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report: add simple metrics provider that just reads files

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This commit is contained in:
Lennart Poettering
2026-06-19 05:23:18 +02:00
parent 2640a3b0e2
commit 9c3e443021
10 changed files with 436 additions and 0 deletions
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src/report/meson.build
+7
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@@ -27,6 +27,13 @@ executables += [
'report-cgroup-server.c',
),
},
libexec_template + {
'name' : 'systemd-report-files',
'sources' : files(
'report-files.c',
'report-files-server.c',
),
},
libexec_template + {
'name' : 'systemd-report-sign-plain',
'conditions' : [
src/report/report-files-server.c
+103
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@@ -0,0 +1,103 @@
/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include "sd-varlink.h"
#include "build.h"
#include "format-table.h"
#include "help-util.h"
#include "log.h"
#include "main-func.h"
#include "options.h"
#include "report-files.h"
#include "varlink-io.systemd.Metrics.h"
#include "varlink-util.h"
static int vl_server(void) {
_cleanup_(sd_varlink_server_unrefp) sd_varlink_server *vs = NULL;
int r;
r = varlink_server_new(&vs, /* flags= */ 0, /* userdata= */ NULL);
if (r < 0)
return log_error_errno(r, "Failed to allocate Varlink server: %m");
r = sd_varlink_server_add_interface(vs, &vl_interface_io_systemd_Metrics);
if (r < 0)
return log_error_errno(r, "Failed to add Varlink interface: %m");
r = sd_varlink_server_bind_method_many(
vs,
"io.systemd.Metrics.List", vl_method_list_metrics,
"io.systemd.Metrics.Describe", vl_method_describe_metrics);
if (r < 0)
return log_error_errno(r, "Failed to bind Varlink methods: %m");
r = sd_varlink_server_loop_auto(vs);
if (r < 0)
return log_error_errno(r, "Failed to run Varlink event loop: %m");
return 0;
}
static int help(void) {
_cleanup_(table_unrefp) Table *options = NULL;
int r;
r = option_parser_get_help_table(&options);
if (r < 0)
return r;
help_cmdline("[OPTIONS...]");
help_abstract("Report the contents of files as system report metrics.");
help_section("Options");
r = table_print_or_warn(options);
if (r < 0)
return r;
help_man_page_reference("systemd-report-files@.service", "8");
return 0;
}
static int parse_argv(int argc, char *argv[]) {
int r;
assert(argc >= 0);
assert(argv);
OptionParser opts = { argc, argv };
FOREACH_OPTION_OR_RETURN(c, &opts)
switch (c) {
OPTION_COMMON_HELP:
return help();
OPTION_COMMON_VERSION:
return version();
}
if (option_parser_get_n_args(&opts) > 0)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
"This program takes no arguments.");
r = sd_varlink_invocation(SD_VARLINK_ALLOW_ACCEPT);
if (r < 0)
return log_error_errno(r, "Failed to check if invoked in Varlink mode: %m");
if (r == 0)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
"This program can only run as a Varlink service.");
return 1;
}
static int run(int argc, char *argv[]) {
int r;
log_setup();
r = parse_argv(argc, argv);
if (r <= 0)
return r;
return vl_server();
}
DEFINE_MAIN_FUNCTION(run);
src/report/report-files.c
+193
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@@ -0,0 +1,193 @@
/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include "sd-json.h"
#include "sd-varlink.h"
#include "alloc-util.h"
#include "chase.h"
#include "conf-files.h"
#include "fd-util.h"
#include "fileio.h"
#include "log.h"
#include "metrics.h"
#include "path-util.h"
#include "report-files.h"
#include "string-util.h"
#include "strv.h"
#include "utf8.h"
#include "varlink-idl-util.h"
/* Upper bounds, to protect against pathologically large directories or files. */
#define REPORT_FILES_MAX 1024U
#define REPORT_FILE_SIZE_MAX (4U * 1024U * 1024U)
/* The directories we look for files to report in. This is the usual CONF_PATHS() set (/etc/, /run/,
* /usr/local/lib/, /usr/lib/), plus an extra directory below /var/lib/ for persistent local additions. Files
* (typically symlinks to the actual files to report) dropped into any of these are reported as metrics, keyed
* by their name. Entries in earlier directories override identically named ones in later directories. */
static const char* const report_files_dirs[] = {
"/etc/systemd/report.files",
"/run/systemd/report.files",
"/var/lib/systemd/report.files",
"/usr/local/lib/systemd/report.files",
"/usr/lib/systemd/report.files",
NULL,
};
static MetricFamily* metric_family_array_free(MetricFamily *families) {
if (!families)
return NULL;
/* The array is NULL-name terminated. We own the name/description strings. */
for (MetricFamily *mf = families; mf->name; mf++) {
free((char*) mf->name);
free((char*) mf->description);
}
return mfree(families);
}
DEFINE_TRIVIAL_CLEANUP_FUNC(MetricFamily*, metric_family_array_free);
static int file_metric_generate(const MetricFamily *mf, sd_varlink *link, void *userdata) {
int r;
assert(mf && mf->name);
assert(link);
/* Recover the file name from the metric family name: it is the part following the interface prefix.
* We look it up across our directories again (rather than caching the path found while building the
* metric list), and read the first instance we find, matching the precedence used at enumeration. */
const char *field = startswith(mf->name, METRIC_IO_SYSTEMD_FILES_PREFIX);
assert(field);
_cleanup_free_ char *buf = NULL, *discovered_path = NULL;
size_t size = 0;
STRV_FOREACH(d, report_files_dirs) {
_cleanup_free_ char *path = path_join(*d, field);
if (!path)
return log_oom();
_cleanup_free_ char *resolved = NULL;
_cleanup_close_ int fd = chase_and_open(path, /* root= */ NULL, CHASE_MUST_BE_REGULAR, O_RDONLY|O_CLOEXEC, &resolved);
if (fd == -ENOENT) /* Not in this directory (or dangling symlink): try the next one. */
continue;
if (fd < 0) {
log_warning_errno(fd, "Failed to open '%s', skipping: %m", path);
return 0;
}
r = read_full_file_full(
fd,
/* filename= */ NULL,
/* offset= */ UINT64_MAX,
REPORT_FILE_SIZE_MAX,
READ_FULL_FILE_FAIL_WHEN_LARGER,
/* bind_name= */ NULL,
&buf,
&size);
if (r < 0) {
log_warning_errno(r, "Failed to read '%s', skipping: %m", path);
return 0;
}
discovered_path = TAKE_PTR(resolved);
break;
}
if (!discovered_path) {
log_debug("File for metric '%s' unavailable, skipping.", mf->name);
return 0;
}
/* Metric values are JSON strings, so we can only report text files. Skip anything that isn't valid,
* NUL-free UTF-8. */
if (memchr(buf, 0, size) || !utf8_is_valid(buf)) {
log_debug("File for metric '%s' is not valid UTF-8 text, skipping.", mf->name);
return 0;
}
return metric_build_send_string(mf, link, discovered_path, buf, /* fields= */ NULL);
}
static int build_file_metrics(MetricFamily **ret) {
_cleanup_(metric_family_array_freep) MetricFamily *families = NULL;
_cleanup_strv_free_ char **files = NULL;
size_t n = 0;
int r;
assert(ret);
/* Enumerate the files to report across all our directories, deduplicated by name. The entry name is
* used as the metric field name. */
r = conf_files_list_strv(&files, /* suffix= */ NULL, /* root= */ NULL, CONF_FILES_REGULAR, report_files_dirs);
if (r < 0)
return log_error_errno(r, "Failed to enumerate report files: %m");
STRV_FOREACH(f, files) {
_cleanup_free_ char *base = NULL;
r = path_extract_filename(*f, &base);
if (r < 0)
return log_error_errno(r, "Failed to extract file name from '%s': %m", *f);
/* The name becomes the metric field name, so it must be a valid one. */
if (!varlink_idl_field_name_is_valid(base)) {
log_debug("Report file '%s' does not have a valid metric field name, skipping.", *f);
continue;
}
if (n >= REPORT_FILES_MAX) {
log_warning("More than %u report files found, not reporting the rest.", REPORT_FILES_MAX);
break;
}
_cleanup_free_ char *name = strjoin(METRIC_IO_SYSTEMD_FILES_PREFIX, base);
_cleanup_free_ char *description = strjoin("Contents of the '", base, "' report file");
if (!name || !description)
return log_oom();
/* Room for the new entry plus the NULL-name terminator. */
if (!GREEDY_REALLOC(families, n + 2))
return log_oom();
families[n++] = (MetricFamily) {
.name = TAKE_PTR(name),
.description = TAKE_PTR(description),
.type = METRIC_FAMILY_TYPE_STRING,
.generate = file_metric_generate,
};
families[n] = (MetricFamily) {}; /* terminator */
}
/* The metrics helpers expect a valid, terminated array even when empty. */
if (!families) {
families = new0(MetricFamily, 1);
if (!families)
return log_oom();
}
*ret = TAKE_PTR(families);
return 0;
}
int vl_method_list_metrics(sd_varlink *link, sd_json_variant *parameters, sd_varlink_method_flags_t flags, void *userdata) {
int r;
_cleanup_(metric_family_array_freep) MetricFamily *families = NULL;
r = build_file_metrics(&families);
if (r < 0)
return r;
return metrics_method_list(families, link, parameters, flags, /* userdata= */ NULL);
}
int vl_method_describe_metrics(sd_varlink *link, sd_json_variant *parameters, sd_varlink_method_flags_t flags, void *userdata) {
int r;
_cleanup_(metric_family_array_freep) MetricFamily *families = NULL;
r = build_file_metrics(&families);
if (r < 0)
return r;
return metrics_method_describe(families, link, parameters, flags, /* userdata= */ NULL);
}
src/report/report-files.h
+9
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@@ -0,0 +1,9 @@
/* SPDX-License-Identifier: LGPL-2.1-or-later */
#pragma once
#include "shared-forward.h"
#define METRIC_IO_SYSTEMD_FILES_PREFIX "io.systemd.Files."
int vl_method_list_metrics(sd_varlink *link, sd_json_variant *parameters, sd_varlink_method_flags_t flags, void *userdata);
int vl_method_describe_metrics(sd_varlink *link, sd_json_variant *parameters, sd_varlink_method_flags_t flags, void *userdata);