Low latency/High performance Logging

Asynchronous Vs Synchronous

Synchronous way: It waits for each operation to complete, after that only it executes the next operation. For your query: The console.log() command will not be executed until & unless the query has finished executing to get all the result from Database.

Asynchronous way: It never waits for each operation to complete, rather it executes all operations in the first GO only. The result of each operation will be handled once the result is available. For your query: The console.log() command will be executed soon after the DB sql method. While the Database query runs in the background and loads the result once it is finished retrieving the data.

In a traditional synchronous log model, the caller cannot execute further unless the log service returns successfully. All calls are blocked until the record is persisted or acknowledged by the log service. That clearly results in an overhead, especially if an application is designed to code numerous log messages. Imagine a source file consisting of a large number (sometimes hundreds) of log statements. Each statement should be logged before the following statement is processed—clearly a time-consuming process. In a distributed-computing environment, obviously, clients operate concurrently. The alternative is to build a concurrent client architecture using the traditional log service, although performance may remain an issue. Distributed computing architectures may also have deployments spread across many servers (geographically similar or dissimilar locations), in which case, logging to a central database synchronously is cumbersome, if not impossible.

Asynchronous Loggers for Low-Latency Logging (Log4j 2.0)

Asynchronous logging can improve your application’s performance by executing the I/O operations in a separate thread. Log4j 2 makes a number of improvements in this area.

  • Asynchronous Loggers are a new addition in Log4j 2. Their aim is to return from the call to Logger.log to the application as soon as possible. You can choose between making all Loggers asynchronous or using a mixture of synchronous and asynchronous Loggers. Making all Loggers asynchronous will give the best performance, while mixing gives you more flexibility.
  • LMAX Disruptor technology. Asynchronous Loggers internally use the Disruptor, a lock-free inter-thread communication library, instead of queues, resulting in higher throughput and lower latency.
  • As part of the work for Async Loggers, Asynchronous Appenders have been enhanced to flush to disk at the end of a batch (when the queue is empty). This produces the same result as configuring “immediateFlush=true”, that is, all received log events are always available on disk, but is more efficient because it does not need to touch the disk on each and every log event. (Async Appenders use ArrayBlockingQueue internally and do not need the disruptor jar on the classpath.)

The difference between old AsynAppenders and new AsyncLoggers

“The Asynchronous Loggers do two things differently than the AsyncAppender”, he told me, “they try to do the minimum amount of work before handing off the log message to another thread, and they use a different mechanism to pass information between the producer and consumer threads. AsyncAppender uses an ArrayBlockingQueue to hand off the messages to the thread that writes to disk, and Asynchronous Loggers use the LMAX Disruptor library. Especially the Disruptor has made a large performance difference.”

In other terms, the AsyncAppender use a first-in-first-out Queue to work through messages. But the Async Logger uses something new – the Disruptor. To be honest, I had never heard of it. And furthermore, I never thought much about scaling my logging framework. When somebody said “scale the system”, I thought about the database, the app server and much more, but usually not logging. In production, logging was off. End of story.

“Comparing synchronous to asynchronous, you would expect any asynchronous mechanism to scale much better than synchronous logging because you don’t do the I/O in the producing thread any more, and we all know that ‘I/O is slow’

LMAX Disruptor?

“The LMAX team did a lot of research on this and found that these queues have a lot of lock contention. An interesting thing they found is that queues are always either full or empty: If your producer is faster, your queue will be full most of the time (and that may be a problem in itself 🙂 ). If your consumer is fast enough, your queue will be empty most of the time. Either way, you will have contention on the head or on the tail of the queue, where both the producer and the consumer thread want to update the same field. To resolve this, the LMAX team came up with the Disruptor library, which is a lock-free data structure for passing messages between threads

 

Synchronous Loggers.

“One thing I came across that I should mention here is Peter Lawrey’s Chronicle library. Chronicle uses memory-mapped files to write tens of millions of messages per second to disk with very low latency. Remember that above I said that “we all know that I/O is slow”? Chronicle shows that synchronous I/O can be very, very fast.“.

What is Chronicle Logger

Chronicle Logger is an extremely fast java logger. We feel logging should not slow down your system.

Chronicle logger is able to aggregate all your logs to a central store. It has built in resilience, so you will never loose messages.

Chronicle logger supports most of the standard logging API’s including slf4j, sun logging, commons logging, log4j.

Today most programs require the logging of large amounts of data, especially in trading systems where this is a regulatory requirement. Loggers can affect your system performance, therefore logging is sometimes kept to a minimum, With chronicle we aim to eliminate this added overhead, freeing your system to focus on the business logic

Chronicle

This library is an ultra low latency, high throughput, persisted, messaging and event driven in memory database. The typical latency is as low as 80 nano-seconds and supports throughputs of 5-20 million messages/record updates per second.

This library also supports distributed, durable, observable collections (Map, List, Set) The performance depends on the data structures used, but simple data structures can achieve throughputs of 5 million elements or key/value pairs in batches (eg addAll or putAll) and 500K elements or key/values per second when added/updated/removed individually.

It uses almost no heap, trivial GC impact, can be much larger than your physical memory size (only limited by the size of your disk) and can be shared between processes with better than 1/10th latency of using Sockets over loopback. It can change the way you design your system because it allows you to have independent processes which can be running or not at the same time (as no messages are lost) This is useful for restarting services and testing your services from canned data. e.g. like sub-microsecond durable messaging. You can attach any number of readers, including tools to see the exact state of the data externally. e.g. I use; od -t cx1 {file} to see the current state.

 

 

How it works

Chronicle logger is built on Chronicle Queue. It provides multiple Chronicle Queue adapters and is a low latency, high throughput synchronous writer. Unlike asynchronous writers, you will always see the last message before the application dies. As the last message is often the most valuable.

You want to log the message you have faster, but you don’t want to change your logging API.

  • You want to log all your messages with out losing any data, even in the event of a system failure.
  • You want to aggregate your logs across logging libraries, across processes, or across machines.

 

Conclusion

Chronicle Logger with Apache log4j 2 Binding with MongoDB appender ::::)

 

yasas

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