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Jaroslaw Kijanowski commented on CASSANDRA-18798: ------------------------------------------------- After applying [the patch|https://gist.githubusercontent.com/kijanowski/31e9534467d2c96ac3fcc7e9fff50465/raw/d6b0514c34dcd193e154d49184cd956909aac157/list-order.patch] the anomaly is still present. For register "1": {code:java} {:type :ok, :process 2, :value [[:r 3 []] [:r 1 []]], :tid 0, :n 1, :time 1695883304794618396} {:type :ok, :process 3, :value [[:append 1 2001] [:append 4 2002]], :tid 4, :n 1, :time 1695883304832554708} {:type :ok, :process 7, :value [[:r 1 [2001]]], :tid 1, :n 1, :time 1695883304854012471} {:type :ok, :process 1, :value [[:append 1 4501]], :tid 9, :n 1, :time 1695883304869167769} {:type :ok, :process 6, :value [[:r 4 [2002]] [:append 1 1501]], :tid 3, :n 1, :time 1695883304885126603} {:type :ok, :process 2, :value [[:r 1 [4501 2001 1501]] [:append 5 1]], :tid 0, :n 2, :time 1695883305831707192} {code} Process 7 reads 2001 and then process 2 reads 4501 2001 1501. sstable dump output: {code:java} [1]@5724 Row[info=[ts=-9223372036854775808] ]: | , [contents[17b726c0-5dca-11ee-a720-095e87595144]=4501 ts=1695883305918000], [contents[17b774e0-5dca-11ee-a7e1-9776011062ce]=2001 ts=1695883305913000], [contents[17b774ea-5dca-11ee-a7e1-9776011062ce]=1501 ts=1695883305922000], ... {code} Based on the timestamps 2001 should come before 4501. > Appending to list in Accord transactions uses insertion timestamp > ----------------------------------------------------------------- > > Key: CASSANDRA-18798 > URL: https://issues.apache.org/jira/browse/CASSANDRA-18798 > Project: Cassandra > Issue Type: Bug > Components: Accord > Reporter: Jaroslaw Kijanowski > Assignee: Henrik Ingo > Priority: Normal > Attachments: image-2023-09-26-20-05-25-846.png > > > Given the following schema: > {code:java} > CREATE KEYSPACE IF NOT EXISTS accord WITH replication = {'class': > 'SimpleStrategy', 'replication_factor': 3}; > CREATE TABLE IF NOT EXISTS accord.list_append(id int PRIMARY KEY,contents > LIST<bigint>); > TRUNCATE accord.list_append;{code} > And the following two possible queries executed by 10 threads in parallel: > {code:java} > BEGIN TRANSACTION > LET row = (SELECT * FROM list_append WHERE id = ?); > SELECT row.contents; > COMMIT TRANSACTION;" > BEGIN TRANSACTION > UPDATE list_append SET contents += ? WHERE id = ?; > COMMIT TRANSACTION;" > {code} > there seems to be an issue with transaction guarantees. Here's an excerpt in > the edn format from a test. > {code:java} > {:type :invoke :process 8 :value [[:append 5 352]] :tid 3 :n 52 > :time 1692607285967116627} > {:type :invoke :process 9 :value [[:r 5 nil]] :tid 1 :n 54 > :time 1692607286078732473} > {:type :invoke :process 6 :value [[:append 5 553]] :tid 5 :n 53 > :time 1692607286133833428} > {:type :invoke :process 7 :value [[:append 5 455]] :tid 4 :n 55 > :time 1692607286149702511} > {:type :ok :process 8 :value [[:append 5 352]] :tid 3 :n 52 > :time 1692607286156314099} > {:type :invoke :process 5 :value [[:r 5 nil]] :tid 9 :n 52 > :time 1692607286167090389} > {:type :ok :process 9 :value [[:r 5 [303 304 604 6 306 509 909 409 912 > 411 514 415 719 419 19 623 22 425 24 926 25 832 130 733 430 533 29 933 333 > 537 934 538 740 139 744 938 544 42 646 749 242 546 547 548 753 450 150 349 48 > 852 352]]] :tid 1 :n 54 :time 1692607286168657534} > {:type :invoke :process 1 :value [[:r 5 nil]] :tid 0 :n 51 > :time 1692607286201762938} > {:type :ok :process 7 :value [[:append 5 455]] :tid 4 :n 55 > :time 1692607286245571513} > {:type :invoke :process 7 :value [[:r 5 nil]] :tid 4 :n 56 > :time 1692607286245655775} > {:type :ok :process 5 :value [[:r 5 [303 304 604 6 306 509 909 409 912 > 411 514 415 719 419 19 623 22 425 24 926 25 832 130 733 430 533 29 933 333 > 537 934 538 740 139 744 938 544 42 646 749 242 546 547 548 753 450 150 349 48 > 852 352 455]]] :tid 9 :n 52 :time 1692607286253928906} > {:type :invoke :process 5 :value [[:r 5 nil]] :tid 9 :n 53 > :time 1692607286254095215} > {:type :ok :process 6 :value [[:append 5 553]] :tid 5 :n 53 > :time 1692607286266263422} > {:type :ok :process 1 :value [[:r 5 [303 304 604 6 306 509 909 409 912 > 411 514 415 719 419 19 623 22 425 24 926 25 832 130 733 430 533 29 933 333 > 537 934 538 740 139 744 938 544 42 646 749 242 546 547 548 753 450 150 349 48 > 852 352 553 455]]] :tid 0 :n 51 :time 1692607286271617955} > {:type :ok :process 7 :value [[:r 5 [303 304 604 6 306 509 909 409 912 > 411 514 415 719 419 19 623 22 425 24 926 25 832 130 733 430 533 29 933 333 > 537 934 538 740 139 744 938 544 42 646 749 242 546 547 548 753 450 150 349 48 > 852 352 553 455]]] :tid 4 :n 56 :time 1692607286271816933} > {:type :ok :process 5 :value [[:r 5 [303 304 604 6 306 509 909 409 912 > 411 514 415 719 419 19 623 22 425 24 926 25 832 130 733 430 533 29 933 333 > 537 934 538 740 139 744 938 544 42 646 749 242 546 547 548 753 450 150 349 48 > 852 352 553 455]]] :tid 9 :n 53 :time 1692607286281483026} > {:type :invoke :process 9 :value [[:r 5 nil]] :tid 1 :n 56 > :time 1692607286284097561} > {:type :ok :process 9 :value [[:r 5 [303 304 604 6 306 509 909 409 912 > 411 514 415 719 419 19 623 22 425 24 926 25 832 130 733 430 533 29 933 333 > 537 934 538 740 139 744 938 544 42 646 749 242 546 547 548 753 450 150 349 48 > 852 352 553 455]]] :tid 1 :n 56 :time 1692607286306445242} > {code} > Processes process 6 and process 7 are appending the values 553 and 455 > respectively. 455 succeeded and a read by process 5 confirms that. But then > also 553 is appended and a read by process 1 confirms that as well, however > it sees 553 before 455. > process 5 reads [... 852 352 455] where as process 1 reads [... 852 352 553 > 455] and the latter order is returned in subsequent reads as well. > [~blambov] suggested that one reason for that behavior could be the way how > unfrozen lists are updated. The backing datatype is a _kind of a map_ which > uses insertion timestamps as indexes which are used to sort the list when the > list is composed from chunks from various sources/sstables before being > returned to the client. > In such a case it indeed can happen, that process 5 reads [... 852 352 455] > but later process 1 reads [... 852 352 553 455] because 553 has been > _appended_ with an earlier timestamp than 455 but it has been _committed_ > with a later timestamp. > Now with Accord we have the timestamp _of the transaction_ at hand. Could > Accord use that for the index instead? Which would lead to the correct > behavior? The value 553 has been appended after 455 and using the transaction > id/timestamp as the list index would place it properly in the underlying map, > wouldn't it? > Steps to reproduce: > > {code:java} > git clone https://github.com/datastax/accordclient.git > git checkout append-to-list-index > lein run --list-append -t 10 -r 1,2,3,4,5 -n 1000 -H <host-ips> -s `date > +%s%N` > test-la.edn > > curl -L -o elle-cli.zip > https://github.com/ligurio/elle-cli/releases/download/0.1.6/elle-cli-bin-0.1.6.zip > unzip -d elle-cli elle-cli.zip > java -jar elle-cli/target/elle-cli-0.1.6-standalone.jar --model list-append > --anomalies G0 --consistency-models strict-serializable --directory out-la > --verbose test-la.edn > {code} > -- This message was sent by Atlassian Jira (v8.20.10#820010) --------------------------------------------------------------------- To unsubscribe, e-mail: commits-unsubscr...@cassandra.apache.org For additional commands, e-mail: commits-h...@cassandra.apache.org