redis memory usage increasing (nodebb + mongodb & redis).

  • Have a machine with 4gb ram. Running on mongodb + redis with 4 nodebb backends (proxying to them with nginx). Running nodebb 1.4.5.

    I have noticed recently redis is using a lot of memory (40-50%). This seems a lot for session storage etc. Is there any way to reduce memory used?. I can for example clear the redis cache, but I'm wondering why it seems to be growing - I suspect there is old data in there such as old sessions etc ? We have 8.5k users, and about 70k posts.

    Just for reference - my config.

        "url": "",
        "bind_address": "",
        "secret": "REMOVED",
        "database": "mongo",
        "port": [4567, 4568, 4569, 4570],
        "mongo": {
            "host": "",
            "port": "27017",
            "username": "REMOVED",
            "database": "REMOVED",
            "password": "REMOVED"
        "redis": {
            "database": 0

    admin stats

    MongoDB Version 3.2.12
    Uptime in Seconds 7,716
    Storage Engine wiredTiger
    Collections 3
    Objects 3,151,142
    Avg. Object Size 100.16 b
    Data Size 301.00 mb
    Storage Size 255.95 mb
    Index Size 270.75 mb
    Resident Memory 651 mb
    Virtual Memory 965 mb
    Mapped Memory 0 mb
    Redis Version 3.2.8
    Uptime in Seconds 7,717
    Uptime in Days 0
    Connected Clients 20
    Connected Slaves 0
    Blocked Clients 0
    Used Memory 1.79G
    Memory Fragmentation Ratio 0.75
    Total Connections Received 31
    Total Commands Processed 108,891
    Instantaneous Ops. Per Second 16
    Keyspace Hits 48,982
    Keyspace Misses 422
  • NodeBB

    @BuZz Can you post the entire details for the redis block? It should be on the same page, 1.8gb seems high for just sessions. Is there anything else on the server that's using redis?

  • @barisThanks for the reply.

    Nothing else should be using redis on the server. Apart from nodebb we just have a wordpress site on it, and service up static content from nginx.

    Here's the full redis info

        "aof_current_rewrite_time_sec": "-1",
        "aof_enabled": "0",
        "aof_last_bgrewrite_status": "ok",
        "aof_last_rewrite_time_sec": "-1",
        "aof_last_write_status": "ok",
        "aof_rewrite_in_progress": "0",
        "aof_rewrite_scheduled": "0",
        "arch_bits": "64",
        "blocked_clients": "0",
        "client_biggest_input_buf": "0",
        "client_longest_output_list": "0",
        "cluster_enabled": "0",
        "config_file": "/etc/redis/redis.conf",
        "connected_clients": "20",
        "connected_slaves": "0",
        "db0": "keys=5814342,expires=5814342,avg_ttl=1206519971687",
        "evicted_keys": "0",
        "executable": "/usr/bin/redis-server",
        "expired_keys": "0",
        "gcc_version": "4.9.2",
        "hz": "10",
        "instantaneous_input_kbps": "1.64",
        "instantaneous_ops_per_sec": "15",
        "instantaneous_output_kbps": "2.22",
        "keyspace_hits": "438506",
        "keyspace_misses": "3627",
        "latest_fork_usec": "40722",
        "loading": "0",
        "lru_clock": "15957072",
        "master_repl_offset": "0",
        "maxmemory": "0",
        "maxmemory_human": "0B",
        "maxmemory_policy": "noeviction",
        "mem_allocator": "jemalloc-4.0.3",
        "mem_fragmentation_ratio": "0.26",
        "migrate_cached_sockets": "0",
        "multiplexing_api": "epoll",
        "os": "Linux 3.16.0-4-amd64 x86_64",
        "process_id": "682",
        "pubsub_channels": "2077",
        "pubsub_patterns": "0",
        "rdb_bgsave_in_progress": "0",
        "rdb_changes_since_last_save": "964",
        "rdb_current_bgsave_time_sec": "-1",
        "rdb_last_bgsave_status": "ok",
        "rdb_last_bgsave_time_sec": "65",
        "rdb_last_save_time": "1492351903",
        "redis_build_id": "56206ba45ffc95ca",
        "redis_git_dirty": "0",
        "redis_git_sha1": "00000000",
        "redis_mode": "standalone",
        "redis_version": "3.2.8",
        "rejected_connections": "0",
        "repl_backlog_active": "0",
        "repl_backlog_first_byte_offset": "0",
        "repl_backlog_histlen": "0",
        "repl_backlog_size": "1048576",
        "role": "master",
        "run_id": "774d8aa38bad1c0ed3bab3af7be6a0a23f8b7180",
        "sync_full": "0",
        "sync_partial_err": "0",
        "sync_partial_ok": "0",
        "tcp_port": "6379",
        "total_commands_processed": "965441",
        "total_connections_received": "31",
        "total_net_input_bytes": "382839654",
        "total_net_output_bytes": "1172279275",
        "total_system_memory": "4156342272",
        "total_system_memory_human": "3.87G",
        "uptime_in_days": "0",
        "uptime_in_seconds": "84451",
        "used_cpu_sys": "144.46",
        "used_cpu_sys_children": "1518.90",
        "used_cpu_user": "134.70",
        "used_cpu_user_children": "6927.99",
        "used_memory": "1943342064",
        "used_memory_human": "1.81G",
        "used_memory_lua": "37888",
        "used_memory_lua_human": "37.00K",
        "used_memory_peak": "1943542624",
        "used_memory_peak_human": "1.81G",
        "used_memory_rss": "513413120",
        "used_memory_rss_human": "489.63M"

  • @baris Sorry, didn't reply/tag you correctly - but can't edit post due to the akismet spam filter flagging it on edit (I have noticed this issue with the spam plugin on retropie also when editing posts - even as an admin editing a users post - but that's another issue).

  • NodeBB

    Yeah looks like something is up with the sessions I don't suppose you have that much traffic to have 5.8m session keys

  • NodeBB

  • @baris Thanks for the fix! 🙂

  • NodeBB

    We are writing an upgrade script to delete all sessions on the next version so the memory usage should go down once that is released.

  • @baris Doing the update now. It's taking a long time to delete all the sessions. Can I just clear the redis cache completely in my set-up without breaking anything or use redis commandline to just clear the sessions ?


  • I decided to clear the redis cache completely as I don't think it's going to complete anytime soon otherwise (I assume this is ok, since using mongodb backend).

  • NodeBB

    If you are only using redis for cache yes you can just flush it.

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