[ Breaking Change Request ] Drop reference to Observatory in VM service message

[bkonyi]

Intended Behavior Change

Update the VM service message to no longer reference Observatory as it will no longer be shipped with the SDK in a future release (2.17). Observatory users will instead be directed to use DevTools for debugging via an existing message and the Observatory string will be replaced by the a message similar to the following:

A Dart VM service is listening on http://127.0.0.1:8181/abc123=/

Current Behavior

Currently, invoking the VM with either --observe or --enable-vm-service outputs a message to stdout similar to Observatory listening on http://127.0.0.1:8181/bKrWeCYueRo=/. Various pieces of tooling and testing infrastructure scrape stdout for this message in order to determine the VM service URI (e.g., flutter_tools).

Expected Impact

Tooling which relies on the Observatory message being printed to stdout will fail to connect to running Dart applications. This will mostly only impact tooling and tests which are not already relying on the --write-service-info= flag to write the VM service connection information to disk.

Mitigation

Impacted tooling should be updated to support the new VM service message and also support the legacy Observatory message if the tool supports arbitrary Dart versions.

Related issues

• Update service protocol startup message to not reference Observatory #38419

cc for review: @franklinyow @mit-mit @vsmenon @kevmoo @Hixie

FYI: @a-siva @jonahwilliams @devoncarew @jacob314

[a-siva]

/cc @zanderso

[jonahwilliams]

We can't use --write-service-info on iOS or Android, since we don't have access to the filesystem where those are written.

[Piero512]

DevTools is great for Flutter, but I was able to debug performance issues from a compute() isolate through the observatory, something that I wasn't able to do in DevTools , even though the observatory doesn't have all the bell and whistles of Observatory DevTools.

[DanTup]

will be replaced by the a message similar to the following

Is the exact message (allowing for URL differences 😛) known? If not, can you ping here when it is?

The VS Code extension mostly doesn't use this now, but there's still a little code to handle it in some cases.

[a-siva]

DevTools is great for Flutter, but I was able to debug performance issues from a compute() isolate through the observatory, something that I wasn't able to do in DevTools , even though the observatory doesn't have all the bell and whistles of the Observatory.

This breaking change will only change the string printed from the VM and will not drop observatory functionality

[a-siva]

We can't use --write-service-info on iOS or Android, since we don't have access to the filesystem where those are written.

For these cases can the tooling be changed to parse the new string ?

[jonahwilliams]

Parsing the new string is fine. IIRC this is all configured in a single place, so we should be able to update the code to accept either and roll.

[jonahwilliams]

https://github.com/flutter/flutter/blob/master/packages/flutter_tools/lib/src/protocol_discovery.dart#L37

[bkonyi]

@DanTup I'll be sure to update here with the CL before it lands so we'll have the exact wording tracked here.

@jonahwilliams thanks for pointing to where we'll need to make the change. I'll update the tool as part of a roll once the change lands.

@Piero512 thanks for the feedback! As @a-siva mentioned, Observatory isn't going away quite yet, but it's no longer under active development and is in maintenance mode. Would you mind filing an issue in the DevTools repository explaining what you were trying to do and why you had to go to Observatory to figure out your performance issue? We want to make sure DevTools is as good (or better) than Observatory before we drop support, so user feedback is always greatly appreciated! cc @kenzieschmoll

[aam]

@bkonyi wrote

@jonahwilliams thanks for pointing to where we'll need to make the change. I'll update the tool as part of a roll once the change lands.

Perhaps it might be simpler to update tools to accommodate both messages before the change in dart vm lands.