Add IO::MultiWriter #3404
Add IO::MultiWriter #3404
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| return if @closed | ||
| @closed = true | ||
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| @writers.each { |writer| writer.close } if sync_close? |
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Can close raise(*)? If so, does that need to be handled?
(*) It is not obvious from reading the code. Flush calls unbuffered write at least in some IO variants that are mixins.
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I don't think it needs to be handled. Errors from write calls bubble up to the caller in #write.
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Maybe we should attempt to write to the remaining writers if one call fails? I'm not entirely sure it's beneficial at all, but it should be considered. |
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| @writers.each { |writer| writer.write(slice) } | ||
| rescue ex | ||
| close |
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Closing the IO on error seemed a good idea at the time. This comes back to the question on what we should do if one of the IOs raises. Should we attempt to recover or just write off the IO as failed.
Is there realistically any reason why an IO would raise if it wouldn't raise on successive calls? Most IO code is written not to handle exceptions from IO objects, and to simply reconnect if such an event happens.
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Here's a reason for closing: if one of the write calls fails, then one of the underlying IOs may have written more than the rest. This means that the IOs are no longer consistent, and so we should fail all subsequent calls so that the two IOs don't go out of sync.
Unfortunately this isn't desired behaviour for logging because you don't want stdout to stop when the disk is full, so maybe it should be configurable?
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For now I'll avoid closing the IO. In other IOs if a write fails the IO doesn't get automatically closed, so I don't think this should be done for this particular IO.
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| property? sync_close | ||
| getter? closed = false | ||
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| @writers : Array(IO) |
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I think this can be removed as it will be correctly inferred from the constructor below
| def write(slice : Slice(UInt8)) | ||
| check_open | ||
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| @writers.each { |writer| writer.write(slice) } |
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This can be @writers.each &.write(slice), but you can leave it like this if you prefer it. Same applies to close
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Updated! |
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@RX14 Thank you for this! ❤️ |
Useful for writing log output to multiple locations (stdout + file) or any sort of parallel processing of IO data.