESTSCRIPTS = \
 	t0016-cron-faketime.t \
 	t0017-security.t \
 	t0018-content-files.t \
+	t0019-tbon-config.t \
 	t0020-terminus.t \
 	t0021-archive-cmd.t \
 	t0022-jj-reader.t \