Added log ring buffer

app/src/main/java/eu/faircode/email/EmailService.java

@@ -45,8 +45,6 @@ import com.sun.mail.util.MailConnectException;
 import com.sun.mail.util.SocketConnectException;
 import com.sun.mail.util.TraceOutputStream;
 
-import org.json.JSONException;
-
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.io.OutputStream;
@@ -80,7 +78,6 @@ import java.util.concurrent.ExecutorService;
 import java.util.regex.Pattern;
 
 import javax.mail.AuthenticationFailedException;
-import javax.mail.Authenticator;
 import javax.mail.Folder;
 import javax.mail.MessagingException;
 import javax.mail.NoSuchProviderException;
@@ -117,6 +114,7 @@ public class EmailService implements AutoCloseable {
     private Service iservice;
     private StoreListener listener;
     private ServiceAuthenticator authenticator;
+    private RingBuffer<String> breadcrumbs;
 
     private ExecutorService executor = Helper.getBackgroundExecutor(0, "mail");
 
@@ -136,6 +134,7 @@ public class EmailService implements AutoCloseable {
     private final static int POOL_SIZE = 1; // connections
     private final static int POOL_TIMEOUT = 60 * 1000; // milliseconds, default 45 sec
     private final static long PROTOCOL_LOG_DURATION = 12 * 3600 * 1000L;
+    private final static int BREADCRUMBS_SIZE = 100;
 
     private final static int MAX_IPV4 = 2;
     private final static int MAX_IPV6 = 1;
@@ -679,6 +678,8 @@ public class EmailService implements AutoCloseable {
             SSLSocketFactoryService factory) throws MessagingException {
         isession = Session.getInstance(properties, authenticator);
 
+        breadcrumbs = new RingBuffer<>(BREADCRUMBS_SIZE);
+
         isession.setDebug(debug || log);
         if (debug || log)
             isession.setDebugOut(new PrintStream(new OutputStream() {
@@ -693,6 +694,7 @@ public class EmailService implements AutoCloseable {
                                 if (log)
                                     EntityLog.log(context, EntityLog.Type.Protocol, user + " " + line);
                                 else {
+                                    breadcrumbs.push(line);
                                     if (BuildConfig.DEBUG)
                                         Log.i("javamail", user + " " + line);
                                 }
@@ -876,6 +878,11 @@ public class EmailService implements AutoCloseable {
         }
     }
 
+    public void dump() {
+        while (breadcrumbs != null && !breadcrumbs.isEmpty())
+            EntityLog.log(context, "Crumb " + breadcrumbs.pop());
+    }
+
     private static class SocketFactoryService extends SocketFactory {
         private SocketFactory factory = SocketFactory.getDefault();
 

app/src/main/java/eu/faircode/email/RingBuffer.java

@@ -0,0 +1,56 @@
+package eu.faircode.email;
+
+/*
+    This file is part of FairEmail.
+
+    FairEmail is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    FairEmail is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with FairEmail.  If not, see <http://www.gnu.org/licenses/>.
+
+    Copyright 2018-2021 by Marcel Bokhorst (M66B)
+*/
+
+public class RingBuffer<T> {
+    private T[] buffer;
+    private int count = 0;
+    private int out = 0;
+    private int in = 0;
+
+    public RingBuffer(int capacity) {
+        buffer = (T[]) new Object[capacity];
+    }
+
+    public synchronized void push(T item) {
+        if (count == buffer.length)
+            pop();
+
+        buffer[in] = item;
+        in = (in + 1) % buffer.length;
+        count++;
+    }
+
+    public synchronized T pop() {
+        T item = buffer[out];
+        buffer[out] = null;
+        count--;
+        out = (out + 1) % buffer.length;
+        return item;
+    }
+
+    public synchronized boolean isEmpty() {
+        return (count == 0);
+    }
+
+    public synchronized int size() {
+        return count;
+    }
+}

app/src/main/java/eu/faircode/email/ServiceSynchronize.java

@@ -2130,6 +2130,7 @@ public class ServiceSynchronize extends ServiceBase implements SharedPreferences
                     Log.i(account.name + " done state=" + state);
                 } catch (Throwable ex) {
                     last_fail = ex;
+                    iservice.dump();
                     Log.e(account.name, ex);
                     EntityLog.log(this, EntityLog.Type.Account,
                             account.name + " connect " + Log.formatThrowable(ex, false));