make variable checking much more DRY

src/main/java/com/zendesk/maxwell/MaxwellMysqlStatus.java

@@ -32,23 +32,13 @@ private String getVariableState(String variableName, boolean throwOnMissing) thr
 		return status;
 	}
 
-	private void ensureNotReadOnly() throws SQLException, MaxwellCompatibilityError {
-		if (!getVariableState("read_only", true).equals("OFF")) {
-			throw new MaxwellCompatibilityError("read_only must be OFF.");
+	private void ensureVariableState(String variable, String state) throws SQLException, MaxwellCompatibilityError
+	{
+		if (!getVariableState(variable, true).equals(state)) {
+			throw new MaxwellCompatibilityError("variable " + variable + " must be set to '" + state + "'");
 		}
 	}
 
-	private void ensureReplicationOn() throws SQLException, MaxwellCompatibilityError {
-		if (!getVariableState("log_bin", true).equals("ON")) {
-			throw new MaxwellCompatibilityError("log_bin status must be ON.");
-		}
-	}
-
-	private void ensureReplicationFormatROW() throws SQLException, MaxwellCompatibilityError {
-		if (!getVariableState("binlog_format", true).equals("ROW")) {
-			throw new MaxwellCompatibilityError("binlog_format must be ROW.");
-		}
-	}
 
 	private void ensureRowImageFormat() throws SQLException, MaxwellCompatibilityError {
 		String rowImageFormat = getVariableState("binlog_row_image", false);
@@ -61,9 +51,10 @@ private void ensureRowImageFormat() throws SQLException, MaxwellCompatibilityErr
 
 	public static void ensureMysqlState(Connection c) throws SQLException, MaxwellCompatibilityError {
 		MaxwellMysqlStatus m = new MaxwellMysqlStatus(c);
-		m.ensureNotReadOnly();
-		m.ensureReplicationOn();
-		m.ensureReplicationFormatROW();
+
+		m.ensureVariableState("read_only", "OFF");
+		m.ensureVariableState("log_bin", "ON");
+		m.ensureVariableState("binlog_format", "ROW");
 		m.ensureRowImageFormat();
 	}
 }