Systemd integration (#24)

Add the ability for pg_autoctl to produce the systemd unit configuration file for the pgautofailover service, using both the current PGDATA and absolute filename for the current program in use.

Makefile

@@ -18,7 +18,7 @@ monitor:
 clean-monitor:
 	$(MAKE) -C src/monitor/ clean
 
-install-monitor:
+install-monitor: monitor
 	$(MAKE) -C src/monitor/ install
 
 check-monitor: install-monitor
@@ -30,7 +30,7 @@ bin:
 clean-bin:
 	$(MAKE) -C src/bin/ clean
 
-install-bin:
+install-bin: bin
 	$(MAKE) -C src/bin/ install
 
 test:

docs/conf.py

@@ -135,7 +135,7 @@ def __init__(self, **options):
 # (source start file, target name, title,
 #  author, documentclass [howto, manual, or own class]).
 latex_documents = [
-    (master_doc, 'pg_auto_failover.tex', 'pg_auto_failover Documentation',
+    (master_doc, 'pg_auto_failover.tex', 'pg\_auto\_failover Documentation',
      'Microsoft', 'manual'),
 ]
 

docs/install.rst

@@ -36,3 +36,41 @@ Fedora, CentOS, or Red Hat
 
   # confirm installation
   /usr/pgsql-11/bin/pg_autoctl --version
+
+Installing a pgautofailover Systemd unit
+----------------------------------------
+
+The command ``pg_autoctl show systemd`` outputs a systemd unit file that you
+can use to setup a boot-time registered service for pg_auto_failover on your
+machine.
+
+Here's a sample output from the command:
+
+.. code-block::
+
+   $ pg_autoctl show systemd
+   13:44:34 INFO  HINT: to complete a systemd integration, run the following commands:
+   13:44:34 INFO  pg_autoctl -q show systemd --pgdata /var/lib/postgresql/monitor | sudo tee /etc/systemd/system/pgautofailover.service
+   13:44:34 INFO  sudo systemctl daemon-reload
+   13:44:34 INFO  sudo systemctl start pgautofailover
+   [Unit]
+   Description = pg_auto_failover
+   
+   [Service]
+   WorkingDirectory = /var/lib/postgresql/monitor
+   Environment = "PGDATA=/var/lib/postgresql/monitor"
+   User = postgres
+   ExecStart = /usr/lib/postgresql/10/bin/pg_autoctl run
+   Restart = always
+   StartLimitBurst = 0
+   
+   [Install]
+   WantedBy = multi-user.target
+   
+Copy/pasting the commands given in the hint output from the command will
+enable the pgautofailer service on your system, when using systemd.
+
+It is important that PostgreSQL is started by ``pg_autoctl`` rather than by
+systemd itself, as it might be that a failover has been done during a
+reboot, for instance, and that once the reboot complete we want the local
+Postgres to re-join as a secondary node where it used to be a primary node.

src/bin/pg_autoctl/cli_common.h

@@ -85,6 +85,9 @@ extern CommandLine show_uri_command;
 extern CommandLine show_events_command;
 extern CommandLine show_state_command;
 
+/* cli_systemd.c */
+extern CommandLine systemd_cat_service_file_command;
+
 
 int cli_create_node_getopts(int argc, char **argv,
 							struct option *long_options,

src/bin/pg_autoctl/cli_root.c

@@ -37,6 +37,7 @@ CommandLine *show_subcommands[] = {
 	&show_uri_command,
 	&show_events_command,
 	&show_state_command,
+	&systemd_cat_service_file_command,
 	NULL
 };
 

src/bin/pg_autoctl/cli_root.h

@@ -13,6 +13,8 @@
 
 #include "commandline.h"
 
+extern char pg_autoctl_argv0[];
+
 extern CommandLine help;
 extern CommandLine version;
 

src/bin/pg_autoctl/cli_systemd.c

@@ -0,0 +1,127 @@
+/*
+ * src/bin/pg_autoctl/cli_do_systemd.c
+ *     Implementation of a CLI which lets you run operations on the local
+ *     postgres server directly.
+ *
+ * Copyright (c) Microsoft Corporation. All rights reserved.
+ * Licensed under the PostgreSQL License.
+ *
+ */
+
+#include <errno.h>
+#include <getopt.h>
+#include <inttypes.h>
+#include <signal.h>
+
+#include "postgres_fe.h"
+
+#include "cli_common.h"
+#include "cli_do_root.h"
+#include "commandline.h"
+#include "config.h"
+#include "defaults.h"
+#include "file_utils.h"
+#include "keeper_config.h"
+#include "keeper.h"
+#include "systemd_config.h"
+
+static SystemdServiceConfig systemdOptions;
+
+
+static int cli_systemd_getopt(int argc, char **argv);
+static void cli_systemd_enable_service(int argc, char **argv);
+static void cli_systemd_cat_service_file(int argc, char **argv);
+
+/* pg_autoctl show systemd, see cli_show.c */
+CommandLine systemd_cat_service_file_command =
+	make_command("systemd",
+				 "Print systemd service file for this node", "", "",
+				 cli_systemd_getopt, cli_systemd_cat_service_file);
+
+
+/*
+ * cli_systemd_getopt parses the command line options necessary to handle
+ * systemd integration for the pg_autoctl keeper service.
+ */
+int
+cli_systemd_getopt(int argc, char **argv)
+{
+	SystemdServiceConfig options = { 0 };
+
+	int c = 0, option_index = 0, errors = 0;
+
+	static struct option long_options[] = {
+		{ "pgdata", required_argument, NULL, 'D' },
+		{ "help", no_argument, NULL, 'h' },
+		{ NULL, 0, NULL, 0 }
+	};
+
+	optind = 0;
+
+	while ((c = getopt_long(argc, argv, "D:h",
+							long_options, &option_index)) != -1)
+	{
+		switch (c)
+		{
+			case 'D':
+			{
+				strlcpy(options.pgSetup.pgdata, optarg, MAXPGPATH);
+				log_trace("--pgdata %s", options.pgSetup.pgdata);
+				break;
+			}
+
+		}
+	}
+
+	if (IS_EMPTY_STRING_BUFFER(options.pgSetup.pgdata))
+	{
+		char *pgdata = getenv("PGDATA");
+
+		if (pgdata == NULL)
+		{
+			log_fatal("Failed to set PGDATA either from the environment "
+					  "or from --pgdata");
+			exit(EXIT_CODE_BAD_ARGS);
+		}
+
+		strlcpy(options.pgSetup.pgdata, pgdata, MAXPGPATH);
+	}
+
+	if (!keeper_config_set_pathnames_from_pgdata(&options.pathnames,
+												 options.pgSetup.pgdata))
+	{
+		/* errors have already been logged */
+		exit(EXIT_CODE_BAD_CONFIG);
+	}
+
+	/* publish our option parsing in the global variable */
+	systemdOptions = options;
+
+	return optind;
+}
+
+
+/*
+ * cli_systemd_cat_service_file prints the systemd service file for this
+ * pg_autoctl node.
+ */
+static void
+cli_systemd_cat_service_file(int argc, char **argv)
+{
+	SystemdServiceConfig config = systemdOptions;
+	PostgresSetup pgSetup = { 0 };
+
+	(void) systemd_config_init(&config, pgSetup.pgdata);
+
+	log_info("HINT: to complete a systemd integration, "
+			 "run the following commands:");
+	log_info("pg_autoctl -q show systemd --pgdata \"%s\" | sudo tee %s",
+			 config.pgSetup.pgdata, config.pathnames.systemd);
+	log_info("sudo systemctl daemon-reload");
+	log_info("sudo systemctl start pgautofailover");
+
+	if (!systemd_config_write(stdout, &config))
+	{
+		exit(EXIT_CODE_INTERNAL_ERROR);
+	}
+}

src/bin/pg_autoctl/config.c

@@ -21,7 +21,6 @@
 #include "pgctl.h"
 
 
-
 /*
  * build_xdg_path is an helper function that builds the full path to an XDG
  * compatible resource: either a configuration file, a runtime file, or a data
@@ -154,28 +153,10 @@ build_xdg_path(char *dst,
 	join_path_components(filename, filename, name);
 
 	/* normalize the path to the configuration file, if it exists */
-	if (file_exists(filename))
-	{
-		char realPath[PATH_MAX];
-
-		if (realpath(filename, realPath) == NULL)
-		{
-			log_fatal("Failed to normalize file name \"%s\": %s",
-					  filename, strerror(errno));
-			return false;
-		}
-
-		if (strlcpy(dst, realPath, MAXPGPATH) >= MAXPGPATH)
-		{
-			log_fatal("Real path \"%s\" is %d bytes long, and pg_autoctl "
-					  "is limited to handling paths of %d bytes long, maximum",
-					  realPath, (int) strlen(realPath), MAXPGPATH);
-			return false;
-		}
-	}
-	else
+	if (!normalize_filename(filename, dst, MAXPGPATH))
 	{
-		strlcpy(dst, filename, MAXPGPATH);
+		/* errors have already been logged */
+		return false;
 	}
 
 	return true;
@@ -325,3 +306,39 @@ ProbeConfigurationFileRole(const char *filename)
 	/* can't happen: keep compiler happy */
 	return PG_AUTOCTL_ROLE_UNKNOWN;
 }
+
+
+/*
+ * normalize_filename returns the real path of a given filename, resolving
+ * symlinks and pruning double-slashes and other weird constructs.
+ */
+bool
+normalize_filename(const char *filename, char *dst, int size)
+{
+	/* normalize the path to the configuration file, if it exists */
+	if (file_exists(filename))
+	{
+		char realPath[PATH_MAX];
+
+		if (realpath(filename, realPath) == NULL)
+		{
+			log_fatal("Failed to normalize file name \"%s\": %s",
+					  filename, strerror(errno));
+			return false;
+		}
+
+		if (strlcpy(dst, realPath, size) >= size)
+		{
+			log_fatal("Real path \"%s\" is %d bytes long, and pg_autoctl "
+					  "is limited to handling paths of %d bytes long, maximum",
+					  realPath, (int) strlen(realPath), size);
+			return false;
+		}
+	}
+	else
+	{
+		strlcpy(dst, filename, MAXPGPATH);
+	}
+
+	return true;
+}

src/bin/pg_autoctl/config.h

@@ -37,6 +37,7 @@ typedef struct ConfigFilePaths
 	char state[MAXPGPATH];  /* ~/.local/share/pg_autoctl/${PGDATA}/pg_autoctl.state */
 	char pid[MAXPGPATH];	/* /tmp/${PGDATA}/pg_autoctl.pid */
 	char init[MAXPGPATH];	/* /tmp/${PGDATA}/pg_autoctl.init */
+	char systemd[MAXPGPATH];	/* ~/.config/systemd/user/pgautofailover.service */
 } ConfigFilePaths;
 
 /*
@@ -65,6 +66,7 @@ typedef enum
 
 bool build_xdg_path(char *dst, XDGResourceType xdgType,
 						   const char *pgdata, const char *name);
+bool normalize_filename(const char *filename, char *dst, int size);
 
 bool SetConfigFilePath(ConfigFilePaths *pathnames, const char *pgdata);
 bool SetStateFilePath(ConfigFilePaths *pathnames, const char *pgdata);

src/bin/pg_autoctl/defaults.h

@@ -53,6 +53,9 @@
 #define KEEPER_PID_FILENAME "pg_autoctl.pid"
 #define KEEPER_INIT_FILENAME "pg_autoctl.init"
 
+#define KEEPER_SYSTEMD_SERVICE "pgautofailover"
+#define KEEPER_SYSTEMD_FILENAME "pgautofailover.service"
+
 /* pg_auto_failover monitor related constants */
 #define PG_AUTOCTL_HEALTH_USERNAME "pgautofailover_monitor"
 #define PG_AUTOCTL_REPLICA_USERNAME "pgautofailover_replicator"