diff --git a/bin/compose-core b/bin/compose-core
index ffec7dc..00434a6 100755
--- a/bin/compose-core
+++ b/bin/compose-core
@@ -82,6 +82,9 @@ $WHITE$exname$NORMAL reads '/etc/compose.conf' for global variables, and
 "
 
 
+time_now() { date +%s.%3N; }
+time_elapsed() { echo "scale=3; $2 - $1" | bc; }
+
 ## XXXvlab: this doesn't seem to work when 'compose' is called in
 ## a hook of a charm.
 #[[ "${BASH_SOURCE[0]}" == "" ]] && SOURCED=true
@@ -1454,7 +1457,6 @@ export -f _get_service_charm_cached
 get_service_charm () {
     local service="$1"
     if [ -z "$service" ]; then
-        echo ${FUNCNAME[@]} >&2
         print_syntax_error "$FUNCNAME: Please specify a service as first argument."
         return 1
     fi
@@ -2474,10 +2476,15 @@ export -f get_compose_relations
 
 
 get_all_services() {
-    local cache_file="$state_tmpdir/$FUNCNAME.cache.$GLOBAL_ALL_RELATIONS_HASH" \
+    local services compose_yml_services service
+    if [ -z "$GLOBAL_ALL_RELATIONS_HASH" ]; then
+        err-d "Can't access global \$GLOBAL_ALL_RELATIONS_HASH"
+        return 1
+    fi
+    local cache_file="$CACHEDIR/$FUNCNAME.cache.$(H "$GLOBAL_ALL_RELATIONS_HASH" "$(declare -f "$FUNCNAME")")" \
           s rn ts rc td services service
     if [ -e "$cache_file" ]; then
-        #debug "$FUNCNAME: SESSION cache hit $1"
+        #debug "$FUNCNAME: cache hit $1"
         cat "$cache_file"
         return 0
     fi
@@ -2494,8 +2501,17 @@ get_all_services() {
             services["$service"]=1
             echo "$service"
         done
-    done < "$GLOBAL_ALL_RELATIONS" > "$cache_file"
+    done < "$GLOBAL_ALL_RELATIONS" > "$cache_file.wip"
+
+    compose_yml_services=($(compose:yml:root:services)) || return 1
 
+    for service in "${compose_yml_services[@]}"; do
+        [ "${services[$service]}" ] && continue
+        services["$service"]=1
+        echo "$service"
+    done >> "$cache_file.wip"
+
+    mv "$cache_file"{.wip,} || return 1
     cat "$cache_file"
 }
 export -f get_all_services
@@ -2559,28 +2575,25 @@ export -f get_service_relation
 ##    (base_service, relation_config)
 ##
 get_service_incoming_relations() {
-    local service="$1" relation="$2" cache_file="$state_tmpdir/$FUNCNAME.cache.$(H "$@" "$GLOBAL_ALL_RELATIONS_HASH")" \
-          s rn ts rc td
-    if [ -z "$GLOBAL_ALL_RELATIONS" ]; then
-        err-d "Can't access global \$GLOBAL_ALL_RELATIONS"
+    if [ -z "$SUBSET_ALL_RELATIONS_HASH" ]; then
+        err-d "Expected \$SUBSET_ALL_RELATIONS_HASH to be set."
         return 1
     fi
+    local service="$1" relation="$2" \
+          cache_file="$state_tmpdir/$FUNCNAME.cache.$(H "$@" "$SUBSET_ALL_RELATIONS_HASH")" \
+          s rn ts rc td
     if [ -e "$cache_file" ]; then
         #debug "$FUNCNAME: SESSION cache hit $1"
         cat "$cache_file"
         return 0
     fi
-    if [ -z "$GLOBAL_ALL_RELATIONS" ]; then
-        err "Can't access global \$GLOBAL_ALL_RELATIONS"
-        return 1
-    fi
-
     while read-0 s rn ts rc _td; do
         [[ "$ts" == "$service" ]] || continue
         [[ "$rn" == "$relation" ]] || continue
         relation_data_file=$(get_relation_data_file "$s" "$ts" "$rn" "$rc") || return 1
-        printf "%s\0" "$s" "$(cat "$relation_data_file")"
-    done < "$GLOBAL_ALL_RELATIONS" > "$cache_file"
+        printf "%s\0" "$s" "$(cat "$relation_data_file")" || return 1
+        debug "Found relation $rn from $s to $ts" >&2
+    done < "$SUBSET_ALL_RELATIONS" > "$cache_file"
 
     cat "$cache_file"
 }
@@ -2921,14 +2934,170 @@ _out_after_value_from_def() {
 }
 
 
-get_all_relations () {
-    local cache_file="$state_tmpdir/$FUNCNAME.cache.$(H "$@" "$(declare -p without_relations)")" \
-          services
+get_all_compose_yml_service() {
+    if [ -z "$COMPOSE_YML_CONTENT_HASH" ]; then
+        COMPOSE_YML_CONTENT_HASH=$(compose:yml:hash) || {
+            err "Failed to get compose yml hash"
+            return 1
+        }
+    fi
+    local cache_file="$CACHEDIR/$FUNCNAME.cache.$COMPOSE_YML_CONTENT_HASH"
+    if [ -e "${cache_file}" ]; then
+        #debug "$FUNCNAME: cache hit: ${cache_file}"
+        cat "${cache_file}"
+        return 0
+    fi
+    compose_yml_content=$(get_compose_yml_content) || return 1
+    printf "%s" "${compose_yml_content}" | shyaml keys-0 2>/dev/null > "${cache_file}.wip" || {
+        err "Failed to get keys of compose content."
+        return 1
+    }
+    mv "${cache_file}"{.wip,} || return 1
+    cat "${cache_file}"
+}
+
+
+## Outputs all relations array.
+_service:all:relations_cached() {
+    local services service E
+    services=($(compose:yml:root:services)) || return 1
+    get_all_relations "${services[@]}" || return 1
+}
+
+
+## Outputs all relations array.
+service:all:relations() {
+    if [ -z "$COMPOSE_YML_CONTENT_HASH" ]; then
+        COMPOSE_YML_CONTENT_HASH=$(compose:yml:hash) || {
+            err "Failed to get compose yml hash."
+            return 1
+        }
+    fi
+    local cache_file="$CACHEDIR/$FUNCNAME.cache.$COMPOSE_YML_CONTENT_HASH"
+    if [ -e "${cache_file}" ]; then
+        # debug "$FUNCNAME: SESSION cache hit $1"
+        cat "${cache_file}"
+        return 0
+    fi
+
+    _service:all:relations_cached > "${cache_file}.wip" || {
+        err-d "Failed to compute all relations."
+        return 1
+    }
+
+    mv "${cache_file}"{.wip,} || return 1
+    cat "${cache_file}"
+}
+
+_service:all:relations_hash_cached() {
+    if [ -z "$COMPOSE_YML_CONTENT_HASH" ]; then
+        COMPOSE_YML_CONTENT_HASH=$(compose:yml:hash) || {
+            err "Failed to get compose yml hash."
+            return 1
+        }
+    fi
+    local cache_file="$CACHEDIR/$FUNCNAME.cache.$COMPOSE_YML_CONTENT_HASH" \
+          hash
+    if [ -e "${cache_file}" ]; then
+        # debug "$FUNCNAME: SESSION cache hit $1"
+        cat "${cache_file}"
+        return 0
+    fi
+
+    service:all:relations > "${cache_file}.pre" || {
+        err-d "Failed to get all relations."
+        return 1
+    }
+    {
+        p0 "$(hash_get < "${cache_file}.pre")" || return 1
+        cat "${cache_file}.pre"
+        rm "${cache_file}.pre"
+    } > "${cache_file}".wip || return 1
+
+    mv "${cache_file}"{.wip,} || return 1
+    cat "${cache_file}"
+}
 
+
+## Get all relations from all services in the current compose file.
+## Sets GLOBAL_ALL_RELATIONS_HASH and returns all relations array.
+service:all:set_relations_hash() {
+    if [ -n "$GLOBAL_ALL_RELATIONS" ]; then
+        if [ -z "$GLOBAL_ALL_RELATIONS_HASH" ]; then
+            err "Can't access global \$GLOBAL_ALL_RELATIONS_HASH"
+            echo "  (despite \$GLOBAL_ALL_RELATIONS being set)" >&2
+            return 1
+        fi
+        return 0
+    fi
+    ## sets COMPOSE_YML_CONTENT_HASH
+    _service:all:relations_hash_cached >/dev/null || return 1
+    {
+        read-0 GLOBAL_ALL_RELATIONS_HASH || return 1
+        export GLOBAL_ALL_RELATIONS_HASH
+        ## transfer to statedir
+        export GLOBAL_ALL_RELATIONS="$state_tmpdir/$FUNCNAME.cache.$COMPOSE_YML_CONTENT_HASH"
+        cat > "$GLOBAL_ALL_RELATIONS"
+    } < <(_service:all:relations_hash_cached)
+    if [ -z "$GLOBAL_ALL_RELATIONS" ]; then
+        err "Failed to set \$GLOBAL_ALL_RELATIONS."
+        return 1
+    fi
+    if [ -z "$GLOBAL_ALL_RELATIONS_HASH" ]; then
+        err "Failed to set \$GLOBAL_ALL_RELATIONS_HASH."
+        return 1
+    fi
+}
+
+get_subset_relations () {
+    local service all_services services start
+    if [ -n "$SUBSET_ALL_RELATIONS" ]; then
+        return 0
+    fi
+    if [ -z "$GLOBAL_ALL_RELATIONS_HASH" ]; then
+        err-d "Can't access global \$GLOBAL_ALL_RELATIONS_HASH"
+        return 1
+    fi
+    cache_hash=$(H "$@" "$GLOBAL_ALL_RELATIONS_HASH" "$(declare -f get_subset_relations)")
+    local cache_file="$CACHEDIR/$FUNCNAME.cache.$cache_hash"
+    if [ -e "${cache_file}" ]; then
+        export SUBSET_ALL_RELATIONS="$cache_file"
+        hash=$(hash_get < "$cache_file") || return 1
+        export SUBSET_ALL_RELATIONS_HASH="$hash"
+        cat "${cache_file}"
+        return 0
+    fi
+    ## collect all connected services first
+    all_services=("$@")
+    while [ "${#all_services[@]}" != 0 ]; do
+        array_pop all_services service
+        #debug "  Getting relations for $DARKYELLOW$service$NORMAL"
+        while read-0 s rn ts rc td; do
+            [[ "$s" == "$service" ]] || continue
+            #debug "    adding relation $DARKBLUE$rn$NORMAL to $DARKYELLOW$ts$NORMAL"
+            p0 "$service" "$rn" "$ts" "$rc" "$td"
+            [ -n "${services[$ts]}" ] || all_services+=("$ts")
+        done < "$GLOBAL_ALL_RELATIONS"
+        services["$service"]=1
+    done  > "$cache_file.wip"
+    mv "$cache_file"{.wip,} || return 1
+    export SUBSET_ALL_RELATIONS="$cache_file"
+    hash=$(hash_get < "$cache_file") || return 1
+    export SUBSET_ALL_RELATIONS_HASH="$hash"
+    cat "$cache_file"
+}
+
+get_all_relations () {
+    if [ -z "$COMPOSE_YML_CONTENT_HASH" ]; then
+        COMPOSE_YML_CONTENT_HASH=$(compose:yml:hash) || return 1
+    fi
     if [ -n "$GLOBAL_ALL_RELATIONS" ]; then
         cat "$GLOBAL_ALL_RELATIONS" || return 1
         return 0
     fi
+    local cache_file="$state_tmpdir/$FUNCNAME.cache.$(H "$@" "$COMPOSE_YML_CONTENT_HASH" "$(declare -p without_relations)")" \
+          services all_services service services_uses services_provides \
+          changed summon required recommended optional
 
     if [ -e "${cache_file}" ]; then
         #debug "$FUNCNAME: SESSION cache hit $1"
@@ -3176,7 +3345,7 @@ get_all_relations () {
         while read-0 p s rn ts rc td; do
             if [ -z "$p" ] || [ "$p" == "," ]; then
                 relation_done["$s:$rn"]=1
-                # printf "  ..  %-30s %-30s %-30s\n" "--" "$s" "$rn" >&2
+                # printf "  ..  %-30s %-30s %-30s\n" "$s" "$ts" "$rn" >&2
                 printf "%s\0" "$s" "$rn" "$ts" "$rc" "$td" >> "${cache_file}.wip.final"
                 had_new_relation=1
             else
@@ -4080,7 +4249,7 @@ get_compose_yml_content() {
         COMPOSE_YML_FILE=$(get_compose_yml_location) || return 1
     fi
     if [ -e "$COMPOSE_YML_FILE" ]; then
-        debug "Found $WHITE$exname$NORMAL YAML file in '$COMPOSE_YML_FILE'."
+        # debug "Found $WHITE$exname$NORMAL YAML file in '$COMPOSE_YML_FILE'."
         COMPOSE_YML_CONTENT=$(cat "$COMPOSE_YML_FILE") || {
             err "Could not read '$COMPOSE_YML_FILE'."
             return 1
@@ -4111,6 +4280,37 @@ get_compose_yml_content() {
 }
 export -f get_compose_yml_content
 
+compose:yml:hash() {
+    local cache_file="$state_tmpdir/$FUNCNAME.cache"
+    if [ -e "$cache_file" ]; then
+        cat "$cache_file" &&
+        touch "$cache_file" || return 1
+        return 0
+    fi
+
+    compose_yml_content=$(get_compose_yml_content) || return 1
+    compose_yml_hash=$(echo "$compose_yml_content" | hash_get) || return 1
+
+    e "$compose_yml_hash" | tee "$cache_file" || return 1
+}
+export -f compose:yml:hash
+
+
+compose:yml:root:services() {
+    local cache_file="$state_tmpdir/$FUNCNAME.cache" services compose_yml_content
+    if [ -e "$cache_file" ]; then
+        cat "$cache_file" &&
+        touch "$cache_file" || return 1
+        return 0
+    fi
+
+    compose_yml_content=$(get_compose_yml_content) || return 1
+    services=($(e "$compose_yml_content" | shyaml keys)) || return 1
+
+    e "${services[*]}" | tee "$cache_file" || return 1
+}
+export -f compose:yml:root:services
+
 
 get_default_target_services() {
     local services=("$@")
@@ -4349,9 +4549,12 @@ display_commands_help() {
 
 get_docker_charm_action() {
     local services service charm relation_name target_service relation_config \
-          target_charm
-    services=($(get_compose_yml_content | yq -r 'keys().[]' 2>/dev/null)) || return 1
-    NO_CONSTRAINT_CHECK=1 get_all_relations "${services[@]}" >/dev/null || return 1
+          target_charm services
+    ## XXXvlab: this is for get_service_relations
+    NO_CONSTRAINT_CHECK=True service:all:set_relations_hash || {
+        err-d "Failed to set relations hash."
+        return 1
+    }
     services=($(get_all_services)) || return 1
     for service in "${services[@]}"; do
         printf "%s:\n" "$service"
@@ -4375,8 +4578,12 @@ export -f get_docker_charm_action
 get_docker_charm_action_help() {
     local services service charm relation_name target_service relation_config \
           target_charm
-    services=($(get_compose_yml_content | shyaml keys 2>/dev/null))
-    NO_CONSTRAINT_CHECK=1 get_all_relations "${services[@]}" >/dev/null || return 1
+    ## XXXvlab: this is for get_service_relations
+    NO_CONSTRAINT_CHECK=True service:all:set_relations_hash || {
+        err-d "Failed to set relations hash."
+        return 1
+    }
+    services=($(get_all_services)) || return 1
     for service in "${services[@]}"; do
         out=$(
             charm=$(get_service_charm "$service") || return 1
@@ -4667,6 +4874,7 @@ no_init=
 action=
 stage="main"  ## switches from 'main', to 'action', 'remainder'
 is_docker_compose_action=
+is_docker_compose_action_multi_service=
 rebuild_relations_to_service=()
 color=
 declare -A without_relations
@@ -4806,6 +5014,12 @@ while read-0 arg; do
                         fi
                         pos_args=($(echo "$DC_USAGE" | sed -r 's/\[-[^]]+\] ?//g;s/\[options\] ?//g'))
                         pos_args=("${pos_args[@]:1}")
+                        if [[ "${pos_args[0]}" == "[SERVICE...]" ]]; then
+                            is_docker_compose_action_multi_service=1
+                        elif [[ "${pos_args[0]}" == "SERVICE" ]]; then
+                            is_docker_compose_action_multi_service=0
+                        fi
+
                         # echo "USAGE: $DC_USAGE"
                         # echo "pos_args: ${pos_args[@]}"
                         # echo "MULTI: $DC_MATCH_MULTI"
@@ -4916,8 +5130,8 @@ aexport remainder_args
 
 COMPOSE_YML_FILE=$(get_compose_yml_location) || exit 1
 COMPOSE_YML_CONTENT=$(get_compose_yml_content) || exit 1
-export COMPOSE_YML_FILE COMPOSE_YML_CONTENT
-
+COMPOSE_YML_CONTENT_HASH=$(compose:yml:hash) || exit 1
+export COMPOSE_YML_FILE COMPOSE_YML_CONTENT COMPOSE_YML_CONTENT_HASH
 
 charm.sanity_checks || die "Sanity checks about charm-store failed. Please correct."
 
@@ -4933,10 +5147,9 @@ if [ -z "$is_docker_compose_action" -a "$action" ]; then
         exit 1
     fi
 
-
+    services_args=($(compose:yml:root:services)) || return 1
     ## Required by has_service_action
-    array_read-0 services_args < <(printf "%s" "$COMPOSE_YML_CONTENT" | shyaml keys-0 2>/dev/null)
-    NO_CONSTRAINT_CHECK=1 get_all_relations "${services_args[@]}" >/dev/null || exit 1
+    service:all:set_relations_hash
 
     remainder_args=("${remainder_args[@]:1}")
     if has_service_action "$action_service" "$action" >/dev/null; then
@@ -4971,7 +5184,7 @@ else
     case "$action" in
         ps|up)
             if [ "${#services_args[@]}" == 0 ]; then
-                array_read-0 services_args < <(printf "%s" "$COMPOSE_YML_CONTENT" | shyaml keys-0 2>/dev/null)
+                services_args=($(compose:yml:root:services)) || return 1
             fi
             ;;
         config)
@@ -4985,11 +5198,48 @@ NO_CONSTRAINT_CHECK=True
 case "$action" in
     up)
         NO_CONSTRAINT_CHECK=
+        if [ -n "$DEBUG" ]; then
+            Elt "solve all relations"
+            start=$(time_now)
+        fi
+        service:all:set_relations_hash || exit 1
+
+        if [ -n "$DEBUG" ]; then
+            elapsed="$(time_elapsed $start "$(time_now)")" || exit 1
+            print_info "$(printf "%.3fs" "$elapsed")"
+            Feedback
+        fi
+
+        all_services=($(get_all_services)) || exit 1
+        ## check that services_args is a subset of all_services
+        for service in "${services_args[@]}"; do
+            [[ " ${all_services[*]} " == *" $service "* ]] || {
+                err "Service ${DARKYELLOW}$service${NORMAL} is not defined in the current compose file."
+                echo "  Neither is is a dependency of a service in the compose file." >&2
+                echo "  These are the services directly or indirectly available from current compose file:" >&2
+                for service in "${all_services[@]}"; do
+                    echo "    - ${DARKYELLOW}$service${NORMAL}" >&2
+                done
+                exit 1
+            }
+        done
         ;;
 esac
 
+if [ -n "$is_docker_compose_action_multi_service" ]; then
+    if [ -n "$DEBUG" ]; then
+        Elt "get relation subet"
+        start=$(time_now)
+    fi
+
+    get_subset_relations "${services_args[@]}" >/dev/null || exit 1
 
-get_all_relations "${services_args[@]}" >/dev/null || exit 1
+    if [ -n "$DEBUG" ]; then
+        elapsed="$(time_elapsed $start "$(time_now)")" || exit 1
+        print_info "$(printf "%.3fs" "$elapsed")"
+        Feedback
+    fi
+fi
 
 if [ "$is_docker_compose_action" -a "${#services_args[@]}" -gt 0 ]; then
     services=($(get_master_services "${services_args[@]}")) || exit 1
@@ -5006,8 +5256,10 @@ if [ "$is_docker_compose_action" -a "${#services_args[@]}" -gt 0 ]; then
             seen[$mservice]=1
             action_posargs+=("$mservice")
         done
-    else
+    elif [ "$is_docker_compose_action_multi_service" == "1" ]; then
         action_posargs+=("${services[@]}")
+    elif [ "$is_docker_compose_action_multi_service" == "0" ]; then
+        action_posargs+=("${services[0]}")  ## only the first service is the legit one
     fi
     ## Get rid of subordinates
     action_posargs=($(get_master_services "${action_posargs[@]}")) || exit 1