Re: Concurrency in m3 - a status report - performance
Den 26.04.2010 04:02, skrev Igor Fedorenko: I am sorry if this has been answered already, but do you have any info that shows performance comparison single vs milti threaded build? If you happen to have any profiler snapshots that show where time is spent during single and multi threaded builds, I am interested to see these too. PS: we got first // build question on tycho-users list last week ;-) Interesting question; and the answer is not /always/ as clear cut as one would think. Regarding overall performance I added another linear build for comparison. This is not a particuarly good showcase project, but such is life: Linear: http://rosenvold.dyndns.org:8085/browse/PARALLEL-CH (~36-37 seconds) Parallel: http://rosenvold.dyndns.org:8085/browse/PARALLEL-CH1 (~34-35 seconds) http://rosenvold.dyndns.org:8085/browse/PARALLEL-CH1W (~29-30 seconds) Remember it's a build cluster with one C2D and one i7-980X, so the tall columns are the C2D. There's a third node being added any day now (i7 920). Please remember that this build cluster is heavily loaded, also with non-public jobs - so per build variantions can be significant. Unfortunately bamboo's average build time calculation does not produce reliable results in a cluster with very different nodes, so this is just my estimate: The topology of your build is the most important factor governing parallel performance. Weave mode is less sensitive to this. Both parallel modes are sensitive to indidivudal mojo executions being slow, and it effects the overall build. If your build process ends up creating a 500mb EAR file, it'll tend to marginalize effects of a few modules running in parallel here there. Weave mode does a real good job with projects that have tasks evenly distributed across modules (as opposed to all the real work happening in just a few specific mojo executions in one or two modules). Surefire in test-phase is not phase-locked to the upstream test phases in weave mode (Haven't done this for it-phase yet). Parallel is not always faster than linear, weave is always fastest. Focus up to now has been on achieving stability and functionality, and for the next month or so making all mojos work reliably will be my top priority. Regarding performance I have not really investigated too much yet, but I will ;) I have a short list of things I want to investigate: - According to strace, File.exists() is being called twice for all access to any file in the local repository (affects all modes) - I am almost sure there's one or more synchronization points somewhere within surefire that is reducing surefire performance needlessly. Only the first issue is within core, and my gut feeling is that not much more performance will be tweaked out of the core unless one manages to re-think at a higher level an even smarter way of executing mojos and respecting dependencies. Someone please prove me wrong, but I think the remaining performance will have to be found in the plugins/libraries - and it will be found. I have run serveral profiler tests, but I'm mostly studying threading effects currently. Most of the stuff I've seen is as expected, and only a small percentage of execution happens within core (and a fair size of that is related to xml parsing, surprise...) - To unsubscribe, e-mail: dev-unsubscr...@maven.apache.org For additional commands, e-mail: dev-h...@maven.apache.org
Re: Concurrency in m3 - a status report
Plugins = I have only managed to find real concurrency problems in the EAR plugin and modello as of yet. Modello is fixed in trunk, ear is not started AFIK. All the other stuff I've seen in the core plugins relate to the plexus-issues. Our jira issue is from a user who's complaining about plugins not working, and I think he's somewhat right in that we have to make some kind of system to indicate compatibility with the -T option. Although several strategies may be recommended, my personal favourite is to make a @threadsafe javadoc annotation and make M3 core COMPLAIN LOUDLY about plugins that are unmarked, then proceed as requested (i.e. complain but still run threaded). The problem with these things is that thread safety is not necessarily a constant, and in the next 9 months there will be issues. So for some plugins @threadsafe might equally much express an intent as much as it reflects reality. So that makes me a bit sceptical to @threadsafe too. +1, I can't see any way to ENSURE a plugin is threadsafe as it depends on project and (maybe overriden) plugin dependencies. We can just tag a plugin to be expected to work fine in multithreaded context I'd suggest to get a @NotThreadSafe annotation for plugins that are KNOWN to not be thread safe, mostly due ti the embedded tools. I got ConcurrentModification issues with aspectJ plugin, so I don't think any AJC-based plugin could work fine with // build. I don't know the way the weave mode is expected to work, but it could maybe support such @NotThreadSafe plugins by locking concurrent execution of the same plugin, but still runing other ones/othe phases in // modules. Aggressively displaying the link to the wiki page containing the most up-todate threading info may be an equally good solution; maybe even adding a WARNING: Experimental or something to the build output. +1 As we can't make the world thread safe, let the user know what's possible and how to tweak the build. http://cwiki.apache.org/confluence/display/MAVEN/Parallel+builds+in +Maven+3 (if it's up), should contain all the information needed on which plugins are known to have issues. But as we all know, it's an open ecosystem. Documentation I will keep the wiki page updated, provided cwiki.a.o actually stays up ;) I will add a section on mojo threading models/threading concerns to the mojo api specification. I think we have to take some extra measures to keep users out of the issue trackers on this one, or at least make sure they go to the right place. What do you think ? Kristian - To unsubscribe, e-mail: dev-unsubscr...@maven.apache.org For additional commands, e-mail: dev-h...@maven.apache.org
Re: Concurrency in m3 - a status report
I agree that a @NotThreadSafe annotation is the best way to go. On 26 April 2010 09:13, nicolas de loof nicolas.del...@gmail.com wrote: Plugins = I have only managed to find real concurrency problems in the EAR plugin and modello as of yet. Modello is fixed in trunk, ear is not started AFIK. All the other stuff I've seen in the core plugins relate to the plexus-issues. Our jira issue is from a user who's complaining about plugins not working, and I think he's somewhat right in that we have to make some kind of system to indicate compatibility with the -T option. Although several strategies may be recommended, my personal favourite is to make a @threadsafe javadoc annotation and make M3 core COMPLAIN LOUDLY about plugins that are unmarked, then proceed as requested (i.e. complain but still run threaded). The problem with these things is that thread safety is not necessarily a constant, and in the next 9 months there will be issues. So for some plugins @threadsafe might equally much express an intent as much as it reflects reality. So that makes me a bit sceptical to @threadsafe too. +1, I can't see any way to ENSURE a plugin is threadsafe as it depends on project and (maybe overriden) plugin dependencies. We can just tag a plugin to be expected to work fine in multithreaded context I'd suggest to get a @NotThreadSafe annotation for plugins that are KNOWN to not be thread safe, mostly due ti the embedded tools. I got ConcurrentModification issues with aspectJ plugin, so I don't think any AJC-based plugin could work fine with // build. I don't know the way the weave mode is expected to work, but it could maybe support such @NotThreadSafe plugins by locking concurrent execution of the same plugin, but still runing other ones/othe phases in // modules. Aggressively displaying the link to the wiki page containing the most up-todate threading info may be an equally good solution; maybe even adding a WARNING: Experimental or something to the build output. +1 As we can't make the world thread safe, let the user know what's possible and how to tweak the build. http://cwiki.apache.org/confluence/display/MAVEN/Parallel+builds+in +Maven+3 (if it's up), should contain all the information needed on which plugins are known to have issues. But as we all know, it's an open ecosystem. Documentation I will keep the wiki page updated, provided cwiki.a.o actually stays up ;) I will add a section on mojo threading models/threading concerns to the mojo api specification. I think we have to take some extra measures to keep users out of the issue trackers on this one, or at least make sure they go to the right place. What do you think ? Kristian - To unsubscribe, e-mail: dev-unsubscr...@maven.apache.org For additional commands, e-mail: dev-h...@maven.apache.org
Re: Concurrency in m3 - a status report
Den 26.04.2010 10:13, skrev nicolas de loof: The problem with these things is that thread safety is not necessarily a constant, and in the next 9 months there will be issues. So for some plugins @threadsafe might equally much express an intent as much as it reflects reality. So that makes me a bit sceptical to @threadsafe too. +1, I can't see any way to ENSURE a plugin is threadsafe as it depends on project and (maybe overriden) plugin dependencies. We can just tag a plugin to be expected to work fine in multithreaded context The issue is http://jira.codehaus.org/browse/MNG-4642, and as an alternative solution we could simply make a list somewhere that blacklists/whitelists/greylists plugins, as long as there's a reasonable way to update such a list. Maybe something enforcer-like; org.codehaus.plexus:plexus-io:[,1.0), BAN:Serious compromises of thread integrity org.apache.maven:plugins:maven-era-plugin:*:WARN:Can only run once per reactor org.codehaus.modell:modello-maven-plugin:(,1.3]:BAN:Does not work -period If there was some place we could put such a list and update it we could probably provide the best possible information. How could we do this ? not be thread safe, mostly due ti the embedded tools. I got ConcurrentModification issues with aspectJ plugin, so I don't think any AJC-based plugin could work fine with // build. I don't mean to be disrespectful of aspectj, but from what I've seen of the code wrt thread safety I think the appropriate solution is to syncrhonize the execute method of all aspectj-related mojos. This is basically the same as @NotThreadSafe I don't know the way the weave mode is expected to work, but it could maybe support such @NotThreadSafe plugins by locking concurrent execution of the same plugin, but still runing other ones/othe phases in // modules. Oh we can do all sorts of weird and wonderful magics ;) The trick is not to deadlock the build - I /think/ it should be ok but it's not the first thing I would like to do. I will update m3 to add more warnings and possibly also update the link to the wiki page when builds fail in parallel build mode. Ok to put a wiki link in release binaries ? Kristian - To unsubscribe, e-mail: dev-unsubscr...@maven.apache.org For additional commands, e-mail: dev-h...@maven.apache.org
Re: Concurrency in m3 - a status report
The issue is http://jira.codehaus.org/browse/MNG-4642, and as an alternative solution we could simply make a list somewhere that blacklists/whitelists/greylists plugins, as long as there's a reasonable way to update such a list. Maybe something enforcer-like; org.codehaus.plexus:plexus-io:[,1.0), BAN:Serious compromises of thread integrity org.apache.maven:plugins:maven-era-plugin:*:WARN:Can only run once per reactor org.codehaus.modell:modello-maven-plugin:(,1.3]:BAN:Does not work -period If there was some place we could put such a list and update it we could probably provide the best possible information. How could we do this ? We could maintain such compatibility matrix using a wiki page, but - to be usable from the build by various enforcer/check plugins - it should be deployed on central / downloaded to local repository in some computer-compliant format.
Re: Concurrency in m3 - a status report
Which implies that it should be a versioned file Sounds like a jar with a resource containing the parallel compatibility info We'd have to maintain it versioned and perhaps provide some system property to ovrerride the version via settings.xml... but each release of m3 would have it's own compatibility info and we would have another state: unknown e.g. thread-safety plugin groupId=... artifactId=... wieve-mode action=ban versions=...message/wieve-mode wieve-mode action=warn versions=...message/wieve-mode wieve-mode action=checked versions=.../ parallel-mode action=ban versions=...message/paralle-mode parallel-mode action=warn versions=...message/paralle-mode parallel-mode action=checked versions=...message/paralle-mode /plugin /thread-safety Any plugins not in the list would be unknown and the user gets a big fat warning -Stephen On 26 April 2010 10:15, nicolas de loof nicolas.del...@gmail.com wrote: The issue is http://jira.codehaus.org/browse/MNG-4642, and as an alternative solution we could simply make a list somewhere that blacklists/whitelists/greylists plugins, as long as there's a reasonable way to update such a list. Maybe something enforcer-like; org.codehaus.plexus:plexus-io:[,1.0), BAN:Serious compromises of thread integrity org.apache.maven:plugins:maven-era-plugin:*:WARN:Can only run once per reactor org.codehaus.modell:modello-maven-plugin:(,1.3]:BAN:Does not work -period If there was some place we could put such a list and update it we could probably provide the best possible information. How could we do this ? We could maintain such compatibility matrix using a wiki page, but - to be usable from the build by various enforcer/check plugins - it should be deployed on central / downloaded to local repository in some computer-compliant format.
Re: Concurrency in m3 - a status report
Stephen Connolly wrote: ... but each release of m3 would have it's own compatibility info and we would have another state: unknown e.g. thread-safety plugin groupId=... artifactId=... wieve-mode action=ban versions=...message/wieve-mode wieve-mode action=warn versions=...message/wieve-mode wieve-mode action=checked versions=.../ parallel-mode action=ban versions=...message/paralle-mode parallel-mode action=warn versions=...message/paralle-mode parallel-mode action=checked versions=...message/paralle-mode /plugin /thread-safety Any plugins not in the list would be unknown and the user gets a big fat warning Did you also consider the maintainability aspect of such a list? No user wants to see big fat warnings that are irrelevant for their builds so I envision users will either bug the plugin author or us directly to add plugin X to this list and ask us to roll a new release of this list such that they get rid of that warning. Plugins should be self-describing, that's why mojo annotations and the plugin descriptor exists. I definitively don't want to see us maintaining the metadata for 3rd party plugins. For this reason, I prefer the original suggestion to introduce a new mojo annotation. Apparently, whatever mojo annotation we come up with, it's not present in any existing plugin release. Now, for plugins missing the threading anno, what is the safer assumption with respect to proper build results: That mojo X is thread-safe (when this was never before a concern) or that it isn't? IMHO, there's only way to limit this oh, I deliberately enabled nitro injection and now my engine blew up, how am I supposed to know that this is dangerous?: Unless a mojo is explicitly marked with @threadsafe, issue a warning like Goal X does not appear to support concurrent execution and might fail the build, use parallel building at your own risk. Benjamin - To unsubscribe, e-mail: dev-unsubscr...@maven.apache.org For additional commands, e-mail: dev-h...@maven.apache.org
Re: Concurrency in m3 - a status report
On 26 April 2010 12:05, Benjamin Bentmann benjamin.bentm...@udo.edu wrote: Stephen Connolly wrote: ... but each release of m3 would have it's own compatibility info and we would have another state: unknown e.g. thread-safety plugin groupId=... artifactId=... wieve-mode action=ban versions=...message/wieve-mode wieve-mode action=warn versions=...message/wieve-mode wieve-mode action=checked versions=.../ parallel-mode action=ban versions=...message/paralle-mode parallel-mode action=warn versions=...message/paralle-mode parallel-mode action=checked versions=...message/paralle-mode /plugin /thread-safety Any plugins not in the list would be unknown and the user gets a big fat warning Did you also consider the maintainability aspect of such a list? No user wants to see big fat warnings that are irrelevant for their builds so I envision users will either bug the plugin author or us directly to add plugin X to this list and ask us to roll a new release of this list such that they get rid of that warning. Plugins should be self-describing, that's why mojo annotations and the plugin descriptor exists. I definitively don't want to see us maintaining the metadata for 3rd party plugins. For this reason, I prefer the original suggestion to introduce a new mojo annotation. Apparently, whatever mojo annotation we come up with, it's not present in any existing plugin release. Now, for plugins missing the threading anno, what is the safer assumption with respect to proper build results: That mojo X is thread-safe (when this was never before a concern) or that it isn't? IMHO, there's only way to limit this oh, I deliberately enabled nitro injection and now my engine blew up, how am I supposed to know that this is dangerous?: Unless a mojo is explicitly marked with @threadsafe, issue a warning like Goal X does not appear to support concurrent execution and might fail the build, use parallel building at your own risk. Fair enough, but I would also like to be able to annotate a mojo such that I explicitly don't want it invoked in parallel and not warn the user (perhaps explain to the user why certain mojos cannot be executed in parallel) -Stephen Benjamin - To unsubscribe, e-mail: dev-unsubscr...@maven.apache.org For additional commands, e-mail: dev-h...@maven.apache.org
Re: Concurrency in m3 - a status report
What about adding such concurrency metadata aside plugin artifact in local repository, either by extending metadata.xml or using a new concurrency-metadata.xml file ? In such case users/repo maintainers could easily tag plugin as (not) beeing thread-safe 2010/4/26 Stephen Connolly stephen.alan.conno...@gmail.com On 26 April 2010 12:05, Benjamin Bentmann benjamin.bentm...@udo.edu wrote: Stephen Connolly wrote: ... but each release of m3 would have it's own compatibility info and we would have another state: unknown e.g. thread-safety plugin groupId=... artifactId=... wieve-mode action=ban versions=...message/wieve-mode wieve-mode action=warn versions=...message/wieve-mode wieve-mode action=checked versions=.../ parallel-mode action=ban versions=...message/paralle-mode parallel-mode action=warn versions=...message/paralle-mode parallel-mode action=checked versions=...message/paralle-mode /plugin /thread-safety Any plugins not in the list would be unknown and the user gets a big fat warning Did you also consider the maintainability aspect of such a list? No user wants to see big fat warnings that are irrelevant for their builds so I envision users will either bug the plugin author or us directly to add plugin X to this list and ask us to roll a new release of this list such that they get rid of that warning. Plugins should be self-describing, that's why mojo annotations and the plugin descriptor exists. I definitively don't want to see us maintaining the metadata for 3rd party plugins. For this reason, I prefer the original suggestion to introduce a new mojo annotation. Apparently, whatever mojo annotation we come up with, it's not present in any existing plugin release. Now, for plugins missing the threading anno, what is the safer assumption with respect to proper build results: That mojo X is thread-safe (when this was never before a concern) or that it isn't? IMHO, there's only way to limit this oh, I deliberately enabled nitro injection and now my engine blew up, how am I supposed to know that this is dangerous?: Unless a mojo is explicitly marked with @threadsafe, issue a warning like Goal X does not appear to support concurrent execution and might fail the build, use parallel building at your own risk. Fair enough, but I would also like to be able to annotate a mojo such that I explicitly don't want it invoked in parallel and not warn the user (perhaps explain to the user why certain mojos cannot be executed in parallel) -Stephen Benjamin - To unsubscribe, e-mail: dev-unsubscr...@maven.apache.org For additional commands, e-mail: dev-h...@maven.apache.org
Re: Concurrency in m3 - a status report
On Apr 26, 2010, at 7:05 AM, Benjamin Bentmann wrote: Stephen Connolly wrote: ... but each release of m3 would have it's own compatibility info and we would have another state: unknown e.g. thread-safety plugin groupId=... artifactId=... wieve-mode action=ban versions=...message/wieve-mode wieve-mode action=warn versions=...message/wieve-mode wieve-mode action=checked versions=.../ parallel-mode action=ban versions=...message/paralle-mode parallel-mode action=warn versions=...message/paralle-mode parallel-mode action=checked versions=...message/paralle-mode /plugin /thread-safety Any plugins not in the list would be unknown and the user gets a big fat warning Did you also consider the maintainability aspect of such a list? No user wants to see big fat warnings that are irrelevant for their builds so I envision users will either bug the plugin author or us directly to add plugin X to this list and ask us to roll a new release of this list such that they get rid of that warning. Plugins should be self-describing, that's why mojo annotations and the plugin descriptor exists. I definitively don't want to see us maintaining the metadata for 3rd party plugins. For this reason, I prefer the original suggestion to introduce a new mojo annotation. Apparently, whatever mojo annotation we come up with, it's not present in any existing plugin release. Now, for plugins missing the threading anno, what is the safer assumption with respect to proper build results: That mojo X is thread-safe (when this was never before a concern) or that it isn't? IMHO, there's only way to limit this oh, I deliberately enabled nitro injection and now my engine blew up, how am I supposed to know that this is dangerous?: Unless a mojo is explicitly marked with @threadsafe, issue a warning like Right. It's pretty simple. If the author has worked on and tested then they can mark the mojo as such. Otherwise the mojo gets no benefit from the parallel mode. A @nothreadsafe annotation makes no sense. We're going to go around and mark everyone else's mojos? That's not going to work and neither is maintaining third party information. If we start the process of adding the annotation we can easily get the basic mojos in the default lifecycle annotated accordingly. If we deem this a requirement for the 3.0 release then we'll work on plugins for a little while before releasing 3.0. Goal X does not appear to support concurrent execution and might fail the build, use parallel building at your own risk. Benjamin - To unsubscribe, e-mail: dev-unsubscr...@maven.apache.org For additional commands, e-mail: dev-h...@maven.apache.org Thanks, Jason -- Jason van Zyl Founder, Apache Maven http://twitter.com/jvanzyl --
Re: Concurrency in m3 - a status report
On 26 April 2010 13:40, Jason van Zyl ja...@sonatype.com wrote: On Apr 26, 2010, at 7:05 AM, Benjamin Bentmann wrote: Stephen Connolly wrote: ... but each release of m3 would have it's own compatibility info and we would have another state: unknown e.g. thread-safety plugin groupId=... artifactId=... wieve-mode action=ban versions=...message/wieve-mode wieve-mode action=warn versions=...message/wieve-mode wieve-mode action=checked versions=.../ parallel-mode action=ban versions=...message/paralle-mode parallel-mode action=warn versions=...message/paralle-mode parallel-mode action=checked versions=...message/paralle-mode /plugin /thread-safety Any plugins not in the list would be unknown and the user gets a big fat warning Did you also consider the maintainability aspect of such a list? No user wants to see big fat warnings that are irrelevant for their builds so I envision users will either bug the plugin author or us directly to add plugin X to this list and ask us to roll a new release of this list such that they get rid of that warning. Plugins should be self-describing, that's why mojo annotations and the plugin descriptor exists. I definitively don't want to see us maintaining the metadata for 3rd party plugins. For this reason, I prefer the original suggestion to introduce a new mojo annotation. Apparently, whatever mojo annotation we come up with, it's not present in any existing plugin release. Now, for plugins missing the threading anno, what is the safer assumption with respect to proper build results: That mojo X is thread-safe (when this was never before a concern) or that it isn't? IMHO, there's only way to limit this oh, I deliberately enabled nitro injection and now my engine blew up, how am I supposed to know that this is dangerous?: Unless a mojo is explicitly marked with @threadsafe, issue a warning like Right. It's pretty simple. If the author has worked on and tested then they can mark the mojo as such. Otherwise the mojo gets no benefit from the parallel mode. A @nothreadsafe annotation makes no sense. We're going to go around and mark everyone else's mojos? That's not going to work and neither is maintaining third party information. If we start the process of adding the annotation we can easily get the basic mojos in the default lifecycle annotated accordingly. If we deem this a requirement for the 3.0 release then we'll work on plugins for a little while before releasing 3.0. This is not an @nothreadsafe annotation I was suggesting, but a @noparallel annotation i.e. for the plugin author to mark a mojo as specifically banning parallel execution -Stephen Goal X does not appear to support concurrent execution and might fail the build, use parallel building at your own risk. Benjamin - To unsubscribe, e-mail: dev-unsubscr...@maven.apache.org For additional commands, e-mail: dev-h...@maven.apache.org Thanks, Jason -- Jason van Zyl Founder, Apache Maven http://twitter.com/jvanzyl --
Re: Concurrency in m3 - a status report
Den 26.04.2010 14:40, skrev Jason van Zyl: On Apr 26, 2010, at 7:05 AM, Benjamin Bentmann wrote: IMHO, there's only way to limit this oh, I deliberately enabled nitro injection and now my engine blew up, how am I supposed to know that this is dangerous?: Unless a mojo is explicitly marked with @threadsafe, issue a warning like LOL. I think you're right. Enable nitro injection, you get warnings for any plugin not marked @threadsafe. If the build fails too you get an additional warning at the end that you're running on your own, please go see our marvellous wiki site. Right. It's pretty simple. If the author has worked on and tested then they can mark the mojo as such. Otherwise the mojo gets no benefit from the parallel mode. A @nothreadsafe annotation makes no sense. We're going to go around and mark everyone else's mojos? That's not going to work and neither is maintaining third party information. If we start the process of adding the annotation we can easily get the basic mojos in the default lifecycle annotated accordingly. If we deem this a requirement for the 3.0 release then we'll work on plugins for a little while before releasing 3.0. @notthreadsafe/@noparallel makes only marginal sense, since you'd achieve the intended effect by sunchronizing execute. But on the other hand I suppose a thread-reluctant mojo would end up with a @threadsafe annotation and a synchronized execute method. But it shows that threading has been considered, which is fine with me. I think an important issue to settle is if the annotations should have any impact on run-time behaviour (other than complaining...) I somewhat dislike the idea of only running mojos marked with @threadsafe concurrently; it also decreases overall performance and increases risks of deadlocks in weave mode significantly. And you're only getting parallel-mode because you asked for it, right ? So my 2cents are: Add @threadsafe annotation, complain loudly about executions missing annotations but proceed as requested. Increases community motivation to make plugins thread-safe. This solution would allow future extensions if required. Kristian - To unsubscribe, e-mail: dev-unsubscr...@maven.apache.org For additional commands, e-mail: dev-h...@maven.apache.org
Re: Concurrency in m3 - a status report
On Apr 26, 2010, at 9:09 AM, Kristian Rosenvold wrote: Den 26.04.2010 14:40, skrev Jason van Zyl: On Apr 26, 2010, at 7:05 AM, Benjamin Bentmann wrote: IMHO, there's only way to limit this oh, I deliberately enabled nitro injection and now my engine blew up, how am I supposed to know that this is dangerous?: Unless a mojo is explicitly marked with @threadsafe, issue a warning like LOL. I think you're right. Enable nitro injection, you get warnings for any plugin not marked @threadsafe. If the build fails too you get an additional warning at the end that you're running on your own, please go see our marvellous wiki site. Right. It's pretty simple. If the author has worked on and tested then they can mark the mojo as such. Otherwise the mojo gets no benefit from the parallel mode. A @nothreadsafe annotation makes no sense. We're going to go around and mark everyone else's mojos? That's not going to work and neither is maintaining third party information. If we start the process of adding the annotation we can easily get the basic mojos in the default lifecycle annotated accordingly. If we deem this a requirement for the 3.0 release then we'll work on plugins for a little while before releasing 3.0. @notthreadsafe/@noparallel makes only marginal sense, since you'd achieve the intended effect by sunchronizing execute. But on the other hand I suppose a thread-reluctant mojo would end up with a @threadsafe annotation and a synchronized execute method. But it shows that threading has been considered, which is fine with me. I think an important issue to settle is if the annotations should have any impact on run-time behaviour (other than complaining...) I somewhat dislike the idea of only running mojos marked with @threadsafe concurrently; it also decreases overall performance and increases risks of deadlocks in weave mode significantly. And you're only getting parallel-mode because you asked for it, right ? So my 2cents are: Add @threadsafe annotation, complain loudly about executions missing annotations but proceed as requested. Increases community motivation to make plugins thread-safe. This solution would allow future extensions if required. We have until 3.0 is out and we can push out the release date if we need to do some mojo housecleaning first. Nothing dire. Kristian - To unsubscribe, e-mail: dev-unsubscr...@maven.apache.org For additional commands, e-mail: dev-h...@maven.apache.org Thanks, Jason -- Jason van Zyl Founder, Apache Maven http://twitter.com/jvanzyl --
Re: Concurrency in m3 - a status report
I am sorry if this has been answered already, but do you have any info that shows performance comparison single vs milti threaded build? If you happen to have any profiler snapshots that show where time is spent during single and multi threaded builds, I am interested to see these too. PS: we got first // build question on tycho-users list last week ;-) -- Regards, Igor Kristian Rosenvold wrote: Now that the first Jira issue has arrived on parallel maven, I think it's time I do a little summary of how things are ATM. For those of you that don't routinely hang around at #maven-dev on irc: I have found and fixed a series of insidious concurrency problems in several plexus components (thanks a million Benjamin for all help with discussing patching those!) The issues were: http://jira.codehaus.org/browse/MNG-4632 http://jira.codehaus.org/browse/PLXUTILS-130 http://jira.codehaus.org/browse/PLXCOMP-149 The last two of these issues affect linear-maven-2.2.1 too and can be the cause of deadlocks (in numerous plugins) and data corruption/deadlock/other interesting behaviour in the jar/war/ear/?ar plugins. plexus-utils (2.0.5), plexus-io (1.0) and plexus-archiver (1.0) are the required dependencies to stay clear. I will file issues on the affected plugins/modules RSN. Both parallel mode and weave mode now work stunningly well, and all my test builds are green (or otherwise accounted for). I have one last minor update on weave that's running the tests now, and I'm targetting http://jira.codehaus.org/browse/MNG-4633 for beta-2. All of Arnaud's projects that I was able to build with regular m3 on java 6 also build with parallel m3 now. The CI running the tests can be seen here; and it's quite interesting. I'll leave it to the reader to spot the 6-core i7 980X vs the C2D 2.5 Ghz in those graphs ;) Weave mode: http://rosenvold.dyndns.org:8085/browse/PARALLEL-CH1W PArallel: http://rosenvold.dyndns.org:8085/browse/PARALLEL-CH1 m3 weave: http://rosenvold.dyndns.org:8085/browse/PARALLEL-M31W m3 parallel: http://rosenvold.dyndns.org:8085/browse/PARALLEL-M31 This CI has now run 40.000 parallel builds (most of which are non-public) and all errors are accounted for. Those of you surfing around a little more will see a couple of disabled builds, which also has known causes. Plugins = I have only managed to find real concurrency problems in the EAR plugin and modello as of yet. Modello is fixed in trunk, ear is not started AFIK. All the other stuff I've seen in the core plugins relate to the plexus-issues. Our jira issue is from a user who's complaining about plugins not working, and I think he's somewhat right in that we have to make some kind of system to indicate compatibility with the -T option. Although several strategies may be recommended, my personal favourite is to make a @threadsafe javadoc annotation and make M3 core COMPLAIN LOUDLY about plugins that are unmarked, then proceed as requested (i.e. complain but still run threaded). The problem with these things is that thread safety is not necessarily a constant, and in the next 9 months there will be issues. So for some plugins @threadsafe might equally much express an intent as much as it reflects reality. So that makes me a bit sceptical to @threadsafe too. Aggressively displaying the link to the wiki page containing the most up-todate threading info may be an equally good solution; maybe even adding a WARNING: Experimental or something to the build output. http://cwiki.apache.org/confluence/display/MAVEN/Parallel+builds+in +Maven+3 (if it's up), should contain all the information needed on which plugins are known to have issues. But as we all know, it's an open ecosystem. Documentation I will keep the wiki page updated, provided cwiki.a.o actually stays up ;) I will add a section on mojo threading models/threading concerns to the mojo api specification. I think we have to take some extra measures to keep users out of the issue trackers on this one, or at least make sure they go to the right place. What do you think ? Kristian - To unsubscribe, e-mail: dev-unsubscr...@maven.apache.org For additional commands, e-mail: dev-h...@maven.apache.org - To unsubscribe, e-mail: dev-unsubscr...@maven.apache.org For additional commands, e-mail: dev-h...@maven.apache.org
