cats-effect Resource is extremely handy for managing the lifecycle of stateful resources, for example database or queue connections. It gives a main interface of:
trait Resource[F[_], A] {
/** - Acquire resource
* - Run f
* - guarantee that if acquire ran, release will run, even if `use` is cancelled or `f` fails
There exist several DI frameworks / libraries in the Scala ecosystem. But the more functional code you write the more you'll realize there's no need to use any of them.
A few of the most claimed benefits are the following:
| Latency Comparison Numbers | |
| -------------------------- | |
| L1 cache reference 0.5 ns | |
| Branch mispredict 5 ns | |
| L2 cache reference 7 ns 14x L1 cache | |
| Mutex lock/unlock 25 ns | |
| Main memory reference 100 ns 20x L2 cache, 200x L1 cache | |
| Compress 1K bytes with Zippy 3,000 ns 3 us | |
| Send 1K bytes over 1 Gbps network 10,000 ns 10 us | |
| Read 4K randomly from SSD* 150,000 ns 150 us ~1GB/sec SSD |
L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns
L2 cache reference ........................... 7 ns
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns
Compress 1K bytes with Zippy ............. 3,000 ns = 3 µs
Send 2K bytes over 1 Gbps network ....... 20,000 ns = 20 µs
SSD random read ........................ 150,000 ns = 150 µs
Read 1 MB sequentially from memory ..... 250,000 ns = 250 µs
originally written in Dec 2011, needs updating
Log analysis has always struck me as one of those things that gets too much superficial attention without enough attention to detail. That is, we know that we need to do it, but we don’t talk about how we need to do it. At best, we talk about making sure we collect and archive logs. Analysis plays second fiddle, even though in reality logs without analysis provide almost no value to an organization. And you’ll find greatest value in discovery of the earliest stages of an incident rather than in hindsight to understand what went wrong. Unfortunately, less than 1% of data breach investigations in the 2011 Verizon DBIR started with log analysis and review!
The analysis ideas I present below don’t even begin to represent a comprehensive view. And of course every network is different, so you will need to think about your specific needs. But this may get
The term variance describes how subtyping between higher kinded types is related to subtyping relations of their type arguments.
A higher kinded type composes type arguments to a new type. I use square bracket notation to define a higher kinded type:
C[T] // The higher kinded type `C` composes type argument `T` to a new type `C[T]`.The same works with multiple type arguments:
Twelve Go Best Practices
Francesc Campoy Flores Gopher at Google @francesc http://campoy.cat/+
... or Why Pipelining Is Not That Easy
Golang Concurrency Patterns for brave and smart.
By @kachayev