[bug] out of memory due to span data accumulation inside phoenix

[RogerHYang]

a user reporting that due to slow rate of postgres insertion, span data can accumulate inside phoenix, resulting in out of memory

[dosubot]

This can happen if the rate of span ingestion exceeds the rate at which Phoenix can insert spans into Postgres, causing in-memory buffers to grow until the process runs out of memory. There are several contributing factors and mitigations discussed in the Phoenix repo:

• Slow Postgres queries or contention (like deadlocks) can delay insertion, causing span data to accumulate in memory. Tuning your database (indexes, query plans, connection pooling, and affinity settings) can help reduce these bottlenecks example example.
• Phoenix recommends using batch processing for spans, with configurable batch size, timeout, and max batch size to help control memory usage. Place the batch processor after any memory limiter in your pipeline for best results details.
• There is no explicit buffer size or backpressure mechanism documented in Phoenix to prevent OOM if Postgres is slow, so tuning batch processor settings (batch size, queue size, export timeout) and scaling up memory or horizontally scaling Phoenix may be necessary for high-throughput workloads details.
• Optimizing queries and limiting the number of spans loaded or processed at once can help reduce memory pressure example.

If you need strict memory limits or backpressure, you may need to explore architectural changes or further configuration. Monitoring memory usage and database performance is key to preventing this scenario.

To reply, just mention @dosu.

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