dart-sdk/pkg/dds/dds_protocol.md

Dart Development Service Protocol 1.4

This document describes version 1.4 of the Dart Development Service Protocol. This protocol is an extension of the Dart VM Service Protocol and implements it in it's entirety. For details on the VM Service Protocol, see the Dart VM Service Protocol Specification.

The Service Protocol uses JSON-RPC 2.0.

Table of Contents

• RPCs, Requests, and Responses
• Events
• Types
• IDs and Names
• Revision History
• Public RPCs
  • getAvailableCachedCpuSamples
  • getCachedCpuSamples[
  • getClientName
  • getDartDevelopmentServiceVersion
  • getLogHistorySize
  • getStreamHistory[
  • requirePermissionToResume
  • setClientName
  • setLogHistorySize
• Public Types
  • AvailableCachedCpuSamples[
  • CachedCpuSamples
  • ClientName
  • DartDevelopmentServiceVersion
  • Size
  • StreamHistory[

RPCs, Requests, and Responses

See the corresponding section in the VM Service protocol here.

Events

See the corresponding section in the VM Service protocol here.

Binary Events

See the corresponding section in the VM Service protocol here.

Types

See the corresponding section in the VM Service protocol here.

IDs and Names

See the corresponding section in the VM Service protocol here.

Streams

For a list of core VM service streams, see streamListen.

DDS will keep a history of events on certain streams and send historical events when a client first subscribes to a stream with history. These streams currently consist of the following:

• Logging
• Stdout
• Stderr
• Extension

In addition, subscribing to the Service stream will result in a ServiceRegistered event being sent to the subscribing client for each existing service extension.

From protocol version 1.4, custom streams of any name can be listened to via DDS.

Public RPCs

The DDS Protocol supports all public RPCs defined in the VM Service protocol.

getAvailableCachedCpuSamples

AvailableCachedCpuSamples getAvailableCachedCpuSamples();

The getAvailableCachedCpuSamples RPC is used to determine which caches of CPU samples are available. Caches are associated with individual UserTag names and are specified when DDS is started via the cachedUserTags parameter.

See AvailableCachedCpuSamples.

getCachedCpuSamples

CachedCpuSamples getCachedCpuSamples(string isolateId, string userTag);

The getCachedCpuSamples RPC is used to retrieve a cache of CPU samples collected under a UserTag with name userTag.

See CachedCpuSamples.

getClientName

ClientName getClientName()

The getClientName RPC is used to retrieve the name associated with the currently connected VM service client. If no name was previously set through the setClientName RPC, a default name will be returned.

See ClientName

getDartDevelopmentServiceVersion

Version getDartDevelopmentServiceVersion()

The getDartDevelopmentServiceVersion RPC is used to determine what version of the Dart Development Service Protocol is served by a DDS instance.

See Version.

getLogHistorySize

Size getLogHistorySize()

The getLogHistorySize RPC is used to retrieve the current size of the log history buffer. If the returned Size is zero, then log history is disabled.

See Size.

getStreamHistory

StreamHistory getStreamHistory(string streamId)

The getStreamHistory RPC is used to retrieve historical events for streams which support event history (see Streams for a list of supported streams).

See StreamHistory.

requirePermissionToResume

Success requirePermissionToResume(bool onPauseStart [optional],
                                  bool onPauseReload[optional],
                                  bool onPauseExit [optional])

The requirePermissionToResume RPC is used to change the pause/resume behavior of isolates by providing a way for the VM service to wait for approval to resume from some set of clients. This is useful for clients which want to perform some operation on an isolate after a pause without it being resumed by another client.

If the onPauseStart parameter is true, isolates will not resume after pausing on start until the client sends a resume request and all other clients which need to provide resume approval for this pause type have done so.

If the onPauseReload parameter is true, isolates will not resume after pausing after a reload until the client sends a resume request and all other clients which need to provide resume approval for this pause type have done so.

If the onPauseExit parameter is true, isolates will not resume after pausing on exit until the client sends a resume request and all other clients which need to provide resume approval for this pause type have done so.

Important Notes:

• All clients with the same client name share resume permissions. Only a single client of a given name is required to provide resume approval.
• When a client requiring approval disconnects from the service, a paused isolate may resume if all other clients requiring resume approval have already given approval. In the case that no other client requires resume approval for the current pause event, the isolate will be resumed if at least one other client has attempted to resume the isolate.

setClientName

Success setClientName(string name)

The setClientName RPC is used to set a name to be associated with the currently connected VM service client. If the name parameter is a non-empty string, name will become the new name associated with the client. If name is an empty string, the client's name will be reset to its default name.

See Success.

setLogHistorySize

Success setLogHistorySize(int size)

The setLogHistorySize RPC is used to set the size of the ring buffer used for caching a limited set of historical log messages. If size is 0, logging history will be disabled. The maximum history size is 100,000 messages, with the default set to 10,000 messages.

See Success.

Public Types

The DDS Protocol supports all public types defined in the VM Service protocol.

AvailableCachedCpuSamples

class AvailableCachedCpuSamples extends Response {
  // A list of UserTag names associated with CPU sample caches.
  string[] cacheNames;
}

A collection of [UserTag] names associated with caches of CPU samples.

See getAvailableCachedCpuSamples.

CachedCpuSamples

class CachedCpuSamples extends CpuSamples {
  // The name of the UserTag associated with this cache of samples.
  string userTag;

  // Provided if the CPU sample cache has filled and older samples have been
  // dropped.
  bool truncated [optional];
}

An extension of CpuSamples which represents a set of cached samples, associated with a particular [UserTag] name.

See getCachedCpuSamples.

ClientName

class ClientName extends Response {
  // The name of the currently connected VM service client.
  string name;
}

See getClientName and setClientName.

Size

class Size extends Response {
  int size;
}

A simple object representing a size response.

StreamHistory

class StreamHistory extends Response {
  // A list of historical Events for a stream.
  List<Event> history;
}

See getStreamHistory.

Revision History

version	comments
1.0	Initial revision
1.1	Added getDartDevelopmentServiceVersion RPC.
1.2	Added getStreamHistory RPC.
1.3	Added getAvailableCachedCpuSamples and getCachedCpuSamples RPCs.
1.4	Added the ability to subscribe to custom streams (which can be specified when calling dart:developer's postEvent).