Re: [go-nuts] Memory leak from sqlite3 leads to go runtime?

[Robert Engels]

I suspect that they added the SetFinalizer calls to help those using that driver that weren’t properly managing the driver resources (connections, queries, etc. ).  On Mar 9, 2025, at 10:52 PM, 'Michael Knyszek' via golang-nuts <golang-nuts@googlegroups.com> wrote: I suspect this fact is going to be the most relevant thing to your investigation: > Upgrading the sqlite3 driver which had one non-negligible change: adding SetFinalizer to all these objects.  See https://go.dev/doc/gc-guide#Common_finalizer_issues for a variety of ways finalizers can cause leaks (on both the Go and C side). Go 1.24's cleanups (runtime.AddCleanup) might work be better, provided a deterministic execution order isn't required. (This point might be moot since it's in go-sqlite3, which sounds like it's something you don't have control over.) I have a patch that provides a finalizer/cleanup leak detector by setting GODEBUG=detectcleanupleaks=1, if you want to try it. It's https://go.dev/cl/634599. Happy to explain how to patch and build the Go toolchain if you're up for it. On Sunday, March 9, 2025 at 5:49:03 PM UTC-4 robert engels wrote: Looks to me like you are reading a lot of rows under a lock, and never releasing the lock, so the rows remain in memory. I don’t know the internals of the SQLite very well, but my understanding is that it is not really a “driver” in the traditional sense that communicates with a db - but rather it is the implementation as well. Since it is the implementation, holding the lock seems reasonable to also hold the rows. On Mar 9, 2025, at 2:59 PM, Gavra <gav...@gmail.com> wrote: Hi, So we have been trying really hard to understand a major leak in our product. We are using this sqlite3 driver: https://github.com/mattn/go-sqlite3 The pprof heap profile indicates the source is the call to SQLiteRows.Columns func and two additional calls, one on SQLiteStmt and the other on SQLiteConn. According to the code 1. SQLiteRows references SQLiteStmt which then references to SQLiteConn 2. The SQLiteRows instance is the sole object holding a ref to the allocation by Columns(). This is a strong indication that refs to SQLiteRows are leaked. We can confirm the leak is increasing over time and does not appear to reflect a burst or large data. We thought we forgot to close rows or somehow appened refs to rows etc but we ruled it out completely since. Note the heap profile only shows SQLite allocations, no app objects allocated. We verified that forgetting to call SQLiteRows.Close leaks only memory in CGO which means it is not visible in the heap profile. So on one hand we are convinced someone is holding a reference to SQLiteRows but on the other hand it is not our application and not the SQLite driver. We tracked back our source code changes and noticed that correlate to the appearance of this issue: 1. Upgrading go: 1.22.6 to 1.22.9 2. Upgrading the sqlite3 driver which had one non-negligible change: adding SetFinalizer to all these objects.  This is a very weird thing to suggest, but we think this could be caused by the go runtime, somehow. I attached a screenshot of the heap profile, focused on the major leak around the sqlite3 driver. (our current plans is to use goref or dlv on a core dump to understand who is holding these references but that could take a few more days). Thank you. -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts...@googlegroups.com. To view this discussion visit https://groups.google.com/d/msgid/golang-nuts/8a8b608b-e501-403a-b7a7-0d0bda657e4cn%40googlegroups.com. <Screenshot 2025-03-09 at 21.40.22.png> -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. To view this discussion visit https://groups.google.com/d/msgid/golang-nuts/b5c236d6-1a90-4776-b33b-1234d0b58e02n%40googlegroups.com. -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. To view this discussion visit https://groups.google.com/d/msgid/golang-nuts/2B907B52-C0D4-4C42-8513-95BA4BFF3CF0%40ix.netcom.com.