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Report pulled image size #752
Comments
The download in particular and diskspace are less.
fedora-toolbox:35 skopeo image Size is currently ~340MB
fedora-toolbox:35 skopeo image Size is currently ~340MB
We should be careful not to add a hard dependency on skopeo. Toolbx is part of size-constrained operating systems like Fedora CoreOS, where an extra mandatory dependency on skopeo might be problematic. We should attempt to use it, but if it's absent, we should have a fallback of some sort. |
That commit from @juhp that is showing up against this issue can be ignored. It was addressed earlier in #875 (comment) |
In order to add this feature, I'm going through the create.go file. The variable %s is used all along this file and it gets the following value |
That |
The main lines I've been looking at are from the 700-705 of the create.go file. The variable |
You mean these lines in src/cmd/create.go:
Yes, |
containers#752 Signed-off-by: Nieves Montero <[email protected]>
containers#752 Signed-off-by: Nieves Montero <[email protected]>
containers#752 Signed-off-by: Nieves Montero <[email protected]>
containers#752 Signed-off-by: Nieves Montero <[email protected]>
containers#752 Signed-off-by: Nieves Montero <[email protected]>
containers#752 Signed-off-by: Nieves Montero <[email protected]>
containers#752 Signed-off-by: Nieves Montero <[email protected]>
Fix containers#752 The following package and file have been created src/pkg/skopeo/skopeo.go Signed-off-by: Nieves Montero <[email protected]>
Fix containers#752 The following package and file have been created src/pkg/skopeo/skopeo.go Signed-off-by: Nieves Montero <[email protected]>
Fix containers#752 The following package and file have been created src/pkg/skopeo/skopeo.go Signed-off-by: Nieves Montero <[email protected]>
Fix containers#752 The following package and file have been created src/pkg/skopeo/skopeo.go Signed-off-by: Nieves Montero <[email protected]>
Fix containers#752 The following package and file have been created src/pkg/skopeo/skopeo.go Signed-off-by: Nieves Montero <[email protected]>
Fix containers#752 The following package and file have been created src/pkg/skopeo/skopeo.go Signed-off-by: Nieves Montero <[email protected]>
Fix containers#752 The following package and file have been created src/pkg/skopeo/skopeo.go Signed-off-by: Nieves Montero <[email protected]>
Fix containers#752 The following package and file have been created src/pkg/skopeo/skopeo.go Signed-off-by: Nieves Montero <[email protected]>
A subsequent commit will use this to ensure that the user can still interact with the image download prompt while 'skopeo inspect' fetches the image size from the remote registry. To do this, at some point, the terminal device will be put into non-canonical mode input and the echoing of input characters will be disabled to retain full control of the cursor position. Unfortunately, this will require access to the full termios(3) struct that isn't given by golang.org/x/term, and, hence, the code needs to be written using the underlying termios(3) API. This future code will have enough overlap with the IsTerminal API from golang.org/x/term that it doesn't make sense to use a separate module (ie., golang.org/x/term) for it. containers#752 containers#1263
A subsequent commit will use this to ensure that the user can still interact with the image download prompt while 'skopeo inspect' fetches the image size from the remote registry. Initially, the prompt will be shown without the image size. Once the size has been fetched, the older prompt will be cancelled and a new one will be shown that includes the size. containers#752 containers#1263
This is meant to avoid duplicating the code that shows the prompt, and reads and parses the user's input. containers#752 containers#1263
A subsequent commit will use this to ensure that the user can still interact with the image download prompt while 'skopeo inspect' fetches the image size from the remote registry. Initially, the prompt will be shown without the image size. Once the size has been fetched, the older prompt will be cancelled and a new one will be shown that includes the size. While the prompt is getting updated, the terminal device will be put into non-canonical mode input and the echoing of input characters will be disabled to retain full control of the cursor position. Once the new prompt is in place, the previous state of the terminal will be restored. However, anything that was typed in the interim will be discarded to avoid surprising the user with invisible input. containers#752 containers#1263
A subsequent commit will use this to ensure that the user can still interact with the image download prompt while 'skopeo inspect' fetches the image size from the remote registry. To do this, at some point, the terminal device will be put into non-canonical mode input and the echoing of input characters will be disabled to retain full control of the cursor position. Unfortunately, this will require access to the full termios(3) struct that isn't given by golang.org/x/term, and, hence, the code needs to be written using the underlying termios(3) API. This future code will have enough overlap with the IsTerminal API from golang.org/x/term that it doesn't make sense to use a separate module (ie., golang.org/x/term) for it. containers#752 containers#1263
A subsequent commit will use this to ensure that the user can still interact with the image download prompt while 'skopeo inspect' fetches the image size from the remote registry. To do this, at some point, the terminal device will be put into non-canonical mode input and the echoing of input characters will be disabled to retain full control of the cursor position. containers#752 containers#1263
A subsequent commit will use this to ensure that the user can still interact with the image download prompt while 'skopeo inspect' fetches the image size from the remote registry. To do this, at some point, the terminal device will be put into non-canonical mode input and the echoing of input characters will be disabled to retain full control of the cursor position. Unfortunately, this will require access to the full termios(3) struct that isn't given by golang.org/x/term, and, hence, the code needs to be written using the underlying termios(3) API. This future code will have enough overlap with the IsTerminal API from golang.org/x/term that it doesn't make sense to use a separate module (ie., golang.org/x/term) for it. containers#752 containers#1263
A subsequent commit will use this to ensure that the user can still interact with the image download prompt while 'skopeo inspect' fetches the image size from the remote registry. To do this, at some point, the terminal device will be put into non-canonical mode input and the echoing of input characters will be disabled to retain full control of the cursor position. containers#752 containers#1263
A subsequent commit will use this to ensure that the user can still interact with the image download prompt while 'skopeo inspect' fetches the image size from the remote registry. Initially, the prompt will be shown without the image size. If the user responds before the size is fetched, then the pending 'skopeo inspect' will be cancelled. containers#752 containers#1263
A subsequent commit will use this to ensure that the user can still interact with the image download prompt while 'skopeo inspect' fetches the image size from the remote registry. Initially, the prompt will be shown without the image size. If the user responds before the size is fetched, then the pending 'skopeo inspect' will be cancelled. containers#752 containers#1263
It takes 'skopeo inspect' a few seconds to fetch the image size from the remote registry, and while that happens the user can't interact with the image download prompt: $ toolbox create Image required to create toolbox container. <wait for a few seconds> Download registry.fedoraproject.org/fedora-toolbox:39 (359.8MB)? [y/N]: This feels awkward because it's not clear to the user what's going on during those few seconds. Moreover, while knowing the image size can be convenient at times, for example when disk space and network bandwidth are limited, it's not always important. It will be better if 'skopeo inspect' ran in the background, while waiting for the user to respond to the image download prompt, and once the image size has been fetched, the image download prompt can be updated to include it. So, initially: $ toolbox create Image required to create toolbox container. Download registry.fedoraproject.org/fedora-toolbox:39 (...)? [y/N]: ... and then once the size is available: $ toolbox create Image required to create toolbox container. Download registry.fedoraproject.org/fedora-toolbox:39 (359.8MB)? [y/N]: If skopeo(1) is missing or too old, then the prompt can continue without the size, as it did before: $ toolbox create Image required to create toolbox container. Download registry.fedoraproject.org/fedora-toolbox:39 [y/N]: Updating the image download prompt with the results of 'skopeo inspect' is vulnerable to races. At the same time as the terminal's cursor is moved to the beginning of the current line to overwrite the earlier prompt with the new one, the user can keep typing, which will keep moving the cursor forward. This competition over the cursor can lead to awkward outcomes. For example, the prompt can overwrite the characters typed in by the user, leaving characters in the terminal's input buffer waiting for the user to hit ENTER, even though they are not visible on the screen. Another example is that hitting BACKSPACE can end up deleting parts of the prompt, instead of stopping at the edge. This is solved by putting the terminal device into non-canonical mode input and disabling the echoing of input characters, while the prompt is being updated. This prevents input from moving the terminal's cursor forward, and from accumulating in the terminal's input buffer even if it might not be visible. Any input during this interim period is discarded and replaced by '...', and a fresh new prompt is shown in the following line. In practice, this race shouldn't be too common. It can only happen if the user is typing right when the prompt is being updated, which is unlikely because it's only supposed to be a short 'yes' or 'no' input. The use of the context.Cause and context.WithCancelCause functions [1] requires Go >= 1.20. Bumping the Go version in src/go.mod then requires a 'go mod tidy'. Otherwise, it leads to: $ meson compile -C builddir --verbose ... /home/rishi/devel/containers/git/toolbox/src/go-build-wrapper /home/rishi/devel/containers/git/toolbox/src /home/rishi/devel/containers/git/toolbox/builddir src/toolbox 0.0.99.4 cc /lib64/ld-linux-x86-64.so.2 false go: updates to go.mod needed; to update it: go mod tidy ninja: build stopped: subcommand failed. [1] https://pkg.go.dev/context containers#752 containers#1263
It takes 'skopeo inspect' a few seconds to fetch the image size from the remote registry, and while that happens the user can't interact with the image download prompt: $ toolbox create Image required to create toolbox container. <wait for a few seconds> Download registry.fedoraproject.org/fedora-toolbox:39 (359.8MB)? [y/N]: This feels awkward because it's not clear to the user what's going on during those few seconds. Moreover, while knowing the image size can be convenient at times, for example when disk space and network bandwidth are limited, it's not always important. It will be better if 'skopeo inspect' ran in the background, while waiting for the user to respond to the image download prompt, and once the image size has been fetched, the image download prompt can be updated to include it. So, initially: $ toolbox create Image required to create toolbox container. Download registry.fedoraproject.org/fedora-toolbox:39 (...)? [y/N]: ... and then once the size is available: $ toolbox create Image required to create toolbox container. Download registry.fedoraproject.org/fedora-toolbox:39 (359.8MB)? [y/N]: If skopeo(1) is missing or too old, then the prompt can continue without the size, as it did before: $ toolbox create Image required to create toolbox container. Download registry.fedoraproject.org/fedora-toolbox:39 [y/N]: Updating the image download prompt with the results of 'skopeo inspect' is vulnerable to races. At the same time as the terminal's cursor is moved to the beginning of the current line to overwrite the earlier prompt with the new one, the user can keep typing, which will keep moving the cursor forward. This competition over the cursor can lead to awkward outcomes. For example, the prompt can overwrite the characters typed in by the user, leaving characters in the terminal's input buffer waiting for the user to hit ENTER, even though they are not visible on the screen. Another example is that hitting BACKSPACE can end up deleting parts of the prompt, instead of stopping at the edge. This is solved by putting the terminal device into non-canonical mode input and disabling the echoing of input characters, while the prompt is being updated. This prevents input from moving the terminal's cursor forward, and from accumulating in the terminal's input buffer even if it might not be visible. Any input during this interim period is discarded and replaced by '...', and a fresh new prompt is shown in the following line. In practice, this race shouldn't be too common. It can only happen if the user is typing right when the prompt is being updated, which is unlikely because it's only supposed to be a short 'yes' or 'no' input. The use of the context.Cause and context.WithCancelCause functions [1] requires Go >= 1.20. Bumping the Go version in src/go.mod then requires a 'go mod tidy'. Otherwise, it leads to: $ meson compile -C builddir --verbose ... /home/rishi/devel/containers/git/toolbox/src/go-build-wrapper /home/rishi/devel/containers/git/toolbox/src /home/rishi/devel/containers/git/toolbox/builddir src/toolbox 0.0.99.4 cc /lib64/ld-linux-x86-64.so.2 false go: updates to go.mod needed; to update it: go mod tidy ninja: build stopped: subcommand failed. [1] https://pkg.go.dev/context containers#752 containers#1263
A subsequent commit will use this to ensure that the user can still interact with the image download prompt while 'skopeo inspect' fetches the image size from the remote registry. Initially, the prompt will be shown without the image size. Once the size has been fetched, the older prompt will be cancelled and a new one will be shown that includes the size. Even though this code is only expected to be used to read from the standard input stream, when it's connected to a terminal device, the use of poll(2) here was tested with FIFOs or named pipes and regular files as well, in case they might be necessary in future. An eventfd(2) file descriptor expects a 8-byte or 64-bit integer value to be given to write(2) to increase its counter by that amount [1]. In C, it could be phrased as: uint64_t one = 1; write (eventfd, &one, sizeof(one)); However, Go's wrapper for write(2) expects a sequence of bytes (ie., []byte), and not an arbitrary memory address. Therefore the 'binary' package [3] is used to encode the integer into a byte sequence as a varint. Even though a varint-encoded 64-bit integer takes a maximum of 10 bytes, as defined by binary.MaxVarintLen64, 1 byte is enough to encode the number 1 as an unsigned 64-bit integer [3]. That's enough to fit into a byte sequence of length 8 to satisfy what an eventfd(2) file descriptor expects. Ultimately, it doesn't matter exactly what value the receiving end assigns to the number given to write(2), as long as it's not zero. [1] https://man7.org/linux/man-pages/man2/eventfd.2.html [2] https://pkg.go.dev/golang.org/x/sys/unix#Write [3] https://protobuf.dev/programming-guides/encoding/ containers#752 containers#1263
This is meant to avoid duplicating the code that shows the prompt, and reads and parses the user's input. containers#752 containers#1263
A subsequent commit will use this to ensure that the user can still interact with the image download prompt while 'skopeo inspect' fetches the image size from the remote registry. Initially, the prompt will be shown without the image size. Once the size has been fetched, the older prompt will be cancelled and a new one will be shown that includes the size. While the prompt is getting updated, the terminal device will be put into non-canonical mode input and the echoing of input characters will be disabled to retain full control of the cursor position. Once the new prompt is in place, the previous state of the terminal will be restored. However, anything that was typed in the interim will be discarded to avoid surprising the user with invisible input. Even though this code is only expected to be used to read from the standard input stream, when it's connected to a terminal device, the use of poll(2) here was tested with FIFOs or named pipes and regular files as well, in case they might be necessary in future. containers#752 containers#1263
A subsequent commit will use this to ensure that the user can still interact with the image download prompt while 'skopeo inspect' fetches the image size from the remote registry. To do this, at some point, the terminal device will be put into non-canonical mode input and the echoing of input characters will be disabled to retain full control of the cursor position. Unfortunately, this will require access to the full termios(3) struct that isn't given by golang.org/x/term, and, hence, the code needs to be written using the underlying termios(3) API. This future code will have enough overlap with the IsTerminal API from golang.org/x/term that it doesn't make sense to use a separate module (ie., golang.org/x/term) for it. containers#752 containers#1263
A subsequent commit will use this to ensure that the user can still interact with the image download prompt while 'skopeo inspect' fetches the image size from the remote registry. To do this, at some point, the terminal device will be put into non-canonical mode input and the echoing of input characters will be disabled to retain full control of the cursor position. containers#752 containers#1263
A subsequent commit will use this to ensure that the user can still interact with the image download prompt while 'skopeo inspect' fetches the image size from the remote registry. Initially, the prompt will be shown without the image size. If the user responds before the size is fetched, then the pending 'skopeo inspect' will be cancelled. containers#752 containers#1263
A subsequent commit will use this to ensure that the user can still interact with the image download prompt while 'skopeo inspect' fetches the image size from the remote registry. Initially, the prompt will be shown without the image size. If the user responds before the size is fetched, then the pending 'skopeo inspect' will be cancelled. containers#752 containers#1263
It takes 'skopeo inspect' a few seconds to fetch the image size from the remote registry, and while that happens the user can't interact with the image download prompt: $ toolbox create Image required to create toolbox container. <wait for a few seconds> Download registry.fedoraproject.org/fedora-toolbox:39 (359.8MB)? [y/N]: This feels awkward because it's not clear to the user what's going on during those few seconds. Moreover, while knowing the image size can be convenient at times, for example when disk space and network bandwidth are limited, it's not always important. It will be better if 'skopeo inspect' ran in the background, while waiting for the user to respond to the image download prompt, and once the image size has been fetched, the image download prompt can be updated to include it. So, initially: $ toolbox create Image required to create toolbox container. Download registry.fedoraproject.org/fedora-toolbox:39 ( ... MB)? [y/N]: ... and then once the size is available: $ toolbox create Image required to create toolbox container. Download registry.fedoraproject.org/fedora-toolbox:39 (359.8MB)? [y/N]: If skopeo(1) is missing or too old, then the prompt can continue without the size, as it did before: $ toolbox create Image required to create toolbox container. Download registry.fedoraproject.org/fedora-toolbox:39 [y/N]: The placeholder for the missing image size (ie., ' ... MB') was chosen to have seven characters, so that it matches the most common sizes. The human-readable representation of the image size is capped at four valid numbers [1]. Unless it's a perfect round number like 1KB or 1.2MB, it will likely use all four numbers and the decimal point, which is five characters. Then two more for the unit, because it's very unlikely that there will be an image that's less than 1KB in size and will be shown in bytes with a B. That makes it seven characters in total. Updating the image download prompt with the results of 'skopeo inspect' is vulnerable to races. At the same time as the terminal's cursor is being moved to the beginning of the current line to overwrite the earlier prompt with the new one, the user can keep typing and keep moving the cursor forward. This competition over the cursor can lead to awkward outcomes. For example, the prompt can overwrite the characters typed in by the user, leaving characters in the terminal's input buffer waiting for the user to hit ENTER, even though they are not visible on the screen. Another example is that hitting BACKSPACE can end up deleting parts of the prompt, instead of stopping at the edge. This is solved by putting the terminal device into non-canonical mode input and disabling the echoing of input characters, while the prompt is being updated. This prevents input from moving the terminal's cursor forward, and from accumulating in the terminal's input buffer even if it might not be visible. Any input during this interim period is discarded and replaced by '...', and a fresh new prompt is shown in the following line. In practice, this race shouldn't be too common. It can only happen if the user is typing right when the prompt is being updated, which is unlikely because it's only supposed to be a short 'yes' or 'no' input. The use of the context.Cause and context.WithCancelCause functions [2] requires Go >= 1.20. Bumping the Go version in src/go.mod then requires a 'go mod tidy'. Otherwise, it leads to: $ meson compile -C builddir --verbose ... /home/rishi/devel/containers/git/toolbox/src/go-build-wrapper /home/rishi/devel/containers/git/toolbox/src /home/rishi/devel/containers/git/toolbox/builddir src/toolbox 0.0.99.4 cc /lib64/ld-linux-x86-64.so.2 false go: updates to go.mod needed; to update it: go mod tidy ninja: build stopped: subcommand failed. [1] https://pkg.go.dev/github.com/docker/go-units#HumanSize [2] https://pkg.go.dev/context containers#752 containers#1263
It takes 'skopeo inspect' a few seconds to fetch the image size from the remote registry, and while that happens the user can't interact with the image download prompt: $ toolbox create Image required to create toolbox container. <wait for a few seconds> Download registry.fedoraproject.org/fedora-toolbox:39 (359.8MB)? [y/N]: This feels awkward because it's not clear to the user what's going on during those few seconds. Moreover, while knowing the image size can be convenient at times, for example when disk space and network bandwidth are limited, it's not always important. It will be better if 'skopeo inspect' ran in the background, while waiting for the user to respond to the image download prompt, and once the image size has been fetched, the image download prompt can be updated to include it. So, initially: $ toolbox create Image required to create toolbox container. Download registry.fedoraproject.org/fedora-toolbox:39 ( ... MB)? [y/N]: ... and then once the size is available: $ toolbox create Image required to create toolbox container. Download registry.fedoraproject.org/fedora-toolbox:39 (359.8MB)? [y/N]: If skopeo(1) is missing or too old, then the prompt can continue without the size, as it did before: $ toolbox create Image required to create toolbox container. Download registry.fedoraproject.org/fedora-toolbox:39 [y/N]: The placeholder for the missing image size (ie., ' ... MB') was chosen to have seven characters, so that it matches the most common sizes. The human-readable representation of the image size is capped at four valid numbers [1]. Unless it's a perfect round number like 1KB or 1.2MB, it will likely use all four numbers and the decimal point, which is five characters. Then two more for the unit, because it's very unlikely that there will be an image that's less than 1KB in size and will be shown in bytes with a B. That makes it seven characters in total. Updating the image download prompt with the results of 'skopeo inspect' is vulnerable to races. At the same time as the terminal's cursor is being moved to the beginning of the current line to overwrite the earlier prompt with the new one, the user can keep typing and keep moving the cursor forward. This competition over the cursor can lead to awkward outcomes. For example, the prompt can overwrite the characters typed in by the user, leaving characters in the terminal's input buffer waiting for the user to hit ENTER, even though they are not visible on the screen. Another example is that hitting BACKSPACE can end up deleting parts of the prompt, instead of stopping at the edge. This is solved by putting the terminal device into non-canonical mode input and disabling the echoing of input characters, while the prompt is being updated. This prevents input from moving the terminal's cursor forward, and from accumulating in the terminal's input buffer even if it might not be visible. Any input during this interim period is discarded and replaced by '...', and a fresh new prompt is shown in the following line. In practice, this race shouldn't be too common. It can only happen if the user is typing right when the prompt is being updated, which is unlikely because it's only supposed to be a short 'yes' or 'no' input. The use of the context.Cause and context.WithCancelCause functions [2] requires Go >= 1.20. Bumping the Go version in src/go.mod then requires a 'go mod tidy'. Otherwise, it leads to: $ meson compile -C builddir --verbose ... /home/rishi/devel/containers/git/toolbox/src/go-build-wrapper /home/rishi/devel/containers/git/toolbox/src /home/rishi/devel/containers/git/toolbox/builddir src/toolbox 0.0.99.4 cc /lib64/ld-linux-x86-64.so.2 false go: updates to go.mod needed; to update it: go mod tidy ninja: build stopped: subcommand failed. [1] https://pkg.go.dev/github.com/docker/go-units#HumanSize [2] https://pkg.go.dev/context containers#752 containers#1263
A subsequent commit will use this to ensure that the user can still interact with the image download prompt while 'skopeo inspect' fetches the image size from the remote registry. Initially, the prompt will be shown without the image size. Once the size has been fetched, the older prompt will be cancelled and a new one will be shown that includes the size. Even though this code is only expected to be used to read from the standard input stream when it's connected to a terminal device, the use of poll(2) here was tested with FIFOs or named pipes and regular files as well, in case they might be necessary in future. An eventfd(2) file descriptor expects a 8-byte or 64-bit integer value to be given to write(2) to increase its counter by that amount [1]. In C, it could be phrased as: uint64_t one = 1; write (eventfd, &one, sizeof (one)); However, Go's wrapper for write(2) expects a sequence of bytes (ie., []byte), and not an arbitrary memory address [2]. Therefore, the 'encoding/binary' package [3] is used to encode the integer into a byte sequence as a varint. Even though a varint-encoded 64-bit integer takes a maximum of 10 bytes, as defined by binary.MaxVarintLen64, 1 byte is enough to encode the number 1 as an unsigned 64-bit integer [4]. That's enough to fit into a byte sequence of length 8 to satisfy what an eventfd(2) file descriptor expects. Ultimately, it doesn't matter exactly what value the receiving end assigns to the number given to write(2), as long as it's not zero. [1] https://man7.org/linux/man-pages/man2/eventfd.2.html [2] https://pkg.go.dev/golang.org/x/sys/unix#Write [3] https://pkg.go.dev/encoding/binary [4] https://protobuf.dev/programming-guides/encoding/ containers#752 containers#1263
This is meant to avoid duplicating the code that shows the prompt, and reads and parses the user's input. containers#752 containers#1263
A subsequent commit will use this to ensure that the user can still interact with the image download prompt while 'skopeo inspect' fetches the image size from the remote registry. Initially, the prompt will be shown without the image size. Once the size has been fetched, the older prompt will be cancelled and a new one will be shown that includes the size. While the prompt is getting updated, the terminal device will be put into non-canonical mode input and the echoing of input characters will be disabled to retain full control of the cursor position. Once the new prompt is in place, the previous state of the terminal will be restored. However, anything that was typed in the interim will be discarded to avoid surprising the user with invisible input. Even though this code is only expected to be used to read from the standard input stream when it's connected to a terminal device, the use of poll(2) here was tested with FIFOs or named pipes and regular files as well, in case they might be necessary in future. containers#752 containers#1263
A subsequent commit will use this to ensure that the user can still interact with the image download prompt while 'skopeo inspect' fetches the image size from the remote registry. To do this, at some point, the terminal device will be put into non-canonical mode input and the echoing of input characters will be disabled to retain full control of the cursor position. Unfortunately, this will require access to the full termios(3) struct that isn't given by golang.org/x/term, and, hence, the code needs to be written using the underlying termios(3) API. This future code will have enough overlap with the IsTerminal API from golang.org/x/term that it doesn't make sense to use a separate module (ie., golang.org/x/term) for it. containers#752 containers#1263
A subsequent commit will use this to ensure that the user can still interact with the image download prompt while 'skopeo inspect' fetches the image size from the remote registry. To do this, at some point, the terminal device will be put into non-canonical mode input and the echoing of input characters will be disabled to retain full control of the cursor position. containers#752 containers#1263
A subsequent commit will use this to ensure that the user can still interact with the image download prompt while 'skopeo inspect' fetches the image size from the remote registry. Initially, the prompt will be shown without the image size. If the user responds before the size is fetched, then the pending 'skopeo inspect' will be cancelled. containers#752 containers#1263
A subsequent commit will use this to ensure that the user can still interact with the image download prompt while 'skopeo inspect' fetches the image size from the remote registry. Initially, the prompt will be shown without the image size. If the user responds before the size is fetched, then the pending 'skopeo inspect' will be cancelled. containers#752 containers#1263
It takes 'skopeo inspect' a few seconds to fetch the image size from the remote registry, and while that happens the user can't interact with the image download prompt: $ toolbox create Image required to create toolbox container. <wait for a few seconds> Download registry.fedoraproject.org/fedora-toolbox:39 (359.8MB)? [y/N]: This feels awkward because it's not clear to the user what's going on during those few seconds. Moreover, while knowing the image size can be convenient at times, for example when disk space and network bandwidth are limited, it's not always important. It will be better if 'skopeo inspect' ran in the background, while waiting for the user to respond to the image download prompt, and once the image size has been fetched, the image download prompt can be updated to include it. So, initially: $ toolbox create Image required to create toolbox container. Download registry.fedoraproject.org/fedora-toolbox:39 ( ... MB)? [y/N]: ... and then once the size is available: $ toolbox create Image required to create toolbox container. Download registry.fedoraproject.org/fedora-toolbox:39 (359.8MB)? [y/N]: If skopeo(1) is missing or too old, then the prompt can continue without the size, as it did before: $ toolbox create Image required to create toolbox container. Download registry.fedoraproject.org/fedora-toolbox:39 [y/N]: The placeholder for the missing image size (ie., ' ... MB') was chosen to have seven characters, so that it matches the most common sizes. The human-readable representation of the image size is capped at four valid numbers [1]. Unless it's a perfect round number like 1KB or 1.2MB, it will likely use all four numbers and the decimal point, which is five characters. Then two more for the unit, because it's very unlikely that there will be an image that's less than 1KB in size and will be shown in bytes with a B. That makes it seven characters in total. Updating the image download prompt with the results of 'skopeo inspect' is vulnerable to races. At the same time as the terminal's cursor is being moved to the beginning of the current line to overwrite the earlier prompt with the new one, the user can keep typing and keep moving the cursor forward. This competition over the cursor can lead to awkward outcomes. For example, the prompt can overwrite the characters typed in by the user, leaving characters in the terminal's input buffer waiting for the user to hit ENTER, even though they are not visible on the screen. Another example is that hitting BACKSPACE can end up deleting parts of the prompt, instead of stopping at the edge. This is solved by putting the terminal device into non-canonical mode input and disabling the echoing of input characters, while the prompt is being updated. This prevents input from moving the terminal's cursor forward, and from accumulating in the terminal's input buffer even if it might not be visible. Any input during this interim period is discarded and replaced by '...', and a fresh new prompt is shown in the following line. In practice, this race shouldn't be too common. It can only happen if the user is typing right when the prompt is being updated, which is unlikely because it's only supposed to be a short 'yes' or 'no' input. The use of the context.Cause and context.WithCancelCause functions [2] requires Go >= 1.20. Bumping the Go version in src/go.mod then requires a 'go mod tidy'. Otherwise, it leads to: $ meson compile -C builddir --verbose ... /home/rishi/devel/containers/git/toolbox/src/go-build-wrapper /home/rishi/devel/containers/git/toolbox/src /home/rishi/devel/containers/git/toolbox/builddir src/toolbox 0.0.99.4 cc /lib64/ld-linux-x86-64.so.2 false go: updates to go.mod needed; to update it: go mod tidy ninja: build stopped: subcommand failed. [1] https://pkg.go.dev/github.com/docker/go-units#HumanSize [2] https://pkg.go.dev/context containers#752 containers#1263
Is your feature request related to a problem? Please describe.
When Toolbox offers to pull an image, it estimates the size of the pulled image will be 500MB. This number is hard-coded and in most cases does not represent the reality. Toolbox images are usually less then 400MB big and that is after decompression. Compressed images are even smaller.
Describe the solution you'd like
Have a mechanism for reporting the size of the pulled image.
Additional context
This will, probably, require some work in https://github.com/containers/skopeo. Relevant upstream issue.
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