db: pin utf8mb4_general_ci as the default connection collation

framework/db/pom.xml

@@ -75,7 +75,17 @@
                 <configuration>
                     <excludes>
                         <exclude>com/cloud/utils/testcase/*TestCase*</exclude>
-                        <exclude>com/cloud/utils/db/*Test*</exclude>
+                        <!-- The test classes below are excluded because they require a live database. The remaining
+                             ones in com/cloud/utils/db are plain unit tests and must run in the build. -->
+                        <exclude>com/cloud/utils/db/DbTest*</exclude>
+                        <exclude>com/cloud/utils/db/ElementCollectionTest*</exclude>
+                        <exclude>com/cloud/utils/db/FilterTest*</exclude>
+                        <exclude>com/cloud/utils/db/GenericDaoBaseTest*</exclude>
+                        <exclude>com/cloud/utils/db/GlobalLockTest*</exclude>
+                        <exclude>com/cloud/utils/db/GroupByTest*</exclude>
+                        <exclude>com/cloud/utils/db/Merovingian2Test*</exclude>
+                        <exclude>com/cloud/utils/db/TestTransaction*</exclude>
+                        <exclude>com/cloud/utils/db/TransactionContextBuilderTest*</exclude>
                     </excludes>
                 </configuration>
             </plugin>

framework/db/src/main/java/com/cloud/utils/db/TransactionLegacy.java

@@ -31,6 +31,7 @@
 import java.util.Properties;
 import java.util.Objects;
 import java.util.concurrent.atomic.AtomicLong;
+import java.util.regex.Pattern;
 
 import javax.sql.DataSource;
 
@@ -87,6 +88,17 @@ public class TransactionLegacy implements Closeable {
     public static final short CONNECTED_DB = -1;
     public static final String CONNECTION_PARAMS = "scrollTolerantForwardOnly=true";
 
+    /**
+     * Format of the pattern that matches a parameter of a connection URI: the name must be at the start of the URI
+     * parameters or right after a parameter separator, and must be followed by "=". Searching for the bare name would
+     * consider the parameter as configured when it is just part of a host, of a database name or of the value of
+     * another parameter.
+     */
+    private static final String URI_PARAM_PATTERN_FORMAT = "(?:^|[?&])%s=";
+    private static final String CONNECTION_COLLATION_PARAM = "connectionCollation";
+    private static final String CHARACTER_ENCODING_PARAM = "characterEncoding";
+    private static final String DEFAULT_CONNECTION_COLLATION = "utf8mb4_general_ci";
+
     private static AtomicLong s_id = new AtomicLong();
     private static final TransactionMBeanImpl s_mbean = new TransactionMBeanImpl();
     static {
@@ -1196,6 +1208,9 @@ protected static Pair<String, String> getConnectionUriAndDriver(Properties dbPro
 
             connectionUri = propertyUri;
         }
+
+        connectionUri = addDefaultConnectionCollation(connectionUri);
+
         LOGGER.info("Using the following URI to connect to {} database [{}].", schema, connectionUri);
         return new Pair<>(connectionUri, driver);
     }
@@ -1260,6 +1275,48 @@ protected static String buildConnectionUri(String loadBalanceStrategy, String dr
         return connectionUri.toString();
     }
 
+    /**
+     * Informs whether {@link #DEFAULT_CONNECTION_COLLATION} should be added to a connection URI. It is only added for
+     * connections that do not already define the charset or the collation, either through {@code db.<schema>.url.params}
+     * or directly in {@code db.<schema>.uri}.
+     *
+     * @param connectionUri the connection URI configured by the operator.
+     */
+    protected static boolean shouldPinConnectionCollation(String connectionUri) {
+        return !containsUriParam(connectionUri, CONNECTION_COLLATION_PARAM)
+                && !containsUriParam(connectionUri, CHARACTER_ENCODING_PARAM);
+    }
+
+    /**
+     * Informs whether the given parameter is defined in the connection URI.
+     *
+     * @param connectionUri the connection URI configured by the operator; it also accepts only the parameters of a URI,
+     *                      as in {@code db.<schema>.url.params};
+     * @param param the name of the parameter to look for.
+     */
+    protected static boolean containsUriParam(String connectionUri, String param) {
+        Pattern pattern = Pattern.compile(String.format(URI_PARAM_PATTERN_FORMAT, Pattern.quote(param)), Pattern.CASE_INSENSITIVE);
+        return pattern.matcher(StringUtils.defaultString(connectionUri)).find();
+    }
+
+    /**
+     * Adds {@link #DEFAULT_CONNECTION_COLLATION} to a connection URI configured either through
+     * {@code db.<schema>.url.params} or directly in {@code db.<schema>.uri}, keeping the URI untouched if the operator
+     * already defined the charset or the collation in it.
+     */
+    protected static String addDefaultConnectionCollation(String connectionUri) {
+        if (!shouldPinConnectionCollation(connectionUri)) {
+            return connectionUri;
+        }
+
+        String separator = "?";
+        if (StringUtils.contains(connectionUri, "?")) {
+            separator = StringUtils.endsWithAny(connectionUri, "?", "&") ? StringUtils.EMPTY : "&";
+        }
+
+        return String.format("%s%s%s=%s", connectionUri, separator, CONNECTION_COLLATION_PARAM, DEFAULT_CONNECTION_COLLATION);
+    }
+
     /**
      * Creates a data source
      */