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Posted to users@pulsar.apache.org by Apache Pulsar Slack <ap...@gmail.com> on 2020/10/10 09:11:05 UTC
Slack digest for #general - 2020-10-10
2020-10-09 10:03:40 UTC - Amir Kadoorie: @Amir Kadoorie has joined the channel
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2020-10-09 10:58:49 UTC - yaodr: @yaodr has joined the channel
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2020-10-09 12:15:26 UTC - Marcio Martins: Ok, so I increased resources, now they can go up to 16gb and 4 cores, and I removed all non-essential traffic from the cluster, so now there is only 1 topic, with 1 producer, producing ~ 5Mbits/per sec - I would say this is over provisioned (9x bookie, 5x broker, 3x zk). Those 2 bookies are still consuming 100% CPU (1 core) and now about 3gb of memory. If I turn off auto-recovery it goes back to normal. I think you are right that the issue is the cpu and memory usage, but it seems like the trigger for that is the auto-recovery.
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2020-10-09 12:31:55 UTC - Marcio Martins: I just manually deleted those two ledgers and it all went back to normal...
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2020-10-09 12:32:10 UTC - Marcio Martins: I guess there is a bug somewhere in the bookies, which might be fixed by that commit I linked.
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2020-10-09 13:33:44 UTC - Marcio Martins: Thanks @Sijie Guo
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2020-10-09 13:36:12 UTC - Frank Kelly: Hey Addison - Good morning - I might have found something in relation to message ordering with Async Send. I setup a test program here <https://github.com/kellyfj/message-ordering> and can reproduce the problem. Before I filed an issue I want to see if there was anything obvious to you that I was doing incorrectly (probably!). Let me know if you have any questions.
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2020-10-09 14:37:11 UTC - Sijie Guo: @Penghui Li
+1 : Lari Hotari
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2020-10-09 16:26:41 UTC - Alan Hoffmeister: I've created low level bindings for calling libpulsar inside Rust :slightly_smiling_face:
<https://docs.rs/pulsar-sys/2.6.1/pulsar_sys/>
+1 : flafik, Sijie Guo
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2020-10-09 19:54:05 UTC - Andrew Jacobs: @Andrew Jacobs has joined the channel
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2020-10-09 20:23:38 UTC - Lari Hotari: ```root@somehost/pulsar# /tmp/async-profiler-1.8.1-linux-x64/profiler.sh -d 15 -e org.apache.bookkeeper.mledger.impl.ManagedLedgerImpl.startReadOperationOnLedger 1
Started [org.apache.bookkeeper.mledger.impl.ManagedLedgerImpl.startReadOperationOnLedger] profiling
--- Execution profile ---
Total samples : 13176152
skipped : 57730 (0.44%)
Frame buffer usage : 0.0011%
--- 13118422 calls (100.00%), 13118422 samples
[ 0] org.apache.bookkeeper.mledger.impl.ManagedLedgerImpl.startReadOperationOnLedger
[ 1] org.apache.bookkeeper.mledger.impl.OpReadEntry.lambda$checkReadCompletion$1
[ 2] org.apache.bookkeeper.mledger.impl.OpReadEntry$$Lambda$822.800251664.run
[ 3] org.apache.bookkeeper.mledger.util.SafeRun$1.safeRun
[ 4] org.apache.bookkeeper.common.util.SafeRunnable.run
[ 5] org.apache.bookkeeper.common.util.OrderedExecutor$TimedRunnable.run
[ 6] org.apache.bookkeeper.common.util.OrderedExecutor$TimedRunnable.run
[ 7] java.util.concurrent.ThreadPoolExecutor.runWorker
[ 8] java.util.concurrent.ThreadPoolExecutor$Worker.run
[ 9] io.netty.util.concurrent.FastThreadLocalRunnable.run
[10] java.lang.Thread.run
calls percent samples top
---------- ------- ------- ---
13118422 100.00% 13118422 org.apache.bookkeeper.mledger.impl.ManagedLedgerImpl.startReadOperationOnLedger```
I haven't been able to reproduce the issue yet in a development environment. In the k8s based 3 zk, 3 bookie, 3 broker cluster, I still have one broker where the problem is ongoing after about 36 hours. It seems that async-profiler (<https://github.com/jvm-profiling-tools/async-profiler>) is the most effective tool for debugging such problems. I copied the async-profiler binaries directly to the rootfs of the broker container's under /tmp and then opened a shell inside the Pulsar broker container to run async-profiler commands. Async profiler can also observe a single method. In the above example, I observed org.apache.bookkeeper.mledger.impl.ManagedLedgerImpl.startReadOperationOnLedger method calls. async-profiler detected 13118422 calls in 15 seconds (874561op/s). It seems like an extremely tight loop. Looks like 8 cores are running full out since top on the k8s worker node show 700-800% CPU consumption.
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2020-10-09 20:25:53 UTC - Addison Higham: hey @Frank Kelly I just wanted to acknowledge this, I downloaded the repo but haven't had a chance to dig in
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2020-10-09 20:26:31 UTC - Frank Kelly: No worries - I have a workaround - it's probably something silly I did in code but just in case it's not I figured I'd share
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2020-10-09 20:50:56 UTC - Lari Hotari: This verifies that no new calls are arriving. org.apache.bookkeeper.mledger.impl.ManagedCursorImpl.asyncReadEntries is not called at all.
```root@somehost:/pulsar# /tmp/async-profiler-1.8.1-linux-x64/profiler.sh -d 15 -e org.apache.bookkeeper.mledger.impl.ManagedCursorImpl.asyncReadEntries 1
Started [org.apache.bookkeeper.mledger.impl.ManagedCursorImpl.asyncReadEntries] profiling
--- Execution profile ---
Total samples : 0
Frame buffer usage : 0%
calls percent samples top
---------- ------- ------- ---```
neither is org.apache.bookkeeper.mledger.impl.ManagedCursorImpl.asyncReadEntriesOrWait called:
```root@somehost:/pulsar# /tmp/async-profiler-1.8.1-linux-x64/profiler.sh -d 15 -e org.apache.bookkeeper.mledger.impl.ManagedCursorImpl.asyncReadEntriesOrWait 1
Started [org.apache.bookkeeper.mledger.impl.ManagedCursorImpl.asyncReadEntriesOrWait] profiling
--- Execution profile ---
Total samples : 0
Frame buffer usage : 0%
calls percent samples top
---------- ------- ------- ---```
This proves that there are entries circulating in a tight loop.
The tight loop can be seen in these stacktraces and by looking at the code:
```root@somehost:/pulsar# /tmp/async-profiler-1.8.1-linux-x64/profiler.sh -d 15 -e org.apache.bookkeeper.mledger.impl.OpReadEntry.checkReadCompletion 1
Started [org.apache.bookkeeper.mledger.impl.OpReadEntry.checkReadCompletion] profiling
--- Execution profile ---
Total samples : 13613401
skipped : 48177 (0.35%)
Frame buffer usage : 0.0026%
--- 13565114 calls (100.00%), 13565114 samples
[ 0] org.apache.bookkeeper.mledger.impl.OpReadEntry.checkReadCompletion
[ 1] org.apache.bookkeeper.mledger.impl.ManagedLedgerImpl.internalReadFromLedger
[ 2] org.apache.bookkeeper.mledger.impl.ManagedLedgerImpl.asyncReadEntries
[ 3] org.apache.bookkeeper.mledger.impl.OpReadEntry.lambda$checkReadCompletion$1
[ 4] org.apache.bookkeeper.mledger.impl.OpReadEntry$$Lambda$1087.1120645357.run
[ 5] org.apache.bookkeeper.mledger.util.SafeRun$1.safeRun
[ 6] org.apache.bookkeeper.common.util.SafeRunnable.run
[ 7] org.apache.bookkeeper.common.util.OrderedExecutor$TimedRunnable.run
[ 8] org.apache.bookkeeper.common.util.OrderedExecutor$TimedRunnable.run
[ 9] java.util.concurrent.ThreadPoolExecutor.runWorker
[10] java.util.concurrent.ThreadPoolExecutor$Worker.run
[11] io.netty.util.concurrent.FastThreadLocalRunnable.run
[12] java.lang.Thread.run
--- 110 calls (0.00%), 110 samples
[ 0] org.apache.bookkeeper.mledger.impl.OpReadEntry.checkReadCompletion
[ 1] org.apache.bookkeeper.mledger.impl.ManagedLedgerImpl.internalReadFromLedger
[ 2] org.apache.bookkeeper.mledger.impl.ManagedLedgerImpl.asyncReadEntries
[ 3] org.apache.bookkeeper.mledger.impl.OpReadEntry.lambda$checkReadCompletion$1
[ 4] org.apache.bookkeeper.mledger.impl.OpReadEntry$$Lambda$822.800251664.run
[ 5] org.apache.bookkeeper.mledger.util.SafeRun$1.safeRun
[ 6] org.apache.bookkeeper.common.util.SafeRunnable.run
[ 7] org.apache.bookkeeper.common.util.OrderedExecutor$TimedRunnable.run
[ 8] org.apache.bookkeeper.common.util.OrderedExecutor$TimedRunnable.run
[ 9] java.util.concurrent.ThreadPoolExecutor.runWorker
[10] java.util.concurrent.ThreadPoolExecutor$Worker.run
[11] io.netty.util.concurrent.FastThreadLocalRunnable.run
[12] java.lang.Thread.run
calls percent samples top
---------- ------- ------- ---
13565224 100.00% 13565224 org.apache.bookkeeper.mledger.impl.OpReadEntry.checkReadCompletion```
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2020-10-09 20:50:56 UTC - Lari Hotari: Would it be possible that one of the authors of "Managed Ledger" could take a look? Is there something in the solution that could cause a tight loop that I'm observing. @Matteo Merli? @Rajan Dhabalia? @xiaolong.ran ? Some recent modifications in this <https://github.com/apache/pulsar/commit/c635d08a448f7b2a4868bb6aefc13dd5f17000a1> (since 2.5.0)
<https://github.com/apache/pulsar/commit/45ee784f5ef92fc25e970bbf0be34412472173b1> (since 2.6.0)
I'm sorry I haven't yet been able to reproduce and isolate the issue. I seem to run into some other bugs when I tried to isolate and reproduce this issue... :slightly_smiling_face:
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2020-10-09 20:52:59 UTC - Lari Hotari: There's a lot of information bits in this thread about the issue. For example, I uploaded quite a few thread dumps to a GH gist.
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2020-10-09 20:57:29 UTC - Lari Hotari: If someone is wondering why I'm posting this information in this thread is that I have one broker running in a tight loop currently and I can easily observe it now since it's in the problem state. I cannot attach a debugger to the process. The only way to debug it seems to be the async-profiler and it's awesome features.
One more profiling from async-profiler to verify whether OpReadEntry.readEntriesFailed gets called. No it doesn't:
```root@somehost:/pulsar# /tmp/async-profiler-1.8.1-linux-x64/profiler.sh -d 15 -e org.apache.bookkeeper.mledger.impl.OpReadEntry.readEntriesFailed 1
Started [org.apache.bookkeeper.mledger.impl.OpReadEntry.readEntriesFailed] profiling
--- Execution profile ---
Total samples : 0
Frame buffer usage : 0%
calls percent samples top
---------- ------- ------- ---```
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2020-10-09 21:10:22 UTC - Lari Hotari: I also extracted some data from the heapdump using Eclipse MAT's OQL: <https://gist.github.com/lhotari/41a4f86ca45018c0c54f479c9af3d4e5> . I believe that the information can be used to understand why the code chooses certain branches and runs into an infinite loop. However there might be something else going on, for example that the topic has been deleted. In the current case, topics are getting deleted using the forceful flag. I wonder if deleting a topic in a forceful way could trigger the infinite looping behavior?
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2020-10-09 21:12:07 UTC - Alexandre DUVAL: Did you know <https://github.com/wyyerd/pulsar-rs|https://github.com/wyyerd/pulsar-rs>?
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2020-10-09 21:56:06 UTC - Lari Hotari: one more profiling to determine the branch chosen in org.apache.bookkeeper.mledger.impl.ManagedCursorImpl#hasMoreEntries()
```root@somehost:/pulsar# /tmp/async-profiler-1.8.1-linux-x64/profiler.sh -d 15 -e org.apache.bookkeeper.mledger.impl.ManagedLedgerImpl.getNextValidPosition 1
Started [org.apache.bookkeeper.mledger.impl.ManagedLedgerImpl.getNextValidPosition] profiling
--- Execution profile ---
Total samples : 0
Frame buffer usage : 0%
calls percent samples top
---------- ------- ------- ---
root@somehost:/pulsar# /tmp/async-profiler-1.8.1-linux-x64/profiler.sh -d 15 -e org.apache.bookkeeper.mledger.impl.ManagedCursorImpl.hasMoreEntries 1
Started [org.apache.bookkeeper.mledger.impl.ManagedCursorImpl.hasMoreEntries] profiling
--- Execution profile ---
Total samples : 12220914
skipped : 36586 (0.30%)
Frame buffer usage : 0.0014%
--- 12184328 calls (100.00%), 12184328 samples
[ 0] org.apache.bookkeeper.mledger.impl.ManagedCursorImpl.hasMoreEntries
[ 1] org.apache.bookkeeper.mledger.impl.OpReadEntry.checkReadCompletion
[ 2] org.apache.bookkeeper.mledger.impl.ManagedLedgerImpl.internalReadFromLedger
[ 3] org.apache.bookkeeper.mledger.impl.ManagedLedgerImpl.asyncReadEntries
[ 4] org.apache.bookkeeper.mledger.impl.OpReadEntry.lambda$checkReadCompletion$1
[ 5] org.apache.bookkeeper.mledger.impl.OpReadEntry$$Lambda$1108.1400779947.run
[ 6] org.apache.bookkeeper.mledger.util.SafeRun$1.safeRun
[ 7] org.apache.bookkeeper.common.util.SafeRunnable.run
[ 8] org.apache.bookkeeper.common.util.OrderedExecutor$TimedRunnable.run
[ 9] org.apache.bookkeeper.common.util.OrderedExecutor$TimedRunnable.run
[10] java.util.concurrent.ThreadPoolExecutor.runWorker
[11] java.util.concurrent.ThreadPoolExecutor$Worker.run
[12] io.netty.util.concurrent.FastThreadLocalRunnable.run
[13] java.lang.Thread.run
calls percent samples top
---------- ------- ------- ---
12184328 100.00% 12184328 org.apache.bookkeeper.mledger.impl.ManagedCursorImpl.hasMoreEntries
root@somehost:/pulsar# /tmp/async-profiler-1.8.1-linux-x64/profiler.sh -d 15 -e org.apache.bookkeeper.mledger.impl.ManagedCursorImpl.getNumberOfEntries 1
Started [org.apache.bookkeeper.mledger.impl.ManagedCursorImpl.getNumberOfEntries] profiling
--- Execution profile ---
Total samples : 0
Frame buffer usage : 0%
calls percent samples top
---------- ------- ------- ---```
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2020-10-09 22:05:28 UTC - Lari Hotari: By reading the code and trying to understand what it does, it seems that the "forceful topic deletion" changes on the broker side (<https://github.com/apache/pulsar/commit/35b67b0ec1fdba3baab1927095086a44c8ada174>) could be the one that triggers the behavior. In my case, the application code sets the force flag to true when some temporary topics get deleted. That is part of the load test in question. Is the forceful topic deletion feature a "last resort" type of thing and it shouldn't be used in normal cases at all? The forceful deletion feature seems to have been around forever (since <https://github.com/apache/pulsar/pull/1656>).
How could the Managed ledger get into the state that it thinks that more entries are arriving, but nothing ever comes? :thinking_face:
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2020-10-09 23:35:40 UTC - Lari Hotari: I'm trying to answer the question to myself. :slightly_smiling_face: the usage of `cursor.hasMoreEntries()` in `org.apache.bookkeeper.mledger.impl.OpReadEntry#checkReadCompletion` looks wrong.
In the table of data extracted from the heap dump, I can see that OpRead.readPosition.ledgerId != OpRead.cursor.readPosition.ledgerId and OpRead.nextReadPosition.ledgerId != OpRead.cursor.ledger.lastConfirmedEntry.ledgerId (cursor write position) .
Based on this data, I would understand that calling cursor.hasMoreEntries() without passing the OpRead's readPosition's ledger id is the wrong thing to do. I feel pretty confident so I'll file a bug in Github. /cc @Sijie Guo @Addison Higham
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2020-10-09 23:49:40 UTC - Alan Hoffmeister: yup! I've helped fixing some bugs in that project already :slightly_smiling_face:
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2020-10-09 23:50:38 UTC - Alan Hoffmeister: but I'm trying to learn rust so I thought using the native libpulsar would be a good side-project
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2020-10-10 00:03:48 UTC - Addison Higham: Wow, this looks pretty comprehensive, sounds like a good path, we will get this in front of the team early next week
+1 : Lari Hotari
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2020-10-10 00:04:02 UTC - Alexandre DUVAL: Oh cool! Was just a tip in case you didnt.
+1 : Alan Hoffmeister
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2020-10-10 00:05:58 UTC - Lari Hotari: I created <https://github.com/apache/pulsar/issues/8229>
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2020-10-10 02:15:00 UTC - Chloe: Last 5 days to submit your presentation for Pulsar Summit Asia 2020: <https://pulsar-summit.org/en/event/asia-2020/cfp>, CFP closes on Oct 14, 9am PT.
At the mean time, don't forget to sign up: <https://hopin.to/events/pulsar-summit-asia-2020>
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2020-10-10 02:53:11 UTC - Sijie Guo: @Chloe don’t use `@ here`
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2020-10-10 04:03:11 UTC - Rattanjot Singh: Let's say I update a bookie with new configuration and the old bookie are with older configuration. Which configuration will be picked . What about the conflicts. What about the messages being stored.
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2020-10-10 04:04:58 UTC - Rattanjot Singh: What about other components like zookeeper ,broker and proxy.
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2020-10-10 05:09:57 UTC - stephen: @stephen has joined the channel
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