Method ensureLog

solr/core/src/java/org/apache/solr/update/UpdateLog.java:1643–1679

Ensures a transaction log is ready. It is either the current one, or a new one. This method must be called with the synchronization monitor on this UpdateLog.

()

  }

  /**
   * Ensures a transaction log is ready. It is either the current one, or a new one. This method
   * must be called with the synchronization monitor on this {@link UpdateLog}.
   */
  protected void ensureLog() {
    if (tlog == null) {
      Path newLogPath;
      int numAttempts = 0;
      while (true) {
        String newLogName = String.format(Locale.ROOT, LOG_FILENAME_PATTERN, TLOG_NAME, id);
        newLogPath = tlogDir.resolve(newLogName);
        // We expect that the log file does not exist since id is designed to give the index of the
        // next transaction log to create. But in very rare cases, the log files listed in the
        // init() method may be stale here (file system delay?), and id may point to an existing
        // file.
        if (!Files.exists(newLogPath)) {
          break;
        }
        // If the "new" log file already exists, refresh the log list and recompute id.
        // Ideally we would want to include the missing log in the old logs tracking (see init()),
        // but the init() method is not designed to be executed twice. Given that in the rare cases
        // we have seen this missing log, the log was always empty (file size 0), then we simply
        // refresh log list and update the id.
        try {
          log.error(
              "New transaction log already exists {} size={}, skipping it",
              newLogPath,
              Files.size(newLogPath));
        } catch (IOException e) {
          log.error("New transaction log already exists {} size unknown, skipping it", newLogPath);
        }
        if (++numAttempts >= 2) {
          throw new SolrException(
              ErrorCode.SERVER_ERROR, "Cannot recover from already existing logs");
        }
        tlogFiles = getLogList(tlogDir);
        id = scanLastLogId(tlogFiles) + 1; // add 1 since we create a new log
      }
      tlog = newTransactionLog(newLogPath, globalStrings, false);
    }