pcmk_sched_resource.c

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/*
 * Copyright 2014-2022 the Pacemaker project contributors
 *
 * The version control history for this file may have further details.
 *
 * This source code is licensed under the GNU General Public License version 2
 * or later (GPLv2+) WITHOUT ANY WARRANTY.
 */
 
#include <crm_internal.h>
 
#include <stdlib.h>
#include <string.h>
#include <crm/msg_xml.h>
#include <pacemaker-internal.h>
 
#include "libpacemaker_private.h"
 
// Resource allocation methods that vary by resource variant
static resource_alloc_functions_t allocation_methods[] = {
    {
        pcmk__primitive_assign,
        pcmk__primitive_create_actions,
        pcmk__probe_rsc_on_node,
        pcmk__primitive_internal_constraints,
        pcmk__primitive_apply_coloc_score,
        pcmk__colocated_resources,
        pcmk__apply_location,
        pcmk__primitive_action_flags,
        pcmk__update_ordered_actions,
        pcmk__output_resource_actions,
        pcmk__add_rsc_actions_to_graph,
        pcmk__primitive_add_graph_meta,
        pcmk__primitive_add_utilization,
        pcmk__primitive_shutdown_lock,
    },
    {
        pcmk__group_assign,
        pcmk__group_create_actions,
        pcmk__probe_rsc_on_node,
        pcmk__group_internal_constraints,
        pcmk__group_apply_coloc_score,
        pcmk__group_colocated_resources,
        pcmk__group_apply_location,
        pcmk__group_action_flags,
        pcmk__group_update_ordered_actions,
        pcmk__output_resource_actions,
        pcmk__add_rsc_actions_to_graph,
        pcmk__noop_add_graph_meta,
        pcmk__group_add_utilization,
        pcmk__group_shutdown_lock,
    },
    {
        pcmk__clone_allocate,
        clone_create_actions,
        clone_create_probe,
        clone_internal_constraints,
        pcmk__clone_apply_coloc_score,
        pcmk__colocated_resources,
        clone_rsc_location,
        clone_action_flags,
        pcmk__multi_update_actions,
        pcmk__output_resource_actions,
        clone_expand,
        clone_append_meta,
        pcmk__clone_add_utilization,
        pcmk__clone_shutdown_lock,
    },
    {
        pcmk__bundle_allocate,
        pcmk__bundle_create_actions,
        pcmk__bundle_create_probe,
        pcmk__bundle_internal_constraints,
        pcmk__bundle_apply_coloc_score,
        pcmk__colocated_resources,
        pcmk__bundle_rsc_location,
        pcmk__bundle_action_flags,
        pcmk__multi_update_actions,
        pcmk__output_bundle_actions,
        pcmk__bundle_expand,
        pcmk__noop_add_graph_meta,
        pcmk__bundle_add_utilization,
        pcmk__bundle_shutdown_lock,
    }
};
 
bool
pcmk__rsc_agent_changed(pe_resource_t *rsc, pe_node_t *node,
                        const xmlNode *rsc_entry, bool active_on_node)
{
    bool changed = false;
    const char *attr_list[] = {
        XML_ATTR_TYPE,
        XML_AGENT_ATTR_CLASS,
        XML_AGENT_ATTR_PROVIDER
    };
 
    for (int i = 0; i < PCMK__NELEM(attr_list); i++) {
        const char *value = crm_element_value(rsc->xml, attr_list[i]);
        const char *old_value = crm_element_value(rsc_entry, attr_list[i]);
 
        if (!pcmk__str_eq(value, old_value, pcmk__str_none)) {
            changed = true;
            trigger_unfencing(rsc, node, "Device definition changed", NULL,
                              rsc->cluster);
            if (active_on_node) {
                crm_notice("Forcing restart of %s on %s "
                           "because %s changed from '%s' to '%s'",
                           rsc->id, pe__node_name(node), attr_list[i],
                           pcmk__s(old_value, ""), pcmk__s(value, ""));
            }
        }
    }
    if (changed && active_on_node) {
        // Make sure the resource is restarted
        custom_action(rsc, stop_key(rsc), CRMD_ACTION_STOP, node, FALSE, TRUE,
                      rsc->cluster);
        pe__set_resource_flags(rsc, pe_rsc_start_pending);
    }
    return changed;
}
 
static GList *
add_rsc_if_matching(GList *result, pe_resource_t *rsc, const char *id)
{
    if ((strcmp(rsc->id, id) == 0)
        || ((rsc->clone_name != NULL) && (strcmp(rsc->clone_name, id) == 0))) {
        result = g_list_prepend(result, rsc);
    }
    for (GList *iter = rsc->children; iter != NULL; iter = iter->next) {
        pe_resource_t *child = (pe_resource_t *) iter->data;
 
        result = add_rsc_if_matching(result, child, id);
    }
    return result;
}
 
GList *
pcmk__rscs_matching_id(const char *id, pe_working_set_t *data_set)
{
    GList *result = NULL;
 
    CRM_CHECK((id != NULL) && (data_set != NULL), return NULL);
    for (GList *iter = data_set->resources; iter != NULL; iter = iter->next) {
        result = add_rsc_if_matching(result, (pe_resource_t *) iter->data, id);
    }
    return result;
}
 
static void
set_allocation_methods_for_rsc(pe_resource_t *rsc, void *ignored)
{
    rsc->cmds = &allocation_methods[rsc->variant];
    g_list_foreach(rsc->children, (GFunc) set_allocation_methods_for_rsc, NULL);
}
 
void
pcmk__set_allocation_methods(pe_working_set_t *data_set)
{
    g_list_foreach(data_set->resources, (GFunc) set_allocation_methods_for_rsc,
                   NULL);
}
 
// Shared implementation of resource_alloc_functions_t:colocated_resources()
GList *
pcmk__colocated_resources(pe_resource_t *rsc, pe_resource_t *orig_rsc,
                          GList *colocated_rscs)
{
    GList *gIter = NULL;
 
    if (orig_rsc == NULL) {
        orig_rsc = rsc;
    }
 
    if ((rsc == NULL) || (g_list_find(colocated_rscs, rsc) != NULL)) {
        return colocated_rscs;
    }
 
    pe_rsc_trace(orig_rsc, "%s is in colocation chain with %s",
                 rsc->id, orig_rsc->id);
    colocated_rscs = g_list_append(colocated_rscs, rsc);
 
    // Follow colocations where this resource is the dependent resource
    for (gIter = rsc->rsc_cons; gIter != NULL; gIter = gIter->next) {
        pcmk__colocation_t *constraint = (pcmk__colocation_t *) gIter->data;
        pe_resource_t *primary = constraint->primary;
 
        if (primary == orig_rsc) {
            continue; // Break colocation loop
        }
 
        if ((constraint->score == INFINITY) &&
            (pcmk__colocation_affects(rsc, primary, constraint,
                                      true) == pcmk__coloc_affects_location)) {
 
            colocated_rscs = primary->cmds->colocated_resources(primary,
                                                                orig_rsc,
                                                                colocated_rscs);
        }
    }
 
    // Follow colocations where this resource is the primary resource
    for (gIter = rsc->rsc_cons_lhs; gIter != NULL; gIter = gIter->next) {
        pcmk__colocation_t *constraint = (pcmk__colocation_t *) gIter->data;
        pe_resource_t *dependent = constraint->dependent;
 
        if (dependent == orig_rsc) {
            continue; // Break colocation loop
        }
 
        if (pe_rsc_is_clone(rsc) && !pe_rsc_is_clone(dependent)) {
            continue; // We can't be sure whether dependent will be colocated
        }
 
        if ((constraint->score == INFINITY) &&
            (pcmk__colocation_affects(dependent, rsc, constraint,
                                      true) == pcmk__coloc_affects_location)) {
 
            colocated_rscs = dependent->cmds->colocated_resources(dependent,
                                                                  orig_rsc,
                                                                  colocated_rscs);
        }
    }
 
    return colocated_rscs;
}
 
// No-op function for variants that don't need to implement add_graph_meta()
void
pcmk__noop_add_graph_meta(pe_resource_t *rsc, xmlNode *xml)
{
}
 
void
pcmk__output_resource_actions(pe_resource_t *rsc)
{
    pcmk__output_t *out = rsc->cluster->priv;
 
    pe_node_t *next = NULL;
    pe_node_t *current = NULL;
 
    if (rsc->children != NULL) {
        for (GList *iter = rsc->children; iter != NULL; iter = iter->next) {
            pe_resource_t *child = (pe_resource_t *) iter->data;
 
            child->cmds->output_actions(child);
        }
        return;
    }
 
    next = rsc->allocated_to;
    if (rsc->running_on) {
        current = pe__current_node(rsc);
        if (rsc->role == RSC_ROLE_STOPPED) {
            /* This can occur when resources are being recovered because
             * the current role can change in pcmk__primitive_create_actions()
             */
            rsc->role = RSC_ROLE_STARTED;
        }
    }
 
    if ((current == NULL) && pcmk_is_set(rsc->flags, pe_rsc_orphan)) {
        /* Don't log stopped orphans */
        return;
    }
 
    out->message(out, "rsc-action", rsc, current, next);
}
 
bool
pcmk__finalize_assignment(pe_resource_t *rsc, pe_node_t *chosen, bool force)
{
    pcmk__output_t *out = rsc->cluster->priv;
 
    CRM_ASSERT(rsc->variant == pe_native);
 
    if (!force && (chosen != NULL)) {
        if ((chosen->weight < 0)
            // Allow the graph to assume that guest node connections will come up
            || (!pcmk__node_available(chosen, true, false)
                && !pe__is_guest_node(chosen))) {
 
            crm_debug("All nodes for resource %s are unavailable, unclean or "
                      "shutting down (%s can%s run resources, with weight %d)",
                      rsc->id, pe__node_name(chosen),
                      (pcmk__node_available(chosen, true, false)? "" : "not"),
                      chosen->weight);
            pe__set_next_role(rsc, RSC_ROLE_STOPPED, "node availability");
            chosen = NULL;
        }
    }
 
    pcmk__unassign_resource(rsc);
    pe__clear_resource_flags(rsc, pe_rsc_provisional);
 
    if (chosen == NULL) {
        crm_debug("Could not allocate a node for %s", rsc->id);
        pe__set_next_role(rsc, RSC_ROLE_STOPPED, "unable to allocate");
 
        for (GList *iter = rsc->actions; iter != NULL; iter = iter->next) {
            pe_action_t *op = (pe_action_t *) iter->data;
 
            crm_debug("Updating %s for allocation failure", op->uuid);
 
            if (pcmk__str_eq(op->task, RSC_STOP, pcmk__str_casei)) {
                pe__clear_action_flags(op, pe_action_optional);
 
            } else if (pcmk__str_eq(op->task, RSC_START, pcmk__str_casei)) {
                pe__clear_action_flags(op, pe_action_runnable);
                //pe__set_resource_flags(rsc, pe_rsc_block);
 
            } else {
                // Cancel recurring actions, unless for stopped state
                const char *interval_ms_s = NULL;
                const char *target_rc_s = NULL;
                char *rc_stopped = pcmk__itoa(PCMK_OCF_NOT_RUNNING);
 
                interval_ms_s = g_hash_table_lookup(op->meta,
                                                    XML_LRM_ATTR_INTERVAL_MS);
                target_rc_s = g_hash_table_lookup(op->meta,
                                                  XML_ATTR_TE_TARGET_RC);
                if ((interval_ms_s != NULL)
                    && !pcmk__str_eq(interval_ms_s, "0", pcmk__str_none)
                    && !pcmk__str_eq(rc_stopped, target_rc_s, pcmk__str_none)) {
                    pe__clear_action_flags(op, pe_action_runnable);
                }
                free(rc_stopped);
            }
        }
        return false;
    }
 
    crm_debug("Assigning %s to %s", rsc->id, pe__node_name(chosen));
    rsc->allocated_to = pe__copy_node(chosen);
 
    chosen->details->allocated_rsc = g_list_prepend(chosen->details->allocated_rsc,
                                                    rsc);
    chosen->details->num_resources++;
    chosen->count++;
    pcmk__consume_node_capacity(chosen->details->utilization, rsc);
 
    if (pcmk_is_set(rsc->cluster->flags, pe_flag_show_utilization)) {
        out->message(out, "resource-util", rsc, chosen, __func__);
    }
    return true;
}
 
bool
pcmk__assign_resource(pe_resource_t *rsc, pe_node_t *node, bool force)
{
    bool changed = false;
 
    if (rsc->children == NULL) {
        if (rsc->allocated_to != NULL) {
            changed = true;
        }
        pcmk__finalize_assignment(rsc, node, force);
 
    } else {
        for (GList *iter = rsc->children; iter != NULL; iter = iter->next) {
            pe_resource_t *child_rsc = (pe_resource_t *) iter->data;
 
            changed |= pcmk__assign_resource(child_rsc, node, force);
        }
    }
    return changed;
}
 
void
pcmk__unassign_resource(pe_resource_t *rsc)
{
    pe_node_t *old = rsc->allocated_to;
 
    if (old == NULL) {
        return;
    }
 
    crm_info("Unassigning %s from %s", rsc->id, pe__node_name(old));
    pe__set_resource_flags(rsc, pe_rsc_provisional);
    rsc->allocated_to = NULL;
 
    /* We're going to free the pe_node_t, but its details member is shared and
     * will remain, so update that appropriately first.
     */
    old->details->allocated_rsc = g_list_remove(old->details->allocated_rsc,
                                                rsc);
    old->details->num_resources--;
    pcmk__release_node_capacity(old->details->utilization, rsc);
    free(old);
}
 
bool
pcmk__threshold_reached(pe_resource_t *rsc, pe_node_t *node,
                        pe_resource_t **failed)
{
    int fail_count, remaining_tries;
    pe_resource_t *rsc_to_ban = rsc;
 
    // Migration threshold of 0 means never force away
    if (rsc->migration_threshold == 0) {
        return false;
    }
 
    // If we're ignoring failures, also ignore the migration threshold
    if (pcmk_is_set(rsc->flags, pe_rsc_failure_ignored)) {
        return false;
    }
 
    // If there are no failures, there's no need to force away
    fail_count = pe_get_failcount(node, rsc, NULL,
                                  pe_fc_effective|pe_fc_fillers, NULL,
                                  rsc->cluster);
    if (fail_count <= 0) {
        return false;
    }
 
    // If failed resource is anonymous clone instance, we'll force clone away
    if (!pcmk_is_set(rsc->flags, pe_rsc_unique)) {
        rsc_to_ban = uber_parent(rsc);
    }
 
    // How many more times recovery will be tried on this node
    remaining_tries = rsc->migration_threshold - fail_count;
 
    if (remaining_tries <= 0) {
        crm_warn("%s cannot run on %s due to reaching migration threshold "
                 "(clean up resource to allow again)"
                 CRM_XS " failures=%d migration-threshold=%d",
                 rsc_to_ban->id, pe__node_name(node), fail_count,
                 rsc->migration_threshold);
        if (failed != NULL) {
            *failed = rsc_to_ban;
        }
        return true;
    }
 
    crm_info("%s can fail %d more time%s on "
             "%s before reaching migration threshold (%d)",
             rsc_to_ban->id, remaining_tries, pcmk__plural_s(remaining_tries),
             pe__node_name(node), rsc->migration_threshold);
    return false;
}
 
static void *
convert_const_pointer(const void *ptr)
{
    /* Worst function ever */
    return (void *)ptr;
}
 
static int
get_node_weight(pe_node_t *node, GHashTable *nodes)
{
    pe_node_t *weighted_node = NULL;
 
    if ((node != NULL) && (nodes != NULL)) {
        weighted_node = g_hash_table_lookup(nodes, node->details->id);
    }
    return (weighted_node == NULL)? -INFINITY : weighted_node->weight;
}
 
static gint
cmp_resources(gconstpointer a, gconstpointer b, gpointer data)
{
    const pe_resource_t *resource1 = a;
    const pe_resource_t *resource2 = b;
    GList *nodes = (GList *) data;
 
    int rc = 0;
    int r1_weight = -INFINITY;
    int r2_weight = -INFINITY;
    pe_node_t *r1_node = NULL;
    pe_node_t *r2_node = NULL;
    GHashTable *r1_nodes = NULL;
    GHashTable *r2_nodes = NULL;
    const char *reason = NULL;
 
    // Resources with highest priority should be allocated first
    reason = "priority";
    r1_weight = resource1->priority;
    r2_weight = resource2->priority;
    if (r1_weight > r2_weight) {
        rc = -1;
        goto done;
    }
    if (r1_weight < r2_weight) {
        rc = 1;
        goto done;
    }
 
    // We need nodes to make any other useful comparisons
    reason = "no node list";
    if (nodes == NULL) {
        goto done;
    }
 
    // Calculate and log node weights
    pcmk__add_colocated_node_scores(convert_const_pointer(resource1),
                                    resource1->id, &r1_nodes, NULL, 1,
                                    pcmk__coloc_select_this_with);
    pcmk__add_colocated_node_scores(convert_const_pointer(resource2),
                                    resource2->id, &r2_nodes, NULL, 1,
                                    pcmk__coloc_select_this_with);
    pe__show_node_weights(true, NULL, resource1->id, r1_nodes,
                          resource1->cluster);
    pe__show_node_weights(true, NULL, resource2->id, r2_nodes,
                          resource2->cluster);
 
    // The resource with highest score on its current node goes first
    reason = "current location";
    if (resource1->running_on != NULL) {
        r1_node = pe__current_node(resource1);
    }
    if (resource2->running_on != NULL) {
        r2_node = pe__current_node(resource2);
    }
    r1_weight = get_node_weight(r1_node, r1_nodes);
    r2_weight = get_node_weight(r2_node, r2_nodes);
    if (r1_weight > r2_weight) {
        rc = -1;
        goto done;
    }
    if (r1_weight < r2_weight) {
        rc = 1;
        goto done;
    }
 
    // Otherwise a higher weight on any node will do
    reason = "score";
    for (GList *iter = nodes; iter != NULL; iter = iter->next) {
        pe_node_t *node = (pe_node_t *) iter->data;
 
        r1_weight = get_node_weight(node, r1_nodes);
        r2_weight = get_node_weight(node, r2_nodes);
        if (r1_weight > r2_weight) {
            rc = -1;
            goto done;
        }
        if (r1_weight < r2_weight) {
            rc = 1;
            goto done;
        }
    }
 
done:
    crm_trace("%s (%d)%s%s %c %s (%d)%s%s: %s",
              resource1->id, r1_weight,
              ((r1_node == NULL)? "" : " on "),
              ((r1_node == NULL)? "" : r1_node->details->id),
              ((rc < 0)? '>' : ((rc > 0)? '<' : '=')),
              resource2->id, r2_weight,
              ((r2_node == NULL)? "" : " on "),
              ((r2_node == NULL)? "" : r2_node->details->id),
              reason);
    if (r1_nodes != NULL) {
        g_hash_table_destroy(r1_nodes);
    }
    if (r2_nodes != NULL) {
        g_hash_table_destroy(r2_nodes);
    }
    return rc;
}
 
void
pcmk__sort_resources(pe_working_set_t *data_set)
{
    GList *nodes = g_list_copy(data_set->nodes);
 
    nodes = pcmk__sort_nodes(nodes, NULL);
    data_set->resources = g_list_sort_with_data(data_set->resources,
                                                cmp_resources, nodes);
    g_list_free(nodes);
}
 
static GHashTable *
new_node_table(pe_node_t *node)
{
    GHashTable *table = pcmk__strkey_table(NULL, free);
 
    node = pe__copy_node(node);
    g_hash_table_insert(table, (gpointer) node->details->id, node);
    return table;
}
 
static void
apply_parent_colocations(const pe_resource_t *rsc, GHashTable **nodes)
{
    GList *iter = NULL;
    pcmk__colocation_t *colocation = NULL;
 
    for (iter = rsc->parent->rsc_cons; iter != NULL; iter = iter->next) {
        colocation = (pcmk__colocation_t *) iter->data;
        pcmk__add_colocated_node_scores(colocation->primary, rsc->id, nodes,
                                        colocation->node_attribute,
                                        colocation->score / (float) INFINITY,
                                        pcmk__coloc_select_default);
    }
    for (iter = rsc->parent->rsc_cons_lhs; iter != NULL; iter = iter->next) {
        colocation = (pcmk__colocation_t *) iter->data;
        if (!pcmk__colocation_has_influence(colocation, rsc)) {
            continue;
        }
        pcmk__add_colocated_node_scores(colocation->dependent, rsc->id, nodes,
                                        colocation->node_attribute,
                                        colocation->score / (float) INFINITY,
                                        pcmk__coloc_select_nonnegative);
    }
}
 
static int
cmp_instance_by_colocation(const pe_resource_t *instance1,
                           const pe_resource_t *instance2)
{
    int rc = 0;
    pe_node_t *node1 = NULL;
    pe_node_t *node2 = NULL;
    pe_node_t *current_node1 = pe__current_node(instance1);
    pe_node_t *current_node2 = pe__current_node(instance2);
    GHashTable *colocated_scores1 = NULL;
    GHashTable *colocated_scores2 = NULL;
 
    CRM_ASSERT((instance1 != NULL) && (instance1->parent != NULL)
               && (instance2 != NULL) && (instance2->parent != NULL)
               && (current_node1 != NULL) && (current_node2 != NULL));
 
    // Create node tables initialized with each node
    colocated_scores1 = new_node_table(current_node1);
    colocated_scores2 = new_node_table(current_node2);
 
    // Apply parental colocations
    apply_parent_colocations(instance1, &colocated_scores1);
    apply_parent_colocations(instance2, &colocated_scores2);
 
    // Find original nodes again, with scores updated for colocations
    node1 = g_hash_table_lookup(colocated_scores1, current_node1->details->id);
    node2 = g_hash_table_lookup(colocated_scores2, current_node2->details->id);
 
    // Compare nodes by updated scores
    if (node1->weight < node2->weight) {
        crm_trace("Assign %s (%d on %s) after %s (%d on %s)",
                  instance1->id, node1->weight, pe__node_name(node1),
                  instance2->id, node2->weight, pe__node_name(node2));
        rc = 1;
 
    } else if (node1->weight > node2->weight) {
        crm_trace("Assign %s (%d on %s) before %s (%d on %s)",
                  instance1->id, node1->weight, pe__node_name(node1),
                  instance2->id, node2->weight, pe__node_name(node2));
        rc = -1;
    }
 
    g_hash_table_destroy(colocated_scores1);
    g_hash_table_destroy(colocated_scores2);
    return rc;
}
 
static bool
did_fail(const pe_resource_t * rsc)
{
    if (pcmk_is_set(rsc->flags, pe_rsc_failed)) {
        return true;
    }
    for (GList *iter = rsc->children; iter != NULL; iter = iter->next) {
        if (did_fail((pe_resource_t *) iter->data)) {
            return true;
        }
    }
    return false;
}
 
static bool
node_is_allowed(const pe_resource_t *rsc, pe_node_t **node)
{
    if (*node != NULL) {
        pe_node_t *allowed = pe_hash_table_lookup(rsc->allowed_nodes,
                                                  (*node)->details->id);
        if ((allowed == NULL) || (allowed->weight < 0)) {
            pe_rsc_trace(rsc, "%s: current location (%s) is unavailable",
                         rsc->id, pe__node_name(*node));
            *node = NULL;
            return false;
        }
    }
    return true;
}
 
gint
pcmk__cmp_instance_number(gconstpointer a, gconstpointer b)
{
    const pe_resource_t *instance1 = (const pe_resource_t *) a;
    const pe_resource_t *instance2 = (const pe_resource_t *) b;
    char *div1 = NULL;
    char *div2 = NULL;
 
    CRM_ASSERT((instance1 != NULL) && (instance2 != NULL));
 
    // Clone numbers are after a colon, bundle numbers after a dash
    div1 = strrchr(instance1->id, ':');
    if (div1 == NULL) {
        div1 = strrchr(instance1->id, '-');
    }
    div2 = strrchr(instance2->id, ':');
    if (div2 == NULL) {
        div2 = strrchr(instance2->id, '-');
    }
    CRM_ASSERT((div1 != NULL) && (div2 != NULL));
 
    return (gint) (strtol(div1 + 1, NULL, 10) - strtol(div2 + 1, NULL, 10));
}
 
gint
pcmk__cmp_instance(gconstpointer a, gconstpointer b)
{
    int rc = 0;
    pe_node_t *node1 = NULL;
    pe_node_t *node2 = NULL;
    unsigned int nnodes1 = 0;
    unsigned int nnodes2 = 0;
 
    bool can1 = true;
    bool can2 = true;
 
    const pe_resource_t *instance1 = (const pe_resource_t *) a;
    const pe_resource_t *instance2 = (const pe_resource_t *) b;
 
    CRM_ASSERT((instance1 != NULL) && (instance2 != NULL));
 
    node1 = pe__find_active_on(instance1, &nnodes1, NULL);
    node2 = pe__find_active_on(instance2, &nnodes2, NULL);
 
    /* If both instances are running and at least one is multiply
     * active, prefer instance that's running on fewer nodes.
     */
    if ((nnodes1 > 0) && (nnodes2 > 0)) {
        if (nnodes1 < nnodes2) {
            crm_trace("Assign %s (active on %d) before %s (active on %d): "
                      "less multiply active",
                      instance1->id, nnodes1, instance2->id, nnodes2);
            return -1;
 
        } else if (nnodes1 > nnodes2) {
            crm_trace("Assign %s (active on %d) after %s (active on %d): "
                      "more multiply active",
                      instance1->id, nnodes1, instance2->id, nnodes2);
            return 1;
        }
    }
 
    /* An instance that is either inactive or active on an allowed node is
     * preferred over an instance that is active on a no-longer-allowed node.
     */
    can1 = node_is_allowed(instance1, &node1);
    can2 = node_is_allowed(instance2, &node2);
    if (can1 && !can2) {
        crm_trace("Assign %s before %s: not active on a disallowed node",
                  instance1->id, instance2->id);
        return -1;
 
    } else if (!can1 && can2) {
        crm_trace("Assign %s after %s: active on a disallowed node",
                  instance1->id, instance2->id);
        return 1;
    }
 
    // Prefer instance with higher configured priority
    if (instance1->priority > instance2->priority) {
        crm_trace("Assign %s before %s: priority (%d > %d)",
                  instance1->id, instance2->id,
                  instance1->priority, instance2->priority);
        return -1;
 
    } else if (instance1->priority < instance2->priority) {
        crm_trace("Assign %s after %s: priority (%d < %d)",
                  instance1->id, instance2->id,
                  instance1->priority, instance2->priority);
        return 1;
    }
 
    // Prefer active instance
    if ((node1 == NULL) && (node2 == NULL)) {
        crm_trace("No assignment preference for %s vs. %s: inactive",
                  instance1->id, instance2->id);
        return 0;
 
    } else if (node1 == NULL) {
        crm_trace("Assign %s after %s: active", instance1->id, instance2->id);
        return 1;
 
    } else if (node2 == NULL) {
        crm_trace("Assign %s before %s: active", instance1->id, instance2->id);
        return -1;
    }
 
    // Prefer instance whose current node can run resources
    can1 = pcmk__node_available(node1, false, false);
    can2 = pcmk__node_available(node2, false, false);
    if (can1 && !can2) {
        crm_trace("Assign %s before %s: current node can run resources",
                  instance1->id, instance2->id);
        return -1;
 
    } else if (!can1 && can2) {
        crm_trace("Assign %s after %s: current node can't run resources",
                  instance1->id, instance2->id);
        return 1;
    }
 
    // Prefer instance whose parent is allowed to run on instance's current node
    node1 = pcmk__top_allowed_node(instance1, node1);
    node2 = pcmk__top_allowed_node(instance2, node2);
    if ((node1 == NULL) && (node2 == NULL)) {
        crm_trace("No assignment preference for %s vs. %s: "
                  "parent not allowed on either instance's current node",
                  instance1->id, instance2->id);
        return 0;
 
    } else if (node1 == NULL) {
        crm_trace("Assign %s after %s: parent not allowed on current node",
                  instance1->id, instance2->id);
        return 1;
 
    } else if (node2 == NULL) {
        crm_trace("Assign %s before %s: parent allowed on current node",
                  instance1->id, instance2->id);
        return -1;
    }
 
    // Prefer instance whose current node is running fewer other instances
    if (node1->count < node2->count) {
        crm_trace("Assign %s before %s: fewer active instances on current node",
                  instance1->id, instance2->id);
        return -1;
 
    } else if (node1->count > node2->count) {
        crm_trace("Assign %s after %s: more active instances on current node",
                  instance1->id, instance2->id);
        return 1;
    }
 
    // Prefer failed instance
    can1 = did_fail(instance1);
    can2 = did_fail(instance2);
    if (!can1 && can2) {
        crm_trace("Assign %s before %s: failed", instance1->id, instance2->id);
        return -1;
    } else if (can1 && !can2) {
        crm_trace("Assign %s after %s: not failed",
                  instance1->id, instance2->id);
        return 1;
    }
 
    // Prefer instance with higher cumulative colocation score on current node
    rc = cmp_instance_by_colocation(instance1, instance2);
    if (rc != 0) {
        return rc;
    }
 
    // Prefer instance with lower instance number
    rc = pcmk__cmp_instance_number(instance1, instance2);
    if (rc < 0) {
        crm_trace("Assign %s before %s: instance number",
                  instance1->id, instance2->id);
    } else if (rc > 0) {
        crm_trace("Assign %s after %s: instance number",
                  instance1->id, instance2->id);
    } else {
        crm_trace("No assignment preference for %s vs. %s",
                  instance1->id, instance2->id);
    }
    return rc;
}