Add a --socketdir option to pg_upgrade

This is a backport of the below commit from upstream PostgreSQL,
which was originally written for Greenplum and submitted as an
upstream-first feature. The commit didn't cherrypick as upstream
has moved pg_upgrade to src/bin and Greenplum has yet to merge
that.
Reviewed-by: NJacob Champion <pchampion@pivotal.io>

  commit 2d34ad84
  Author: Tom Lane <tgl@sss.pgh.pa.us>
  Date:   Sat Dec 1 15:45:11 2018 -0500

    Add a --socketdir option to pg_upgrade.

    This allows control of the directory in which the postmaster sockets
    are created for the temporary postmasters started by pg_upgrade.
    The default location remains the current working directory, which is
    typically fine, but if it is deeply nested then its pathname might
    be too long to be a socket name.

    In passing, clean up some messiness in pg_upgrade's option handling,
    particularly the confusing and undocumented way that configuration-only
    datadirs were handled.  And fix check_required_directory's substantially
    under-baked cleanup of directory pathnames.

    Daniel Gustafsson, reviewed by Hironobu Suzuki, some code cleanup by me

    Discussion: https://postgr.es/m/E72DD5C3-2268-48A5-A907-ED4B34BEC223@yesql.se

contrib/pg_upgrade/option.c

@@ -22,8 +22,9 @@
 
 
 static void usage(void);
-static void check_required_directory(char **dirpath, char **configpath,
-				   char *envVarName, char *cmdLineOption, char *description);
+static void check_required_directory(char **dirpath,
+						 const char *envVarName, bool useCwd,
+						 const char *cmdLineOption, const char *description);
 #define FIX_DEFAULT_READ_ONLY "-c default_transaction_read_only=false"
 
 
@@ -53,6 +54,7 @@ parseCommandLine(int argc, char *argv[])
 		{"link", no_argument, NULL, 'k'},
 		{"retain", no_argument, NULL, 'r'},
 		{"jobs", required_argument, NULL, 'j'},
+		{"socketdir", required_argument, NULL, 's'},
 		{"verbose", no_argument, NULL, 'v'},
 
 		/* Greenplum specific parameters */
@@ -111,7 +113,7 @@ parseCommandLine(int argc, char *argv[])
 	if ((log_opts.internal = fopen_priv(INTERNAL_LOG_FILE, "a")) == NULL)
 		pg_fatal("cannot write to log file %s\n", INTERNAL_LOG_FILE);
 
-	while ((option = getopt_long(argc, argv, "d:D:b:B:cj:ko:O:p:P:rU:v",
+	while ((option = getopt_long(argc, argv, "d:D:b:B:cj:ko:O:p:P:rs:U:v",
 								 long_options, &optindex)) != -1)
 	{
 		switch (option)
@@ -130,12 +132,10 @@ parseCommandLine(int argc, char *argv[])
 
 			case 'd':
 				old_cluster.pgdata = pg_strdup(optarg);
-				old_cluster.pgconfig = pg_strdup(optarg);
 				break;
 
 			case 'D':
 				new_cluster.pgdata = pg_strdup(optarg);
-				new_cluster.pgconfig = pg_strdup(optarg);
 				break;
 
 			case 'j':
@@ -179,6 +179,10 @@ parseCommandLine(int argc, char *argv[])
 				log_opts.retain = true;
 				break;
 
+			case 's':
+				user_opts.socketdir = pg_strdup(optarg);
+				break;
+
 			case 'U':
 				pg_free(os_info.user);
 				os_info.user = pg_strdup(optarg);
@@ -260,14 +264,16 @@ parseCommandLine(int argc, char *argv[])
 		pg_putenv("PGOPTIONS", FIX_DEFAULT_READ_ONLY);
 
 	/* Get values from env if not already set */
-	check_required_directory(&old_cluster.bindir, NULL, "PGBINOLD", "-b",
-							 "old cluster binaries reside");
-	check_required_directory(&new_cluster.bindir, NULL, "PGBINNEW", "-B",
-							 "new cluster binaries reside");
-	check_required_directory(&old_cluster.pgdata, &old_cluster.pgconfig,
-							 "PGDATAOLD", "-d", "old cluster data resides");
-	check_required_directory(&new_cluster.pgdata, &new_cluster.pgconfig,
-							 "PGDATANEW", "-D", "new cluster data resides");
+	check_required_directory(&old_cluster.bindir, "PGBINOLD", false,
+							 "-b", "old cluster binaries reside");
+	check_required_directory(&new_cluster.bindir, "PGBINNEW", false,
+							 "-B", "new cluster binaries reside");
+	check_required_directory(&old_cluster.pgdata, "PGDATAOLD", false,
+							 "-d", "old cluster data resides");
+	check_required_directory(&new_cluster.pgdata, "PGDATANEW", false,
+							 "-D", "new cluster data resides");
+	check_required_directory(&user_opts.socketdir, "PGSOCKETDIR", true,
+							 "-s", "sockets will be created");
 
 	/* Ensure we are only adding checksums in copy mode */
 	if (user_opts.transfer_mode != TRANSFER_MODE_COPY &&
@@ -296,6 +302,7 @@ Options:\n\
   -p, --old-port=PORT           old cluster port number (default %d)\n\
   -P, --new-port=PORT           new cluster port number (default %d)\n\
   -r, --retain                  retain SQL and log files after success\n\
+  -s, --socketdir=DIR           socket directory to use (default CWD)\n\
   -U, --username=NAME           cluster superuser (default \"%s\")\n\
   -v, --verbose                 enable verbose internal logging\n\
   -V, --version                 display version information, then exit\n\
@@ -342,29 +349,32 @@ or\n"), old_cluster.port, new_cluster.port, os_info.user);
  * check_required_directory()
  *
  * Checks a directory option.
- *	dirpath		  - the directory name supplied on the command line
- *	configpath	  - optional configuration directory
+ *	dirpath		  - the directory name supplied on the command line, or NULL
  *	envVarName	  - the name of an environment variable to get if dirpath is NULL
- *	cmdLineOption - the command line option corresponds to this directory (-o, -O, -n, -N)
+ *	useCwd		  - true if OK to default to CWD
+ *	cmdLineOption - the command line option for this directory
  *	description   - a description of this directory option
  *
  * We use the last two arguments to construct a meaningful error message if the
  * user hasn't provided the required directory name.
  */
 static void
-check_required_directory(char **dirpath, char **configpath,
-						 char *envVarName, char *cmdLineOption,
-						 char *description)
+check_required_directory(char **dirpath, const char *envVarName, bool useCwd,
+						 const char *cmdLineOption, const char *description)
 {
 	if (*dirpath == NULL || strlen(*dirpath) == 0)
 	{
 		const char *envVar;
 
 		if ((envVar = getenv(envVarName)) && strlen(envVar))
-		{
 			*dirpath = pg_strdup(envVar);
-			if (configpath)
-				*configpath = pg_strdup(envVar);
+		else if (useCwd)
+		{
+			char		cwd[MAXPGPATH];
+
+			if (!getcwd(cwd, MAXPGPATH))
+				pg_fatal("could not determine current directory\n");
+			*dirpath = pg_strdup(cwd);
 		}
 		else
 			pg_fatal("You must identify the directory where the %s.\n"
@@ -373,16 +383,10 @@ check_required_directory(char **dirpath, char **configpath,
 	}
 
 	/*
-	 * Trim off any trailing path separators because we construct paths by
-	 * appending to this path.
+	 * Clean up the path, in particular trimming any trailing path separators,
+	 * because we construct paths by appending to this path.
 	 */
-#ifndef WIN32
-	if ((*dirpath)[strlen(*dirpath) - 1] == '/')
-#else
-	if ((*dirpath)[strlen(*dirpath) - 1] == '/' ||
-		(*dirpath)[strlen(*dirpath) - 1] == '\\')
-#endif
-		(*dirpath)[strlen(*dirpath) - 1] = 0;
+	canonicalize_path(*dirpath);
 }
 
 /*
@@ -391,6 +395,10 @@ check_required_directory(char **dirpath, char **configpath,
  * If a configuration-only directory was specified, find the real data dir
  * by quering the running server.  This has limited checking because we
  * can't check for a running server because we can't find postmaster.pid.
+ *
+ * On entry, cluster->pgdata has been set from command line or env variable,
+ * but cluster->pgconfig isn't set.  We fill both variables with corrected
+ * values.
  */
 void
 adjust_data_dir(ClusterInfo *cluster)
@@ -401,6 +409,9 @@ adjust_data_dir(ClusterInfo *cluster)
 	FILE	   *fp,
 			   *output;
 
+	/* Initially assume config dir and data dir are the same */
+	cluster->pgconfig = pg_strdup(cluster->pgdata);
+
 	/* If there is no postgresql.conf, it can't be a config-only dir */
 	snprintf(filename, sizeof(filename), "%s/postgresql.conf", cluster->pgconfig);
 	if ((fp = fopen(filename, "r")) == NULL)
@@ -465,12 +476,7 @@ get_sock_dir(ClusterInfo *cluster, bool live_check)
 	if (GET_MAJOR_VERSION(cluster->major_version) >= 901)
 	{
 		if (!live_check)
-		{
-			/* Use the current directory for the socket */
-			cluster->sockdir = pg_malloc(MAXPGPATH);
-			if (!getcwd(cluster->sockdir, MAXPGPATH))
-				pg_fatal("cannot find current directory\n");
-		}
+			cluster->sockdir = user_opts.socketdir;
 		else
 		{
 			/*

contrib/pg_upgrade/pg_upgrade.h

@@ -424,7 +424,8 @@ typedef struct
 	bool		check;			/* TRUE -> ask user for permission to make
 								 * changes */
 	transferMode transfer_mode; /* copy files or link them? */
-	int			jobs;
+	int			jobs;			/* number of processes/threads to use */
+	char	   *socketdir;		/* directory to use for Unix sockets */
 
 	bool		progress;
 	segmentMode	segment_mode;