[metrics] Add metrics-specific varlink sockets in /run/systemd/metrics

Author: YapingLi04

src/core/manager.h

@@ -463,6 +463,8 @@ typedef struct Manager {
          * systemd-oomd to report changes in ManagedOOM settings (systemd client - oomd server). */
         sd_varlink *managed_oom_varlink;
 
+        sd_varlink_server *metrics_varlink_server;
+
         /* Reference to RestrictFileSystems= BPF program */
         struct restrict_fs_bpf *restrict_fs;
 

src/core/varlink.c

@@ -1,11 +1,14 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 
+#include <assert.h>
+
 #include "sd-varlink.h"
 
 #include "constants.h"
 #include "errno-util.h"
 #include "json-util.h"
 #include "manager.h"
+#include "metrics.h"
 #include "path-util.h"
 #include "pidref.h"
 #include "string-util.h"
@@ -402,6 +405,21 @@ int manager_setup_varlink_server(Manager *m) {
         return 1;
 }
 
+static int vl_method_list(sd_varlink *link, sd_json_variant *parameters, sd_varlink_method_flags_t flags, void *userdata) {
+        Manager *m = ASSERT_PTR(userdata);
+        int r;
+
+        assert(link);
+
+        r = sd_varlink_dispatch(link, parameters, /* dispatch_table= */ NULL, /* userdata= */ NULL);
+        if (r != 0)
+                return r;
+
+        return sd_varlink_replybo(
+                link,
+                SD_JSON_BUILD_PAIR("units.active_units", SD_JSON_BUILD_INTEGER(hashmap_size(m->units))));
+}
+
 static int manager_varlink_init_system(Manager *m) {
         int r;
 
@@ -430,6 +448,15 @@ static int manager_varlink_init_system(Manager *m) {
                 }
         }
 
+        r = metrics_setup_varlink_server(
+                        &m->metrics_varlink_server,
+                        m->event,
+                        vl_method_list,
+                        m,
+                        "/run/systemd/metrics/io.systemd.Manager");
+        if (r < 0)
+                return log_error_errno(r, "Failed to set up metrics varlink server: %m");
+
         return 1;
 }
 
@@ -464,6 +491,7 @@ static int manager_varlink_init_user(Manager *m) {
                         return log_error_errno(r, "Failed to bind to varlink socket '%s': %m", address);
         }
 
+        // TODO: Make metrics server work for user manager
         return manager_varlink_managed_oom_connect(m);
 }
 
@@ -482,4 +510,5 @@ void manager_varlink_done(Manager *m) {
 
         m->varlink_server = sd_varlink_server_unref(m->varlink_server);
         m->managed_oom_varlink = sd_varlink_close_unref(m->managed_oom_varlink);
+        m->metrics_varlink_server = sd_varlink_server_unref(m->metrics_varlink_server);
 }

src/shared/meson.build

@@ -125,6 +125,7 @@ shared_sources = files(
         'machine-pool.c',
         'macvlan-util.c',
         'main-func.c',
+        'metrics.c',
         'mkdir-label.c',
         'mkfs-util.c',
         'module-util.c',

src/shared/metrics.c

@@ -0,0 +1,35 @@
+#include "log.h"
+#include "metrics.h"
+#include "mkdir-label.h"
+#include "varlink-io.systemd.Metrics.h"
+#include "varlink-util.h"
+
+int metrics_setup_varlink_server(sd_varlink_server **m, sd_event *event, sd_varlink_method_t vl_method_list_cb, void *userdata, const char *socket) {
+        _cleanup_(sd_varlink_server_unrefp) sd_varlink_server *s = NULL;
+        int r;
+
+        r = varlink_server_new(&s, SD_VARLINK_SERVER_INHERIT_USERDATA, userdata);
+        if (r < 0)
+                return log_error_errno(r, "Failed to allocate varlink server object: %m");
+
+        r = sd_varlink_server_add_interface(s, &vl_interface_io_systemd_Metrics);
+        if (r < 0)
+                return log_error_errno(r, "Failed to add Metrics interface to varlink server: %m");
+
+        r = sd_varlink_server_bind_method(
+                        s, "io.systemd.Metrics.List", vl_method_list_cb);
+        if (r < 0)
+                return r;
+
+        (void) mkdir_label("/run/systemd/metrics", 0755);
+        r = sd_varlink_server_listen_address(s, socket, 0600);
+        if (r < 0)
+                return r;
+
+        r = sd_varlink_server_attach_event(s, event, SD_EVENT_PRIORITY_NORMAL);
+        if (r < 0)
+                return r;
+
+        *m = TAKE_PTR(s);
+        return 0;
+}

src/shared/metrics.h

@@ -0,0 +1,5 @@
+#pragma once
+
+#include "sd-varlink.h"
+
+int metrics_setup_varlink_server(sd_varlink_server **m, sd_event *event, sd_varlink_method_t vl_method_list_cb, void *userdata, const char *socket);

src/shared/varlink-io.systemd.Metrics.c

@@ -1,21 +1,24 @@
 #include "varlink-io.systemd.Metrics.h"
 
+static SD_VARLINK_DEFINE_STRUCT_TYPE(
+                MetricsStruct,
+                SD_VARLINK_FIELD_COMMENT("Metric family name"),
+                SD_VARLINK_DEFINE_FIELD(name, SD_VARLINK_STRING, 0),
+                SD_VARLINK_FIELD_COMMENT("Value of the metric"),
+                SD_VARLINK_DEFINE_FIELD(value, SD_VARLINK_INT, 0),
+                SD_VARLINK_FIELD_COMMENT("fields"),
+                SD_VARLINK_DEFINE_FIELD(fields, SD_VARLINK_STRUCT, SD_VARLINK_NULLABLE));
 
 static SD_VARLINK_DEFINE_METHOD(
-               List,
-               SD_VARLINK_FIELD_COMMENT("Metric name"),
-               SD_VARLINK_DEFINE_OUTPUT(name, SD_VARLINK_STRING, SD_VARLINK_NULLABLE),
-               SD_VARLINK_FIELD_COMMENT("Value of the metric"),
-               SD_VARLINK_DEFINE_OUTPUT(value, SD_VARLINK_INT, 0),
-               SD_VARLINK_FIELD_COMMENT("fields"),
-               SD_VARLINK_DEFINE_OUTPUT(fields, SD_VARLINK_STRUCT, SD_VARLINK_NULLABLE));
-
+                List,
+                SD_VARLINK_DEFINE_OUTPUT_BY_TYPE(metrics, MetricsStruct, 0));
 
 SD_VARLINK_DEFINE_INTERFACE(
                io_systemd_Metrics,
                "io.systemd.Metrics",
                SD_VARLINK_INTERFACE_COMMENT("Metrics APIs"),
                SD_VARLINK_SYMBOL_COMMENT(
-                               "Return key -> value dictionary of relevant metrics, optionally filtered by object."),
-               &vl_method_List);
-
+                               "APIs for getting relevant metrics, optionally filtered by object."),
+               &vl_method_List,
+               SD_VARLINK_SYMBOL_COMMENT("The metrics object"),
+               &vl_type_MetricsStruct);