pkg: add support to consume snapshots #202
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@jaypipes PRs will follow soon against |
jaypipes
reviewed
Dec 14, 2020
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Thanks for the quick review @jaypipes ! I'm happy you like the direction. I'll be more than happy to address your comments and fix the docs in the next uploads. |
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update: I'd love to add a couple unit test before to the next upload to address review comments. This will take a little while more. |
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(clicked wrong button again) |
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@jaypipes hey, just FYI I'm intentionally keeping the commits separated to make review (hopefully) easier, if you want me to squash them no problem at all, just let me know and I'll do that right away. |
jaypipes
reviewed
Dec 15, 2020
No worries, no problem at all. I'll fix ,squash and push again. Thanks for your quick reviews! |
Add support to allow `ghw` read from snapshots (created with `ghw-snapshot`) using environment variables or programmatically. This is meant to be used mostly in the testsuite, but can be useful for users in general. Added environment variables (and counterpart in golang pkgs): - `GHW_SNAPSHOT_PATH` let users specify a snapshot that `ghw` will automatically consume. - `GHW_SNAPSHOT_ROOT` let users specify the directory on which the snapshot should be unpacked. - `GHW_SNAPSHOT_EXCLUSIVE` is relevant iff `GHW_SNAPSHOT_ROOT` is given. Tells `ghw` that the directory is meant only to contain the given snapshot, thus `ghw` will *not* attempt to unpack it (and will go ahead silently!) unless the directory is empty. - `GHW_SNAPSHOT_PRESERVE` if set, `ghw` will *not* clean up the unpacked snapshot once done, leaving it into the system. Signed-off-by: Francesco Romani <fromani@redhat.com>
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jaypipes
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Dec 16, 2020
My pleasure! thank you for the quick and insightful reviews! |
This was referenced Dec 17, 2020
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The PR jaypipes#236 fixes a snapshot directory leakage issue, but also highlight a context lifecycle/ownership issue. In general in ghw each package creates its own context, including the cases on which a package is consumed by another, for example `topology` and `pci`. However, in this case, it would make more sense to reuse the context from the parent package, because the two packages are tightly coupled. Before the introduction of the the transparent snapshot support (jaypipes#202), the above mechanism worked, because each context, each time, was consuming over and over again the same parameters (e.g. environment variables); besides some resource waste, this had no negative effect. When introducing snapshots in the picture, repeatedly unpacking the same snapshot to consume the same data is much more wasteful. So it makes sense to introduce explicitly the concept of dependent context. We add a functio to create a context subordinate to another. The subordinate context will effectively borrow all the resources from the parent one. The parent is in charge to perform any setup/teardown (e.g. for snapshot, to learn which chroot should be used, if at all) and so forth. Making this dependency explicit allow the client code to manage correctly the lifecycle of the topmost context, hence of all the resources. Signed-off-by: Francesco Romani <fromani@redhat.com>
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The PR jaypipes#236 fixes a snapshot directory leakage issue, but also highlight a context lifecycle/ownership issue. In general in ghw each package creates its own context, including the cases on which a package is consumed by another, for example `topology` and `pci`. However, in this case, it would make more sense to reuse the context from the parent package, because the two packages are tightly coupled. Before the introduction of the the transparent snapshot support (jaypipes#202), the above mechanism worked, because each context, each time, was consuming over and over again the same parameters (e.g. environment variables); besides some resource waste, this had no negative effect. When introducing snapshots in the picture, repeatedly unpacking the same snapshot to consume the same data is much more wasteful. So it makes sense to introduce explicitly the concept of dependent context. We add a functio to create a context subordinate to another. The subordinate context will effectively borrow all the resources from the parent one. The parent is in charge to perform any setup/teardown (e.g. for snapshot, to learn which chroot should be used, if at all) and so forth. Making this dependency explicit allow the client code to manage correctly the lifecycle of the topmost context, hence of all the resources. Signed-off-by: Francesco Romani <fromani@redhat.com>
ffromani
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The PR jaypipes#236 fixes a snapshot directory leakage issue, but also highlight a context lifecycle/ownership issue. In general in ghw each package creates its own context, including the cases on which a package is consumed by another, for example `topology` and `pci`. However, in this case, it would make more sense to reuse the context from the parent package, because the two packages are tightly coupled. Before the introduction of the the transparent snapshot support (jaypipes#202), the above mechanism worked, because each context, each time, was consuming over and over again the same parameters (e.g. environment variables); besides some resource waste, this had no negative effect. When introducing snapshots in the picture, repeatedly unpacking the same snapshot to consume the same data is much more wasteful. So it makes sense to introduce explicitly the concept of dependent context. We add a functio to create a context subordinate to another. The subordinate context will effectively borrow all the resources from the parent one. The parent is in charge to perform any setup/teardown (e.g. for snapshot, to learn which chroot should be used, if at all) and so forth. Making this dependency explicit allow the client code to manage correctly the lifecycle of the topmost context, hence of all the resources. Signed-off-by: Francesco Romani <fromani@redhat.com>
ffromani
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The PR jaypipes#236 fixes a snapshot directory leakage issue, but also highlight a context lifecycle/ownership issue. In general in ghw each package creates its own context, including the cases on which a package is consumed by another, for example `topology` and `pci`. However, in this case, it would make more sense to reuse the context from the parent package, because the two packages are tightly coupled. Before the introduction of the the transparent snapshot support (jaypipes#202), the above mechanism worked, because each context, each time, was consuming over and over again the same parameters (e.g. environment variables); besides some resource waste, this had no negative effect. When introducing snapshots in the picture, repeatedly unpacking the same snapshot to consume the same data is much more wasteful. So it makes sense to introduce explicitly the concept of dependent context. We add a functio to create a context subordinate to another. The subordinate context will effectively borrow all the resources from the parent one. The parent is in charge to perform any setup/teardown (e.g. for snapshot, to learn which chroot should be used, if at all) and so forth. Making this dependency explicit allow the client code to manage correctly the lifecycle of the topmost context, hence of all the resources. Signed-off-by: Francesco Romani <fromani@redhat.com>
ffromani
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The PR jaypipes#236 fixes a snapshot directory leakage issue, but also highlight a context lifecycle/ownership issue. In general in ghw each package creates its own context, including the cases on which a package is consumed by another, for example `topology` and `pci`. However, in this case, it would make more sense to reuse the context from the parent package, because the two packages are tightly coupled. Before the introduction of the the transparent snapshot support (jaypipes#202), the above mechanism worked, because each context, each time, was consuming over and over again the same parameters (e.g. environment variables); besides some resource waste, this had no negative effect. When introducing snapshots in the picture, repeatedly unpacking the same snapshot to consume the same data is much more wasteful. So it makes sense now to introduce explicitly the concept of dependent context. We add a function to create a context subordinate to another. The subordinate context will effectively borrow all the resources from the parent one. The parent is in charge to perform any setup/teardown (e.g. for snapshot, to learn which chroot should be used, if at all) and so forth. Making this dependency explicit allow the client code to manage correctly the lifecycle of the topmost context, hence of all the resources. Signed-off-by: Francesco Romani <fromani@redhat.com>
ffromani
added a commit
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May 14, 2021
The PR jaypipes#236 fixes a snapshot directory leakage issue, but also highlight a context lifecycle/ownership issue. In general in ghw each package creates its own context, including the cases on which a package is consumed by another, for example `topology` and `pci`. However, in this case, it would make more sense to reuse the context from the parent package, because the two packages are tightly coupled. Before the introduction of the the transparent snapshot support (jaypipes#202), the above mechanism worked, because each context, each time, was consuming over and over again the same parameters (e.g. environment variables); besides some resource waste, this had no negative effect. When introducing snapshots in the picture, repeatedly unpacking the same snapshot to consume the same data is much more wasteful. So it makes sense now to introduce explicitly the concept of dependent context. We add a function to create a context subordinate to another. The subordinate context will effectively borrow all the resources from the parent one. The parent is in charge to perform any setup/teardown (e.g. for snapshot, to learn which chroot should be used, if at all) and so forth. Making this dependency explicit allow the client code to manage correctly the lifecycle of the topmost context, hence of all the resources. Signed-off-by: Francesco Romani <fromani@redhat.com>
ffromani
added a commit
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May 26, 2021
The PR jaypipes#236 fixes a snapshot directory leakage issue, but also highlight a context lifecycle/ownership issue. In general in ghw each package creates its own context, including the cases on which a package is consumed by another, for example `topology` and `pci`. However, in this case, it would make more sense to reuse the context from the parent package, because the two packages are tightly coupled. Before the introduction of the the transparent snapshot support (jaypipes#202), the above mechanism worked, because each context, each time, was consuming over and over again the same parameters (e.g. environment variables); besides some resource waste, this had no negative effect. When introducing snapshots in the picture, repeatedly unpacking the same snapshot to consume the same data is much more wasteful. So it makes sense now to introduce explicitly the concept of dependent context. To move forward and make the ownership more explicit, we add an internal reference count in context. This is used only to track the context setup/teardown process. When contexts are reused, we always have a parent module -which creates and owns the context- which passes its context to a subordinate module, because the parent wants to consume the service offered by the subordinate. The subordinate (possibly further nested, or more than one) should never attempt Setup() and Teardown(). These are responsabilities of the parent, outer module, which owns the context. It's impractical to conditionally call Setup() and Teardown(), so the functions internally use and check the reference count to do the right thing automatically. The following are are idempotent (and safe and quickly return success) - calling multiple times Setup() on a ready context - calling multiple times Teardown() on a un-ready context Signed-off-by: Francesco Romani <fromani@redhat.com>
ffromani
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May 26, 2021
The PR jaypipes#236 fixes a snapshot directory leakage issue, but also highlight a context lifecycle/ownership issue. In general in ghw each package creates its own context, including the cases on which a package is consumed by another, for example `topology` and `pci`. However, in this case, it would make more sense to reuse the context from the parent package, because the two packages are tightly coupled. Before the introduction of the the transparent snapshot support (jaypipes#202), the above mechanism worked, because each context, each time, was consuming over and over again the same parameters (e.g. environment variables); besides some resource waste, this had no negative effect. When introducing snapshots in the picture, repeatedly unpacking the same snapshot to consume the same data is much more wasteful. So it makes sense now to introduce explicitly the concept of dependent context. To move forward and make the ownership more explicit, we add an internal reference count in context. This is used only to track the context setup/teardown process. When contexts are reused, we always have a parent module -which creates and owns the context- which passes its context to a subordinate module, because the parent wants to consume the service offered by the subordinate. The subordinate (possibly further nested, or more than one) should never attempt Setup() and Teardown(). These are responsabilities of the parent, outer module, which owns the context. It's impractical to conditionally call Setup() and Teardown(), so the functions internally use and check the reference count to do the right thing automatically. The following are are idempotent (and safe and quickly return success) - calling multiple times Setup() on a ready context - calling multiple times Teardown() on a un-ready context Signed-off-by: Francesco Romani <fromani@redhat.com>
ffromani
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Jun 25, 2021
The PR jaypipes#236 fixes a snapshot directory leakage issue, but also highlight a context lifecycle/ownership issue. In general in ghw each package creates its own context, including the cases on which a package is consumed by another, for example `topology` and `pci`. However, in this case, it would make more sense to reuse the context from the parent package, because the two packages are tightly coupled. Before the introduction of the the transparent snapshot support (jaypipes#202), the above mechanism worked, because each context, each time, was consuming over and over again the same parameters (e.g. environment variables); besides some resource waste, this had no negative effect. When introducing snapshots in the picture, repeatedly unpacking the same snapshot to consume the same data is much more wasteful. So it makes sense now to introduce explicitly the concept of dependent context. To move forward and make the ownership more explicit, we add an internal reference count in context. This is used only to track the context setup/teardown process. When contexts are reused, we always have a parent module -which creates and owns the context- which passes its context to a subordinate module, because the parent wants to consume the service offered by the subordinate. The subordinate (possibly further nested, or more than one) should never attempt Setup() and Teardown(). These are responsabilities of the parent, outer module, which owns the context. It's impractical to conditionally call Setup() and Teardown(), so the functions internally use and check the reference count to do the right thing automatically. The following are are idempotent (and safe and quickly return success) - calling multiple times Setup() on a ready context - calling multiple times Teardown() on a un-ready context Signed-off-by: Francesco Romani <fromani@redhat.com>
ffromani
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Sep 21, 2021
The PR jaypipes#236 fixes a snapshot directory leakage issue, but also highlight a context lifecycle/ownership issue. In general in ghw each package creates its own context, including the cases on which a package is consumed by another, for example `topology` and `pci`. However, in this case, it would make more sense to reuse the context from the parent package, because the two packages are tightly coupled. Before the introduction of the the transparent snapshot support (jaypipes#202), the above mechanism worked, because each context, each time, was consuming over and over again the same parameters (e.g. environment variables); besides some resource waste, this had no negative effect. When introducing snapshots in the picture, repeatedly unpacking the same snapshot to consume the same data is much more wasteful. So it makes sense now to introduce explicitly the concept of dependent context. To move forward and make the ownership more explicit, we add an internal reference count in context. This is used only to track the context setup/teardown process. When contexts are reused, we always have a parent module -which creates and owns the context- which passes its context to a subordinate module, because the parent wants to consume the service offered by the subordinate. The subordinate (possibly further nested, or more than one) should never attempt Setup() and Teardown(). These are responsabilities of the parent, outer module, which owns the context. It's impractical to conditionally call Setup() and Teardown(), so the functions internally use and check the reference count to do the right thing automatically. The following are are idempotent (and safe and quickly return success) - calling multiple times Setup() on a ready context - calling multiple times Teardown() on a un-ready context Signed-off-by: Francesco Romani <fromani@redhat.com>
ffromani
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Sep 21, 2021
The PR jaypipes#236 fixes a snapshot directory leakage issue, but also highlight a context lifecycle/ownership issue. In general in ghw each package creates its own context, including the cases on which a package is consumed by another, for example `topology` and `pci`. However, in this case, it would make more sense to reuse the context from the parent package, because the two packages are tightly coupled. Before the introduction of the the transparent snapshot support (jaypipes#202), the above mechanism worked, because each context, each time, was consuming over and over again the same parameters (e.g. environment variables); besides some resource waste, this had no negative effect. When introducing snapshots in the picture, repeatedly unpacking the same snapshot to consume the same data is much more wasteful. So it makes sense now to introduce explicitly the concept of dependent context. To move forward and make the ownership more explicit, we make the context management more explict. We refactor the Do method of context.Context as a top level function so we can pass it through in all the NewWithContext functions. With these changes: - the top-level packages, which owns the context, will keep working as usual with just a bit of extra verbosity - it will need to pass around `context.Do` which as implicit before - the auxiliary packages, which do NOT own the context and thus should not act upon it, will be created by the top-level packages using `NewWithContext` with the new `context.Bypass` helper, which is a NOP from the context setup/teardown perspective. Signed-off-by: Francesco Romani <fromani@redhat.com>
ffromani
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Sep 23, 2021
The PR jaypipes#236 fixes a snapshot directory leakage issue, but also highlight a context lifecycle/ownership issue. In general in ghw each package creates its own context, including the cases on which a package is consumed by another, for example `topology` and `pci`. However, in this case, it would make more sense to reuse the context from the parent package, because the two packages are tightly coupled. Before the introduction of the the transparent snapshot support (jaypipes#202), the above mechanism worked, because each context, each time, was consuming over and over again the same parameters (e.g. environment variables); besides some resource waste, this had no negative effect. When introducing snapshots in the picture, repeatedly unpacking the same snapshot to consume the same data is much more wasteful. So it makes sense now to introduce explicitly the concept of dependent context. To move forward and make the ownership more explicit, we add a new function `NewWithContext` in all the subpackages. The function `NewWithContext` will assume the context it gets as argument is ready to be consumed and it will use as-is, attempting no setup or teardown in any circumstances. The usage rules are pretty simple: 1. In your client code, you most likely just need to use `New` as usual. 2. When consuming a package from another (e.g. `toppology` from `pci`), always use the `NewWithContext` function to get a handle for the auxiliary package, passin through the context from the top-level package. 3. Within a `NewWithContext` function, ally calls to other `NewWithContext` functions should be made to preserve the properties. Signed-off-by: Francesco Romani <fromani@redhat.com>
ffromani
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Sep 23, 2021
The PR jaypipes#236 fixes a snapshot directory leakage issue, but also highlight a context lifecycle/ownership issue. In general in ghw each package creates its own context, including the cases on which a package is consumed by another, for example `topology` and `pci`. However, in this case, it would make more sense to reuse the context from the parent package, because the two packages are tightly coupled. Before the introduction of the the transparent snapshot support (jaypipes#202), the above mechanism worked, because each context, each time, was consuming over and over again the same parameters (e.g. environment variables); besides some resource waste, this had no negative effect. When introducing snapshots in the picture, repeatedly unpacking the same snapshot to consume the same data is much more wasteful. So it makes sense now to introduce explicitly the concept of dependent context. To move forward and make the ownership more explicit, we add a new function `NewWithContext` in all the subpackages. The function `NewWithContext` will assume the context it gets as argument is ready to be consumed and it will use as-is, attempting no setup or teardown in any circumstances. The usage rules are pretty simple: 1. In your client code, you most likely just need to use `New` as usual. 2. When consuming a package from another (e.g. `toppology` from `pci`), always use the `NewWithContext` function to get a handle for the auxiliary package, passin through the context from the top-level package. 3. Within a `NewWithContext` function, ally calls to other `NewWithContext` functions should be made to preserve the properties. Signed-off-by: Francesco Romani <fromani@redhat.com>
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Needed for #66 (see #66 (comment) and following)
Add support to allow
ghwread from snapshots (created withghw-snapshot) usingenvironment variables or programmatically.
This is meant to be used mostly in the testsuite, but can be useful for
users in general.
Added environment variables (and counterpart in golang pkgs):
GHW_SNAPSHOT_PATHlet users specify a snapshotthat
ghwwill automatically consume.GHW_SNAPSHOT_ROOTlet users specify the directoryon which the snapshot should be unpacked.
GHW_SNAPSHOT_EXCLUSIVEis relevant iffGHW_SNAPSHOT_ROOTis given.Tells
ghwthat the directory is meant only to contain the given snapshot,thus
ghwwill not attempt to unpack it(and will go ahead silently!) unless the directory is empty.
GHW_SNAPSHOT_PRESERVEif set,ghwwill notclean up the unpacked snapshot once done, leaving it into the system.
Signed-off-by: Francesco Romani fromani@redhat.com