lib: Use sd_journal directly (optionally)

This was the last caller of libgsystem that isn't
`gs_file_get_path_cached()`.  I think the use case ostree has where
the same code can be called via command line and via a shared library
*and* via a daemon is rather unusual, so let's just copy the code for
logging from libgsystem into here.

For example rpm-ostree hard depends on a daemon mode, so it'll just
use `sd_journal` directly.

Closes: #341
Approved by: jlebon

src/libostree/ostree-sysroot-deploy.c

@@ -473,7 +473,7 @@ merge_etc_changes (GFile          *orig_etc,
       goto out;
     }
 
-  gs_log_structured_print_id_v (OSTREE_CONFIGMERGE_ID,
+  ot_log_structured_print_id_v (OSTREE_CONFIGMERGE_ID,
                                 "Copying /etc changes: %u modified, %u removed, %u added", 
                                 modified->len,
                                 removed->len,
@@ -773,7 +773,7 @@ selinux_relabel_var_if_needed (OstreeSysroot                 *sysroot,
       
   if (!g_file_query_exists (deployment_var_labeled, NULL))
     {
-      gs_log_structured_print_id_v (OSTREE_VARRELABEL_ID,
+      ot_log_structured_print_id_v (OSTREE_VARRELABEL_ID,
                                     "Relabeling /var (no stamp file '%s' found)",
                                     gs_file_get_path_cached (deployment_var_labeled));
 
@@ -1927,7 +1927,7 @@ ostree_sysroot_write_deployments (OstreeSysroot     *self,
         }
     }
 
-  gs_log_structured_print_id_v (OSTREE_DEPLOYMENT_COMPLETE_ID,
+  ot_log_structured_print_id_v (OSTREE_DEPLOYMENT_COMPLETE_ID,
                                 "%s; bootconfig swap: %s deployment count change: %i",
                                 (bootloader_is_atomic ? "Transaction complete" : "Bootloader updated"),
                                 requires_new_bootversion ? "yes" : "no",

src/libotutil/ot-log-utils.c

@@ -0,0 +1,163 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
+ *
+ * Copyright (C) 2016 Colin Walters <walters@verbum.org>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ *
+ * Author: Colin Walters <walters@verbum.org>
+ */
+
+#include "config.h"
+
+#include <gio/gio.h>
+
+#include <string.h>
+
+#include "otutil.h"
+#include "libglnx.h"
+
+#ifdef HAVE_LIBSYSTEMD
+#define SD_JOURNAL_SUPPRESS_LOCATION
+#include <systemd/sd-journal.h>
+#endif
+#include <glib-unix.h>
+
+/**
+ * ot_log_structured:
+ * @message: Text message to send 
+ * @keys: (allow-none) (array zero-terminated=1) (element-type utf8): Optional structured data
+ * 
+ * Log structured data in an operating-system specific fashion.  The
+ * parameter @opts should be an array of UTF-8 KEY=VALUE strings.
+ * This function does not support binary data.  See
+ * http://www.freedesktop.org/software/systemd/man/systemd.journal-fields.html
+ * for more information about fields that can be used on a systemd
+ * system.
+ */
+static void
+ot_log_structured (const char *message,
+                   const char *const *keys)
+{
+#ifdef HAVE_LIBSYSTEMD
+    const char *const*iter;
+    g_autofree char *msgkey = NULL;
+    guint i, n_opts;
+    struct iovec *iovs;
+
+    for (n_opts = 0, iter = keys; *iter; iter++, n_opts++)
+        ;
+
+    n_opts++; /* Add one for MESSAGE= */
+    iovs = g_alloca (sizeof (struct iovec) * n_opts);
+    
+    for (i = 0, iter = keys; *iter; iter++, i++) {
+        iovs[i].iov_base = (char*)keys[i];
+        iovs[i].iov_len = strlen (keys[i]);
+    }
+    g_assert(i == n_opts-1);
+    msgkey = g_strconcat ("MESSAGE=", message, NULL);
+    iovs[i].iov_base = msgkey;
+    iovs[i].iov_len = strlen (msgkey);
+    
+    // The code location isn't useful since we're wrapping
+    sd_journal_sendv (iovs, n_opts);
+#else
+    g_print ("%s\n", message);
+#endif
+}
+
+/**
+ * ot_stdout_is_journal:
+ *
+ * Use this function when you want your code to behave differently
+ * depeneding on whether your program was started as a systemd unit,
+ * or e.g. interactively at a terminal.
+ *
+ * Returns: %TRUE if stdout is (probably) connnected to the systemd journal
+ */
+static gboolean
+ot_stdout_is_journal (void)
+{
+  static gsize initialized;
+  static gboolean stdout_is_socket;
+
+  if (g_once_init_enter (&initialized))
+    {
+      guint64 pid = (guint64) getpid ();
+      g_autofree char *fdpath = g_strdup_printf ("/proc/%" G_GUINT64_FORMAT "/fd/1", pid);
+      char buf[1024];
+      ssize_t bytes_read;
+
+      if ((bytes_read = readlink (fdpath, buf, sizeof(buf) - 1)) != -1)
+        {
+          buf[bytes_read] = '\0';
+          stdout_is_socket = g_str_has_prefix (buf, "socket:");
+        }
+      else
+        stdout_is_socket = FALSE;
+
+      g_once_init_leave (&initialized, TRUE);
+    }
+
+  return stdout_is_socket;
+}
+
+/**
+ * gs_log_structured_print:
+ * @message: A message to log
+ * @keys: (allow-none) (array zero-terminated=1) (element-type utf8): Optional structured data
+ *
+ * Like gs_log_structured(), but also print to standard output (if it
+ * is not already connected to the system log).
+ */
+static void
+ot_log_structured_print (const char *message,
+                         const char *const *keys)
+{
+  ot_log_structured (message, keys);
+
+#ifdef HAVE_LIBSYSTEMD
+  if (!ot_stdout_is_journal ())
+    g_print ("%s\n", message);
+#endif
+}
+
+/**
+ * ot_log_structured_print_id_v:
+ * @message_id: A unique MESSAGE_ID
+ * @format: A format string
+ *
+ * The provided @message_id is a unique MESSAGE_ID (see <ulink url="http://www.freedesktop.org/software/systemd/man/systemd.journal-fields.html"> for more information).
+ *
+ * This function otherwise acts as ot_log_structured_print(), taking
+ * @format as a format string.
+ */
+void
+ot_log_structured_print_id_v (const char *message_id,
+                              const char *format,
+                              ...)
+{
+  const char *key0 = glnx_strjoina ("MESSAGE_ID=", message_id);
+  const char *keys[] = { key0, NULL };
+  g_autofree char *msg = NULL;
+  va_list args;
+
+  va_start (args, format);
+  msg = g_strdup_vprintf (format, args);
+  va_end (args);
+
+  ot_log_structured_print (msg, (const char *const *)keys);
+}

src/libotutil/ot-log-utils.h

@@ -0,0 +1,31 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
+ *
+ * Copyright (C) 2016 Colin Walters <walters@verbum.org>.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#pragma once
+
+#include "ot-unix-utils.h"
+
+G_BEGIN_DECLS
+
+void ot_log_structured_print_id_v (const char *message_id,
+                                   const char *format,
+                                   ...);
+
+G_END_DECLS

src/libotutil/otutil.h

@@ -47,5 +47,6 @@
 #include <ot-spawn-utils.h>
 #include <ot-checksum-utils.h>
 #include <ot-gpg-utils.h>
+#include <ot-log-utils.h>
 
 void ot_ptrarray_add_many (GPtrArray  *a, ...) G_GNUC_NULL_TERMINATED;