Loki

Loki client simplifies querying of Loki logs with LogQL.

The way it's designed now implies that:

• you need to create a new client instance for each query
• query results are returned as string

New instance

To create a new instance you to provide the following at the very least:

• Loki URL
• query to execute
• time range

// scheme is required
lokiUrl := "http://loki-host.io"
// can be empty
tenantId := "promtail"
basicAuth := LokiBasicAuth{
    Login: "admin",
    Password: "oh-so-secret",
}
queryParams := LokiQueryParams{
				Query:     "quantile_over_time(0.5, {name='my awesome app'} | json| unwrap duration [10s]) by name",
				StartTime: time.Now().Add(1 * time.Hour),
				EndTime:   time.Now(),
				Limit:     1000,
}
lokiClient := client.NewLokiClient(lokiUrl, tenantId, basicAuth, queryParams)

If your instance doesn't have basic auth you should use an empty string:

basicAuth := LokiBasicAuth{}

Executing a query

Once you have the client instance created you can execute the query with:

ctx, cancelFn := context.WithTimeout(context.Background, 3 * time.Minute)
defer cancelFn()
results, err := lokiClient.QueryLogs(ctx)
if err != nil {
    panic(err)
}

for _, logEntry := range results {
    fmt.Println("At " + logEntry.Timestamp + " found following log: " + logEntry.Log)
}

Log entry types

Loki can return various data types in responses to queries. We will try to convert the following ones to string:

• int
• float64

If it's neither of these types nor a string the client will return an error. Same will happen if nil is returned.

Troubleshooting

If you find yourself in trouble these two environment variables might help you:

• RESTY_DEBUG set to true will enable debug mode for the underlaying HTTP client
• LOKI_CLIENT_LOG_LEVEL controls log level of Loki client (for supported log levels check logging package documentation)