Hi, On Mon, Apr 13, 2020 at 8:30 AM Yang Wang <danrtsey...@gmail.com> wrote:
> Although the latter option is more stable, > i think it is not acceptable for all the developers to execute `mvn > generate-sources` first. Otherwise, the Flink project is just broken and could not run tests, Flink > jobs in IDE. > > It is important to realize that this discussion is essentially around the fact that systems like IntelliJ (what I use) execute various ways of generating code that have been written in a maven pom.xml in different ways. Simply put: They don't execute all instructions that have been defined in the pom.xml automatically when needed. - With the properties file variant (which uses resource filtering) IntelliJ does resource filtering automatically yet no maven plugins are run that affect the properties that are replaced. So the git variables are NOT populated when running in IntelliJ and I have seen several values in the propersites file are nonsense. As a consequence the Java code reading those needs to catch things like "missing properties file" and various kinds of "nonsense values" and replace them with a workable default. So when running this code you are actually running something different from what will be run when doing a `mvn clean install`, yet the developer is under the illusion it all works because of the code that catches all of those problems. Depending on the way these variables are used this may lead to "It fails in production but it works fine in IntelliJ" situations. In my mind the code that catches all of those exceptional situations in poorly generated properties only exists so that developers can run the (otherwise perfectly fine) software in a "broken" build/development environment. - With the way I propose to generate the code the effect is indeed slightly harder: If you do not run the pom.xml based code generation it will not work. I understand that this requires the developers to think a bit more about the code they are working on. The upside is that the code either works perfectly or does not compile. There is no "it compiles but is really nonsense". I prefer this. Also at this point in time this is already true for Flink: There are quite a few modules where the developer MUST run mvn generate-sources for all tests to run successfully. Like I indicated there is a javacc SQL parser and there are a lot of tests that rely on generating Avro code before they are able to run. I have several projects where systems like Avro and Antlr force me in this direction, there is simply no other way to do this. So i think the version properties file is enough for now. +1 for the first > option. > Like I said. I'm fine with either choice by the committers. I would choose the `mvn generate-sources` code variant as it is much simpler and much more reliable. Niels Niels Basjes <ni...@basjes.nl> 于2020年4月9日周四 下午4:47写道： > > > Hi, > > > > I'm working on https://issues.apache.org/jira/browse/FLINK-16871 to make > > more build time variables (like the scala version) into the code > available > > at runtime. > > > > During the review process there was discussion around a basic question: > *Is > > generating java code during the build ok?* > > See > > > > - https://github.com/apache/flink/pull/11245#discussion_r400035133 > > - https://github.com/apache/flink/pull/11592 > > - https://github.com/apache/flink/pull/11592#issuecomment-610282450 > > > > As suggested by Chesnay Schepler I'm putting this question to the mailing > > list. > > https://github.com/apache/flink/pull/11592#issuecomment-610963947 > > > > The main discussion was around the ease of use when running in an IDE > like > > IntelliJ. > > > > So essentially we have two solution directions available: > > > > 1. *Generate a properties file and then use the classloader to load > this > > file as a resource and then parse it as a property file.* > > This is the currently used solution direction for this part of the > code. > > A rough version of this (to be improved) : > > > > > https://github.com/apache/flink/commit/47099f663b7644056e9d87b262cd4dba034f513e > > This method has several effects: > > 1. The developer can run the project immediately from within the > IDE > > as fallback values are provided if the 'actual' values are missing. > > 2. This property file (with stuff that should never be overwritten) > > can be modified by placing a different one in the classpath. In > > fact it IS > > modified in the flink-dist as it generates a new file with the same > > name > > into the binary distribution (I consider this to be bad). > > 3. Loading resources means loading, parsing and a lot of error > > handling. Lots of things "can be null" or be a default value. So > the > > values are unreliable and lots of code needs to handle this. In > fact > > when > > running from IntelliJ the properties file is generated poorly most > > of the > > time, only during a normal maven build will it work correctly. > > 2. *Generate a Java source file and then simply compile this and make > it > > part of the project.* > > Essentially the same model as you would have when using Apache Avro, > > Protobuf, Antlr 4 and javacc (several of those are used in Flink!). > > A rough version of this (to be improved) : > > > > > https://github.com/apache/flink/commit/d215e4df60dc9d647dcee1aa9a2114cbf49d0566 > > This method has several effects: > > 1. The developer MUST run 'mvn generate-sources' before the actual the > > project immediately from within the IDE as fallback values are > > provided if > > the 'actual' values are missing. > > 2. The code/test will not run until this step is done. > > 3. Because the file is generated by a plugin it is always correct. > As > > a consequence all variables are always available and the downstream > > users > > no longer have to handle the "can be null" or "default value" > > situations. > > > > So is generating code similar to what I created a desired change? > > My opinion is that it is the better solution, the data available is more > > reliable and as a consequence the rest of the code is simpler. > > It would probably mean that during development of flink you should be > aware > > of this and do an 'extra step' to get it running. > > > > What do you guys think? > > > > -- > > Best regards / Met vriendelijke groeten, > > > > Niels Basjes > > > -- Best regards / Met vriendelijke groeten, Niels Basjes
