Timeouts

There are several types of Timeout in Kitex: Client connection timeout, Client RPC timeout, Server read/write timeout, and Server exit timeout.

How to Use

Client Timeouts

Config Items

Connection Timeout (default=50ms)

Note:

  1. This is the maximum waiting time for establishing a new connection;
  2. It can be set to any value (no upper limit); if not set, the default value is 50ms;
  3. If you frequently encounter “dial timeout”, try increasing the value and using the long connection pool (see client.WithLongConnection).
RPC Timeout (default=0, no limit)

Note:

  1. This is the maximum time limit for one RPC call; If timeout occurs, kerrors.ErrRPCTimeout is returned;
  2. Any value can be specified (no upper limit); if not specified, the default value is 0, meaning no timeout limit;
  3. No retry will be sent by default in case of timeout.

Configuration method

By code - Client Option (per-client config)

Specified when initializing client:

import "github.com/cloudwego/kitex/client"

cli, err := xxx.NewClient(targetService,
    client.WithConnectTimeout(100 * time.Millisecond),
    client.WithRPCTimeout(2 * time.Second))

Note: The two configuration items can be specified independently as needed.

By code - Call Option(per-request config; priority over client option)

Specified when sending the request:

import "github.com/cloudwego/kitex/client/callopt"

rsp, err := cli.YourMethod(ctx, req, 
    callopt.WithConnectTimeout(100 * time.Millisecond))
    callopt.WithRPCTimeout(2 * time.Second))

Note: The two configuration items can be specified independently as needed.

Dynamic Config - TimeoutProvider (priority lower than the options above)

Applicable to scenarios that require dynamic configuration. Before each request, the Client will call the `TimeoutProvider`` specified to obtain RPCTimeout and ConnectionTimeout.

Specify a user-defined rpcinfo.TimeoutProvider when initializing the client:

import (
    "github.com/cloudwego/kitex/client"
    "github.com/cloudwego/kitex/pkg/rpcinfo"
)

type UserTimeoutProvider struct {}

func (UserTimeoutProvider) Timeouts(ri rpcinfo.RPCInfo) rpcinfo.Timeouts {
    // Should return RPCTimeout、ConnectTimeout
    // ReadWriteTimeout is not used; recommended to have the same value as RPCTimeout
}

opt := client.WithTimeoutProvider(&UserTimeoutProvider{})
cli, err := xxx.NewClient(targetService, opt)
Configuration Center Extension

Available extension(s):

  • config-nacos: Use Nacos as the configuration center, support timeout, retry, circuitbreak, and server side limiter.

Error for Timeout

Request Timeout (kerrors.ErrRPCTimeout)

When a request times out, the error received by the Client will be:

&kerrors.DetailedError {
    basic: kerrors.ErrRPCTimeout,
    cause: errors.New("timeout=100ms, to=ServerName, method=MethodName, location=kitex.rpcTimeoutMW, remote=0.0.0.0:8888"),
}

kerrors.IsTimeoutError(err) can be used to check whether it’s a timeout error.

Splitting the ErrRPCTimeout

Applicable to github.com/cloudwego/kitex >= v0.5.2

By default, reasons of ErrRPCTimeout may be:

  1. Timeout set by Kitex client (by options), causing request timed out
  2. The business code invoked the ctx.Cancel()
  3. The business code set a deadline earlier than set by Kitex

In some scenarios, it’s necessary to distinguish these reasons, such as issuing multiple requests at the same time expecting only one request to be successful, and cancelling other requests. However, other requests cancelled are not regarded as RPC or business error, and should be filtered to avoid unwanted alarms.

Considering compatibility, this configuration is disabled by default and needs to be set by code:

import "github.com/cloudwego/kitex/pkg/rpctimeout"

rpctimeout.EnableGlobalNeedFineGrainedErrCode()

The difference before and after enabling is listed in the following table:

Scenarios Disabled Enabled
Timeout set by kitex kerrors.ErrRPCTimeout kerrors.ErrRPCTimeout
Cancel called by business code (same as above) kerrors.ErrCanceledByBusiness
Timeout set by business code (earlier than timeout set by kitex) (same as above) kerrors.ErrTimeoutByBusiness (*NOTE)

*NOTE:Considering the fact that the timer of go language may not be accurate all the time, when a timeout occurs, it checks whether actualDDL + 50ms < kitex’s DDL, and only returns the error code if the condition is met, otherwise it still returns 103.

For example, Kitex sets a 1s timeout:

  • If the actual timeout returns after < 950ms, it indicates that the timer is most likely set in the business code;
  • If it actually takes >= 1s to timeout, it means that it’s most likely the timer set by Kitex.
  • If the timeout is between 950ms and 1s, it’s currently conservatively determined to be the timer set by Kitex because it can not be accurately judged.

The threshold (50ms) can be modified under Kitex >= 0.7.1 by:

rpctimeout.SetBusinessTimeoutThreshold(10 * time.Millisecond)

Server Timeouts

Config Items

ReadWriteTimeout (default=5s)

NOTE:

  1. This is the maximum waiting time that can be tolerated for reading and writing data on the connection, mainly to prevent abnormal connections from blocking the goroutine.
  2. This is not the Handler execution timeout;
  3. It only takes effect on the server side and it won’t be a problem in most cases.

For example, on the client side, request is sent in multiple segments. If the interval between two segments is too long, it will trigger a server-side read waiting timeout. Upon such a case, try increasing the ReadWriteTimeout.

ExitWaitTime(default=5s)

NOTE:

  1. After receiving an exit signal, the server will wait for an ExitWaitTime before exit;
  2. If the waiting time is exceeded, the server will forcibly terminate all requests being processed (the client will receive an error).

Configuration method

By code - Server Option

Specified when initializing a server:

import "github.com/cloudwego/kitex/server"

svr := xxx.NewServer(handler,
    server.WithReadWriteTimeout(5 * time.Second),
    server.WithExitWaitTime(5 * time.Second),
)

Note: The two configuration items can be specified independently as needed.

FAQ

Q: Will the server report a timeout if a handler executes more than ReadWriteTimeout(5s)?

This is the timeout time waiting for the packet during server-side decoding, and has nothing to do with the execution of the server handler (decoding has already been completed when the server handler is executed).

Q: Does the server support handler timeout?

Currently, the server side does not support handler execution timeout.


Last modified February 29, 2024 : docs: add doc for command cwgo-doc (#955) (7213e1f)