BP-47 (task3): Abstract interface for entrylogger (#3197)

* Interface for entrylogger

Define the interface and contract for entrylogger. This is mostly
taking the entrylogger methods used by other components and prettying
them up a bit.

Notable changes are:
- internalReadEntry is now readEntry. There is no 'validate'
  flag. Instead there are two overloads for the method, and validation
  only runs if ledgerId and entryId are passed in.
- shutdown has been renamed to close.
- the compaction entrylog methods have been put behind an
  interface. As it was they were leaking implementation
  details. Ultimitely compaction itself should be hidden behind the
  entrylogger, but that's a larger refactor.

(cherry picked from commit c927f4b)

* abstract interface for entrylogger

* format code

* format code

* address comments

* Apply suggestions from code review

Co-authored-by: Andrey Yegorov <8622884+dlg99@users.noreply.github.com>

* address comments

* format code

Co-authored-by: Ivan Kelly <ikelly@splunk.com>
Co-authored-by: Andrey Yegorov <8622884+dlg99@users.noreply.github.com>

bookkeeper-server/src/main/java/org/apache/bookkeeper/bookie/AbstractLogCompactor.java

@@ -57,7 +57,10 @@ public AbstractLogCompactor(ServerConfiguration conf, LogRemovalListener logRemo
      */
     public void cleanUpAndRecover() {}
 
-    static class Throttler {
+    /**
+     * class Throttler.
+     */
+    public static class Throttler {
         private final RateLimiter rateLimiter;
         private final boolean isThrottleByBytes;
 

bookkeeper-server/src/main/java/org/apache/bookkeeper/bookie/BookieShell.java

@@ -38,6 +38,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.stream.Collectors;
+import org.apache.bookkeeper.bookie.storage.EntryLogger;
 import org.apache.bookkeeper.client.LedgerEntry;
 import org.apache.bookkeeper.client.api.LedgerMetadata;
 import org.apache.bookkeeper.common.annotation.InterfaceAudience.Private;
@@ -2441,7 +2442,7 @@ public static void main(String[] argv) throws Exception {
     private synchronized void initEntryLogger() throws IOException {
         if (null == entryLogger) {
             // provide read only entry logger
-            entryLogger = new ReadOnlyEntryLogger(bkConf);
+            entryLogger = new ReadOnlyDefaultEntryLogger(bkConf);
         }
     }
 

bookkeeper-server/src/main/java/org/apache/bookkeeper/bookie/CompactableLedgerStorage.java

@@ -22,7 +22,7 @@
 package org.apache.bookkeeper.bookie;
 
 import java.io.IOException;
-
+import org.apache.bookkeeper.bookie.storage.EntryLogger;
 /**
  * Interface that identifies LedgerStorage implementations using EntryLogger and running periodic entries compaction.
  */