Address handling of OS pretty name on some OS (#35451)

Some OS (e.g., Oracle Linux Server 6.9) have a trailing space at the end
of the PRETTY_NAME line in /etc/os-release. This commit addresses this
by accounting for this trailing space when extracting the pretty name.

Author: jasontedor

qa/evil-tests/src/test/java/org/elasticsearch/monitor/os/EvilOsProbeTests.java

@@ -39,8 +39,10 @@ public void testOsPrettyName() throws IOException  {
             final List<String> lines = Files.readAllLines(PathUtils.get("/etc/os-release"));
             for (final String line : lines) {
                 if (line != null && line.startsWith("PRETTY_NAME=")) {
-                    final Matcher matcher = Pattern.compile("PRETTY_NAME=(\"?|'?)?([^\"']+)\\1").matcher(line);
-                    assert matcher.matches() : line;
+                    final Matcher matcher = Pattern.compile("PRETTY_NAME=(\"?|'?)?([^\"']+)\\1").matcher(line.trim());
+                    final boolean matches = matcher.matches();
+                    assert matches : line;
+                    assert matcher.groupCount() == 2 : line;
                     final String prettyName = matcher.group(2);
                     assertThat(osInfo.getPrettyName(), equalTo(prettyName));
                     return;

server/src/main/java/org/elasticsearch/monitor/os/OsProbe.java

@@ -37,6 +37,8 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
 import java.util.stream.Collectors;
 
 public class OsProbe {
@@ -547,16 +549,13 @@ private String getPrettyName() throws IOException {
             final Optional<String> maybePrettyNameLine =
                     prettyNameLines.size() == 1 ? Optional.of(prettyNameLines.get(0)) : Optional.empty();
             if (maybePrettyNameLine.isPresent()) {
-                final String prettyNameLine = maybePrettyNameLine.get();
-                final String[] prettyNameFields = prettyNameLine.split("=");
-                assert prettyNameFields.length == 2 : prettyNameLine;
-                if (prettyNameFields[1].length() >= 3 &&
-                        (prettyNameFields[1].startsWith("\"") && prettyNameFields[1].endsWith("\"")) ||
-                        (prettyNameFields[1].startsWith("'") && prettyNameFields[1].endsWith("'"))) {
-                    return prettyNameFields[1].substring(1, prettyNameFields[1].length() - 1);
-                } else {
-                    return prettyNameFields[1];
-                }
+                // we trim since some OS contain trailing space, for example, Oracle Linux Server 6.9 has a trailing space after the quote
+                final String trimmedPrettyNameLine = maybePrettyNameLine.get().trim();
+                final Matcher matcher = Pattern.compile("PRETTY_NAME=(\"?|'?)?([^\"']+)\\1").matcher(trimmedPrettyNameLine);
+                final boolean matches = matcher.matches();
+                assert matches : trimmedPrettyNameLine;
+                assert matcher.groupCount() == 2 : trimmedPrettyNameLine;
+                return matcher.group(2);
             } else {
                 return Constants.OS_NAME;
             }

server/src/test/java/org/elasticsearch/monitor/os/OsProbeTests.java

@@ -27,6 +27,7 @@
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
+import java.util.Locale;
 
 import static org.hamcrest.Matchers.allOf;
 import static org.hamcrest.Matchers.anyOf;
@@ -55,12 +56,10 @@ public void testOsInfo() throws IOException {
             List<String> readOsRelease() throws IOException {
                 assert Constants.LINUX : Constants.OS_NAME;
                 if (prettyName != null) {
-                    final String quote = randomFrom("\"", "'", null);
-                    if (quote == null) {
-                        return Arrays.asList("NAME=" + randomAlphaOfLength(16), "PRETTY_NAME=" + prettyName);
-                    } else {
-                        return Arrays.asList("NAME=" + randomAlphaOfLength(16), "PRETTY_NAME=" + quote + prettyName + quote);
-                    }
+                    final String quote = randomFrom("\"", "'", "");
+                    final String space = randomFrom(" ", "");
+                    final String prettyNameLine = String.format(Locale.ROOT, "PRETTY_NAME=%s%s%s%s", quote, prettyName, quote, space);
+                    return Arrays.asList("NAME=" + randomAlphaOfLength(16), prettyNameLine);
                 } else {
                     return Collections.singletonList("NAME=" + randomAlphaOfLength(16));
                 }