Copy situational configuration using a temporary file and mv to improve concurrency (#3359)

* Use mv while updating situational configuration files to improve concurrency

Author: rjeberhard

operator/src/main/resources/scripts/livenessProbe.sh

@@ -1,6 +1,6 @@
 #!/bin/bash
 
-# Copyright (c) 2017, 2021, Oracle and/or its affiliates.
+# Copyright (c) 2017, 2022, Oracle and/or its affiliates.
 # Licensed under the Universal Permissive License v 1.0 as shown at https://oss.oracle.com/licenses/upl.
 
 # Kubernetes periodically calls this liveness probe script to determine whether
@@ -35,9 +35,9 @@ if [ ! "${DYNAMIC_CONFIG_OVERRIDE:-notset}" = notset ]; then
       tgt_file=$tgt_dir/$tgt_file             # add back in tgt dir path
       [ -f "$tgt_file" ] && [ -z "$(diff $local_fname $tgt_file 2>&1)" ] && continue  # nothing changed
       trace "Copying file '$local_fname' to '$tgt_file'."
-      cp $local_fname $tgt_file # TBD ignore any error?
+      copyIfChanged $local_fname $tgt_file
       if [ -O "$tgt_file" ]; then
-        chmod 770 $tgt_file # TBD ignore any error?
+        chmod 770 $tgt_file
       fi
     done
     for local_fname in ${tgt_dir}/*.xml ; do

operator/src/main/resources/scripts/startServer.sh

@@ -1,6 +1,6 @@
 #!/bin/bash
 
-# Copyright (c) 2017, 2021, Oracle and/or its affiliates.
+# Copyright (c) 2017, 2022, Oracle and/or its affiliates.
 # Licensed under the Universal Permissive License v 1.0 as shown at https://oss.oracle.com/licenses/upl.
 
 #
@@ -29,25 +29,6 @@ fi
 exportInstallHomes
 
 #
-# Define helper fn to copy a file only if src & tgt differ
-#
-
-function copyIfChanged() {
-  [ ! -f "${1?}" ] && trace SEVERE "File '$1' not found." && exit 1
-  if [ ! -f "${2?}" ] || [ ! -z "`diff $1 $2 2>&1`" ]; then
-    trace "Copying '$1' to '$2'."
-    cp $1 $2
-    [ $? -ne 0 ] && trace SEVERE "failed cp $1 $2" && exitOrLoop
-    if [ -O "$2" ]; then
-      chmod 770 $2
-      [ $? -ne 0 ] && trace SEVERE "failed chmod 770 $2" && exitOrLoop
-    fi
-  else
-    trace "Skipping copy of '$1' to '$2' -- these files already match."
-  fi
-}
-
-# 
 # if the auxiliary image feature is active, verify the mount, and log mount information
 #
 checkAuxiliaryImage || exitOrLoop

operator/src/main/resources/scripts/utils.sh

@@ -1,4 +1,4 @@
-# Copyright (c) 2017, 2021, Oracle and/or its affiliates.
+# Copyright (c) 2017, 2022, Oracle and/or its affiliates.
 # Licensed under the Universal Permissive License v 1.0 as shown at https://oss.oracle.com/licenses/upl.
 
 set -o pipefail
@@ -17,6 +17,31 @@ source ${SCRIPTPATH}/utils_base.sh
 #   [ $? -ne 0 ] && echo "[SEVERE] Missing file ${SCRIPTPATH}/utils.sh" && exit 1
 #
 
+#
+# Define helper fn to copy a file only if src & tgt differ
+#
+
+function copyIfChanged() {
+  [ ! -f "${1?}" ] && trace SEVERE "File '$1' not found." && exit 1
+  if [ ! -f "${2?}" ] || [ ! -z "`diff $1 $2 2>&1`" ]; then
+    trace "Copying '$1' to '$2'."
+    # Copy the source file to a temporary file in the same directory as the target and then
+    # move the temporary file to the target. This is done because the target file may be read by another
+    # process during the copy operation, such as can happen for situational configuration files stored in a
+    # domain home on a persistent volume.
+    tmp_file=$(mktemp -p $(dirname $2))
+    cp $1 $tmp_file
+    mv $tmp_file $2
+    [ $? -ne 0 ] && trace SEVERE "failed cp $1 $2" && exitOrLoop
+    if [ -O "$2" ]; then
+      chmod 770 $2
+      [ $? -ne 0 ] && trace SEVERE "failed chmod 770 $2" && exitOrLoop
+    fi
+  else
+    trace "Skipping copy of '$1' to '$2' -- these files already match."
+  fi
+}
+
 # exportInstallHomes
 #   purpose:  export MW_HOME, WL_HOME, ORACLE_HOME
 #             with defaults as needed