Diagnostics and crash reporting

This page explains what the MultiTaction Canvus client records when something goes wrong, what it sends to MultiTaction, how to turn crash reporting off, and what to collect before you contact support.

Log files

Canvus writes a log for each run. The folder and file name depend on the operating system and on how Canvus was started.

Platform and start method	Folder	File name
Windows, desktop shortcut	`%LOCALAPPDATA%\MultiTaction\canvus\logs`	`mt-canvus-<yyyy-mm-dd>.log`
Windows, `mt-canvus.bat`	`%LOCALAPPDATA%\MultiTaction\canvus\logs`	`log_<yymmdd_hhmmss>_<n>.log`
Windows, MT Launcher	Launcher pipeline log, see file locations
Ubuntu, desktop entry or `mt-canvus.sh`	`~/MultiTaction/canvus/logs`	`log<yymmdd-hh-mm-ss>-.txt` for Canvus and `mt-canvus-daemon-log<yymmdd-hh-mm-ss>-.txt` for the helper service
macOS	`~/MultiTaction/canvus/logs`	`mt-canvus-macos.log`

On Ubuntu and macOS the launcher writes the log. If you start mt-canvus-app directly, the output goes to the terminal only.

The first lines of each log show the Canvus version, the Cornerstone package versions and the configuration file in use (Loading MT Canvus settings from ...).

To print the version without starting Canvus, run:

mt-canvus-app --version

Crash reporting

Crash reporting is on by default on Windows and Linux. The macOS client has no crash reporter.

When Canvus crashes, the crash reporter writes a crash report. The report contains:

a minidump: the state of the application threads and their stacks at the moment of the crash, which can include fragments of the data Canvus was handling;
the computer host name;
the Canvus version and build date;
the OpenGL renderer, vendor and version;
the most recent part of the application log (up to 128 kB);
the screen.xml and config.txt files in use, and the audio configuration if one is set.

The report does not include your canvases or assets as files.

Where crash reports go

Windows: the crash reporter keeps reports on the computer, in %LOCALAPPDATA%\MultiTaction\CrashDumps of the account that runs Canvus. The Windows client does not upload crash reports to MultiTaction. To share a report with support, send the files from that folder (see collect diagnostics for support).
Linux: the crash reporter writes dumps to ~/cornerstone-crash-dumps. The mt-canvus.sh launcher passes an upload address on diagnostics.multitaction.com that uses plain HTTP, not HTTPS. The upload itself needs a separate helper program that is not part of the Canvus package or of any other MultiTaction package, so on a standard installation dumps stay on the computer. To send a dump to MultiTaction support, attach the file from that folder to your support request.
macOS: no crash reports.

MultiTaction uses the crash reports you send to find and fix the cause of crashes.

Windows Error Reporting dumps

The Windows installer also turns on Windows Error Reporting local dumps for the computer. Windows then keeps up to 10 mini dumps of crashed programs in %LOCALAPPDATA%\CrashDumps. These dumps stay on the computer. Windows Error Reporting applies this setting to every program on the computer, not only Canvus, and uninstalling Canvus does not remove it.

To turn it off, delete the registry key HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\Windows Error Reporting\LocalDumps.

Turn crash reporting off

Use either method. Both stop the crash reporter from writing reports.

Command-line flag: start Canvus with --no-crash-reporter.
- Windows, MT Launcher: add it to the arguments= line of the Launcher pipeline file, separated by a comma, for example arguments=--disable-dialogs,--no-crash-reporter. See unattended deployment.
- Windows, desktop shortcut: add it to the shortcut target after mt-canvus-app.exe.
- Ubuntu: pass it to the launcher, mt-canvus.sh --no-crash-reporter. To make it apply to the desktop entry, add it to the Exec= line of /usr/share/applications/mt-canvus-<version>.desktop.
Environment variable: set MULTI_DISABLE_CRASH_REPORTER (any value) in the environment Canvus starts in. On Ubuntu, add MULTI_DISABLE_CRASH_REPORTER=1 to /etc/environment. On Windows, add it as a system environment variable. This method survives updates.

The Windows Error Reporting dumps described above are separate. Turning the crash reporter off does not change them.

When Canvus stops responding

If the application stops responding for about 30 to 60 s, the built-in watchdog closes it. With the crash reporter on (the default), Canvus first records a diagnostic report and then exits with code 1. With the crash reporter off, Canvus writes the watchdog message to its log and is stopped by the operating system without a Canvus report, so the exit is reported as a crash rather than an exit code. Restart Canvus as usual. On Windows, MT Launcher restarts it for you (see unattended deployment).

From Canvus 26.09.8, quitting Canvus takes at most about 10 s, even if part of the application cannot stop.

Restoring the previous session

From Canvus 26.10.1:

After an unexpected shutdown (a crash or a power cut), Canvus reopens the workspaces and canvases that were open.
After a normal shutdown, Canvus starts at the welcome screen. Restore previous session on the welcome screen reopens the canvases that were open.

If a restore does not complete, the next start returns to the welcome screen instead of trying again.

Exit codes

Canvus returns these exit codes. Use them in scripts and in MT Launcher.

Code	Meaning
0	Normal exit
1	Start-up failed. For example, the configuration file given with `--mt-canvus-config` does not exist, an unknown command-line argument was given, or Cornerstone could not start. Canvus also exits with 1 when the watchdog closes it after it stops responding and the crash reporter is on.
2	The data folder is locked by another Canvus process
3	No valid license
4	The graphics hardware does not meet the requirements (see system requirements)
5	The data folder is invalid, for example it was written by a newer version
6	Email settings are invalid: `mail/allow-user-email=false` without a `mail/default-email-address`
7	The license is for an older version of Canvus
8	Canvus is already running. If a canvas link was given, the running Canvus opens it.

The mt-canvus.sh and mt-canvus.bat launchers print a short message for codes 1 to 5.

Warning

Codes 5 and 6 are returned when Canvus shows its error dialog and the user closes it. When Canvus runs with --disable-dialogs (as the MT Launcher pipeline does), it writes the error to the log and exits with code 0 in these two cases. Check the log when a wall installation exits with 0 at start-up.

Already running

Only one Canvus process runs per data folder. If you start Canvus with a canvas link while it is already running, the running Canvus opens the canvas and the new process exits with code 8. If you start it without a link, it reports that Canvus is already running and exits with code 8.

Connection overlay

Start Canvus with --connection-overlay to show a live table of each Canvus Server connection. It shows, per server:

server name and signed-in user;
ping time in ms;
average incoming and outgoing bandwidth in Mbit/s;
total data received and sent in MB;
pending downloads and uploads, the data left in MB, and the file in transfer.

Use it to see whether a slow canvas is caused by the network.

Collect diagnostics for support

Before you contact MultiTaction support, collect:

The Canvus version (mt-canvus-app --version).
The log files from the time of the problem (see log files).
The configuration files in use: mt-canvus.ini, screen.xml and config.txt (see file locations). Remove passwords from mt-canvus.ini before you send it.
On Linux, any dumps in ~/cornerstone-crash-dumps from the time of the problem.
On Windows, the crash reports from the time of the problem: the .dmp files in %LOCALAPPDATA%\MultiTaction\CrashDumps\reports of the account that runs Canvus, and any mt-canvus-app.exe dumps in %LOCALAPPDATA%\CrashDumps. Other MultiTaction applications on the same computer also write to the first folder, so pick the files by time.
A short description: what was on screen, what people did, and the time it happened.