From 6b6625e28c77ab5236fa275d78f082ee1635299c Mon Sep 17 00:00:00 2001
From: Casey Bodley <cbodley@redhat.com>
Date: Thu, 18 Feb 2016 11:20:34 -0500
Subject: [PATCH] rgw: get period history cursor when starting sync

Signed-off-by: Casey Bodley <cbodley@redhat.com>
---
 src/rgw/rgw_period_history.h |  2 +-
 src/rgw/rgw_sync.cc          | 50 +++++++++++++++++++++++++++++++++++-
 2 files changed, 50 insertions(+), 2 deletions(-)

diff --git a/src/rgw/rgw_period_history.h b/src/rgw/rgw_period_history.h
index 78049d03782..ca380251338 100644
--- a/src/rgw/rgw_period_history.h
+++ b/src/rgw/rgw_period_history.h
@@ -69,6 +69,7 @@ class RGWPeriodHistory final {
   class Cursor final {
    public:
     Cursor() = default;
+    explicit Cursor(int error) : error(error) {}
 
     int get_error() const { return error; }
 
@@ -88,7 +89,6 @@ class RGWPeriodHistory final {
     // private constructors for RGWPeriodHistory
     friend class RGWPeriodHistory;
 
-    explicit Cursor(int error) : error(error) {}
     Cursor(Set::const_iterator history, std::mutex* mutex, epoch_t epoch)
       : history(history), mutex(mutex), epoch(epoch) {}
 
diff --git a/src/rgw/rgw_sync.cc b/src/rgw/rgw_sync.cc
index 4b491e2fd5c..4a230d09a00 100644
--- a/src/rgw/rgw_sync.cc
+++ b/src/rgw/rgw_sync.cc
@@ -1563,6 +1563,47 @@ int RGWRemoteMetaLog::store_sync_info()
 				 sync_env.status_oid(), sync_status.sync_info));
 }
 
+// return a cursor to the period at our sync position
+static RGWPeriodHistory::Cursor get_period_at(RGWRados* store,
+                                              const rgw_meta_sync_info& info)
+{
+  if (info.period.empty()) {
+    // return an empty cursor with error=0
+    return RGWPeriodHistory::Cursor{};
+  }
+
+  // look for an existing period in our history
+  auto cursor = store->period_history->lookup(info.realm_epoch);
+  if (cursor) {
+    // verify that the period ids match
+    auto& existing = cursor.get_period().get_id();
+    if (existing != info.period) {
+      lderr(store->ctx()) << "ERROR: sync status period=" << info.period
+          << " does not match period=" << existing
+          << " in history at realm epoch=" << info.realm_epoch << dendl;
+      return RGWPeriodHistory::Cursor{-EEXIST};
+    }
+    return cursor;
+  }
+
+  // read the period from rados
+  RGWPeriod period(info.period);
+  int r = period.init(store->ctx(), store, store->realm.get_id());
+  if (r < 0) {
+    lderr(store->ctx()) << "ERROR: failed to read period id "
+        << info.period << ": " << cpp_strerror(r) << dendl;
+    return RGWPeriodHistory::Cursor{r};
+  }
+  // attach the period to our history
+  cursor = store->period_history->attach(std::move(period));
+  if (!cursor) {
+    r = cursor.get_error();
+    lderr(store->ctx()) << "ERROR: failed to read period history back to "
+        << info.period << ": " << cpp_strerror(r) << dendl;
+  }
+  return cursor;
+}
+
 int RGWRemoteMetaLog::run_sync()
 {
   if (store->is_meta_master()) {
@@ -1617,6 +1658,7 @@ int RGWRemoteMetaLog::run_sync()
     return r;
   }
 
+  RGWPeriodHistory::Cursor cursor;
   do {
     r = run(new RGWReadSyncStatusCoroutine(&sync_env, obj_ctx, &sync_status));
     if (r < 0 && r != -ENOENT) {
@@ -1647,7 +1689,13 @@ int RGWRemoteMetaLog::run_sync()
         /* fall through */
       case rgw_meta_sync_info::StateSync:
         ldout(store->ctx(), 20) << __func__ << "(): sync" << dendl;
-        meta_sync_cr = new RGWMetaSyncCR(&sync_env, sync_status);
+        // find our position in the period history (if any)
+        cursor = get_period_at(store, sync_status.sync_info);
+        r = cursor.get_error();
+        if (r < 0) {
+          return r;
+        }
+        meta_sync_cr = new RGWMetaSyncCR(&sync_env, cursor, sync_status);
         r = run(meta_sync_cr);
         if (r < 0) {
           ldout(store->ctx(), 0) << "ERROR: failed to fetch all metadata keys" << dendl;
-- 
2.39.5