Conan 1.31.0 features a few more significant steps toward our new toolchain strategy, coupled with a lengthy list of quality-of-life features and fixes.
Upload Performance Improvements
This release includes a long-overdue change, which represents an optimization
which is so impactful that it effectively amounts to a bug fix for some use
cases. The change is such that the Conan client will now keep the
conan_package.tgz in the local
cache after it is done extracting the contents. Previously, these files were
deleted once extracted.
How is this an optimization? Well buckle up because this is a long and sordid
story. It turns out that its rather common for numerous workflows (including
continuous integration) to perform the command
conan upload * as a final step.
When using this command in previous releases, every single package would go
through the process of having all of it’s
sources, and all of
package directory files compressed prior to being uploaded. This
compression time actually adds up to become a significant percentage of overall
job time. This problem is amplified by the knowledge that Conan can easily
verify that none of the contents have changed, so both the compression and
upload steps are known to be completely un-necessary, making them even more
difficult to accept once you understand what’s happening.
But wait, it was even worse than that! Many people will already know that Conan
client already compares the checksums for these
.tgz files with a server
before uploading them. If the checksums match, then it will skip the upload.
However, it also turns out that the
.tgz compression results on all operating
systems are not equal. The compressions of identical files can (and often will)
.tgz files with different checksums on different operating systems!
conan_exports.tgz, orgnanizations which build
on multiple operating systems in parallel would have the unfortunate situation
conan upload commands from different operating systems would start
to upload these files, and then see that the remote has these files already, but
with a different checksum than it wants to upload, causing a failure. The net
result of this was that virtually everyone in this situation added
their upload scripts for their CI services to bypass the errors. But that had
another negative side effect. Build servers would repeatedly take turns
re-uploading the “same”
.tgz files over and over due to checksum mismatch.
This also means that if you had two operating systems uploading to a remote,
which one uploads the “last”
.tgz that remains on the remote after the job is
effectively random. So, the next time any user or CI job with the other
operating system(s) installs the package, the re-compression step before a
re-upload would always result in a new checksum. So, lots of workflows ended up
--force when it should not have been necessary.
The good news is that this is now largely fixed moving forward. Now that Conan
will keep the
.tgz files in the cache, the re-compressions and re-uploads will
be effectively skipped as explained before. Also, while the Conan team was
unable to fix the fundamental problem that different operating systems will
.tgz files with different checksums, there is a workaround to solve the
remaining problem. That is, the problem where parallel build servers on
different operating systems take turns re-uploading and overwrite the
the server. Now, these CI jobs can be reconfigured to start with a single
“stage” which performs
conan export and
conan upload, putting a single pair
conan_source.tgz on the remote. This stage can then
be followed by any number of parallel build stages which do
conan install with
--build flag (or equivalent). Those stages will then download and share
.tgz files. Then, crucially, when they all reach the
command, they will all have identical
.tgz files, so the redundant uploads
will all be skipped.
New iOS and Android Toolchains
Note: These features are considered “draft” or “alpha” level POC. We expect additional feedback and changes will be required to make them work properly.
Just like our past several releases, this release continues to make progress on our Toolchain initiative. This time, we’ve made two big additions with POC’s for both iOS and Android. For both of these toolchains, we’ve based the POC’s on the use of CMake, but plan to explore the alternatives in the future after we have some feedback on these preliminary implementations. Cross-building for these mobile platforms is one of the major use-cases for Conan, so we believe this step is pretty significant in maturing the toolchain abstraction.
New MsBuildCmd Helper
Note: This feature summary references an old helper and a new helper. To keep
them distinct for the purposes of explanation, the old helper will be referred
MsBuild and the new will be referred to as
MsBuildCmd. However, in the
current implementation, the new
MsBuildCmd helper has actually been given an
MsBuild so that it matches the old one.
In the previous release, we’ve included a POC of the new
This was part of the effort to restructure the way we interact with
This release contains another part of that effort which is the new
helper, intended to work alongside the
MsBuildToolchain. The predecessor to
MsBuildCmd helper is the
MsBuild helper. Let’s talk about that briefly
before we explain the differences with
MsBuild helper was focused on providing maximum convenience with
minimum ceremony in the form of a single python class with many member
functions. It handled three distinct responsibilities:
Handle the complex task of finding and executing the Microsoft tools, including the
msbuild.exe, and choosing of the appropriate version passed to Conan in the
Ensure that the following primary
settingsare passed to Conan via the command-line arguments:
archsetting in Conan)
Ensure that the following secondary
settingsare passed to Conan via a
- Visual Studio runtime (Mapped from
- Visual Studio platform toolset (Mapped from
- C++ standard (Mapped from
cppstdsetting in Conan)
- Visual Studio runtime (Mapped from
While slightly oversimplified, this perspective on the
MsBuild helper makes
it very easy easy to explain how the new
MsBuildCmd helper is distinct, and
MsBuildToolchain factors into the equation. Simply put,
is completely focused on numbers 1 and 2 above.
MsBuildToolchain is completely
focused on number 3 above.
Note: The configuration item “Visual Studio platform toolset” has been removed from the toolchain in this release and will no longer be set by Conan at all.
This separation of responsibilities might not seem that significant, but internally it allows us to address and resolve a wide variety of actual bugs as well as serious UX issues which have been raised over the past three years.
Filter Search Results by Profile
One of the most common errors which comes up regularly for packagers and users is the following error:
ERROR: Missing prebuilt package for 'package/version@user/channel' Try to build it from sources with "--build package" Or read "http://docs.conan.io/en/latest/faq/troubleshooting.html#error-missing-prebuilt-package"
Technically speaking, this error means precisely what it says. A prebuilt binary was requested but not found in the local cache, nor any of the configured remotes. However, from a user-experience perspective, this error typically indicates one of two scenarios, which typically indicate one of two next-steps:
The user is building a unique configuration for which they know that binaries will not be found. In this case, they have forgotten to include the necessary
--buildflag, and the suggestion in the error message is relevant, correct, and extremely helpful.
The user is building a common configuration for which they expected binaries to be found. In this case, it is typically implied that they expected those binaries to be built and uploaded to a remote repository by a continuous integration (CI) service. Here, the suggestion in the error message would allow them to work around the problem, but indicates some other problem or prior failure in the CI service. The problem might be that the CI job failed. More often however, the problem is that the CI job built the package with an incorrect or incomplete list of build configurations (conan profiles).
There have been many github issues and conversations in slack created by users, mostly surrounding the improvement of the user-experience for this second case. The reason it needs improvement is that when this extremely common error is encountered, the next-steps available to the user to resolve it are time-consuming and rather unpleasant. The user must perform a great deal of reasoning, investigation, and manual trial-and-error to identify exactly where the problem lies. The list of questions the user must consider includes:
- Did the CI server build an incorrect or incomplete list of profiles?
- Did it build all the right profiles but partially fail?
- Is my local profile incorrect, or out of date?
- If some profiles were built, what is the difference between mine and those?
This last question is very often the first that a user should (and does) ask.
This is because the safest assumption in most cases is that there is something
different or wrong in the local profile being used (otherwise other users could
possibly have been affected, reported the issue, and resolved it). Thus, one of
the most comman tasks in the existing process of diagnosing this error was to
perform repeated calls to the
conan search command with the
parameter, changing options and settings until the user could answer the last
question listed above. This release provides an alternative way to perform this
In order to use the new feature, the user manually performs a search of the
available binaries for the package that has produced the error, but this time,
--query. This is similar to the old process, but now the user adds
--html flag to produce the HTML output. Then, the user can open the
generated HTML output in a web browser. Finally, the user can leverage the new
feature, by copying the “effective profile” from the failed
conan install or
conan create log and pasting it into a new dialog box on the search results
web page. At first, this will show empty results, because we’re pasting in the
profile for a binary which we already know does not exist. However, now the user
can perform their trial-and-error by adding and removing profile lines in the
dialog box and analyzing the HTML GUI instead of repeated calls to the
search command and looking at the results in the terminal. We hope that many
users find this workflow preferrable.
Here is a screenshot of the new input box in the search results page.
Other Notable Features
This release also featured several other significant features:
conanfilehas been added as an argument to
conan infocommand learned how to output some new fields. This includes the relatively new
deprecatedattributes from the
conanfile.py. It also learned how to render package revisions when the revisions feature is enabled.
CONAN_LOGIN_ENCRYPTION_KEYhas been added to provide an obfuscation mechanism intended for continuous integration server logs. In several places (including this blog), we emphasize that this does not constitue a secure encryption mechanism, and is intended for a very narrow and specific purpose which is explained in the documentation.
conan config installcan now install a single file.
Besides the items listed above, there was a long list of fairly impactful bug fixes you may wish to read about. If so, please refer to the changelog for the complete list.
We hope you enjoy this release, and look forward to your feedback.