- Lettuce vs Jedis
- Connection Pool
- Important client config
Lettuce vs Jedis
Jedis - A blazingly small and sane redis java client
Lettuce - Advanced Redis client for thread-safe sync, async, and reactive usage. Supports Cluster, Sentinel, Pipelining, and codecs.
If you haven't made your decision, I would recommend
If you alread used Jedis in your project, stick it unless you need Cluster SSL support.
- Used Netty - asynchronous event-driven high performance network framework to do network communication, and it supports sync, async and react pattern.
- Quicker community response. I opened issues in both community, now Lettuce already fixed it and Jedis is still in process
- Cleaner design and code. I really doesn't like the constructor of
- Better docmentation. You could find everything you need in the offical doc
When to use connection pool
- Connection pool is only needed when you need many dedicated connections such as transactions or blocking operation with each worker thread get its dedicated connection
- Use many connections doesn't necessarily improve the performance and concurrency since Redis is single threaded and every reqeust is handled serially.
Connectionobject is thread-safe and can be used from multiple threads at the same time.
- This pool should be configured once and reused.
- Make sure to return the
Connectionback to the pool when done, otherwise you will leak it. Recommend to use try-with-resource, which return it automatically.
Choose pool config with care
|maxTotal||This setting controls the max number of connections that can be created at a given time. Note that each connection does have some memory and CPU overhead, so setting this to a very high value may have negative side effects. If not set, the default value is 8, which is probably too low for most applications. When chosing a value, consider how many concurrent calls into Redis you think you will have under load.|
|maxIdle||This is the max number of connections that can be idle in the pool without being immediately evicted (closed). If not set, the default value is 8. I would recommend that this setting be configured the same as maxTotal to help avoid connection ramp-up costs when your application has many bursts of load in a short period of time. If a connection is idle for a long time, it will still be evicted until the idle connection count hits minIdle (described below).|
|minIdle||This is the number of "warm" connections (e.g. ready for immediate use) that remain in the pool even when load has reduced. If not set, the default is 0. When choosing a value, consider your steady-state concurrent requests to Redis. For instance, if your application is calling into Redis from 10 threads simultaneously, then you should set this to at least 10 (probably a bit higher to give you some room.|
|blockWhenExhausted||This controls behavior when a thread asks for a connection, but there aren't any that are free and the pool can't create more (due to maxTotal). If set to true, the calling thread will block for maxWaitMillis before throwing an exception. The default is true and I recommend true for production environments. You could set it to false in testing environments to help you more easily discover what value to use for maxTotal.|
|maxWaitMillis||How long to wait in milliseconds if calling Pool.getResource() will block. The default is -1, which means block indefinitely. I would set this to the same as the socketTimeout configured. Related to blockWhenExhausted.|
|TestOnBorrow||Controls whether or not the connection is tested before it is returned from the pool. The default is false. Setting to true may increase resilience to connection blips but may also have a performance cost when taking connections from the pool. In my quick testing, I saw a noticable increase in the 50th percentile latencies, but no significant increase in 98th percentile latencies.|
- Sample code here
Log pool usage periodically
- Debugging performance problems due to JedisPool contention issues will be easier if you log the pool usage regularly.
- If you ever get an error when trying to get a connection from the pool, you should definitely log usage stats.
- Sample code here
Important client config
|connectTimeout||How long to allow for new connections to be established (in milliseconds). In general, this should be at least 5000ms. If your client application tends to have high spikes CPU usage, setting this to 15000ms or 20000ms would be a good idea.|
|port||In Azure, 6379 is non-ssl and 6380 is SSL/TLS. Important Note: 6379 is disabled by default - you have to explicitly enable this insecure port if you wish to use it.|
Async vs Sync vs React
- If your project already used React pattern, go for React API without doubt. Read more here https://github.com/lettuce-io/lettuce-core/wiki/Reactive-API-%284.
- If you don't know which one to use, go for Async API since both async and sync are implemented asyncly. Lettuce facilitates asynchronicity from building the client on top of netty that is a multithreaded, event-driven I/O framework. All communication is handled asynchronously. Read more here https://github.com/lettuce-io/lettuce-core/wiki/Asynchronous-API
- If you need to block on some commands execution, synchronously block on
Pipeline used implicitly
- Pipeline will improve the throughput of the application. Read more about redis pipelining here https://redis.io/topics/pipelining.
- Lettuce do pipelining automatically for you. Read more here https://github.com/lettuce-io/lettuce-core/wiki/Pipelining-and-command-flushing
- When you use Azure Redis Standard or Premium, you could use Master/Salve API or normal API. Read more here https://github.com/lettuce-io/lettuce-core/wiki/Master-Slave
- Only worked after 4.4.3.Final if you use Master/Salve API and SSL.
- Sample code here
- When you enabled cluster mode in Azure redis, you should use cluster API. Read more here https://github.com/lettuce-io/lettuce-core/wiki/Redis-Cluster
- One known issue you should be aware lettuce-io/lettuce-core#712. This issue has been fixed in 4.5.0-SNAPSHOT.
- Sample code here
Important Lettuce cluster config to consider
|enablePeriodicRefresh||Periodically refresh nodes topology|
|enableAllAdaptiveRefreshTriggers||Recommend to enable this. This will trigger nodes topology refresh when encounter
Sample code here
More details here https://github.com/lettuce-io/lettuce-core/wiki/Client-Options
Jedis instances are not thread-safe
- Don't use the same
Jedisinstance from multiple threads at the same time.
- Doing this will result in socket connection errors/resets or strange error messages like "expected '$' but got ' '".
- This will improve the throughput of the application. Read more about redis pipelining here https://redis.io/topics/pipelining.
- Jedis does not do pipelining automatically for you. You have to call diffeent APIs in order to get the significant performance benefits that can come from using pipelining.
- Examples can be found here
JedisClustermaintains a pool for each node slot, so no need to do pool again. So pool config take effect for all the pools.
- JedisCluster doesn't support SSL. You need build your own version based on this PR
- Sample code here
Important Jedis cluster config to consider
|maxAttempts||Max times of reconnect attempts before refresh local in-memory cluster slots map. This means if cluster topology changed,