- Pharo-users - lists.pharo.org

Re: [Pharo-users] About DuneSt / ChartJs

by Guillaume Larcheveque

Le mar. 11 fÃ©vr. 2020 Ã 17:07, Sven Van Caekenberghe <sven(a)stfx.eu> a Ã©crit : > Hi, > > I am trying to use DuneSt / ChartJs [ https://github.com/DuneSt/ChartJs ] > and it looks good. Thanks for another nice library. > You're welcome and we are pleased that you use it :-) > > My first question is about loading the code. I would like to load the > minimum possible. I guess the stylesheet code is needed, but not the prism > code ? > You are totally right, Prism is required by the demo to display the code. You will not load it by using the 'core' group > > NeoJSON and Seaside are already in my project's dependencies, but Seaside3 > seems to never resolve to the same thing, so I would like to skip that. Is > that possible ? I have this issue often with Seaside. I could fork and edit > the baseline, but I'd rather not. > I have the same opinion, if you have a solution to manage it in a nice way i would be pleased to add it. I only see as a solution to create a group that do not load Seaside3 but maybe Cyril know a better way to do it (he is far better than me about baselines) > > I got a Bar chart on 2D data running right away. > > But how can I use 'horizontalBar' as type ? > > var myBarChart = new Chart(ctx, { > type: 'horizontalBar', > data: data, > options: options > }); > > I see that the types are encoded a classes, but the list seems rather > limited. > We implemented the minimum that is required for us. It is really easy to add new ones as you already discovered. I will add these as soon as possible or if you already did it, create a pull request. There is many improvement that can be done in this project and it would be great to have your contribution about it. We will move to the new version of the ChartJs library when we will have time to improve it. Of course the API of our project will stay the same and changes will not impact your project. > > Thx, > > Sven > > > -- *Guillaume Larcheveque*

Feb. 11, 2020

Spec2 and Nuklear?

by Offray Vladimir Luna CÃ¡rdenas

Hi, This is not a question, but more like a blue plan thinking about minimalist native UI toolkits that can talk with Spec 2. I just found Nuklear[1] and I'm kind of wondering if this could take the place of GTK in the Spec2 world. [1] https://github.com/Immediate-Mode-UI/Nuklear Maybe this is just a public note for my future self, put in a bottle, so future others in this community can find it :-). Cheers, Offray

Feb. 11, 2020

About DuneSt / ChartJs

by Sven Van Caekenberghe

Hi, I am trying to use DuneSt / ChartJs [ https://github.com/DuneSt/ChartJs ] and it looks good. Thanks for another nice library. My first question is about loading the code. I would like to load the minimum possible. I guess the stylesheet code is needed, but not the prism code ? NeoJSON and Seaside are already in my project's dependencies, but Seaside3 seems to never resolve to the same thing, so I would like to skip that. Is that possible ? I have this issue often with Seaside. I could fork and edit the baseline, but I'd rather not. I got a Bar chart on 2D data running right away. But how can I use 'horizontalBar' as type ? var myBarChart = new Chart(ctx, { type: 'horizontalBar', data: data, options: options }); I see that the types are encoded a classes, but the list seems rather limited. Thx, Sven

Feb. 11, 2020

Re: [Pharo-users] The results are in!

by horrido

I shall endeavour to make my posts more meaningful, starting with [ANN]. My bad. Guillermo Polito wrote > Hi Ben, > >> El 9 feb 2020, a las 21:01, Ben Coman < > btc@ > > escribiÃ³: >> >> > This list is for people to *ask* questions about Pharo. Not to diffuse >> any kind of propaganda (pharo related or not). >> >> This list is not just for asking questions. There are plenty of [ANN] >> posts advertising new libraries >> and blogs articles. Following completion of the competition, the MIT >> licensed code repository will be announced here. >> Hopefully it may provide an engaging exercise for Pharo teachers to their >> with their students. > > I know, and I donât mind announcements from time to time. > But announcements are generally marked with [ANN], and are kind of self > explanatory. > The mail Richard sent is, and Iâm sorry to be harsh, spam. > >> > I have the feeling this list has been lately flooded with such >> off-topic messages. >> >> Unfortunately the original post was quite bare and failed to show how it >> was Pharo-topical. >> So I can understand how it triggered you. I hope the additional >> background info provided here alleviates some of your concern about it. > > Maybe. Maybe Richard could work his emails a bit more? > > Iâll quote his original email: > >> > El 8 feb 2020, a las 19:12, Richard Kenneth Eng < > horrido.hobbies@ > <mailto: > horrido.hobbies@ > >> escribiÃ³: >> > >> > Round 1 â #1 Leading Team: https://youtu.be/QWHeN5WXfBQ >> <https://youtu.be/QWHeN5WXfBQ> >> > >> > I'm actually quite amazed by their effort. They surpassed my >> expectations. >> > >> > At the risk of sounding immodest, I think this is a terrific way to >> promote Smalltalk (Pharo). I think the video is an absolute blast. >> > >> > Richard > > I particularly, who hasnât followed the competition, am completely lost > with this email. > With the risk of sounding harsh, again, but trying to give some feedback > Richard can work on: > - The subject does not imply it is an announcement, nor what the results > are related to or how they got there > - For those that are not following this competition: what is this round 1? > Are there many of them? What is this about? are there many teams? > - There is no single link to the competition website, what this is about, > whoever contributed to it... > - Clicking on the link gives a video with a title that is as ambiguous as > this email :( > - I check the description of the video: what is there in the video? not > clear. How will it appear in a youtube search in the future? > At least it seems there are links to the website... > Yet, Really? do I have to watch the video before I can know if this is > interesting for me or not? :P > > Happily these points could be addressed in the future. > >> So with this additional perspective, may one post a week be allowed to >> share the progress of the competition? > > Can the posts have better quality? :/ > > Still, Iâd feel more confortable with an alternative, such as using > discord. > What about having a dedicated #jmrpc channel on discord where people could > ask questions too? > > What about twitter? I havent seen this on twitter. Is it there? > > Now, I already spent too much on this :) > Time to get back to something productive. > > Cheers, > Guille -- Sent from: http://forum.world.st/Pharo-Smalltalk-Users-f1310670.html

Feb. 11, 2020

Re: [Pharo-users] Voluntarily cancelling requests ("applying an expiration date")

by Sabine Manaa

Hi Holger, I did not completely understand your mail but when reading the answer of Sven I remembered that some time ago we also had problems with running out of semaphores. After writing with Esteban Lorenzano, we did the following: 1) Smalltalk vm maxExternalSemaphoresSilently: 65535. at startup of the application 2) setting the default pool size of VOMongoRepository from 10 to 2 (we have our own VOMongoRepository subclass) Perhaps this is not your topic perhaps it helps. Sabine Am Mo., 10. Feb. 2020 um 15:14 Uhr schrieb Sven Van Caekenberghe < sven(a)stfx.eu>: > Hi Holger, > > That is a complicated story ;-) > > But, you running out of external semaphores means that you are using too > many sockets, are not closing/releasing them (in time) and/or your GC does > not run enough to keep up (it is easy to deplete the external semaphore > table without the GC kicking in). > > You must have a loop somewhere that goes too fast and maybe does not clean > up properly while doing so. > > YMMV, but I do similar things -- implement/offer REST services that call > other REST/network services, all with timeouts, in several variations, for > years, and I do not have problems like you describe. > > I would suggest enabling logging so that you can see better where the > allocations happen and if your cleanup code does its work. > > Sven > > PS: Zinc logging is easy, just do > > ZnLogEvent logToTranscript > > > On 9 Feb 2020, at 16:31, Holger Freyther <holger(a)freyther.de> wrote: > > > > tl;dr: I am searching for a pattern (later code) to apply expiration to > operations. > > > > > > > > Introduction: > > > > One nice aspect of Mongodb is that it has built-in data distribution[1] > and configurable retention[2]. The upstream project has a document called > "Server Discovery and Monitoring (SDAM)", defining how a client should > behave. Martin Dias is currently implementing SDAM in MongoTalk/Voyage and > I took it on a test drive. > > > > > > Behavior: > > > > My software stack is using Zinc, Zinc-REST, Voyage and Mongo. When a new > REST requests arrives I am using Voyage (e.g. >>#selectOne:) which will use > MongoTalk. The MongoTalk code needs to select the right server. It's > currently done by waiting for a result. > > > > Next I started to simulate database outages. The rest clients retried > when not receiving a result within two seconds (no back-off/jitter). What > happened was roughly the following: > > > > > > [ > > 1.) ZnServer accepts a new connection > > 2.) MongoTalk waits for a server longer than 2s > > "nothing.. the above waits..." > > ] repeat. > > > > > > > > > > Problem: > > > > What happened next surprised me. I expected to have a bad time when the > database recovers and all the stale (remember the REST clients already gave > up and closed the socket) requests will be answered. Instead my image > crashed early in my test as the ExternalSemaphoreTable was full. > > > > Let's focus on the timeout behavior and discuss the existence of the > ExternalSemaphoreTable and the number of entries separately at a different > time. > > > > > > > > > > To me the two main problems I see are: > > > > > > 1.) Lack of back-pressure for ZnManagingMultiThreadedServer > > > > 2.) Disconnect of time between the Application Layer handling REST is > allowed to take and down the stack how long MongoTalk may sleep and wait > for a server. > > > > > > The first item is difficult. Even answering HTTP 500 when we are out of > space in the ExternalSemaphore is difficult... Let's ignore this for now as > well. > > > > > > > > > > > > > > What I look for: > > > > > > 1.) Voluntarily Timeout > > > > Inside my Application code I would like to tag an operation with a > timeout. This means everything that is done should complete within X > seconds. It can be used on a voluntarily basis. > > > > > >>> #lookupPerson > > > > "We expect all database operations to complete within two seconds" > > person := ComputeContext current withTimeout: 2 seconds during: [ > > repository selectOne: Person where: [:each name | ...], > > ]. > > > > > > > > MongoTalk>>stuff > > "See if the outer context timeout has expired and signal. E.g. before > writing > > something into the socket to keep consistency." > > ComputeContext current checkExpired. > > > > > > MongoTalk>>other > > "Sleep for up to the remaining time out > > (someSemaphore waitTimeoutContext: ComputeContext current) ifFalse: [ > > SomethingExpired signal. > > ] > > > > > > > > 2.) Cancellation > > > > > > More difficult to write in pseudo code (without TaskIt?). In my above > case we are waiting for the database to be ready while the client already > closed the file descriptor. Now we are not able to see this until much > later. > > > > The idea is that in addition to the timeout we can pass a block that is > called when an operation should be cancelled and the ComputeContext can be > checked if something has been cancelled? > > > > > > > > > > The above takes inspiration from Go's context package[3]. In Go the > context should be passed as parameter but we could make it a Process > variable? > > > > > > > > > > > > Question: > > > > How do you handle this in your systems? Is this something we can > consider for Pharo9? > > > > > > > > thanks > > holger > > > > > > > > > > > > > > > > > > [1] It has the concept of "replicationSet" and works by having a > primary, secondary and arbiters running. > > [2] For every write one can configure if the write should succeed > immediately (before it is even on disk) or when it has been written to > multiple stores (e.g. majority, US and EMEA) > > [3] https://golang.org/pkg/context/ > > > > > > > > >

Feb. 11, 2020

Re: [Pharo-users] [Pharo-dev] [Ann] Concurrent Programming in Pharo is available

by Eliot Miranda

Hi Stef, here's my review/feedback On Sun, Feb 9, 2020 at 5:05 AM StÃ©phane Ducasse <stephane.ducasse(a)inria.fr> > wrote: > > > > On http://books.pharo.org/booklet-ConcurrentProgramming/ > In fig 1.1 there needs to be a back arrow from Executing to Runnable which is labelled "Preempted by a higher priority process" or similar. In the label for fig 1.2 the word "pending" should be replaced with "runnable". Page 8, section "Process Priorities" "At any time only one process is executed." should read "At any time only one process is executing." The line starting "Next table lists..." in the last paragraph on page 8 should read "The following table lists...". The section might want to state some thing like "there that the current implementation of the Pharo scheduler has process priorities from 1 to 100. Only some of these are named. But the programmer is free to use any priority within that range that they see fit." It would be good to include examples which did things like "forkAt: Processor userPriority + 1", etc. In the label for Fig 2.1 "ressources" should read "resources". But throughout that section I would word it that "processes need to share resources", but "the process is waiting to acquire the resource". So use the plural for the general case and the singular for the specific case. Sentences such as this: "P0 has finished to use the resources." should read "P0 has finished using the resource." In Section 2.1 Conclusion "Semaphores are the lower synchronisation mechanisms." should read "Semaphores are the lowest level synchronisation mechanisms." Chapter 3, "Scheduler's Principles" should state that "The Smalltalk scheduler is a real-time, cooperative, preemptive across priorities, non-preemptive within priorities, scheduler." The title to Chapter 4.5 "ShareQueue: a nice semaphore example" should read "Share*d*Queue: a nice semaphore example" Most of the paragraphs on page 49 in section 4.5 are still in French and need translating. > S. > > -------------------------------------------- > StÃ©phane Ducasse > http://stephane.ducasse.free.fr / http://www.pharo.org > 03 59 35 87 52 > Assistant: Julie Jonas > FAX 03 59 57 78 50 > TEL 03 59 35 86 16 > S. Ducasse - Inria > 40, avenue Halley, > Parc Scientifique de la Haute Borne, BÃ¢t.A, Park Plaza > Villeneuve d'Ascq 59650 > France > > -- _,,,^..^,,,_ best, Eliot

Feb. 10, 2020

Re: [Pharo-users] P3 and concurrenty

by ducasse

Amazing experience! This is the power of Pharo at work. Thanks a lot Sven. S > On 10 Feb 2020, at 21:24, Petter Egesund <petter.egesund(a)gmail.com> wrote: > > Perfect, this is exactly what I needed. Thank so much!! > > Petter > > On Mon, Feb 10, 2020 at 8:44 PM Sven Van Caekenberghe <sven(a)stfx.eu <mailto:sven@stfx.eu>> wrote: > Hi Petter, > > > On 10 Feb 2020, at 16:46, Petter Egesund <petter.egesund(a)gmail.com <mailto:petter.egesund@gmail.com>> wrote: > > > > Yes, I see - that sounds sensible. > > > > Could it be an idea to subclass the pool-class and to prepare statements in this method, if there is a kind of init-method in the class? What do you think? > > That would have indeed been one approach but for this situation I opted for a configurator block. > > P3ConnectionPool>>#configurator: oneArgumentBlock > "Set oneArgumentBlock to be my configurator. > This is code that will be executed once on each newly created connection (P3Client). > The default configuration asserts #isWorking on the argument" > > The default is > > configurator := [ :p3Client | self assert: p3Client isWorking ] > > which basically does an extra validation and ensures the opening of the connection. > > Now, a little piece of functionality was still missing, I added it with the following commit: > > https://github.com/svenvc/P3/commit/e3f161d9f9ae34b3b020ad924b3c0f116f68c0b0 <https://github.com/svenvc/P3/commit/e3f161d9f9ae34b3b020ad924b3c0f116f68c0b0> > > Your usage scenario should now be like this: you create a P3ConnectionPool with the proper URL, then you set your configurator to add your prepared statements (you could delegate this to a helper class if you have a lot of them). > > pool configurator: [ :p3Client | > p3Client prepare: 'SELECT ...' named: 'select1'. > p3Client prepare: 'INSET ...' named: 'insert1' ] > > Later, when using a connection from the pool, you refer to your prepared statements by name. > > pool withConnection: [ :p3Client | > (p3Client preparedStatementNamed: 'select1') > execute: { args } ] > > Sven > > PS: have a look at P3PreparedStatementTest>>#testNamedPreparedStatement for an operation example (minus the connection pooling). > > > On Mon, Feb 10, 2020 at 4:36 PM Sven Van Caekenberghe <sven(a)stfx.eu <mailto:sven@stfx.eu>> wrote: > > > > > > > On 10 Feb 2020, at 16:30, Petter Egesund <petter.egesund(a)gmail.com <mailto:petter.egesund@gmail.com>> wrote: > > > > > > Hi and thanks for an answer above my expectations to our problem. > > > > > > This is really awesome, I was just about to start coding a pool myself, but getting it directly from the author of the base library is off course way better :) > > > > > > I will try out and get back as soon as we have tested. > > > > > > One quick question - are the prepared statements which are connected to the pool thread safe? > > > > Prepared statements are scoped to a single connection in PSQL, AFAIK. > > > > What you will probably want to do is use a #configurator: block to set up your prepared statements once, like you do now. Then each thread/process grabs its own connection from the pool, (which will be already configured properly) and uses it, for itself, and finally returns it to the pool. > > > > Interacting with the pool should be fully thread safe. Once you are using a connection, it not longer is, but is also does not have to, since one connection equals one client thread. > > > > > Petter > > > > > > On Mon, Feb 10, 2020 at 12:13 PM Sven Van Caekenberghe <sven(a)stfx.eu <mailto:sven@stfx.eu>> wrote: > > > Hi Petter, > > > > > > https://github.com/svenvc/P3/commit/a6b409d0d92cb92bf9b44452908bb9033523b863 <https://github.com/svenvc/P3/commit/a6b409d0d92cb92bf9b44452908bb9033523b863> adds a connection pool. > > > > > > Here is the class comment: > > > > > > ====== > > > > > > I am P3ConnectionPool. > > > > > > I offer a pool of shared PSQL connections (P3Client instances) as a resource. > > > > > > After configuring me with at least a url, you use me by calling #withConnection: > > > > > > pool := P3ConnectionPool url: 'psql://sven@localhost'. > > > pool withConnection: [ :p3Client | > > > p3Client query: 'SELECT table_name FROM information_schema.tables' ]. > > > pool close. > > > > > > When a connection is in use, it is not part of the pool. > > > When a connection is returned/released to the pool, it becomes available for reuse. > > > > > > The pool's size is the number of open connection ready to be reused. > > > The pool's capacity is the maximum number of connection that will be pooled. > > > Excess connections will be closed when they are returned/released to the pool. > > > > > > New connections are created as needed. > > > You can set a #configurator to further initialize new connections. > > > You can use #warmUp or #warmUp: to precreate a number of connections. > > > > > > When an error occurs, the connection should not be reused and be closed by the caller. > > > > > > ====== > > > > > > There are some unit tests as well. > > > > > > Let me know if this works for you. > > > > > > Sven > > > > > > > On 9 Feb 2020, at 19:04, Petter Egesund <petter.egesund(a)gmail.com <mailto:petter.egesund@gmail.com>> wrote: > > > > > > > > Yes, thanks for good feedback. > > > > > > > > I will try the pooled way, I think - not primarily because of speed, but due to that our library is built around prepared connections. > > > > > > > > Petter > > > > > > > > On Sun, Feb 9, 2020 at 6:01 PM Sven Van Caekenberghe <sven(a)stfx.eu <mailto:sven@stfx.eu>> wrote: > > > > Hi Petter, > > > > > > > > > On 9 Feb 2020, at 17:27, Petter Egesund <petter.egesund(a)gmail.com <mailto:petter.egesund@gmail.com>> wrote: > > > > > > > > > > Hi Sven and thanks for answering! > > > > > > > > > > I use Teapot with one common sql-connecton, not one for each user session. At startup I create several sql statements and these does not seem to be usable from different Teapot request at the same time. > > > > > > > > It is useable, but not concurrently. > > > > > > > > > I could create one connection pr. session and then close the database connection when the user leaves, but then I also would need to create all the prepared sql-statements for each session, which does not sound right to me? > > > > > > > > Yes and no, see further. > > > > > > > > > It seems I have will have to look into the other solution, and see if I can use some mutex stuff to avoid several tasks acessessing the same resources at the same time. > > > > > > > > Yes, follow the pointer that I gave you, it is not hard. > > > > > > > > > Creating a pool sounds like the right solution to me now - any meaning about this? > > > > > > > > Yes, you could create a connection pool. But that is harder than it sounds: what is the minimum size, the maximum size, what do you do when you go over it, how do you make sure that a resource (connection) is clean when returning it to the pool (given authentication, possible errors), ... > > > > > > > > I don't know what you are doing, but I think you focus too much on performance issues. I would first try to get the code correct and worry about performance later on. > > > > > > > > Running > > > > > > > > P3ClientTest new runBenchmark1Bench. > > > > > > > > on my machine gives me a BenchmarkResult(67 iterations in 5 seconds 57 milliseconds. 13.249 per second). This is a query that returns 10.000 records with 5 columns. It is reusing the same client/connection for all iterations. > > > > > > > > If I modify this slightly to use a new client/connection each time, like this > > > > > > > > [ > > > > (P3Client url: 'psql://sven@localhost') > > > > query: 'SELECT * FROM benchmark1'; > > > > close > > > > ] benchFor: 5 seconds > > > > > > > > I get a BenchmarkResult(65 iterations in 5 seconds 34 milliseconds. 12.912 per second) which almost as fast. Of course, for smaller queries, the connect/disconnect overhead will be more significant. > > > > > > > > And note that this is not using prepared statements. > > > > > > > > So I would start by opening/closing a connection each time you need it. > > > > > > > > HTH, > > > > > > > > Sven > > > > > > > > > Petter > > > > > > > > > > > > > > > On Sun, Feb 9, 2020 at 4:52 PM Sven Van Caekenberghe <sven(a)stfx.eu <mailto:sven@stfx.eu>> wrote: > > > > > Hi Petter, > > > > > > > > > > [ CC-ing the Pharo Users list ] > > > > > > > > > > P3Client is not built/designed to be used by multiple processes concurrently. Each database connection is represented by an instance of P3Client and holds some state both at the client as well as at the server side. > > > > > > > > > > Typically, in a multi user server application, each connection should have its own P3Client / psql connection. For example, in Seaside, a custom WASession subclass gives each session/user its own p3 connection/client. > > > > > > > > > > Is that what you are doing ? > > > > > > > > > > If not, you could wrap your db accessing code so that mutual exclusion is provided. For example, you can have a look at AbstractCache #beThreadSafe and #critical: > > > > > > > > > > That will then serialise requests and possibly block one onto the other. > > > > > > > > > > HTH, > > > > > > > > > > Sven > > > > > > > > > > PS: another thing to take care of if closing your sql connections when the session is no longer needed. > > > > > > > > > > PS: Zinc HTTP does also provide a session mechanism (ZnServerSession[Manager]) but these work with cookies and typically won't help with a REST access pattern. > > > > > > > > > > > On 9 Feb 2020, at 14:21, Petter Egesund <petter.egesund(a)gmail.com <mailto:petter.egesund@gmail.com>> wrote: > > > > > > > > > > > > Hi Sven > > > > > > > > > > > > We are using Pharo as our backend in a project and we have run into a problem with P3. > > > > > > > > > > > > The problem seems to be connected to compiled sql statements and concurrency. > > > > > > > > > > > > We keep getting this error: Bindcomplete message expected > > > > > > > > > > > > Problem seems to be easy to reproduce: > > > > > > > > > > > > 1) Compile any sql statement > > > > > > 2) Use this statement in a query twice (!) in a teapot endpoint > > > > > > > > > > > > The run some concurrent queries, like "curl http://localhost:8080/endpoint <http://localhost:8080/endpoint> & curl http://localhost:8080/endpoint. <http://localhost:8080/endpoint.>." (add several curls after here). > > > > > > > > > > > > One could also use ex. siege (https://manpages.ubuntu.com/manpages/trusty/man1/siege.1.html <https://manpages.ubuntu.com/manpages/trusty/man1/siege.1.html>) for easy reproducing. > > > > > > > > > > > > If we chain the curls after each other, like "curl http://localhost:8080/endpoint <http://localhost:8080/endpoint> && https://manpages.ubuntu.com/manpages/trusty/man1/siege.1.html <https://manpages.ubuntu.com/manpages/trusty/man1/siege.1.html> && https://manpages.ubuntu.com/manpages/trusty/man1/siege.1.html. <https://manpages.ubuntu.com/manpages/trusty/man1/siege.1.html.>." it seems to work fine, so doing the request sequentially seem to work fine. > > > > > > > > > > > > My conclusion is that this must be connected to how teapot handles concurrency in companion with the compiled statements? > > > > > > > > > > > > Any clues on this one? We are on Pharo 8.0 with latest version of P3, PG 9.x) > > > > > > > > > > > > Best regards > > > > > > > > > > > > Petter Egesund (I wrote the heysql-package based on P3) > > > > > > > > > > > > > > >

Feb. 10, 2020

Re: [Pharo-users] P3 and concurrenty

by Petter Egesund

Perfect, this is exactly what I needed. Thank so much!! Petter On Mon, Feb 10, 2020 at 8:44 PM Sven Van Caekenberghe <sven(a)stfx.eu> wrote: > Hi Petter, > > > On 10 Feb 2020, at 16:46, Petter Egesund <petter.egesund(a)gmail.com> > wrote: > > > > Yes, I see - that sounds sensible. > > > > Could it be an idea to subclass the pool-class and to prepare statements > in this method, if there is a kind of init-method in the class? What do you > think? > > That would have indeed been one approach but for this situation I opted > for a configurator block. > > P3ConnectionPool>>#configurator: oneArgumentBlock > "Set oneArgumentBlock to be my configurator. > This is code that will be executed once on each newly created > connection (P3Client). > The default configuration asserts #isWorking on the argument" > > The default is > > configurator := [ :p3Client | self assert: p3Client isWorking ] > > which basically does an extra validation and ensures the opening of the > connection. > > Now, a little piece of functionality was still missing, I added it with > the following commit: > > > https://github.com/svenvc/P3/commit/e3f161d9f9ae34b3b020ad924b3c0f116f68c0b0 > > Your usage scenario should now be like this: you create a P3ConnectionPool > with the proper URL, then you set your configurator to add your prepared > statements (you could delegate this to a helper class if you have a lot of > them). > > pool configurator: [ :p3Client | > p3Client prepare: 'SELECT ...' named: 'select1'. > p3Client prepare: 'INSET ...' named: 'insert1' ] > > Later, when using a connection from the pool, you refer to your prepared > statements by name. > > pool withConnection: [ :p3Client | > (p3Client preparedStatementNamed: 'select1') > execute: { args } ] > > Sven > > PS: have a look at P3PreparedStatementTest>>#testNamedPreparedStatement > for an operation example (minus the connection pooling). > > > On Mon, Feb 10, 2020 at 4:36 PM Sven Van Caekenberghe <sven(a)stfx.eu> > wrote: > > > > > > > On 10 Feb 2020, at 16:30, Petter Egesund <petter.egesund(a)gmail.com> > wrote: > > > > > > Hi and thanks for an answer above my expectations to our problem. > > > > > > This is really awesome, I was just about to start coding a pool > myself, but getting it directly from the author of the base library is off > course way better :) > > > > > > I will try out and get back as soon as we have tested. > > > > > > One quick question - are the prepared statements which are connected > to the pool thread safe? > > > > Prepared statements are scoped to a single connection in PSQL, AFAIK. > > > > What you will probably want to do is use a #configurator: block to set > up your prepared statements once, like you do now. Then each thread/process > grabs its own connection from the pool, (which will be already configured > properly) and uses it, for itself, and finally returns it to the pool. > > > > Interacting with the pool should be fully thread safe. Once you are > using a connection, it not longer is, but is also does not have to, since > one connection equals one client thread. > > > > > Petter > > > > > > On Mon, Feb 10, 2020 at 12:13 PM Sven Van Caekenberghe <sven(a)stfx.eu> > wrote: > > > Hi Petter, > > > > > > > https://github.com/svenvc/P3/commit/a6b409d0d92cb92bf9b44452908bb9033523b863 > adds a connection pool. > > > > > > Here is the class comment: > > > > > > ====== > > > > > > I am P3ConnectionPool. > > > > > > I offer a pool of shared PSQL connections (P3Client instances) as a > resource. > > > > > > After configuring me with at least a url, you use me by calling > #withConnection: > > > > > > pool := P3ConnectionPool url: 'psql://sven@localhost'. > > > pool withConnection: [ :p3Client | > > > p3Client query: 'SELECT table_name FROM > information_schema.tables' ]. > > > pool close. > > > > > > When a connection is in use, it is not part of the pool. > > > When a connection is returned/released to the pool, it becomes > available for reuse. > > > > > > The pool's size is the number of open connection ready to be reused. > > > The pool's capacity is the maximum number of connection that will be > pooled. > > > Excess connections will be closed when they are returned/released to > the pool. > > > > > > New connections are created as needed. > > > You can set a #configurator to further initialize new connections. > > > You can use #warmUp or #warmUp: to precreate a number of connections. > > > > > > When an error occurs, the connection should not be reused and be > closed by the caller. > > > > > > ====== > > > > > > There are some unit tests as well. > > > > > > Let me know if this works for you. > > > > > > Sven > > > > > > > On 9 Feb 2020, at 19:04, Petter Egesund <petter.egesund(a)gmail.com> > wrote: > > > > > > > > Yes, thanks for good feedback. > > > > > > > > I will try the pooled way, I think - not primarily because of speed, > but due to that our library is built around prepared connections. > > > > > > > > Petter > > > > > > > > On Sun, Feb 9, 2020 at 6:01 PM Sven Van Caekenberghe <sven(a)stfx.eu> > wrote: > > > > Hi Petter, > > > > > > > > > On 9 Feb 2020, at 17:27, Petter Egesund <petter.egesund(a)gmail.com> > wrote: > > > > > > > > > > Hi Sven and thanks for answering! > > > > > > > > > > I use Teapot with one common sql-connecton, not one for each user > session. At startup I create several sql statements and these does not seem > to be usable from different Teapot request at the same time. > > > > > > > > It is useable, but not concurrently. > > > > > > > > > I could create one connection pr. session and then close the > database connection when the user leaves, but then I also would need to > create all the prepared sql-statements for each session, which does not > sound right to me? > > > > > > > > Yes and no, see further. > > > > > > > > > It seems I have will have to look into the other solution, and see > if I can use some mutex stuff to avoid several tasks acessessing the same > resources at the same time. > > > > > > > > Yes, follow the pointer that I gave you, it is not hard. > > > > > > > > > Creating a pool sounds like the right solution to me now - any > meaning about this? > > > > > > > > Yes, you could create a connection pool. But that is harder than it > sounds: what is the minimum size, the maximum size, what do you do when you > go over it, how do you make sure that a resource (connection) is clean when > returning it to the pool (given authentication, possible errors), ... > > > > > > > > I don't know what you are doing, but I think you focus too much on > performance issues. I would first try to get the code correct and worry > about performance later on. > > > > > > > > Running > > > > > > > > P3ClientTest new runBenchmark1Bench. > > > > > > > > on my machine gives me a BenchmarkResult(67 iterations in 5 seconds > 57 milliseconds. 13.249 per second). This is a query that returns 10.000 > records with 5 columns. It is reusing the same client/connection for all > iterations. > > > > > > > > If I modify this slightly to use a new client/connection each time, > like this > > > > > > > > [ > > > > (P3Client url: 'psql://sven@localhost') > > > > query: 'SELECT * FROM benchmark1'; > > > > close > > > > ] benchFor: 5 seconds > > > > > > > > I get a BenchmarkResult(65 iterations in 5 seconds 34 milliseconds. > 12.912 per second) which almost as fast. Of course, for smaller queries, > the connect/disconnect overhead will be more significant. > > > > > > > > And note that this is not using prepared statements. > > > > > > > > So I would start by opening/closing a connection each time you need > it. > > > > > > > > HTH, > > > > > > > > Sven > > > > > > > > > Petter > > > > > > > > > > > > > > > On Sun, Feb 9, 2020 at 4:52 PM Sven Van Caekenberghe <sven(a)stfx.eu> > wrote: > > > > > Hi Petter, > > > > > > > > > > [ CC-ing the Pharo Users list ] > > > > > > > > > > P3Client is not built/designed to be used by multiple processes > concurrently. Each database connection is represented by an instance of > P3Client and holds some state both at the client as well as at the server > side. > > > > > > > > > > Typically, in a multi user server application, each connection > should have its own P3Client / psql connection. For example, in Seaside, a > custom WASession subclass gives each session/user its own p3 > connection/client. > > > > > > > > > > Is that what you are doing ? > > > > > > > > > > If not, you could wrap your db accessing code so that mutual > exclusion is provided. For example, you can have a look at AbstractCache > #beThreadSafe and #critical: > > > > > > > > > > That will then serialise requests and possibly block one onto the > other. > > > > > > > > > > HTH, > > > > > > > > > > Sven > > > > > > > > > > PS: another thing to take care of if closing your sql connections > when the session is no longer needed. > > > > > > > > > > PS: Zinc HTTP does also provide a session mechanism > (ZnServerSession[Manager]) but these work with cookies and typically won't > help with a REST access pattern. > > > > > > > > > > > On 9 Feb 2020, at 14:21, Petter Egesund < > petter.egesund(a)gmail.com> wrote: > > > > > > > > > > > > Hi Sven > > > > > > > > > > > > We are using Pharo as our backend in a project and we have run > into a problem with P3. > > > > > > > > > > > > The problem seems to be connected to compiled sql statements and > concurrency. > > > > > > > > > > > > We keep getting this error: Bindcomplete message expected > > > > > > > > > > > > Problem seems to be easy to reproduce: > > > > > > > > > > > > 1) Compile any sql statement > > > > > > 2) Use this statement in a query twice (!) in a teapot endpoint > > > > > > > > > > > > The run some concurrent queries, like "curl > http://localhost:8080/endpoint & curl http://localhost:8080/endpoint.." > (add several curls after here). > > > > > > > > > > > > One could also use ex. siege ( > https://manpages.ubuntu.com/manpages/trusty/man1/siege.1.html) for easy > reproducing. > > > > > > > > > > > > If we chain the curls after each other, like "curl > http://localhost:8080/endpoint && > https://manpages.ubuntu.com/manpages/trusty/man1/siege.1.html && > https://manpages.ubuntu.com/manpages/trusty/man1/siege.1.html.." it seems > to work fine, so doing the request sequentially seem to work fine. > > > > > > > > > > > > My conclusion is that this must be connected to how teapot > handles concurrency in companion with the compiled statements? > > > > > > > > > > > > Any clues on this one? We are on Pharo 8.0 with latest version > of P3, PG 9.x) > > > > > > > > > > > > Best regards > > > > > > > > > > > > Petter Egesund (I wrote the heysql-package based on P3) > > > > > > > > > > > > > > > >

Feb. 10, 2020

Re: [Pharo-users] [Pharo-dev] [Ann] Concurrent Programming in Pharo is available

by ducasse

You are welcome. This is really one of the few resources on the topic and at this level in the ecosystem. In the future I plan to learn and explain monitors because they are better than semaphores or mutexes but I have the learn about them before :). > On 10 Feb 2020, at 20:46, Todd Blanchard <tblanchard(a)mac.com> wrote: > > > From: Todd Blanchard <tblanchard(a)mac.com> > Subject: Re: [Pharo-dev] [Ann] Concurrent Programming in Pharo is available > Date: 10 February 2020 at 20:46:46 CET > To: Pharo Development List <pharo-dev(a)lists.pharo.org> > Cc: Any question about pharo is welcome <pharo-users(a)lists.pharo.org> > > > I have wanted a clean explanation of semaphores and process scheduling for a long time. > > Thanks for this. > > >> On Feb 9, 2020, at 3:58 AM, StÃ©phane Ducasse <stephane.ducasse(a)inria.fr <mailto:stephane.ducasse@inria.fr>> wrote: >> >> On http://books.pharo.org/booklet-ConcurrentProgramming/ <http://books.pharo.org/booklet-ConcurrentProgramming/> >> >> >> S. >> >> -------------------------------------------- >> StÃ©phane Ducasse >> http://stephane.ducasse.free.fr <http://stephane.ducasse.free.fr/> / http://www.pharo.org <http://www.pharo.org/> >> 03 59 35 87 52 >> Assistant: Julie Jonas >> FAX 03 59 57 78 50 >> TEL 03 59 35 86 16 >> S. Ducasse - Inria >> 40, avenue Halley, >> Parc Scientifique de la Haute Borne, BÃ¢t.A, Park Plaza >> Villeneuve d'Ascq 59650 >> France >> > > >

Feb. 10, 2020

Re: [Pharo-dev] [Ann] Concurrent Programming in Pharo is available

by Todd Blanchard

I have wanted a clean explanation of semaphores and process scheduling for a long time. Thanks for this. > On Feb 9, 2020, at 3:58 AM, StÃ©phane Ducasse <stephane.ducasse(a)inria.fr> wrote: > > On http://books.pharo.org/booklet-ConcurrentProgramming/ <http://books.pharo.org/booklet-ConcurrentProgramming/> > > > S. > > -------------------------------------------- > StÃ©phane Ducasse > http://stephane.ducasse.free.fr <http://stephane.ducasse.free.fr/> / http://www.pharo.org <http://www.pharo.org/> > 03 59 35 87 52 > Assistant: Julie Jonas > FAX 03 59 57 78 50 > TEL 03 59 35 86 16 > S. Ducasse - Inria > 40, avenue Halley, > Parc Scientifique de la Haute Borne, BÃ¢t.A, Park Plaza > Villeneuve d'Ascq 59650 > France >

Feb. 10, 2020