prodash 8.0.0

prodash is a dashboard for displaying progress of concurrent applications.

It's easy to integrate thanks to a pragmatic API, and comes with a terminal user interface by default.

How to use…

Be sure to read the documentation at https://docs.rs/prodash, it contains various examples on how to get started.

Or run the demo application like so cd prodash && cargo run --example dashboard.

Feature Toggles

This crate comes with various cargo features to tailor it to your needs.

• progress-tree (default)
  • Provide a Progress and Root trait implementation for use with the render-line and render-tui backed by dashmap.
  • progress-tree-log (default)
    • If logging in the log crate is initialized, a log will be used to output all messages provided to tree::Item::message(…) and friends. No actual progress is written.
    • May interfere with render-tui or render-line, or any renderer outputting to the console.
• progress-log
  • A Progress implementation which logs messages and progress using the log crate
• local-time (default)
  • If set, timestamps in the message pane of the render-tui will be using the local time, not UTC
  • If set, timestamps of the log messages of the render-line will be using the local time, not UTC
  • Has no effect without the render-tui or render-line respectively
• render-line
  • Provide a minimal line-based progress renderer which can be limited to a subset of the progress hierarchy.
  • It's like the render-tui, but with far less dependencies and less visual fidelity - all it needs is to move the cursor a little while drawing characters and block graphics.
  • Support for clicolors spec and no-color spec
  • Supports initial delay that won't affect log messages, showing progress only when needed, automatically.
  • Requires one of these additional feature flags to be set to be functional
    • one required (mutually exclusive)
      • render-line-crossterm - use the crossterm backend, useful for working on windows
      • render-line-termion - use the termion backend, useful for lean unix-only builds
  • Optional features
    • ctrlc
      • If set, and the hide_cursor line renderer option is set, the cursor will be hidden and SIG_INT and SIG_TERM handlers will be installed to reset the cursor on exit. Otherwise you have to make sure to call shutdown_and_wait() on the JoinHandle returned to give the renderer a chance to undo the terminal changes. Failing to do so will leave the cusor hidden once the program has already finished.
      • Comes at the cost of an extra thread and additional dependencies.
• render-tui
  • Provide a terminal user interface visualizing every detail of the current progress state. It treats the terminal as a matrix display.
  • Requires one of these additional feature flags to be set to be functional ** (one required, mutually exclusive)
    • render-tui-crossterm
      • Use the crossterm crate as terminal backend
      • Works everywhere natively, but has more dependencies
      • You can set additional features like this cargo build --features render-tui-crossterm,crossterm/event-stream
    • render-tui-termion
      • Use the termion crate as terminal backend
      • It has less dependencies but works only on unix systems
      • to get this, disable default features and chose at least render-tui and render-tui-termion.
• unit-bytes
  • Supports dynamic byte display using the tiny bytesize crate.
• unit-human
  • Display counts in a way that is easier to grasp for humans, using the tiny human_format crate.
• unit-duration
  • Displays time in seconds like '5m4s' using the tiny compound_duration crate.

Features

• fast insertions and updates for transparent progress tracking of highly concurrent programs
• a messages buffer for information about success and failure
• a terminal user interface for visualization, with keyboard controls and dynamic re-sizing
• unicode and multi-width character support

Transition to futures-lite

In order for the build-time improvements to become effective, we need…

• crosstermion
  • StreamExt::filter_map(…)
• prodash::tui::engine
  • stream::select_all(…)
  • StreamExt::map(…)
  • StreamExt::boxed(…)
• prodash -> example -> dashboard
  • stream::select(…)
  • future::select(…)
  • future::join_all(…)
  • FutureExt::boxed(…)

Limitations

• the line renderer is inherently limited in the amount of progress it can display without visual artifacts.
• it does copy quite some state each time it displays progress information and messages
• The underlying sync data structure, dashmap, does not document every use of unsafe
  • I also evaluated evmap, which has 25% less uses of unsafe, but a more complex interface.
  • Thus far it seemed 'ok' to use, who knows… we are getting mutable pieces of a hashmap from multiple threads, however, we never hand out multiple handles to the same child which should make actual concurrent access to the same key impossible.
• If there are more than 2^16 tasks
  • then
    • running concurrently on a single level of the tree, they start overwriting each other
    • over its lifetime, even though they do not run concurrently, eventually new tasks will seem like old tasks (their ID wrapped around)
  • why
    • on drop, they never decrement a child count used to generate a new ID
  • fix
    • make the id bigger, like u32
    • we should do that once there is a performance test
• If the log lines are too long for the terminal width when using the line renderer
  • then
    • visual artifacts will appear
  • why
    • trying to draw beyond the terminal boundary will add a line break automatically, which can cause unexpected overdraw.
  • fix
    • count amount of blocks drawn, without ansi codes, and stop drawing at the boundary.

Lessons Learned

• drop() is not garantueed to be called when the future returns Ready and is in the futures::executor::ThreadPool
  • Workaround: drop and cleanup explicitly, prone to forgetting it.
  • This is also why futures::future::abortable() works (by stopping the polling), but doesn't as cleanup is not performed, even though it clearly would be preferred.
  • fix
    • Use a join handle and await it - this will drop the future properly
• select() might not work with complex futures - these should then be boxed() if Unpin isn't implemented.