minio/internal/grid/trace.go

138 lines
3.7 KiB
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perf: websocket grid connectivity for all internode communication (#18461) This PR adds a WebSocket grid feature that allows servers to communicate via a single two-way connection. There are two request types: * Single requests, which are `[]byte => ([]byte, error)`. This is for efficient small roundtrips with small payloads. * Streaming requests which are `[]byte, chan []byte => chan []byte (and error)`, which allows for different combinations of full two-way streams with an initial payload. Only a single stream is created between two machines - and there is, as such, no server/client relation since both sides can initiate and handle requests. Which server initiates the request is decided deterministically on the server names. Requests are made through a mux client and server, which handles message passing, congestion, cancelation, timeouts, etc. If a connection is lost, all requests are canceled, and the calling server will try to reconnect. Registered handlers can operate directly on byte slices or use a higher-level generics abstraction. There is no versioning of handlers/clients, and incompatible changes should be handled by adding new handlers. The request path can be changed to a new one for any protocol changes. First, all servers create a "Manager." The manager must know its address as well as all remote addresses. This will manage all connections. To get a connection to any remote, ask the manager to provide it given the remote address using. ``` func (m *Manager) Connection(host string) *Connection ``` All serverside handlers must also be registered on the manager. This will make sure that all incoming requests are served. The number of in-flight requests and responses must also be given for streaming requests. The "Connection" returned manages the mux-clients. Requests issued to the connection will be sent to the remote. * `func (c *Connection) Request(ctx context.Context, h HandlerID, req []byte) ([]byte, error)` performs a single request and returns the result. Any deadline provided on the request is forwarded to the server, and canceling the context will make the function return at once. * `func (c *Connection) NewStream(ctx context.Context, h HandlerID, payload []byte) (st *Stream, err error)` will initiate a remote call and send the initial payload. ```Go // A Stream is a two-way stream. // All responses *must* be read by the caller. // If the call is canceled through the context, //The appropriate error will be returned. type Stream struct { // Responses from the remote server. // Channel will be closed after an error or when the remote closes. // All responses *must* be read by the caller until either an error is returned or the channel is closed. // Canceling the context will cause the context cancellation error to be returned. Responses <-chan Response // Requests sent to the server. // If the handler is defined with 0 incoming capacity this will be nil. // Channel *must* be closed to signal the end of the stream. // If the request context is canceled, the stream will no longer process requests. Requests chan<- []byte } type Response struct { Msg []byte Err error } ``` There are generic versions of the server/client handlers that allow the use of type safe implementations for data types that support msgpack marshal/unmarshal.
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// Copyright (c) 2015-2023 MinIO, Inc.
//
// This file is part of MinIO Object Storage stack
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
package grid
import (
"context"
"fmt"
perf: websocket grid connectivity for all internode communication (#18461) This PR adds a WebSocket grid feature that allows servers to communicate via a single two-way connection. There are two request types: * Single requests, which are `[]byte => ([]byte, error)`. This is for efficient small roundtrips with small payloads. * Streaming requests which are `[]byte, chan []byte => chan []byte (and error)`, which allows for different combinations of full two-way streams with an initial payload. Only a single stream is created between two machines - and there is, as such, no server/client relation since both sides can initiate and handle requests. Which server initiates the request is decided deterministically on the server names. Requests are made through a mux client and server, which handles message passing, congestion, cancelation, timeouts, etc. If a connection is lost, all requests are canceled, and the calling server will try to reconnect. Registered handlers can operate directly on byte slices or use a higher-level generics abstraction. There is no versioning of handlers/clients, and incompatible changes should be handled by adding new handlers. The request path can be changed to a new one for any protocol changes. First, all servers create a "Manager." The manager must know its address as well as all remote addresses. This will manage all connections. To get a connection to any remote, ask the manager to provide it given the remote address using. ``` func (m *Manager) Connection(host string) *Connection ``` All serverside handlers must also be registered on the manager. This will make sure that all incoming requests are served. The number of in-flight requests and responses must also be given for streaming requests. The "Connection" returned manages the mux-clients. Requests issued to the connection will be sent to the remote. * `func (c *Connection) Request(ctx context.Context, h HandlerID, req []byte) ([]byte, error)` performs a single request and returns the result. Any deadline provided on the request is forwarded to the server, and canceling the context will make the function return at once. * `func (c *Connection) NewStream(ctx context.Context, h HandlerID, payload []byte) (st *Stream, err error)` will initiate a remote call and send the initial payload. ```Go // A Stream is a two-way stream. // All responses *must* be read by the caller. // If the call is canceled through the context, //The appropriate error will be returned. type Stream struct { // Responses from the remote server. // Channel will be closed after an error or when the remote closes. // All responses *must* be read by the caller until either an error is returned or the channel is closed. // Canceling the context will cause the context cancellation error to be returned. Responses <-chan Response // Requests sent to the server. // If the handler is defined with 0 incoming capacity this will be nil. // Channel *must* be closed to signal the end of the stream. // If the request context is canceled, the stream will no longer process requests. Requests chan<- []byte } type Response struct { Msg []byte Err error } ``` There are generic versions of the server/client handlers that allow the use of type safe implementations for data types that support msgpack marshal/unmarshal.
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"net/http"
"net/url"
perf: websocket grid connectivity for all internode communication (#18461) This PR adds a WebSocket grid feature that allows servers to communicate via a single two-way connection. There are two request types: * Single requests, which are `[]byte => ([]byte, error)`. This is for efficient small roundtrips with small payloads. * Streaming requests which are `[]byte, chan []byte => chan []byte (and error)`, which allows for different combinations of full two-way streams with an initial payload. Only a single stream is created between two machines - and there is, as such, no server/client relation since both sides can initiate and handle requests. Which server initiates the request is decided deterministically on the server names. Requests are made through a mux client and server, which handles message passing, congestion, cancelation, timeouts, etc. If a connection is lost, all requests are canceled, and the calling server will try to reconnect. Registered handlers can operate directly on byte slices or use a higher-level generics abstraction. There is no versioning of handlers/clients, and incompatible changes should be handled by adding new handlers. The request path can be changed to a new one for any protocol changes. First, all servers create a "Manager." The manager must know its address as well as all remote addresses. This will manage all connections. To get a connection to any remote, ask the manager to provide it given the remote address using. ``` func (m *Manager) Connection(host string) *Connection ``` All serverside handlers must also be registered on the manager. This will make sure that all incoming requests are served. The number of in-flight requests and responses must also be given for streaming requests. The "Connection" returned manages the mux-clients. Requests issued to the connection will be sent to the remote. * `func (c *Connection) Request(ctx context.Context, h HandlerID, req []byte) ([]byte, error)` performs a single request and returns the result. Any deadline provided on the request is forwarded to the server, and canceling the context will make the function return at once. * `func (c *Connection) NewStream(ctx context.Context, h HandlerID, payload []byte) (st *Stream, err error)` will initiate a remote call and send the initial payload. ```Go // A Stream is a two-way stream. // All responses *must* be read by the caller. // If the call is canceled through the context, //The appropriate error will be returned. type Stream struct { // Responses from the remote server. // Channel will be closed after an error or when the remote closes. // All responses *must* be read by the caller until either an error is returned or the channel is closed. // Canceling the context will cause the context cancellation error to be returned. Responses <-chan Response // Requests sent to the server. // If the handler is defined with 0 incoming capacity this will be nil. // Channel *must* be closed to signal the end of the stream. // If the request context is canceled, the stream will no longer process requests. Requests chan<- []byte } type Response struct { Msg []byte Err error } ``` There are generic versions of the server/client handlers that allow the use of type safe implementations for data types that support msgpack marshal/unmarshal.
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"time"
"github.com/minio/madmin-go/v3"
"github.com/minio/minio/internal/pubsub"
)
// TraceParamsKey allows to pass trace parameters to the request via context.
// This is only needed when un-typed requests are used.
// MSS, map[string]string types are preferred, but any struct with exported fields will work.
type TraceParamsKey struct{}
perf: websocket grid connectivity for all internode communication (#18461) This PR adds a WebSocket grid feature that allows servers to communicate via a single two-way connection. There are two request types: * Single requests, which are `[]byte => ([]byte, error)`. This is for efficient small roundtrips with small payloads. * Streaming requests which are `[]byte, chan []byte => chan []byte (and error)`, which allows for different combinations of full two-way streams with an initial payload. Only a single stream is created between two machines - and there is, as such, no server/client relation since both sides can initiate and handle requests. Which server initiates the request is decided deterministically on the server names. Requests are made through a mux client and server, which handles message passing, congestion, cancelation, timeouts, etc. If a connection is lost, all requests are canceled, and the calling server will try to reconnect. Registered handlers can operate directly on byte slices or use a higher-level generics abstraction. There is no versioning of handlers/clients, and incompatible changes should be handled by adding new handlers. The request path can be changed to a new one for any protocol changes. First, all servers create a "Manager." The manager must know its address as well as all remote addresses. This will manage all connections. To get a connection to any remote, ask the manager to provide it given the remote address using. ``` func (m *Manager) Connection(host string) *Connection ``` All serverside handlers must also be registered on the manager. This will make sure that all incoming requests are served. The number of in-flight requests and responses must also be given for streaming requests. The "Connection" returned manages the mux-clients. Requests issued to the connection will be sent to the remote. * `func (c *Connection) Request(ctx context.Context, h HandlerID, req []byte) ([]byte, error)` performs a single request and returns the result. Any deadline provided on the request is forwarded to the server, and canceling the context will make the function return at once. * `func (c *Connection) NewStream(ctx context.Context, h HandlerID, payload []byte) (st *Stream, err error)` will initiate a remote call and send the initial payload. ```Go // A Stream is a two-way stream. // All responses *must* be read by the caller. // If the call is canceled through the context, //The appropriate error will be returned. type Stream struct { // Responses from the remote server. // Channel will be closed after an error or when the remote closes. // All responses *must* be read by the caller until either an error is returned or the channel is closed. // Canceling the context will cause the context cancellation error to be returned. Responses <-chan Response // Requests sent to the server. // If the handler is defined with 0 incoming capacity this will be nil. // Channel *must* be closed to signal the end of the stream. // If the request context is canceled, the stream will no longer process requests. Requests chan<- []byte } type Response struct { Msg []byte Err error } ``` There are generic versions of the server/client handlers that allow the use of type safe implementations for data types that support msgpack marshal/unmarshal.
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// traceRequests adds request tracing to the connection.
func (c *Connection) traceRequests(p *pubsub.PubSub[madmin.TraceInfo, madmin.TraceType]) {
c.trace = &tracer{
Publisher: p,
TraceType: madmin.TraceInternal,
Prefix: "grid",
perf: websocket grid connectivity for all internode communication (#18461) This PR adds a WebSocket grid feature that allows servers to communicate via a single two-way connection. There are two request types: * Single requests, which are `[]byte => ([]byte, error)`. This is for efficient small roundtrips with small payloads. * Streaming requests which are `[]byte, chan []byte => chan []byte (and error)`, which allows for different combinations of full two-way streams with an initial payload. Only a single stream is created between two machines - and there is, as such, no server/client relation since both sides can initiate and handle requests. Which server initiates the request is decided deterministically on the server names. Requests are made through a mux client and server, which handles message passing, congestion, cancelation, timeouts, etc. If a connection is lost, all requests are canceled, and the calling server will try to reconnect. Registered handlers can operate directly on byte slices or use a higher-level generics abstraction. There is no versioning of handlers/clients, and incompatible changes should be handled by adding new handlers. The request path can be changed to a new one for any protocol changes. First, all servers create a "Manager." The manager must know its address as well as all remote addresses. This will manage all connections. To get a connection to any remote, ask the manager to provide it given the remote address using. ``` func (m *Manager) Connection(host string) *Connection ``` All serverside handlers must also be registered on the manager. This will make sure that all incoming requests are served. The number of in-flight requests and responses must also be given for streaming requests. The "Connection" returned manages the mux-clients. Requests issued to the connection will be sent to the remote. * `func (c *Connection) Request(ctx context.Context, h HandlerID, req []byte) ([]byte, error)` performs a single request and returns the result. Any deadline provided on the request is forwarded to the server, and canceling the context will make the function return at once. * `func (c *Connection) NewStream(ctx context.Context, h HandlerID, payload []byte) (st *Stream, err error)` will initiate a remote call and send the initial payload. ```Go // A Stream is a two-way stream. // All responses *must* be read by the caller. // If the call is canceled through the context, //The appropriate error will be returned. type Stream struct { // Responses from the remote server. // Channel will be closed after an error or when the remote closes. // All responses *must* be read by the caller until either an error is returned or the channel is closed. // Canceling the context will cause the context cancellation error to be returned. Responses <-chan Response // Requests sent to the server. // If the handler is defined with 0 incoming capacity this will be nil. // Channel *must* be closed to signal the end of the stream. // If the request context is canceled, the stream will no longer process requests. Requests chan<- []byte } type Response struct { Msg []byte Err error } ``` There are generic versions of the server/client handlers that allow the use of type safe implementations for data types that support msgpack marshal/unmarshal.
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Local: c.Local,
Remote: c.Remote,
Subroute: "",
}
}
// subroute adds a specific subroute to the request.
func (c *tracer) subroute(subroute string) *tracer {
if c == nil {
return nil
}
c2 := *c
c2.Subroute = subroute
return &c2
}
type tracer struct {
Publisher *pubsub.PubSub[madmin.TraceInfo, madmin.TraceType]
TraceType madmin.TraceType
Prefix string
Local string
Remote string
Subroute string
}
func (c *muxClient) traceRoundtrip(ctx context.Context, t *tracer, h HandlerID, req []byte) ([]byte, error) {
perf: websocket grid connectivity for all internode communication (#18461) This PR adds a WebSocket grid feature that allows servers to communicate via a single two-way connection. There are two request types: * Single requests, which are `[]byte => ([]byte, error)`. This is for efficient small roundtrips with small payloads. * Streaming requests which are `[]byte, chan []byte => chan []byte (and error)`, which allows for different combinations of full two-way streams with an initial payload. Only a single stream is created between two machines - and there is, as such, no server/client relation since both sides can initiate and handle requests. Which server initiates the request is decided deterministically on the server names. Requests are made through a mux client and server, which handles message passing, congestion, cancelation, timeouts, etc. If a connection is lost, all requests are canceled, and the calling server will try to reconnect. Registered handlers can operate directly on byte slices or use a higher-level generics abstraction. There is no versioning of handlers/clients, and incompatible changes should be handled by adding new handlers. The request path can be changed to a new one for any protocol changes. First, all servers create a "Manager." The manager must know its address as well as all remote addresses. This will manage all connections. To get a connection to any remote, ask the manager to provide it given the remote address using. ``` func (m *Manager) Connection(host string) *Connection ``` All serverside handlers must also be registered on the manager. This will make sure that all incoming requests are served. The number of in-flight requests and responses must also be given for streaming requests. The "Connection" returned manages the mux-clients. Requests issued to the connection will be sent to the remote. * `func (c *Connection) Request(ctx context.Context, h HandlerID, req []byte) ([]byte, error)` performs a single request and returns the result. Any deadline provided on the request is forwarded to the server, and canceling the context will make the function return at once. * `func (c *Connection) NewStream(ctx context.Context, h HandlerID, payload []byte) (st *Stream, err error)` will initiate a remote call and send the initial payload. ```Go // A Stream is a two-way stream. // All responses *must* be read by the caller. // If the call is canceled through the context, //The appropriate error will be returned. type Stream struct { // Responses from the remote server. // Channel will be closed after an error or when the remote closes. // All responses *must* be read by the caller until either an error is returned or the channel is closed. // Canceling the context will cause the context cancellation error to be returned. Responses <-chan Response // Requests sent to the server. // If the handler is defined with 0 incoming capacity this will be nil. // Channel *must* be closed to signal the end of the stream. // If the request context is canceled, the stream will no longer process requests. Requests chan<- []byte } type Response struct { Msg []byte Err error } ``` There are generic versions of the server/client handlers that allow the use of type safe implementations for data types that support msgpack marshal/unmarshal.
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if t == nil || t.Publisher.NumSubscribers(t.TraceType) == 0 {
return c.roundtrip(h, req)
}
start := time.Now()
body := bytesOrLength(req)
resp, err := c.roundtrip(h, req)
end := time.Now()
status := http.StatusOK
errString := ""
if err != nil {
errString = err.Error()
if IsRemoteErr(err) == nil {
status = http.StatusInternalServerError
} else {
status = http.StatusBadRequest
}
}
prefix := t.Prefix
if p := handlerPrefixes[h]; p != "" {
prefix = p
}
perf: websocket grid connectivity for all internode communication (#18461) This PR adds a WebSocket grid feature that allows servers to communicate via a single two-way connection. There are two request types: * Single requests, which are `[]byte => ([]byte, error)`. This is for efficient small roundtrips with small payloads. * Streaming requests which are `[]byte, chan []byte => chan []byte (and error)`, which allows for different combinations of full two-way streams with an initial payload. Only a single stream is created between two machines - and there is, as such, no server/client relation since both sides can initiate and handle requests. Which server initiates the request is decided deterministically on the server names. Requests are made through a mux client and server, which handles message passing, congestion, cancelation, timeouts, etc. If a connection is lost, all requests are canceled, and the calling server will try to reconnect. Registered handlers can operate directly on byte slices or use a higher-level generics abstraction. There is no versioning of handlers/clients, and incompatible changes should be handled by adding new handlers. The request path can be changed to a new one for any protocol changes. First, all servers create a "Manager." The manager must know its address as well as all remote addresses. This will manage all connections. To get a connection to any remote, ask the manager to provide it given the remote address using. ``` func (m *Manager) Connection(host string) *Connection ``` All serverside handlers must also be registered on the manager. This will make sure that all incoming requests are served. The number of in-flight requests and responses must also be given for streaming requests. The "Connection" returned manages the mux-clients. Requests issued to the connection will be sent to the remote. * `func (c *Connection) Request(ctx context.Context, h HandlerID, req []byte) ([]byte, error)` performs a single request and returns the result. Any deadline provided on the request is forwarded to the server, and canceling the context will make the function return at once. * `func (c *Connection) NewStream(ctx context.Context, h HandlerID, payload []byte) (st *Stream, err error)` will initiate a remote call and send the initial payload. ```Go // A Stream is a two-way stream. // All responses *must* be read by the caller. // If the call is canceled through the context, //The appropriate error will be returned. type Stream struct { // Responses from the remote server. // Channel will be closed after an error or when the remote closes. // All responses *must* be read by the caller until either an error is returned or the channel is closed. // Canceling the context will cause the context cancellation error to be returned. Responses <-chan Response // Requests sent to the server. // If the handler is defined with 0 incoming capacity this will be nil. // Channel *must* be closed to signal the end of the stream. // If the request context is canceled, the stream will no longer process requests. Requests chan<- []byte } type Response struct { Msg []byte Err error } ``` There are generic versions of the server/client handlers that allow the use of type safe implementations for data types that support msgpack marshal/unmarshal.
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trace := madmin.TraceInfo{
TraceType: t.TraceType,
FuncName: prefix + "." + h.String(),
perf: websocket grid connectivity for all internode communication (#18461) This PR adds a WebSocket grid feature that allows servers to communicate via a single two-way connection. There are two request types: * Single requests, which are `[]byte => ([]byte, error)`. This is for efficient small roundtrips with small payloads. * Streaming requests which are `[]byte, chan []byte => chan []byte (and error)`, which allows for different combinations of full two-way streams with an initial payload. Only a single stream is created between two machines - and there is, as such, no server/client relation since both sides can initiate and handle requests. Which server initiates the request is decided deterministically on the server names. Requests are made through a mux client and server, which handles message passing, congestion, cancelation, timeouts, etc. If a connection is lost, all requests are canceled, and the calling server will try to reconnect. Registered handlers can operate directly on byte slices or use a higher-level generics abstraction. There is no versioning of handlers/clients, and incompatible changes should be handled by adding new handlers. The request path can be changed to a new one for any protocol changes. First, all servers create a "Manager." The manager must know its address as well as all remote addresses. This will manage all connections. To get a connection to any remote, ask the manager to provide it given the remote address using. ``` func (m *Manager) Connection(host string) *Connection ``` All serverside handlers must also be registered on the manager. This will make sure that all incoming requests are served. The number of in-flight requests and responses must also be given for streaming requests. The "Connection" returned manages the mux-clients. Requests issued to the connection will be sent to the remote. * `func (c *Connection) Request(ctx context.Context, h HandlerID, req []byte) ([]byte, error)` performs a single request and returns the result. Any deadline provided on the request is forwarded to the server, and canceling the context will make the function return at once. * `func (c *Connection) NewStream(ctx context.Context, h HandlerID, payload []byte) (st *Stream, err error)` will initiate a remote call and send the initial payload. ```Go // A Stream is a two-way stream. // All responses *must* be read by the caller. // If the call is canceled through the context, //The appropriate error will be returned. type Stream struct { // Responses from the remote server. // Channel will be closed after an error or when the remote closes. // All responses *must* be read by the caller until either an error is returned or the channel is closed. // Canceling the context will cause the context cancellation error to be returned. Responses <-chan Response // Requests sent to the server. // If the handler is defined with 0 incoming capacity this will be nil. // Channel *must* be closed to signal the end of the stream. // If the request context is canceled, the stream will no longer process requests. Requests chan<- []byte } type Response struct { Msg []byte Err error } ``` There are generic versions of the server/client handlers that allow the use of type safe implementations for data types that support msgpack marshal/unmarshal.
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NodeName: t.Local,
Time: start,
Duration: end.Sub(start),
Path: t.Subroute,
Error: errString,
HTTP: &madmin.TraceHTTPStats{
ReqInfo: madmin.TraceRequestInfo{
Time: start,
Proto: "grid",
Method: "REQ",
Client: t.Remote,
Headers: nil,
Path: t.Subroute,
Body: []byte(body),
},
RespInfo: madmin.TraceResponseInfo{
Time: end,
Headers: nil,
StatusCode: status,
Body: []byte(bytesOrLength(resp)),
},
CallStats: madmin.TraceCallStats{
InputBytes: len(req),
OutputBytes: len(resp),
TimeToFirstByte: end.Sub(start),
},
},
}
// If the context contains a TraceParamsKey, add it to the trace path.
v := ctx.Value(TraceParamsKey{})
if p, ok := v.(*MSS); ok && p != nil {
trace.Path += p.ToQuery()
trace.HTTP.ReqInfo.Path = trace.Path
} else if p, ok := v.(map[string]string); ok {
m := MSS(p)
trace.Path += m.ToQuery()
trace.HTTP.ReqInfo.Path = trace.Path
} else if v != nil {
// Print exported fields as single request to path.
trace.Path = fmt.Sprintf("%s?req=%s", trace.Path, url.QueryEscape(fmt.Sprintf("%+v", v)))
trace.HTTP.ReqInfo.Path = trace.Path
}
perf: websocket grid connectivity for all internode communication (#18461) This PR adds a WebSocket grid feature that allows servers to communicate via a single two-way connection. There are two request types: * Single requests, which are `[]byte => ([]byte, error)`. This is for efficient small roundtrips with small payloads. * Streaming requests which are `[]byte, chan []byte => chan []byte (and error)`, which allows for different combinations of full two-way streams with an initial payload. Only a single stream is created between two machines - and there is, as such, no server/client relation since both sides can initiate and handle requests. Which server initiates the request is decided deterministically on the server names. Requests are made through a mux client and server, which handles message passing, congestion, cancelation, timeouts, etc. If a connection is lost, all requests are canceled, and the calling server will try to reconnect. Registered handlers can operate directly on byte slices or use a higher-level generics abstraction. There is no versioning of handlers/clients, and incompatible changes should be handled by adding new handlers. The request path can be changed to a new one for any protocol changes. First, all servers create a "Manager." The manager must know its address as well as all remote addresses. This will manage all connections. To get a connection to any remote, ask the manager to provide it given the remote address using. ``` func (m *Manager) Connection(host string) *Connection ``` All serverside handlers must also be registered on the manager. This will make sure that all incoming requests are served. The number of in-flight requests and responses must also be given for streaming requests. The "Connection" returned manages the mux-clients. Requests issued to the connection will be sent to the remote. * `func (c *Connection) Request(ctx context.Context, h HandlerID, req []byte) ([]byte, error)` performs a single request and returns the result. Any deadline provided on the request is forwarded to the server, and canceling the context will make the function return at once. * `func (c *Connection) NewStream(ctx context.Context, h HandlerID, payload []byte) (st *Stream, err error)` will initiate a remote call and send the initial payload. ```Go // A Stream is a two-way stream. // All responses *must* be read by the caller. // If the call is canceled through the context, //The appropriate error will be returned. type Stream struct { // Responses from the remote server. // Channel will be closed after an error or when the remote closes. // All responses *must* be read by the caller until either an error is returned or the channel is closed. // Canceling the context will cause the context cancellation error to be returned. Responses <-chan Response // Requests sent to the server. // If the handler is defined with 0 incoming capacity this will be nil. // Channel *must* be closed to signal the end of the stream. // If the request context is canceled, the stream will no longer process requests. Requests chan<- []byte } type Response struct { Msg []byte Err error } ``` There are generic versions of the server/client handlers that allow the use of type safe implementations for data types that support msgpack marshal/unmarshal.
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t.Publisher.Publish(trace)
return resp, err
}