Provide progress information with --json option in Client

[jpraynaud]

Issue

In order to facilitate integration of the Mithril Client with third party software (e.g. Lace backend), we need to provide machine readable progress information when the --json flag is used in the snapshot download command.

Question: do we want to make --json a global option?

[michalrus]

Can we get a new JSON on stdout every 333 ms or so? This frequency feels good in a graphical UI, IMO

With:

• bytesDownloaded
• bytesTotal
• maybe secondsLeft – this estimation is available now in TTY

Right now we integrate Lace with Mithril, by running mithril-client in a Pseudo TTY

[michalrus]

😸 input-output-hk/lace#373 (comment)

[Alenar]

@michalrus We just merged #1172 that update the json output of the snapshot download command:
It will now out the current step of the process and, when downloading, a message every ~333ms or so with the current progress of the download:

{"step_num": 1, "total_steps": 7, "message": "Checking local disk info…"}                                                                                                    
{"step_num": 2, "total_steps": 7, "message": "Fetching the certificate's information…"}                                                                                      
{"step_num": 3, "total_steps": 7, "message": "Verifying the certificate chain…"}                                                                                             
{"step_num": 4, "total_steps": 7, "message": "Downloading the snapshot…"}
{ "bytesDownloaded": 376, "bytesTotal": 2438424190, "secondsLeft": 1971633.967, "secondsElapsed": 0.304 }                                                                                                                                     
{ "bytesDownloaded": 11204689, "bytesTotal": 2438424190, "secondsLeft": 442.483, "secondsElapsed": 0.637 }                                                                                                                                    
{ "bytesDownloaded": 23345233, "bytesTotal": 2438424190, "secondsLeft": 212.285, "secondsElapsed": 0.970 }                                                                                                                                    
{ "bytesDownloaded": 35485777, "bytesTotal": 2438424190, "secondsLeft": 154.834, "secondsElapsed": 1.303 }

-- truncated ...

{ "bytesDownloaded": 2116069290, "bytesTotal": 2438424190, "secondsLeft": 9.37, "secondsElapsed": 59.629 }
{ "bytesDownloaded": 2128209834, "bytesTotal": 2438424190, "secondsLeft": 8.694, "secondsElapsed": 59.962 }
{ "bytesDownloaded": 2138122154, "bytesTotal": 2438424190, "secondsLeft": 8.414, "secondsElapsed": 60.295 }
{ "bytesDownloaded": 2147870634, "bytesTotal": 2438424190, "secondsLeft": 8.146, "secondsElapsed": 60.629 }

-- truncated ...

{"step_num": 5, "total_steps": 7, "message": "Unpacking the snapshot…"}

This behavior is available currently on the unstable release: https://github.com/input-output-hk/mithril/releases/tag/unstable

Does this answer your needs for the download command ?

[michalrus]

It looks like exactly what we needed based on your message! I haven't tried to integrate it yet, will try to do so soon 😃

Thank you so much!