From c71d374df83d029220453e46bfa2186febcbff0e Mon Sep 17 00:00:00 2001 From: Marc Lopez Rubio Date: Wed, 2 Jul 2025 23:51:48 +0200 Subject: [PATCH] Add APM Server known issue for TBS (#4862) * Add APM Server known issue for TBS Signed-off-by: Marc Lopez Rubio * Apply suggestions from code review Co-authored-by: Colleen McGinnis --------- Signed-off-by: Marc Lopez Rubio Co-authored-by: Brandon Morelli Co-authored-by: Colleen McGinnis (cherry picked from commit ed75d36fa5094b21c291664110521aa46f8eb64c) --- docs/en/observability/apm/known-issues.asciidoc | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/docs/en/observability/apm/known-issues.asciidoc b/docs/en/observability/apm/known-issues.asciidoc index 94e8828871..21040409b0 100644 --- a/docs/en/observability/apm/known-issues.asciidoc +++ b/docs/en/observability/apm/known-issues.asciidoc @@ -21,6 +21,17 @@ _Versions: XX.XX.XX, YY.YY.YY, ZZ.ZZ.ZZ_ // If applicable, link to fix //// +[discrete] +== Tail Sampling may not compact / expired TTLs as quickly as desired, causing increased storage usage. + +_Elastic Stack versions: All 8.x versions_ + +There are some issues with the tail sampling implementation in all 8.x versions that may prevent buffered traces from being compacted or expired as quickly as expected. This can lead to increased storage usage for longer than the default 30m TTL. + +This may manifest in two ways, increased value log (vlog) file size and increased SST (LSM) file size. LSM growth and late compaction is particularly troublesome given how the underlying K/V database performs compactions on its layers. There is noticeable LSM growth for use-cases where traces are under 1KB in size, since they are written to the LSM layer directly. + +This issue is fixed in 9.0.0, due to a re-implementation of how the underlying tail sampling databases are used. The new implementation uses a more efficient partitioning scheme, allowing more efficient expiration of traces. + [discrete] == APM Server v8.6.x and prior with Elasticsearch v8.15.x and later has broken APM UI