In this lesson, you will learn how to maintain the precision of kernel-generated telemetry as it moves from the eBPF map into your centralized monitoring backend.
When we extract data from the kernel using eBPF, we are essentially sampling the internal state of the OS. The transition from the high-velocity kernel space to user-space collectors—and eventually to a time-series database—introduces several risks to data integrity, primarily due to buffer overflows, event drops, and clock synchronization issues.
Avoiding Race Conditions in BPF Maps
A common integrity failure occurs when reading from an eBPF map while the kernel is concurrently updating it. If you rely on bpf_map_lookup_elem, you might capture a "torn read" or an incomplete metric update. To ensure integrity, use per-CPU maps. By assigning each CPU its own memory area for counters or histograms, you eliminate contention during the write phase.
When aggregating these at the user-space agent level, you must ensure your aggregation logic accounts for the specific timestamp of when each CPU processed the event, rather than simply summing them at the time of the scrape.
Handling Buffer Overflows
If your eBPF program pushes events via a perf or ring buffer, a sudden spike in traffic can cause the kernel to drop events, creating gaps in your observability pipeline. To maintain integrity, implement a robust backpressure mechanism or use bpf_ringbuf_output. Unlike the older perf buffer, the ringbuf allows for better memory efficiency and reduces dropped events by enabling non-blocking writes that respect memory constraints:
// Example of ensuring data delivery via ringbuf
struct data_t *e = bpf_ringbuf_reserve(&my_map, sizeof(*e), 0);
if (e) {
e->value = bpf_ktime_get_ns();
bpf_ringbuf_submit(e, 0);
}
By ensuring that each event is timestamped at the moment of kernel interception using bpf_ktime_get_ns(), you decouple the metric's "source-of-truth" time from the time it arrives at your storage backend, preventing jitter and data skew during transit.
Key Takeaway: To ensure data integrity, utilize per-CPU maps to eliminate contention and capture high-resolution timestamps directly in the kernel to prevent temporal drift during ingestion.