diff --git a/src/main/java/com/googlesource/gerrit/plugins/findowners/Action.java b/src/main/java/com/googlesource/gerrit/plugins/findowners/Action.java
index 45ec043..d232382 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/findowners/Action.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/findowners/Action.java
@@ -143,7 +143,7 @@
         result.add(account.getPreferredEmail());
       }
     } catch (OrmException e) {
-      log.error("Exception", e);
+      log.error("Exception for " + Config.getChangeId(changeData), e);
       result = new ArrayList<>();
     }
     return result;
@@ -199,8 +199,9 @@
   @Override
   public Description getDescription(RevisionResource resource) {
     Change change = resource.getChangeResource().getChange();
+    ChangeData changeData = null;
     try (ReviewDb reviewDb = reviewDbProvider.open()) {
-      ChangeData changeData = changeDataFactory.create(reviewDb, change);
+      changeData = changeDataFactory.create(reviewDb, change);
       if (changeData.change().getDest().get() == null) {
         if (!Checker.isExemptFromOwnerApproval(changeData)) {
           log.error("Cannot get branch of change: " + changeData.getId().get());
@@ -228,7 +229,7 @@
           .setTitle("Find owners to add to Reviewers list")
           .setVisible(needFindOwners);
     } catch (IOException | OrmException e) {
-      log.error("Exception", e);
+      log.error("Exception for " + Config.getChangeId(changeData), e);
       throw new IllegalStateException(e);
     }
   }
diff --git a/src/main/java/com/googlesource/gerrit/plugins/findowners/Cache.java b/src/main/java/com/googlesource/gerrit/plugins/findowners/Cache.java
index 87e40f5..aa43896 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/findowners/Cache.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/findowners/Cache.java
@@ -144,7 +144,7 @@
             }
           });
     } catch (ExecutionException e) {
-      log.error("Cache.get has exception: " + e);
+      log.error("Cache.get has exception for " + Config.getChangeId(changeData), e);
       return new OwnersDb(
           accountCache, emails, key, repository, changeData, project, branch, files);
     }
diff --git a/src/main/java/com/googlesource/gerrit/plugins/findowners/Checker.java b/src/main/java/com/googlesource/gerrit/plugins/findowners/Checker.java
index 5d71c92..ae163d5 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/findowners/Checker.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/findowners/Checker.java
@@ -101,14 +101,15 @@
 
   /** Returns 1 if owner approval is found, -1 if missing, 0 if unneeded. */
   public static int findApproval(Prolog engine, int minVoteLevel) {
+    ChangeData changeData = null;
     try {
+      changeData = StoredValues.CHANGE_DATA.get(engine);
       AccountCache accountCache = StoredValues.ACCOUNT_CACHE.get(engine);
       Emails emails = StoredValues.EMAILS.get(engine);
-      ChangeData changeData = StoredValues.CHANGE_DATA.get(engine);
       Repository repository = StoredValues.REPOSITORY.get(engine);
       return new Checker(repository, changeData, minVoteLevel).findApproval(accountCache, emails);
     } catch (OrmException | IOException e) {
-      log.error("Exception", e);
+      log.error("Exception for " + Config.getChangeId(changeData), e);
       return 0; // owner approval may or may not be required.
     }
   }
@@ -121,7 +122,7 @@
         return true;
       }
     } catch (IOException | OrmException e) {
-      log.error("Cannot get commit message", e);
+      log.error("Cannot get commit message for " + Config.getChangeId(changeData), e);
       return true; // exempt from owner approval due to lack of data
     }
     // Abandoned and merged changes do not need approval again.
diff --git a/src/main/java/com/googlesource/gerrit/plugins/findowners/Config.java b/src/main/java/com/googlesource/gerrit/plugins/findowners/Config.java
index fdadc2b..e450dfb 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/findowners/Config.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/findowners/Config.java
@@ -87,7 +87,11 @@
     return alwaysShowButton;
   }
 
-  static String getOwnersFileName(Project.NameKey project) {
+  static String getChangeId(ChangeData data) {
+    return data == null ? "(unknown change)" : ("change c/" + data.getId().get());
+  }
+
+  static String getOwnersFileName(Project.NameKey project, ChangeData c) {
     if (config != null && project != null) {
       try {
         String name =
@@ -96,12 +100,19 @@
                 .getString(OWNERS_FILE_NAME, OWNERS);
         if (name.trim().equals("")) {
           log.error(
-              "Project " + project.get() + " has wrong " + OWNERS_FILE_NAME + ": \"" + name + "\"");
+              "Project "
+                  + project
+                  + " has wrong "
+                  + OWNERS_FILE_NAME
+                  + ": \""
+                  + name
+                  + "\" for "
+                  + getChangeId(c));
           return OWNERS;
         }
         return name;
       } catch (NoSuchProjectException e) {
-        log.error("Cannot find project: " + project, e);
+        log.error("Cannot find project " + project + " for " + getChangeId(c), e);
       }
     }
     return OWNERS;
@@ -121,7 +132,7 @@
               .getFromProjectConfigWithInheritance(project, PLUGIN_NAME)
               .getInt(MIN_OWNER_VOTE_LEVEL, minOwnerVoteLevel);
     } catch (NoSuchProjectException e) {
-      log.error("Cannot find project: " + project, e);
+      log.error("Cannot find project " + project + " for " + getChangeId(changeData), e);
       return minOwnerVoteLevel;
     }
   }
diff --git a/src/main/java/com/googlesource/gerrit/plugins/findowners/OwnersDb.java b/src/main/java/com/googlesource/gerrit/plugins/findowners/OwnersDb.java
index d551339..2c595b2 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/findowners/OwnersDb.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/findowners/OwnersDb.java
@@ -75,7 +75,7 @@
     this.emails = emails;
     this.key = key;
     preferredEmails.put("*", "*");
-    String ownersFileName = Config.getOwnersFileName(project);
+    String ownersFileName = Config.getOwnersFileName(project, changeData);
     // Some hacked CL could have a target branch that is not created yet.
     ObjectId id = getBranchId(repository, branch, changeData);
     revision = "";
@@ -101,7 +101,7 @@
       try {
         revision = repository.getRef(branch).getObjectId().getName();
       } catch (Exception e) {
-        log.error("Fail to get branch revision", e);
+        log.error("Fail to get branch revision for " + Config.getChangeId(changeData), e);
       }
     }
     countNumOwners(files);
@@ -293,11 +293,11 @@
     try {
       ObjectId id = repo.resolve(branch);
       if (id == null && changeData != null && !Checker.isExemptFromOwnerApproval(changeData)) {
-        log.error("cannot find branch " + branch);
+        log.error("cannot find branch " + branch + " for " + Config.getChangeId(changeData));
       }
       return id;
     } catch (Exception e) {
-      log.error("cannot find branch " + branch, e);
+      log.error("cannot find branch " + branch + " for " + Config.getChangeId(changeData), e);
     }
     return null;
   }
diff --git a/src/test/java/com/googlesource/gerrit/plugins/findowners/FindOwnersIT.java b/src/test/java/com/googlesource/gerrit/plugins/findowners/FindOwnersIT.java
index ab8a7ea..160d5fa 100644
--- a/src/test/java/com/googlesource/gerrit/plugins/findowners/FindOwnersIT.java
+++ b/src/test/java/com/googlesource/gerrit/plugins/findowners/FindOwnersIT.java
@@ -259,9 +259,9 @@
     PushOneCommit.Result cB = createChange("add tB.c", "tB.c", "Hello B!");
 
     // Default owners file name is "OWNERS".
-    assertThat(Config.getOwnersFileName(null)).isEqualTo("OWNERS");
-    assertThat(Config.getOwnersFileName(pA)).isEqualTo("OWNERS");
-    assertThat(Config.getOwnersFileName(pB)).isEqualTo("OWNERS");
+    assertThat(Config.getOwnersFileName(null, null)).isEqualTo("OWNERS");
+    assertThat(Config.getOwnersFileName(pA, null)).isEqualTo("OWNERS");
+    assertThat(Config.getOwnersFileName(pB, null)).isEqualTo("OWNERS");
 
     String ownerX = oneOwnerList("x@x");
     String ownerY = oneOwnerList("y@y");
@@ -273,8 +273,8 @@
     setProjectConfig("ownersFileName", "OWNERS.alpha");
     switchProject(pB);
     setProjectConfig("ownersFileName", "OWNERS.beta");
-    assertThat(Config.getOwnersFileName(pA)).isEqualTo("OWNERS.alpha");
-    assertThat(Config.getOwnersFileName(pB)).isEqualTo("OWNERS.beta");
+    assertThat(Config.getOwnersFileName(pA, null)).isEqualTo("OWNERS.alpha");
+    assertThat(Config.getOwnersFileName(pB, null)).isEqualTo("OWNERS.beta");
     String ownerA = oneOwnerList("a@a");
     String ownerB = oneOwnerList("b@b");
     assertThat(getOwnersResponse(cA)).contains(ownerA + ", files:[ tA.c ]");
@@ -283,24 +283,24 @@
     // Change back to OWNERS in Project_A
     switchProject(pA);
     setProjectConfig("ownersFileName", "OWNERS");
-    assertThat(Config.getOwnersFileName(pA)).isEqualTo("OWNERS");
+    assertThat(Config.getOwnersFileName(pA, null)).isEqualTo("OWNERS");
     assertThat(getOwnersResponse(cA)).contains(ownerX + ", files:[ tA.c ]");
     assertThat(getOwnersResponse(cB)).contains(ownerB + ", files:[ tB.c ]");
 
     // Change back to OWNERS.alpha in Project_B, but there is no OWNERS.alpha
     switchProject(pB);
     setProjectConfig("ownersFileName", "OWNERS.alpha");
-    assertThat(Config.getOwnersFileName(pB)).isEqualTo("OWNERS.alpha");
+    assertThat(Config.getOwnersFileName(pB, null)).isEqualTo("OWNERS.alpha");
     assertThat(getOwnersResponse(cA)).contains(ownerX + ", files:[ tA.c ]");
     assertThat(getOwnersResponse(cB)).contains("owners:[], files:[ tB.c ]");
 
     // Do not accept empty string or all-white-spaces for ownersFileName.
     setProjectConfig("ownersFileName", "   ");
-    assertThat(Config.getOwnersFileName(pB)).isEqualTo("OWNERS");
+    assertThat(Config.getOwnersFileName(pB, null)).isEqualTo("OWNERS");
     setProjectConfig("ownersFileName", " \t  ");
-    assertThat(Config.getOwnersFileName(pB)).isEqualTo("OWNERS");
+    assertThat(Config.getOwnersFileName(pB, null)).isEqualTo("OWNERS");
     setProjectConfig("ownersFileName", "O");
-    assertThat(Config.getOwnersFileName(pB)).isEqualTo("O");
+    assertThat(Config.getOwnersFileName(pB, null)).isEqualTo("O");
   }
 
   @Test