Logging, Serilog, Structured Logging, Seq

Serilog & Seq
Doruk Uluçay
Senior Backend Developer @ InGame Group

Why we are logging
Logging has a crucial part to play in a scenario
where you can’t use interactive debugging (that is,
attaching a debugger like Visual Studio). It allows
us to investigate errors after the problem already
happened. In some cases, like Production
Debugging, logs might be the only information you
have.[1]

Logging Best Practises
● Use log levels appropriately[1]
● Only high severity logs in prod[1]
● Log all exceptions[1]

Logging Best Practises
● Implement logging in all projects. You always
end up needing it at some point.[2]

Logging Best Practises - my advices
● Consider logging http context when needed.
It’s very easy with modern libraries.
● Consider using structured logging when
needed
● Log everything when working with 3rd party
services

log4net, NLog, Serilog
log4net
● Started in 2001
● .NET port of log4j
● A lot of configuration
● The old one - avoid

NLog
● Made for .NET
● Better api
● Less configuration
● Still in very good shape.

Serilog
● Introduced structured logging
● Even lesser configuration
● Even simpler API
● The new one. Best of three. NLog with sugar on top. Adopt it.

Microsoft.Extensions.Logging
● Introduced with .NET Core
● Both abstraction and implementation
● Common practise is to use abstractions of it with NLog or Serilog
behind

log4net, NLog, Serilog - Log Levels
log4net NLog Serilog .NET Core
Logging
Fatal Fatal Fatal Critical
Error Error Error Error
Warn Warn Warning Warning
Info Info Information Information
Debug Debug Debug Debug
- Trace Verbose Trace
Whichever you are gonna use, use them with abstractions introduced with .NET Core Logging.

log4net: Appender
NLog: Target
Serilog: Sink

Install
> Install-Package Serilog
> Install-Package Serilog.Sinks.Console
For beginning;

Setup
var logger = new
LoggerConfiguration()
.WriteTo.Console()
.CreateLogger();
For beginning;

Usage
log.Information("Hello,
Serilog!");
Basic use

Structured logging
var name = "Doruk";
Log.Information("Hello, {Name}!", name
);
[21:38:02 INF] Hello, Doruk!
Looks like just string.format, isn’t it ?
No it isn’t really. We’ll come to that later.

Global Logger
Log.Logger =
new LoggerConfiguration()
.WriteTo.Console().CreateLogger();
Log.Information("Hi from global
logger");
A static logger to use from anywhere

Output formatting
var logger =
.WriteTo.File("log.txt", outputTemplate:
"{Timestamp:yyyy-MM-dd HH:mm:ss.fff zzz}
[{Level:u3}]
{Message:lj}{NewLine}{Exception}").
CreateLogger();
Timestamp
here is an
Enricher.
More on to
that later
u3 here
means first
three
characters,
uppercase

Global Log Level & Overrides
Log.Logger =
.MinimumLevel.Debug()
.WriteTo.Console(restrictedToMinimumLevel:
Serilog.Events.LogEventLevel.Fatal)
CreateLogger();

Dynamic Level Switch
var levelSwitch = new LoggingLevelSwitch();
levelSwitch.MinimumLevel =
LogEventLevel.Warning;
var log = new LoggerConfiguration()
.MinimumLevel.ControlledBy(levelSwitch)
.WriteTo.ColoredConsole()
.CreateLogger();

Enrichers - 1 - Code
.WriteTo.File("log.txt", outputTemplate:
"{Timestamp:yyyy-MM-dd HH:mm:ss.fff zzz} [{Level:u3}]
Version:{Version} {Message:lj}{NewLine}{Exception}")
.Enrich.WithProperty("Version", "1.0.0")

Enrichers - 2 - Output
2020-06-02 22:00:47.826 +03:00 [INF] Version:1.0.0
Hello, Doruk!

Filters
Log.Logger = new LoggerConfiguration()
.WriteTo.Console()
.Filter
.ByExcluding(Matching.WithProperty<int>("Count",
p => p < 10))
.CreateLogger();

Some Sinks
● Amazon Cloudwatch
● Amazon Dynamodb
● Amazon S3
● Application Insights
● Azure Analytics
● Couchdb
● log4net
● Mongodb
● New Relic
● NLog
● Rabbitmq
● Slack
● Seq
● Telegram
● MSSQL
● MySQL
● LiteDB

What is structured logging
A better way to capture and render log messages for machine and
human use.[4]
In structured logging logs are saved in raw json format that contains
your message format and data.

Unstructured logging
//code
log("User %s logged in from %s", username,
ipAddress);
//output
2016-05-27T13:02:11.888 User alice logged in from
123.45.67.89
Lets leave it behind.

Structured Logging
log("User {username} logged in from
{ip_address}", username, ipAddress)
Same logging code

Structured Logging
2016-05-27T13:02:11.888 User alice logged in from
123.45.67.89
Same message, but rendered

Structured Logging
{
"time": "2016-05-27T13:02:11.888",
"template": "User {username} logged in from {ip_address}",
"username": "alice",
"ip_address": "123.45.67.89"
}
Aaaaand the way we store it

Seq - what is it
Seq is a platform that has in it;
● Log store
● Visualizer
● Rest api for directly logging to it

Seq - what is it
Seq is built for modern structured logging with
message templates. Rather than waste time and effort
trying to extract data from plain-text logs with fragile
log parsing, the properties associated with each log
event are captured and sent to Seq in a clean JSON
format. Message templates are supported natively by
ASP.NET Core, Serilog, NLog, and many other libraries,
so your application can use the best available
diagnostic logging for your platform.

Seq - what is it
● It’s a log server. Store your logs in it.
● Use it’s ui to filter logs
● Create charts, analyze
● Integrate it to slack or equivalent for alerts

Serilog & Seq
doing
structured
logging

Serilog & Seq doing structured
logging
public class AccountInformation
{
public string Owner { get; set; }
public decimal Balance { get; set; }
public Dictionary<DateTime, decimal> Transactions { get; set; }
}
Assume we have this class

logging
var info = new AccountInformation()
{
Balance = 1000,
Owner = "Doruk",
Transactions = new System.Collections.Generic.Dictionary<DateTime, decimal>()
{
[DateTime.Now] = 100,
[DateTime.Now.AddDays(-1)] = 200
}
};
Log.Information("New Account Added {@account}", info);
And we log it to Seq through Serilog this way

logging
This is what we get at Seq UI

logging
{
"@t": "2020-06-03T17:50:29.6174552+03:00",
"@mt": "New Account Added {@info}",
"@m": "New Account Added {rn "Owner": "Doruk",rn "Balance": 1068,rn "Transactio",
"@i": "7990e46d",
"info": {
"Owner": "Doruk",
"Balance": 1068,
"Transactions": {
"3.06.2020 17:50:29": 78,
"2.06.2020 17:50:29": 89
},
"_typeTag": "AccountInformation"
}
}
Stored json. m is message, mt is template.

logging
Navigate easily with SQL like language

My humble conclusion is
● NLog is still great but Serilog is easier to use
and has more to offer.
● Structured logging is a lifesaver if we write lots
of logs that has data fused with them.
● Platforms like Seq helps a lot while dealing with
logs.

References
● [1] https://michaelscodingspot.com/dotnet-debugging-tools/
● [2] .NET Web Application Logging Essentials by Thomas Ardal
● [3]https://github.com/serilog/serilog/wiki
● [4]https://messagetemplates.org/
Thanks a lot.
Doruk Uluçay

Logging, Serilog, Structured Logging, Seq

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