Pushing logs with a logging library - Rust - gelf_logger and log4rs-gelf

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Pushing logs with a logging library - Rust - gelf_logger and log4rs-gelf


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Objective

This guide will explain how to push your logs to Logs Data Platform using Rust with two differents libraries. Use the one you prefer.

Rust has a logging implementation (log) which is widely used. OVHcloud has implemented this system to support the GELF format:

  • gelf_logger: This is a minimal logger.
  • log4rs-gelf: Based on gelf_logger, this implementation is compatible with the complex configurable framework log4rs.

Those loggers will:

  • serialize log entries using the serde_gelf crate.
  • bufferize the result into memory.
  • batch send over network using TCP/TLS.
  • ensure fields follow the LDP naming conventions.

Requirements

To complete this guide you will need:

Instructions

First method: gelf_logger

You can install the gelf_logger crate by adding the dependency to your Cargo.toml:

[dependencies]
gelf_logger = { version = "0.3.0", features = ["ovh-ldp"] }

Alternatively, the following cargo command will install it:

$ cargo add gelf_logger -F ovh-ldp

Here is a full main.rs file showing how to use the log and the gelf_logger API.

use gelf_logger::{
    gelf_alert, gelf_critical, gelf_debug, gelf_emergency, gelf_error, gelf_info, gelf_log,
    gelf_notice, gelf_warn, Builder, GelfLevel,
};
use log::{error, info, warn, LevelFilter};
use serde::Serialize;

#[derive(Serialize, Debug)]
struct Request<'a> {
    id: u16,
    method: &'a str,
    path: &'a str,
}

fn main() {
    Builder::new()
        .filter_level(LevelFilter::Info)
        .ovh_ldp(
            "<YOUR-LDP-CLUSTER-ADDRESS>".to_owned(),
            "<YOUR-WRITE-TOKEN>".to_owned(),
        )
        .init();

    // basic logs
    info!("hello from rust");

    // Basic key-value logs.
    info!(count = 5; "packet received");
    warn!(user = "foo"; "unknown user");
    error!(err:err = "abc".parse::<u32>().unwrap_err(); "parse error");

    let req = Request {
        id: 42,
        method: "GET",
        path: "/login",
    };
    // Will serialize as a `Debug` string.
    info!(req:?; "incoming request");
    // Will flatten all the field and add them as additional fields.
    info!(req:serde; "incoming request flattened");

    // Gelf specific levels.
    gelf_log!(GelfLevel::Emergency, foo = "bar"; "an emergency log");
    gelf_emergency!(foo = "bar"; "an emergency log");
    gelf_alert!(foo = "bar"; "an alert log");
    gelf_critical!(foo = "bar"; "a critical log");
    gelf_error!(foo = "bar"; "an error log");
    gelf_warn!(foo = "bar"; "a warn log");
    gelf_notice!(foo = "bar"; "a notice log");
    gelf_info!(foo = "bar"; "an info log");
    gelf_debug!(foo = "bar"; "a debug log");

    // Flush underlying TCP socket.
    // This will only flush. The socket may be dropped without proper closing.
    log::logger().flush();
}

Don't forget to modify the placeholder to the cluster where your stream resides. There is no need to put the Gelf port. Example: "gra3.logs.ovh.com".

Don't forget to modify the placeholder to the actual value of the write token of your stream.

You could also look at the generated API documentaton.

Second method: log4rs-gelf

This method is an alternative to the previous one. Please consider the following as a different rust project. You need to be familiar with the log4rs framework

Install log4rs and log4rs-gelf in your Rust project.

Here is the modified Cargo.toml file:

[dependencies]
log = { version = "0.4.22", features = ["serde"] }
log4rs = "1.3.0"
log4rs-gelf = { version = "0.1.4", features = ["ovh-ldp"] }
serde = { version = "1.0.204", features = ["derive"] }

Alternatively, use the following cargo commands:

$ cargo add log4rs
$ cargo add log4rs-gelf -F ovh-ldp

Examples

From a YAML configuration file

Copy the content of this yaml file in a file log4rs.yaml. This file will be retrieved by the rust program to configure the framework.

appenders:
  stdout:
    kind: console
  ldp:
    additional_fields:
      X-OVH-TOKEN: <YOUR-WRITE-TOKEN>
      component: rust-cs
    buffer_duration: 5
    buffer_size: 5
    hostname: <YOUR-LDP-CLUSTER-ADDRESS>
    kind: buffer
    level: Informational
    null_character: true
    port: 12202
    use_tls: true
root:
  appenders:
  - ldp
  - stdout
  level: info

Don't forget to replace the placeholder with the cluster where your stream resides. There is no need to put the Gelf port. Example: "gra3.logs.ovh.com".

Don't forget to replace the placeholder with the actual value of the write token of your stream

Replace the X-OVH-TOKEN value with your X-OVH-TOKEN stream value and the hostname with your cluster.

Use this configuration in your project:

use core::time;
use std::thread::sleep;

use log::{info, warn};

fn main() {
    // reading
    log4rs_gelf::init_file("./log4rs.yml", None).unwrap();

    // using log crate APIs
    info!("Hello from rust");
    warn!("Warning from rust");

    // simulating some work (log framework is asynchronous)
    sleep(time::Duration::from_secs(5));

    // flushing remaining logs
    log4rs_gelf::flush().expect("Failed to send buffer, log records could be lost !");
}

You could also look at the generated API documentation.

Go further

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