73 lines
3.7 KiB
Markdown
73 lines
3.7 KiB
Markdown
[](https://travis-ci.org/beevik/ntp)
|
|
[](https://godoc.org/github.com/beevik/ntp)
|
|
|
|
ntp
|
|
===
|
|
|
|
The ntp package is an implementation of a Simple NTP (SNTP) client based on
|
|
[RFC5905](https://tools.ietf.org/html/rfc5905). It allows you to connect to
|
|
a remote NTP server and request information about the current time.
|
|
|
|
|
|
## Querying the current time
|
|
|
|
If all you care about is the current time according to a remote NTP server,
|
|
simply use the `Time` function:
|
|
```go
|
|
time, err := ntp.Time("0.beevik-ntp.pool.ntp.org")
|
|
```
|
|
|
|
|
|
## Querying time metadata
|
|
|
|
To obtain the current time as well as some additional metadata about the time,
|
|
use the [`Query`](https://godoc.org/github.com/beevik/ntp#Query) function:
|
|
```go
|
|
response, err := ntp.Query("0.beevik-ntp.pool.ntp.org")
|
|
time := time.Now().Add(response.ClockOffset)
|
|
```
|
|
|
|
Alternatively, use the [`QueryWithOptions`](https://godoc.org/github.com/beevik/ntp#QueryWithOptions)
|
|
function if you want to change the default behavior used by the `Query`
|
|
function:
|
|
```go
|
|
options := ntp.QueryOptions{ Timeout: 30*time.Second, TTL: 5 }
|
|
response, err := ntp.QueryWithOptions("0.beevik-ntp.pool.ntp.org", options)
|
|
time := time.Now().Add(response.ClockOffset)
|
|
```
|
|
|
|
The [`Response`](https://godoc.org/github.com/beevik/ntp#Response) structure
|
|
returned by `Query` includes the following information:
|
|
* `Time`: The time the server transmitted its response, according to its own clock.
|
|
* `ClockOffset`: The estimated offset of the local system clock relative to the server's clock. For a more accurate time reading, you may add this offset to any subsequent system clock reading.
|
|
* `RTT`: An estimate of the round-trip-time delay between the client and the server.
|
|
* `Precision`: The precision of the server's clock reading.
|
|
* `Stratum`: The server's stratum, which indicates the number of hops from the server to the reference clock. A stratum 1 server is directly attached to the reference clock. If the stratum is zero, the server has responded with the "kiss of death".
|
|
* `ReferenceID`: A unique identifier for the consulted reference clock.
|
|
* `ReferenceTime`: The time at which the server last updated its local clock setting.
|
|
* `RootDelay`: The server's aggregate round-trip-time delay to the stratum 1 server.
|
|
* `RootDispersion`: The server's estimated maximum measurement error relative to the reference clock.
|
|
* `RootDistance`: An estimate of the root synchronization distance between the client and the stratum 1 server.
|
|
* `Leap`: The leap second indicator, indicating whether a second should be added to or removed from the current month's last minute.
|
|
* `MinError`: A lower bound on the clock error between the client and the server.
|
|
* `KissCode`: A 4-character string describing the reason for a "kiss of death" response (stratum=0).
|
|
* `Poll`: The maximum polling interval between successive messages to the server.
|
|
|
|
The `Response` structure's [`Validate`](https://godoc.org/github.com/beevik/ntp#Response.Validate)
|
|
method performs additional sanity checks to determine whether the response is
|
|
suitable for time synchronization purposes.
|
|
```go
|
|
err := response.Validate()
|
|
if err == nil {
|
|
// response data is suitable for synchronization purposes
|
|
}
|
|
```
|
|
|
|
## Using the NTP pool
|
|
|
|
The NTP pool is a shared resource used by people all over the world.
|
|
To prevent it from becoming overloaded, please avoid querying the standard
|
|
`pool.ntp.org` zone names in your applications. Instead, consider requesting
|
|
your own [vendor zone](http://www.pool.ntp.org/en/vendors.html) or [joining
|
|
the pool](http://www.pool.ntp.org/join.html).
|