Configurable Retry Logic I - Statement Retry

src/main/java/com/microsoft/sqlserver/jdbc/ConfigurableRetryLogic.java

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+/*
+ * Microsoft JDBC Driver for SQL Server Copyright(c) Microsoft Corporation All rights reserved. This program is made
+ * available under the terms of the MIT License. See the LICENSE file in the project root for more information.
+ */
+
+package com.microsoft.sqlserver.jdbc;
+
+import java.io.BufferedReader;
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.FileReader;
+import java.io.IOException;
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.text.MessageFormat;
+import java.util.Collections;
+import java.util.Date;
+import java.util.HashMap;
+import java.util.LinkedList;
+import java.util.Map;
+
+
+/**
+ * Allows configurable statement retry through the use of the 'retryExec' connection property. Each rule read in is
+ * converted to ConfigRetryRule objects, which are stored and referenced during statement retry.
+ *
+ */
+public class ConfigurableRetryLogic {
+    private final static int INTERVAL_BETWEEN_READS_IN_MS = 30000;
+    private final static String DEFAULT_PROPS_FILE = "mssql-jdbc.properties";
+    private static final java.util.logging.Logger CONFIGURABLE_RETRY_LOGGER = java.util.logging.Logger
+            .getLogger("com.microsoft.sqlserver.jdbc.ConfigurableRetryLogic");
+    private static ConfigurableRetryLogic singleInstance = null;
+    private static long timeLastModified;
+    private static long timeLastRead;
+    private static String lastQuery = ""; // The last query executed (used when rule is process-dependent)
+    private static String prevRulesFromConnectionString = "";
+    private static HashMap<Integer, ConfigurableRetryRule> stmtRules = new HashMap<>();
+    private static final String SEMI_COLON = ";";
+    private static final String COMMA = ",";
+    private static final String FORWARD_SLASH = "/";
+    private static final String EQUALS_SIGN = "=";
+    private static final String RETRY_EXEC = "retryExec";
+
+    private ConfigurableRetryLogic() throws SQLServerException {
+        timeLastRead = new Date().getTime();
+        setUpRules(null);
+    }
+
+    /**
+     * Fetches the static instance of ConfigurableRetryLogic, instantiating it if it hasn't already been.
+     * Each time the instance is fetched, we check if a re-read is needed, and do so if properties should be re-read.
+     *
+     * @return The static instance of ConfigurableRetryLogic
+     * @throws SQLServerException
+     *         an exception
+     */
+    public static ConfigurableRetryLogic getInstance() throws SQLServerException {
+        // No need for lock; static initializer singleInstance is thread-safe
+        if (singleInstance == null) {
+            singleInstance = new ConfigurableRetryLogic();
+        } else {
+            refreshRuleSet();
+        }
+        return singleInstance;
+    }
+
+    /**
+     * If it has been INTERVAL_BETWEEN_READS_IN_MS (30 secs) since last read, see if we last did a file read, if so
+     * only reread if the file has been modified. If no file read, set up rules using the prev. connection string rules.
+     *
+     * @throws SQLServerException
+     *         when an exception occurs
+     */
+    private static void refreshRuleSet() throws SQLServerException {
+        long currentTime = new Date().getTime();
+        if ((currentTime - timeLastRead) >= INTERVAL_BETWEEN_READS_IN_MS) {
+            timeLastRead = currentTime;
+            if (timeLastModified != 0) {
+                // If timeLastModified has been set, we have previously read from a file, so we setUpRules
+                // reading from file
+                File f = new File(getCurrentClassPath());
+                if (f.lastModified() != timeLastModified) {
+                    setUpRules(null);
+                }
+            } else {
+                setUpRules(prevRulesFromConnectionString);
+            }
+        }
+    }
+
+    void setFromConnectionString(String newRules) throws SQLServerException {
+        prevRulesFromConnectionString = newRules;
+        setUpRules(prevRulesFromConnectionString);
+    }
+
+    void storeLastQuery(String newQueryToStore) {
+        lastQuery = newQueryToStore.toLowerCase();
+    }
+
+    String getLastQuery() {
+        return lastQuery;
+    }
+
+    /**
+     * Sets up rules based on either connection string option or file read.
+     *
+     * @param cxnStrRules
+     *        If null, rules are constructed from file, else, this parameter is used to construct rules
+     * @throws SQLServerException
+     *         If an exception occurs
+     */
+    private static void setUpRules(String cxnStrRules) throws SQLServerException {
+        stmtRules = new HashMap<>();
+        lastQuery = "";
+        LinkedList<String> temp;
+
+        if (cxnStrRules == null || cxnStrRules.isEmpty()) {
+            temp = readFromFile();
+        } else {
+            temp = new LinkedList<>();
+            Collections.addAll(temp, cxnStrRules.split(SEMI_COLON));
+        }
+        createRules(temp);
+    }
+
+    private static void createRules(LinkedList<String> listOfRules) throws SQLServerException {
+        stmtRules = new HashMap<>();
+
+        for (String potentialRule : listOfRules) {
+            ConfigurableRetryRule rule = new ConfigurableRetryRule(potentialRule);
+
+            if (rule.getError().contains(COMMA)) {
+                String[] arr = rule.getError().split(COMMA);
+
+                for (String retryError : arr) {
+                    ConfigurableRetryRule splitRule = new ConfigurableRetryRule(retryError, rule);
+                    stmtRules.put(Integer.parseInt(splitRule.getError()), splitRule);
+                }
+            } else {
+                stmtRules.put(Integer.parseInt(rule.getError()), rule);
+            }
+        }
+    }
+
+    private static String getCurrentClassPath() throws SQLServerException {
+        String location = "";
+        String className = "";
+
+        try {
+            className = new Object() {}.getClass().getEnclosingClass().getName();
+            location = Class.forName(className).getProtectionDomain().getCodeSource().getLocation().getPath();
+            location = location.substring(0, location.length() - 16);
+            URI uri = new URI(location + FORWARD_SLASH);
+            return uri.getPath() + DEFAULT_PROPS_FILE; // For now, we only allow "mssql-jdbc.properties" as file name.
+        } catch (URISyntaxException e) {
+            MessageFormat form = new MessageFormat(SQLServerException.getErrString("R_URLInvalid"));
+            Object[] msgArgs = {location + FORWARD_SLASH};
+            throw new SQLServerException(form.format(msgArgs), null, 0, e);
+        } catch (ClassNotFoundException e) {
+            MessageFormat form = new MessageFormat(SQLServerException.getErrString("R_UnableToFindClass"));
+            Object[] msgArgs = {className};
+            throw new SQLServerException(form.format(msgArgs), null, 0, e);
+        }
+    }
+
+    private static LinkedList<String> readFromFile() throws SQLServerException {
+        String filePath = getCurrentClassPath();
+        LinkedList<String> list = new LinkedList<>();
+
+        try {
+            File f = new File(filePath);
+            try (BufferedReader buffer = new BufferedReader(new FileReader(f))) {
+                String readLine;
+                while ((readLine = buffer.readLine()) != null) {
+                    if (readLine.startsWith(RETRY_EXEC)) {
+                        String value = readLine.split(EQUALS_SIGN)[1];
+                        Collections.addAll(list, value.split(SEMI_COLON));
+                    }
+                }
+            }
+            timeLastModified = f.lastModified();
+        } catch (FileNotFoundException e) {
+            // If the file is not found either A) We're not using CRL OR B) the path is wrong. Do not error out, instead
+            // log a message.
+            if (CONFIGURABLE_RETRY_LOGGER.isLoggable(java.util.logging.Level.FINER)) {
+                CONFIGURABLE_RETRY_LOGGER.finest("File not found at path - \"" + filePath + "\"");
+            }
+        } catch (IOException e) {
+            MessageFormat form = new MessageFormat(SQLServerException.getErrString("R_errorReadingStream"));
+            Object[] msgArgs = {e.getMessage() + ", from path - \"" + filePath + "\""};
+            throw new SQLServerException(form.format(msgArgs), null, 0, e);
+        }
+        return list;
+    }
+
+    ConfigurableRetryRule searchRuleSet(int ruleToSearchFor) throws SQLServerException {
+        refreshRuleSet();
+        for (Map.Entry<Integer, ConfigurableRetryRule> entry : stmtRules.entrySet()) {
+            if (entry.getKey() == ruleToSearchFor) {
+                return entry.getValue();
+            }
+        }
+        return null;
+    }
+}