Don't overwrite gpexpand template on the same host (#1100)

In RedOS, when both the master and a segment are on the same host, running
gpexpand correctly was impossible.

Typically, the master is excluded from the gpexpand host array. However, if both
the master and a segment are on the same host, the master's host gets included
in the array. The issue arises due to the scp command corrupting and truncating
the gpexpand_schema.tar file when the host, source and destination paths are the
same.

Don't issue a scp command if we are dealing with the local host with and paths
are the same. Note that gpexpand always uses relative filepaths for scp's
destination, and that they are relative to /home/gpadmin/.

This problem does not occur in GPDB 7, as it uses rsync instead of scp, which
does not have said issue.

Ticket: ADBDEV-6472

Author: bandetto

gpMgmt/bin/gpexpand

@@ -15,6 +15,7 @@ import sys
 import json
 import shutil
 import signal
+import socket
 import traceback
 from collections import defaultdict
 from time import strftime, sleep
@@ -773,8 +774,19 @@ class SegmentTemplate:
 
     def _distribute_tarfile(self):
         """Distributes template tar file to hosts"""
+        localHostAddr = socket.gethostbyname(getLocalHostname())
+        # NOTE: Currently, GP's scp transfers relative file paths into the home
+        # directory by default.
+        pathsAreSame = os.path.realpath(self.segTarFile) == os.path.join(getHomePath(), self.schema_tar_file)
+
         for host in self.hosts:
-            logger.debug('Copying tar file to %s' % host)
+            # If the source and the destination are the same on the local
+            # machine, scp may corrupt the file. Don't overwrite it.
+            if socket.gethostbyname(host) == localHostAddr and pathsAreSame:
+                logger.debug('Skipping tar file (%s) copy to %s' % (self.schema_tar_file, host))
+                continue
+
+            logger.debug('Copying tar file (%s) to %s' % (self.schema_tar_file, host))
             cpCmd = Scp(name='gpexpand distribute tar file to new hosts',
                         srcFile=self.schema_tar_file,
                         dstFile=self.segTarDir,

gpMgmt/bin/gppylib/commands/unix.py

@@ -81,6 +81,10 @@ def getUserName():
     return pwd.getpwuid(os.getuid()).pw_name
 
 
+def getHomePath():
+    return pwd.getpwuid(os.getuid()).pw_dir
+
+
 def check_pid_on_remotehost(pid, host):
     """ Check For the existence of a unix pid on remote host. """
 

gpMgmt/test/behave/mgmt_utils/gpexpand.feature

@@ -804,3 +804,22 @@ Feature: expand the cluster by adding more segments
         And table "test_good_2" should be marked as expanded
         And table "test_already_expanded" should be marked as expanded
         And table "test_broken" should not be marked as expanded
+
+    @gpexpand_avoid_tarfile_overwrite
+    Scenario: Avoid overwriting the tar file on coordinator
+        Given the database is not running
+        # need to remove this log because otherwise SCAN_LOG may pick up a previous error/warning in the log
+        And the user runs command "rm -rf ~/gpAdminLogs/gpinitsystem*"
+        # gpconfigurenewsegment scp's tar file to home by default
+        And a working directory of the test as '/data/gpdata/gpexpand'
+        And a temporary directory under "/data/gpdata/gpexpand/expandedData" to expand into
+        And the cluster is generated with "1" primaries only
+        And database "gptest" exists
+        And the directory is changed to '/home/gpadmin'
+        And there are no gpexpand_inputfiles
+        And the cluster is setup for an expansion on hosts "localhost"
+        When the user runs gpexpand interview to add 1 new segment and 0 new host "ignored.host"
+        Then the number of segments have been saved
+        When the user runs gpexpand with the latest gpexpand_inputfile with additional parameters "--verbose"
+        Then gpexpand should print "[DEBUG]:-Skipping tar file (gpexpand_schema.tar) copy to cdw" escaped to stdout
+        And verify that the cluster has 1 new segments

gpMgmt/test/behave/mgmt_utils/steps/mgmt_utils.py

@@ -3038,6 +3038,11 @@ def impl(context, working_directory, mode):
 def impl(context, working_directory):
     _create_working_directory(context, working_directory)
 
+@given("the directory is changed to '{working_directory}'")
+def impl(context, working_directory):
+    context.working_directory = working_directory
+    os.chdir(working_directory)
+
 def _create_working_directory(context, working_directory, mode=''):
     context.working_directory = working_directory
     # Don't fail if directory already exists, which can occur for the first scenario