Documentation Grafana Tempo Release notes V2.8

Version 2.8 release notes

The Tempo team is pleased to announce the release of Tempo 2.8.

This release gives you:

• New TraceQL features such as most_recent, parent-span filters, sum_over_time, and topk/bottomk to help surface the exact spans and metrics you need.
• Concurrent block flushing, iterator optimizations, and back-pressure make ingestion and queries leaner and quicker.
• Safer defaults with port 3200, distroless images, Go 1.24, and an upgraded OTLP Collector tighten security and simplify ops.

These release notes highlight the most important features and bugfixes. For a complete list, refer to the Tempo changelog.

New language features for TraceQL

We’re excited to roll out three powerful enhancements to TraceQL, giving you more flexibility and performance when querying traces in Grafana Cloud with Tempo.

• Rank your metrics with new topk(n) and bottomk(n) functions to quickly get your highest and lowest ranking time series.
• Aggregate spans over time using sum_over_time() for built-in cumulative sums, such as total bytes, error counts.
• Fetch the latest traces first via the experimental most_recent=true query hint.

Ranking topk and bottomk functions for TraceQL metrics

When you’re looking at latency, error rates, or throughput across hundreds or thousands of services or endpoints, it’s easy to get lost in all the data. Previously, you’d have to pull back the full set of aggregates and then manually inspect or post‑process the results to find your worst offenders or best performers.

With topk(n) and bottomk(n), you can immediately narrow your focus to the top‑ or bottom‑ranked spans in a single, efficient query. This saves time and reduces the data volume you need to scan downstream.

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{} | avg_over_time(span:duration) by (span:name) | topk(10)
{} | count_over_time() by (span:name) | bottomk(10)

These are second stage functions used, where:

• topk(n) returns the n series with the highest values from a first‑stage aggregation.
• bottomk(n) returns the n series with the lowest values.

For more information, refer to the topk and bottomk documentation ( PR 4646).

The sum_over_time function for TraceQL metrics

The sum_over_time() function lets you aggregate numerical values by computing the sum value of them. The time interval that the sum is computed over is set by the step parameter.

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{ span.http.response_content_length > 0 } | sum_over_time(span.http.response_content_length)

With sum_over_time(), you can directly compute cumulative sums inside TraceQL, like total bytes transferred, total error counts, or resource consumption over time.

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{}  | sum_over_time(span.http.response_content_length)

For each step interval, sum_over_time(attr) totals the values of attr across all matching spans.

Refer to TraceQL metrics functions for more information. ( PR 4786)

Experimental query hint most_recent=true to retrieve the most recent traces

When troubleshooting a live incident or monitoring production health, you often need to see the absolute latest traces first. By default, Tempo’s query engine favors speed and returns the first N matching traces, which may not be the newest.

The most_recent hint ensures you’re always looking at the freshest data, so you can diagnose recent errors or performance regressions without missing anything due to early row‑limit cuts.

Examples:

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{} with (most_recent=true)
{ span.foo = "bar" } >> { status = error } with (most_recent=true)

With most_recent=true, Tempo performs a deeper search across data shards, retains the newest candidates, and returns traces sorted by start time rather than stopping at the first limit hit. ( PR 4238

The TraceQL query hint most_recent=true can be used with any TraceQL selection query to force Tempo to return the most recent results ordered by time.

For more information, refer to Retrieve most recent results (experimental).

Query by parent span ID

In addition, you can query by parent span id. Using span:parentID, you can ensure that you are looking at a child span of a specific parent, which is useful for example in span linking. Refer to the documentation for more information. ( PR 4692)

Major performance and memory usage improvements

Tempo 2.8 removes pooling for large traces. In testing, removing large pooling impacted memory, cutting memory high-water marks to less than half in a high traffic/tenant installation. Some amount of pooling is needed to keep CPU, throughput, and GC rate maintained. Now, we have a fixed 1M default allocation size, which covers most traces.

This graph illustrate the amount of memory used by the compactors. In one cell, we saw major improvements in compactor memory usage after PR 4985 was merged. Refer to PR 4985 for more information, including benchmarks and test results.

Performance improvements

TraceQL and Tempo generally see a number of performance improvements in this release. Refer to benchmarks in the PRs for additional information.

• Improve TraceQL performance by reverting EqualRowNumber to an inlineable function. ( PR 4705)
• Improve iterator performance by using max definition level to ignore parts of the RowNumber while nexting. Nexting is a function multiple in Tempo when you do a big query. Even minor improvements in nexting can have a major impact. ( PR 4753)
• Increase query-frontend default batch size. TraceQL performance has improved enough to pass larger batches than before and still complete all jobs on one querier. ( PR 4844)
• Improve Tempo build options. ( PR 4755)
• Rewrite traces using rebatching. ( PR 4690)
• Reorder span iterators. ( PR 4754)
• Improve memcached memory usage by pooling buffers. ( PR 4970)

Features and enhancements

This section highlights the most important features and enhancements in Tempo 2.8.

TraceQL correctness

One of our major focuses with this release has been to improve TraceQL’s performance and correctness. The following list summarizes some of the more important improvements.

• Fixed behavior for queries like {.foo && true} and {.foo || false}. ( PR 4855)
• Make comparison to nil symmetric. ( PR 4869)
• Corrected TraceQL incorrect results for additional spanset filters after a select operation. ( PR 4600)
• Fixed TraceQL metrics incorrect results for queries with multiple filters that reside in non-dedicated columns that also group by the same variable. ( PR 4887)
• Fixed metrics streaming for all non-trivial metrics. ( PR 4624)
• Fixed behavior of {} >> { span.attr-that-doesnt-exist != "foo" }. ( PR 5007)
• Fixed various edge cases for query range. ( PR 4962)
• Excluded nestedSetParent and other values from the compare() function. ( PR 5196)

The query frontend can cache job results for individual blocks when executing TraceQL. These bug fixes impact caching behavior.

• TraceQL results caching bug for floats ending in .0. ( PR 4539)
• Correctly cache frontend jobs for query range in TraceQL metrics. ( PR 4771)
• Fixed frontend cache key generation for TraceQL metrics queries to prevent collisions. ( PR 5017)

TraceQL exemplar improvements and bugfixes

Tempo 2.8 improves exemplars in TraceQL metrics.

• Distribute exemplars over time and hard limit the number of exemplars. ( PR 5158)
• Right exemplars for histogram and quantiles. ( PR 5145)
• Fixed for queried number of exemplars. ( PR 5115)

Security improvements

The following updates were made to address security issues:

• Use distroless base container images for improved security. ( PR 4556)
• Updated to go 1.24.3. ( PR 5110)

Improved error handling and logging

In addition, we’ve updated how Tempo handles errors so it’s easier to troubleshoot.

• Updated query range error message. ( PR 4929)
• Improved rate limit error message when traces size exceeds rate limit. ( PR 4986)
• Restored dedicated columns logging for completed blocks in the compactor. ( PR 4832)
• Query-frontend logs add a message to the log line. ( PR 4975)

Other enhancements and improvements

This release also has these notable updates.

• Added throughput SLO and metrics for the TraceByID endpoint. Configurable via the throughput_bytes_slo field, and it will populate op="traces" label in SLO and throughput metrics. ( PR 4668)
• Prevented queries in the ingester from blocking flushing traces to disk and memory spikes. ( PR 4483)
• Host Info Processor now tracks host identifying resource attribute in metric ( PR 5152)
• Added IPv6 support to the distributor. ( PR 4840)
• Added default mutex and blocking values. ( PR 4979)

Upgrade considerations

When upgrading to Tempo 2.8, be aware of these considerations and breaking changes.

Changed the default listening port

With Tempo 2.8, the default http_listen_port changes from 80 to 3200. Check the configuration options for the server: block in your Tempo configuration file.

yaml Copy

server:
    # HTTP server listen host
    [http_listen_address: <string>]

    # HTTP server listen port
    [http_listen_port: <int> | default = 3200]

Refer to issue 4945 for more information for the rationale. PR 4960

Removed Tempo serverless

Tempo serverless has been removed. The following configuration options are no longer valid and should be removed from your Tempo configuration. ( PR 4599)

yaml Copy

querier:
    search:
        prefer_self: <int>
        external_hedge_requests_at: <duration>
        external_hedge_requests_up_to:  <duration>
        external_backend: <string>
        google_cloud_run: <string>
        external_endpoints: <array>

In addition, these Tempo serverless related metrics have been removed: tempo_querier_external_endpoint_duration_seconds, tempo_querier_external_endpoint_hedged_roundtrips_total, and tempo_feature_enabled.

Updated, removed, or renamed configuration parameters

Other upgrade considerations

• Upgrade OTEL Collector to v0.122.1. The name dimension from tempo_receiver_accepted_span and tempo_receiver_refused_spans changes from tempo/jaeger_receiver to jaeger/jaeger_receiver. ( PR 4893)
• Replace opentracing-contrib/go-grpc by otelgrpc in Tempo query. ( PR 4958)
• Enforce max attribute size at event, link, and instrumentation scope. The configuration is now per-tenant. Renamed max_span_attr_byte to max_attribute_bytes. ( PR 4633)
• Converted SLO metric query_frontend_bytes_processed_per_second from a histogram to a counter as it’s more performant. ( PR 4748)
• Removed the OpenTelemetry Jaeger exporter, which has been deprecated. ( PR 4926)

Bugfixes

For a complete list, refer to the Tempo CHANGELOG.

• Chose a default step for a gRPC streaming query range request if none is provided. Correctly copy exemplars for metrics like | rate() when gRPC streaming. ( PR 4546)
• Fixed distributor issue where a hash collision could lead to spans stored incorrectly ( PR 5186)
• Added object name to cache key in ReadRange ( PR 4982)
• Fixed rare panic during compaction ( PR 4915)
• Returned the operand as the only value if the tag is already filtered in the query ( PR 4673)
• Included cost attribution when converting from default configuration to legacy one. ( PR 4787)
• Updated memcached to respect cancelled context to prevent panic. ( PR 5041)
• Fixed setting processors in user configurations overrides via API. ( PR 4741)
• Fixed panic on startup. ( PR 4744)
• Fixed intrinsic tag lookups dropped when max tag lookup response size is exceeded. ( PR 4784)
• Fixed error propagation in the SyncIterator. ( PR 5045)
• Fixed mixin to include otlp_v1_traces HTTP write route ( PR 5072)
• Fixed TempoBlockListRisingQuickly alert grouping. ( PR 4876)
• Fixed metrics generator host info processor overrides configuration. ( PR 5118)
• Fixed metrics generator target_info to skip attributes with no name to prevent downstream errors. ( PR 5148)