mcap file is unindexed

[jlack1987]

I have an mcap file containing some log data, but when I try to open it to view the data in foxglove studio it says "This file is unindexed". I haven't been able to find anywhere that says what this means or what I can do to fix the file.

[defunctzombie]

MCAP files can be written with or without an index (https://mcap.dev/spec). Files with an index work much better. How did you produce your mcap file?

[jlack1987]

Do I just need to increment that sequence field with each message? I'm looking at the example here

[defunctzombie]

When you create a new mcap::McapWriter you specify options (https://mcap.dev/docs/cpp/r832FE362A16BB6E8). These let you control various features of the file you write. By default indexing is turned on, so your code had to explicitly turn it off.

[jlack1987]

hmm interesting. I'm creating a default constructed options struct and setting compression and profile but leaving everything else as the default 🤔

[achim-k]

Are you correctly closing the writer by calling close() ?

[jlack1987]

It is being called in the destructor of the class that's writing the data. I should probably verify the destructor is getting called

[jlack1987]

using a python script I iterate through the messages and each line has something like,
MessageIndex(channel_id=1, records=[(<rly_big_number>, 0)]

[jlack1987]

It appears that that rly_big_number is too big. I'm not sure what the number means, but it has some relation to size of something i'm guessing bc it looks like there's a 4GB limit and mine is much bigger than that, although my log file size is only 1MB. How is that rly big number calculated?

[jlack1987]

I finally found the problem here and you were right about not calling close(). I am calling close on destruction, but the code wasn't being killed properly. Once I fixed that this problem went away