Seq Forwarder

Seq Forwarder is a client-side log collector that receives events over its local HTTP API and persists them to its own internal storage until a remote Seq server can be reached.

Seq Forwarder listens on port 15341 by default. The HTTP ingestion API is identical to the Seq one, so standard client libraries like Serilog.Sinks.Seq can write to it directly.

Log.Logger = new LoggerConfiguration()  
    .WriteTo.Seq("http://localhost:15341")
    .CreateLogger();

Log.Information("Hello, Seq Forwarder!");

Client applications can specify an API key when logging to Seq Forwarder. In this case the API key supplied by the client will be forwarded along to the target Seq server.

Alternatively, Seq Forwarder can be configured with an API key, and will use this to log to Seq when client applications do not specify one.

Getting started

First, download the release bundle for your platform, and extract it to a suitable location.

The instructions below use the seqfwd command-line. To learn about available commands, try seqfwd help.

On Windows

To set up Seq Forwarder as a Windows service, from an administrative PowerShell prompt in the Seq Forwarder directory, set the target Seq server URL and an optional API key:

./seqfwd config -k output.serverUrl --value="http://seq.example.com/"
./seqfwd config -k output.apiKey --value="1a2b3c4d5e6f"
./seqfwd config -k storage.bufferSizeBytes -v 1073741824
./seqfwd install
./seqfwd start

The default buffer size limit is 64 MB. In the example, this is increased to 1 GB.

To upgrade, stop the service, overwrite the forwarder release bundle, and restart the service.

On Windows, Seq Forwarder will used machine-scoped DPAPI to encrypt the default API key and any API keys supplied by clients.

On macOS or Linux

On Linux, you'll need liblmdb:

apt install liblmdb-dev

To run Seq Forwarder, configure the target Seq server URL, and optionally, an API key:

./seqfwd config -k output.serverUrl --value="http://seq.example.com/"
./seqfwd config -k output.apiKey --value="1a2b3c4d5e6f"
./seqfwd config -k storage.bufferSizeBytes -v 1073741824
./seqfwd run

Note that on macOS and Linux, the output API key and any API keys provided by clients will be stored in plain text.

The default buffer size cap is 64 MB. In the example, this is increased to 1 GB.

Development

Seq Forwarder is a .NET Core application that can be built using the .NET Core SDK on Windows, macOS, and Linux.

To debug, F5 will work, but on Windows you will need to either run the install command (see below) to create an HTTP namespace reservation, or run as Administrator.

Troubleshooting

By default the "forwarder" logs will be stored under %PROGRAMDATA%\Seq\Logs. If the destination Seq server is not available, an exception will be stored in these log files.

If you need to inspect the current configuration, it can be found at: %PROGRAMDATA%\Seq\Forwarder\SeqForwarder.json

Command line usage

> ./seqfwd help
Usage: seqfwd <command> [<args>]

Available commands are:
  bind-ssl   Bind an installed SSL certificate to an HTTPS port served by Seq 
             Forwarder
  config     View and set fields in the SeqForwarder.json file; run with no 
             arguments to list all fields
  dump       Print the complete log buffer contents as JSON
  help       Show information about available commands
  install    Install the Seq Forwarder as a Windows service
  restart    Restart the Windows service
  run        Run the server interactively
  start      Start the Windows service
  status     Show the status of the Seq Forwarder service
  stop       Stop the Windows service
  truncate   Clear the log buffer contents
  uninstall  Uninstall the Windows service
  version    Print the current executable version

Note that the Windows HTTP and service-related commands (bind-ssl, install, restart, start, status, stop, and uninstall) are only available on that platform.

SeqForwarder.json configuration example

The seqfwd config command reads and writes SeqForwarder.json:

{
  "diagnostics": {
    "internalLogPath": "C:\\ProgramData\\Seq\\Logs\\",
    "internalLoggingLevel": "Information"
  },
  "output": {
    "serverUrl": "http://localhost:5341",
    "eventBodyLimitBytes": 262144,
    "rawPayloadLimitBytes": 10485760,
    "apiKey": null
  },
  "storage": {
    "bufferSizeBytes": 67108864
  },
  "api": {
    "listenUri": "http://localhost:15341"
  }
}

On Windows, this file lives in C:\ProgramData\Seq\Forwarder.