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Elastic.Extensions.Logging

Elastic logger provider for Microsoft.Extensions.Logging.

Writes direct to Elasticsearch using the Elastic Common Schema (ECS), with semantic logging of structured data from message and scope values. The results can be viewed and queried in the Kibana console.

Installation

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Add a reference to the Elastic.Extensions.Logging package:

<PackageReference Include="Elastic.Extensions.Logging" Version="8.6.0" />

Usage

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Then, add the provider to the loggingBuilder during host construction, using the provided extension method.

using Elastic.Extensions.Logging;

// ...

    .ConfigureLogging((hostContext, loggingBuilder) =>
    {
        loggingBuilder.AddElasticsearch();
    })

The default configuration will write to a local Elasticsearch running at http://localhost:9200/.

Once you have sent some log event, open Kibana (e.g. http://localhost:5601/) and define an index pattern for "dotnet-*" with the time filter "@timestamp".

You can then discover the log events for the index. Some useful columns to add are log.level, log.logger, event.code, message, tags, and process.thread.id.

If you are running multiple applications or on multiple servers, you might want to include service.type, service.version, and host.hostname.

Additional fields are defined below, and all individual message and scope values are logged as labels.* custom key/value pairs, e.g. labels.CustomerId.

Basic configuration

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For deployment you will usually want to override the configuration with your actual server location(s). The other useful value to configure is a tag for the environment, e.g. Development/Staging/Production.

{
  "Logging": {
    "Elasticsearch": {
      "NodeUris": [ "https://elastic-staging.example.com:9200" ],
      "Tags": [ "Staging" ]
    }
  }
}

NOTE: You don’t need any configuration to just use a local Elasticsearch instance, as it defaults to http://localhost:9200/.

Configuration settings

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The logger provider will be automatically configured with any logging settings under the alias Elasticsearch.

The following default settings are used.

{
  "Logging": {
    "Elasticsearch": {
      "IncludeHost": true,
      "IncludeProcess": true,
      "IncludeScopes": true,
      "IncludeUser": true,
      "Index": "dotnet-{0:yyyy.MM.dd}",
      "IndexOffset": null,
      "IsEnabled": true,
      "ListSeparator": ", ",
      "MapCorrelationValues": true,
      "Tags": [],
      "ShipTo": {
        "NodePoolType": "SingleNode",
        "NodeUris": [ "http://localhost:9200" ]
      }
    }
  }
}

Setting	Type	Description
IncludeHost	boolean	Default `true`; set to `false` to disable logging host values.
IncludeProcess	boolean	Default `true`; set to `false` to disable logging process values.
IncludeScopes	boolean	Default `true`; set to `false` to disable logging scope values.
IncludeUser	boolean	Default `true`; set to `false` to disable logging user details.
Index	format	Format string used to generate the Elasticsearch `index`, using the current timestamp. Default is `dotnet-{0:yyyy.MM.dd}`.
IndexOffset	timespan	Override to set the offset used to generate the `index`. Default value is `null`, which uses the system local offset; use `"00:00&"` for UTC.
IsEnabled	boolean	Default `true`; set to `false` to disable the logger.
ListSeparator	string	Separator to use for `IEnumerable` in `labels.*` values. Default is `", "`.
Tags	array	Additional tags to include in the message. Useful to specify the environment or other details, e.g. `[ "Staging", "Priority"]`

The ShipTo settings can have the following properties, depending on the type of connection pool.

Setting	Type	Description
ApiKey	string	API Key, where connection pool type is Cloud, and authenticating via API Key.
CloudId	string	Cloud ID, where connection pool type is Cloud.
NodePoolType	enum	Default is `Singlenode`, or `Sniffing` for multiple nodes, or `Cloud` if `CloudId` is provided. Other supported values are `Static` or `Sticky`.
NodeUris	array	URI(s) of the Elasticsearch nodes to connect to. Default is a single node `[ "http://localhost:9200" ]`
Password	string	Password, where connection pool type is Cloud, and authenticating via username/password.
Username	string	Username, where connection pool type is Cloud, and authenticating via username/password.

If you want to configure from a different section, it can be configured manually:

    .ConfigureLogging((hostContext, loggingBuilder) =>
    {
        loggingBuilder.AddElasticsearch(options =>
            hostContext.Configuration.Bind("Logging:CustomElasticsearch", options));
    })

Configuration can, of course, also be done in code, e.g. to add the environment as a tag.

Elastic Cloud configuration

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If CloudId is provided, the ConnectionPoolType defaults to Cloud:

{
  "Logging": {
    "Elasticsearch": {
      "ShipTo": {
        "CloudId": "12345",
        "ApiKey": "abcdef"
      }
    }
  }
}

Output - Elastic Common Schema (ECS)

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Log messages sent to Elasticsearch follow the Elastic Common Schema (ECS).

Example document

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The _source field is the message sent from the LoggerProvider, along with the _index and _id (a GUID).

{
  "_index": "dotnet-2020.04.12",
  "_type": "_doc",
  "_id": "563503a8-9d10-46ff-a09f-c6ccbf124db9",
  "_version": 1,
  "_score": null,
  "_source": {
    "MessageTemplate": "Unexpected error processing customer {CustomerId}.",
    "Scopes": [
      "IP address 2001:db8:85a3::8a2e:370:7334",
      "PlainScope"
    ],
    "agent": {
      "version": "1.0.0+bd3ad6",
      "type": "Elastic.Extensions.Logging.LoggerProvider"
    },
    "ecs": {
      "version": "1.5.0"
    },
    "error": {
      "message": "Calculation error",
      "type": "System.Exception",
      "stack_trace": "System.Exception: Calculation error\n ---> System.DivideByZeroException: Attempted to divide by zero.\n   at HelloElasticsearch.Worker.ExecuteAsync(CancellationToken stoppingToken) in /home/sly/Code/essential-logging/examples/HelloElasticsearch/Worker.cs:line 80\n   --- End of inner exception stack trace ---\n   at HelloElasticsearch.Worker.ExecuteAsync(CancellationToken stoppingToken) in /home/sly/Code/essential-logging/examples/HelloElasticsearch/Worker.cs:line 84"
    },
    "event": {
      "code": "5000",
      "action": "ErrorProcessingCustomer",
      "severity": 3
    },
    "host": {
      "os": {
        "platform": "Unix",
        "full": "Linux 4.15.0-91-generic #92-Ubuntu SMP Fri Feb 28 11:09:48 UTC 2020",
        "version": "4.15.0.91"
      },
      "hostname": "VUB1804",
      "architecture": "X64"
    },
    "log": {
      "level": "Error",
      "logger": "HelloElasticsearch.Worker"
    },
    "process": {
      "thread": {
        "id": 10
      },
      "pid": 25982,
      "name": "HelloElasticsearch"
    },
    "service": {
      "type": "HelloElasticsearch",
      "version": "1.0.0"
    },
    "user": {
      "id": "sgryphon+es@live.com",
      "name": "sly",
      "domain": "VUB1804"
    },
    "@timestamp": "2020-04-13T21:25:22.3352989+10:00",
    "tags": [
      "Development"
    ],
    "labels": {
      "ip": "2001:db8:85a3::8a2e:370:7334",
      "CustomerId": "12345"
    },
    "message": "Unexpected error processing customer 12345.",
    "trace": {
      "id": "c20bde1071f7cf4e9a6f368c824e05f7"
    },
    "transaction": {
      "id": "92ba5ee64d963746"
    }
  },
  "fields": {
    "@timestamp": [
      "2020-04-13T11:25:22.335Z"
    ]
  },
  "sort": [
    1586777122335
  ]
}

Standard Fields

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Field	Type	Description
@timestamp	date	`DateTimeOffset` when the message was logged, including local offset.
message	string	The formatted log message and arguments.
tags	array	Custom tags from configuration, e.g. `[ "Staging", "Priority" ]`. Can have multiple values.
event.action	string	The name of the logged EventId, e.g. `ErrorProcessingCustomer`.
event.code	string	The numeric value (as a string) of the EventId, e.g. `5000`.
event.severity	long	The syslog severity corresponding to the log level, 2 = critical, 3 = error, 4 = warning, 6 = information, 7 = debug and trace. (Also used in the Systemd format of ConsoleLoggerProvider)
log.level	string	The log level: `Critical`, `Error`, `Warning`, `Information`, `Debug`, or `Trace`.
log.logger	string	The category name (namespace and class) of the logger, e.g. `HelloElasticsearch.Worker`.

The event.severity field is numeric and can be used to order events by level, e.g. Kibana query event.severity <= 4 will get all messages that have log level Warning or worse.

Error fields

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If the log message includes an exception, the details are reported in the error fields.

Field	Type	Description
error.message	string	The `Message` property of any exception.
error.stack_trace	string	Full details of the exception, `Exception.ToString()`, including the stack trace and the stack trace of any inner exceptions.
error.type	string	The type of the error message, e.g. `System.DivideByZeroException`

Custom fields

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Following the ECS conventions, these use alternative Title casing, to identify them as non-standard fields.

Field	Type	Description
MessageTemplate	string	The original message template, e.g. "Unexpected error processing customer {CustomerId}."
Scopes	array	Array of string formatted scope values, in the order added.

Label values

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Field	Type	Description
labels.*	string	Custom key/value pairs of all named parameter values and named scope values. All values are strings (no nested objects).

Label values can be accessed by their key, for example if the message, or scope, includes a parameter CustomerId, then the value will be logged as labels.CustomerId can be searched in Kibana using "labels.CustomerId: 12345".

Example:

The following will generate two labels, labels.EndTime from the message and labels.CustomerId from the scope:

using (_logger.BeginScope("{CustomerId}", customerId))
{
  _logger.LogWarning("End of processing reached at {EndTime}.", end);
}

Labels are taken from the message (state) and any scope values (may be disabled via the configuration options). In Microsoft.Extensions.Logging an internal FormattedLogValues is used in the ILogger overloads for log levels and scopes; it implements the IEnumerable<KeyValuePair<string,object>> interface that is used to extract the individual parameter values.

The labels property in ECS should not contain nested objects, so values are converted to keyword strings. For most objects this is just calling ToString(), with specific formats for some types, e.g. calling string on a list is usually not very useful, so the contents of the list is logged instead.

Labels value formatting

Type	Formatting
byte	Hex, e.g. "9A"
byte[]	Prefixed hex, e.g. "0x12789AF0"
DateTimeOffset	ISO format, e.g. "2020-01-02T03:04:05.000000+06:00"
DateTime	In most cases `DateTimeOffset` should be used instead (1). Where `DateTime` is used for date only (with no time component), it is formatted as a date, e.g. "2020-01-02". If it has a time component, the roundtrip ("o") format is used.
IEnumerable	Values separated by ", " (configurable)
IDictionary<string, object>	A string containing key value pairs, e.g. `token="0x12789AF0" count="5"`
other values	The result of `ToString()`, including scalar values, e.g. the number `5.3` is logged as the string "5.3"

(1) See https://docs.microsoft.com/en-us/dotnet/standard/datetime/choosing-between-datetime

Agent fields

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These identify the version of the logger provider being used.

Field	Type	Description
agent.type	string	Name of the logger provider assembly, `Elastic.Extensions.Logging.LoggerProvider`.
agent.version	string	Informational version number of the logger assembly, e.g. `1.1.1+bd3ad63`.
ecs.version	string	Version of ECS standard used, currently `1.5`.

Service fields

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This identifies the application/service that is running and generating the logs.

The values are pulled from the entry assemb, Assembly.GetEntryAssembly(), using the Name and AssemblyInformationalVersionAttribute values (if informational version is not set it falls back to assembly Version).

Field	Type	Description
service.type	string	Name of the entry assembly, `HelloElasticsearch`.
service.version	string	Informational version number of the entry assembly, e.g. `1.2.0-beta.1+79d095a`.

Note: You should be using a build process that sets the assembly informational version correctly. e.g. If you have a dotnet project using git you can install the local tool GitVersion.Tool, and use it to automatically generate semantic version numbers from the git branch information.

To install the tool:

dotnet new tool-manifest
dotnet tool install GitVersion.Tool

Then use the tool to create a semantic version number that can be used in your build process:

dotnet tool restore
dotnet gitversion

You are welcome to use the build.ps1 script in this repository as an example.

Tracing fields

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Field	Type	Description
trace.id	string	Cross-service trace correlation identifier. From `Activity.Current.RootId` from `System.Diagnostics`, with a fallback to `CorrelationManager.ActivityId`. Can be overridden by a message or scope value `trace.id`.
transaction.id	string	Transaction for this service, e.g. individual request identifier. If in W3C format, parse out the SpanId from `Activity.Current.Id` from `System.Diagnostics`, otherwise just use the full `Activity.Current.Id` (e.g. if hierarchical). Can be overridden by message or scope value `transaction.id`.

ASP.NET will automatically pass correlation identifiers between tiers; from 3.0 it also supports the W3C Trace Context standard (https://www.w3.org/TR/trace-context/).

The value of Activity.Current.RootId is used as the cross-service identifier (in W3C format this is the Trace ID), if in W3C format the Span ID portion of Activity.Current.Id is used for the transaction, otherwise the full value is used (this is consistent with the way ASP.NET works).

It is recommended to turn on W3C format, for compatibility with other systems:

Activity.DefaultIdFormat = ActivityIdFormat.W3C;

Host fields

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Can be disabled via configuration.

Field	Type	Description
host.architecture	string	The processor architecture, e.g. X64. Value of `RuntimeInformation.OSArchitecture`.
host.hostname	string	The computer name. Value of `Environment.MachineName`.
host.os.full	string	Full description of the operation system. Value of `RuntimeInformation.OSDescription`.
host.os.platform	string	Operating system platform. Value of `Environment.OSVersion.Platform`.
host.os.version	string	Operating system version. Value of `Environment.OSVersion.Version`.

Process fields

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Can be disabled via configuration.

Field	Type	Description
process.name	string	The current process name. From `Process.GetCurrentProcess()`.
process.pid	long	The current process ID. From `Process.GetCurrentProcess()`.
process.thread.id	long	Current thread ID. Value of `Thread.CurrentThread.ManagedThreadId`.
process.thread.name	string	Name of the thread. From `Thread.CurrentThread.Name`.

User fields

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Can be disabled via configuration.

Field	Type	Description
user.domain	string	The current domain, either the machine name or a Windows domain. Value of `Environment.UserDomainName`.
user.id	string	Current user principal name, if set. Value of `Thread.CurrentPrincipal.Identity.Name`.
user.name	string	The current user. Value of `Environment.UserName`.

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