Very long sync delays - high traffic between nodes


for more than 12 hours the network traffic between CB/SG nodes is consistently high. As a result of that syncing documents between clients takes minutes. Initial sign up won’t work with my logic as documents won’t get pulled down in time.

Some SG logs are:

20:39:08.116844 2016-11-02T20:39:08.116+01:00 Cache: Received #13766535 after 1309ms ("bc68be85-fdd4-4c28-ac57-767a3792b46f" / "2305-1111462567bf9a4da45324032c0d7247")

20:39:08.117074 2016-11-02T20:39:08.117+01:00 Cache:   Deferring #13766535 (25 now waiting for #13766483...#13766483)


} --> 403 missing cannel access

20:35:45.782171 2016-11-02T20:35:45.782+01:00   BulkDocs: Doc 
 --> 403 missing channel access (403 mssing channel access)


21:03:10.379071 2016-11-02T21:03:10.379+01:00 Cache:   Deferring #13774732 (40 now waiting for #13774597...#13774597)

21:03:10.379960 2016-11-02T21:03:10.379+01:00 Cache: Received deduplicated #13774680 for ("100748874246403440004_tDictionary" / "577-daa1c5f87c6f6dc045a93960655e5971")

21:03:10.380034 2016-11-02T21:03:10.380+01:00 Cache: Received deduplicated #13774683 for ("100748874246403440004_tDictionary" / "577-daa1c5f87c6f6dc045a93960655e5971")

21:03:10.380055 2016-11-02T21:03:10.380+01:00 Cache: Received deduplicated #13774685 for ("100748874246403440004_tDictionary" / "577-daa1c5f87c6f6dc045a93960655e5971")

21:03:10.380071 2016-11-02T21:03:10.380+01:00 Cache: Received deduplicated #13774687 for ("100748874246403440004_tDictionary" / "577-daa1c5f87c6f6dc045a93960655e5971")

21:03:10.380096 2016-11-02T21:03:10.380+01:00 Cache: Received deduplicated #13774689 for ("100748874246403440004_tDictionary" / "577-daa1c5f87c6f6dc045a93960655e5971")

21:03:10.380116 2016-11-02T21:03:10.380+01:00 Cache: Received #13774692 after 2028ms ("100748874246403440004_tDictionary" / "577-daa1c5f87c6f6dc045a93960655e5971")

21:03:10.380133 2016-11-02T21:03:10.380+01:00 Cache:   Deferring #13774692 (41 now waiting for #13774597...#13774597)

21:03:10.380296 2016-11-02T21:03:10.380+01:00 Cache: Received #13774702 after 771ms ("115509364005524957017_tPrice" / "2-26cb84d3d34236b7086f084dcb1c71cc")

21:03:10.380332 2016-11-02T21:03:10.380+01:00 Cache:   Deferring #13774702 (42 now waiting for #13774597...#13774597)

21:03:10.382377 2016-11-02T21:03:10.382+01:00 Cache: Received #13774701 after 777ms ("115509364005524957017_tDictionary" / "2-d9b32d02816cbfe9dfc51ea0e179e95a")

21:03:10.382432 2016-11-02T21:03:10.382+01:00 Cache:   Deferring #13774701 (43 now waiting for #13774597...#13774597)

21:03:10.383130 2016-11-02T21:03:10.383+01:00 Cache: Received #13774514 after 28707ms ("2eea8abc-99f1-4b11-a4a0-e00bdcb924de" / "2658-d518aea739cc1d9ddc29d80b386b4f44")

21:03:10.383215 2016-11-02T21:03:10.383+01:00 Cache:   Received 
previously skipped out-of-order change (seq 13774514, expecting 
13774597) doc "2eea8abc-99f1-4b11-a4a0-e00bdcb924de" / 

The network traffic increase started at one point without making any changes to the cluster. The cluster setup is:

1x nginx loadbalancer
3x CB 4.1 CE + SG 1.3.1
All machines have 8 CPU cores and 24 GB RAM and SSDs
Ops/s are less than 100 at the moment. RAM is normally at around 15% on the CB/SG nodes but it slowly fills up and is at over 60% now.

I tried restarting services and machines with no luck.

I’m looking forward to hearing from you and what I can do to resolve the problem.


Benjamin Glatzeder

There’s nothing particularly noteworthy in the SG log excerpt provided.

Are you seeing an increase in network traffic between Sync Gateway and Couchbase Server, while external network traffic to Sync Gateway remains constant? Or is there a corresponding increase in external requests?

Hi Adam,

the traffic to the nginx loadbalancer did not increase, it may look a bit different to other days but I do not think that it is attack from outside. I’m now in touch with support (Chris M.) and provided logs from cbcollect_info and sgcollect_info. The traffic increase seemed to happen at one point in time without making any changes to the cluster. I will update this post if the issue was identified. But I’m more than happy to provide you with more information or if you may have a clue what this issue could be please let me know

Benjamin Glatzeder

Support received sg logs, cb logs, zabbix monitoring graphs and cb console summary graphs, TAP queue graphs. I believe that the issue will be investigated today.
Users also tell me that the network traffic usage of my app skyrocketed. My question would be what the Android client (CBL 1.3.1) does when it is impossible to connect to the SG. Is there an exponentiell backoff algo running? Or is it just repeating over and over again until the device’s battery dies?

I’d like to add that SG runs on two machines. 4CPU and 12 GB RAM per machine. SG is the only service which runs on the machines. RAM usage increases consistently until the service will be killed by Ubuntu. Would you recommend to write a cron job which restarts the SG every 30 minutes? I attached a screenshot of the RAM usage of the last 2 days

Issue was that network traffic was capped, upgraded to VLAN and there are no issues anymore. Opened new thread to share average traffic of my cluster: What is your average network load?