--- title: Migration sort_rank: 10 --- # Prometheus 3.0 migration guide In line with our [stability promise](https://prometheus.io/docs/prometheus/latest/stability/), the Prometheus 3.0 release contains a number of backwards incompatible changes. This document offers guidance on migrating from Prometheus 2.x to Prometheus 3.0 and newer versions. ## Flags - The following feature flags have been removed and they have been added to the default behavior of Prometheus v3: - `promql-at-modifier` - `promql-negative-offset` - `remote-write-receiver` - `new-service-discovery-manager` - `expand-external-labels` Environment variable references `${var}` or `$var` in external label values are replaced according to the values of the current environment variables. References to undefined variables are replaced by the empty string. The `$` character can be escaped by using `$$`. - `no-default-scrape-port` Prometheus v3 will no longer add ports to scrape targets according to the specified scheme. Target will now appear in labels as configured. If you rely on scrape targets like `https://example.com/metrics` or `http://exmaple.com/metrics` to be represented as `https://example.com/metrics:443` and `http://example.com/metrics:80` respectively, add them to your target URLs - `agent` Instead use the dedicated `--agent` CLI flag. Prometheus v3 will log a warning if you continue to pass these to `--enable-feature`. ## Configuration - The scrape job level configuration option `scrape_classic_histograms` has been renamed to `always_scrape_classic_histograms`. If you use the `--enable-feature=native-histograms` feature flag to ingest native histograms and you also want to ingest classic histograms that an endpoint might expose along with native histograms, be sure to add this configuration or change your configuration from the old name. - The `http_config.enable_http2` in `remote_write` items default has been changed to `false`. In Prometheus v2 the remote write http client would default to use http2. In order to parallelize multiple remote write queues across multiple sockets its preferable to not default to http2. If you prefer to use http2 for remote write you must now set `http_config.enable_http2: true` in your `remote_write` configuration section. ## PromQL - The `.` pattern in regular expressions in PromQL matches newline characters. With this change a regular expressions like `.*` matches strings that include `\n`. This applies to matchers in queries and relabel configs. For example the following regular expressions now match the accompanying strings, whereas in Prometheus v2 these combinations didn't match. | Regex | Additional matches | | ----- | ------ | | ".*" | "foo\n", "Foo\nBar" | | "foo.?bar" | "foo\nbar" | | "foo.+bar" | "foo\nbar" | If you want Prometheus v3 to behave like v2 did, you will have to change your regular expressions by replacing all `.` patterns with `[^\n]`, e.g. `foo[^\n]*`. - Lookback and range selectors are left open and right closed (previously left closed and right closed). This change affects queries when the evaluation time perfectly aligns with the sample timestamps. For example assume querying a timeseries with evenly spaced samples exactly 1 minute apart. Before Prometheus v3, a range query with `5m` would usually return 5 samples. But if the query evaluation aligns perfectly with a scrape, it would return 6 samples. In Prometheus v3 queries like this will always return 5 samples. This change has likely few effects for everyday use, except for some subquery use cases. Query front-ends that align queries usually align subqueries to multiples of the step size. These subqueries will likely be affected. Tests are more likely to affected. To fix those either adjust the expected number of samples or extend the range by less than one sample interval. - The `holt_winters` function has been renamed to `double_exponential_smoothing` and is now guarded by the `promql-experimental-functions` feature flag. If you want to keep using `holt_winters`, you have to do both of these things: - Rename `holt_winters` to `double_exponential_smoothing` in your queries. - Pass `--enable-feature=promql-experimental-functions` in your Prometheus CLI invocation. ## Scrape protocols Prometheus v3 is more strict concerning the Content-Type header received when scraping. Prometheus v2 would default to the standard Prometheus text protocol if the target being scraped did not specify a Content-Type header or if the header was unparsable or unrecognised. This could lead to incorrect data being parsed in the scrape. Prometheus v3 will now fail the scrape in such cases. If a scrape target is not providing the correct Content-Type header the fallback protocol can be specified using the `fallback_scrape_protocol` parameter. See [Prometheus scrape_config documentation.](https://prometheus.io/docs/prometheus/latest/configuration/configuration/#scrape_config) This is a breaking change as scrapes that may have succeeded with Prometheus v2 may now fail if this fallback protocol is not specified. ## Miscellaneous ### TSDB format and downgrade The TSDB format has been changed in Prometheus v2.55 in preparation for changes to the index format. Consequently, a Prometheus v3 TSDB can only be read by a Prometheus v2.55 or newer. Before upgrading to Prometheus v3 please upgrade to v2.55 first and confirm Prometheus works as expected. Only then continue with the upgrade to v3. ### TSDB storage contract TSDB compatible storage is now expected to return results matching the specified selectors. This might impact some third party implementations, most likely implementing `remote_read`. This contract is not explicitly enforced, but can cause undefined behavior. ### UTF-8 names Prometheus v3 supports UTF-8 in metric and label names. This means metric and label names can change after upgrading according to what is exposed by endpoints. Furthermore, metric and label names that would have previously been flagged as invalid no longer will be. Users wishing to preserve the original validation behavior can update their Prometheus yaml configuration to specify the legacy validation scheme: ``` global: metric_name_validation_scheme: legacy ``` Or on a per-scrape basis: ``` scrape_configs: - job_name: job1 metric_name_validation_scheme: utf8 - job_name: job2 metric_name_validation_scheme: legacy ``` ### Log message format Prometheus v3 has adopted `log/slog` over the previous `go-kit/log`. This results in a change of log message format. An example of the old log format is: ``` ts=2024-10-23T22:01:06.074Z caller=main.go:627 level=info msg="No time or size retention was set so using the default time retention" duration=15d ts=2024-10-23T22:01:06.074Z caller=main.go:671 level=info msg="Starting Prometheus Server" mode=server version="(version=, branch=, revision=91d80252c3e528728b0f88d254dd720f6be07cb8-modified)" ts=2024-10-23T22:01:06.074Z caller=main.go:676 level=info build_context="(go=go1.23.0, platform=linux/amd64, user=, date=, tags=unknown)" ts=2024-10-23T22:01:06.074Z caller=main.go:677 level=info host_details="(Linux 5.15.0-124-generic #134-Ubuntu SMP Fri Sep 27 20:20:17 UTC 2024 x86_64 gigafips (none))" ``` a similar sequence in the new log format looks like this: ``` time=2024-10-24T00:03:07.542+02:00 level=INFO source=/home/user/go/src/github.com/prometheus/prometheus/cmd/prometheus/main.go:640 msg="No time or size retention was set so using the default time retention" duration=15d time=2024-10-24T00:03:07.542+02:00 level=INFO source=/home/user/go/src/github.com/prometheus/prometheus/cmd/prometheus/main.go:681 msg="Starting Prometheus Server" mode=server version="(version=, branch=, revision=7c7116fea8343795cae6da42960cacd0207a2af8)" time=2024-10-24T00:03:07.542+02:00 level=INFO source=/home/user/go/src/github.com/prometheus/prometheus/cmd/prometheus/main.go:686 msg="operational information" build_context="(go=go1.23.0, platform=linux/amd64, user=, date=, tags=unknown)" host_details="(Linux 5.15.0-124-generic #134-Ubuntu SMP Fri Sep 27 20:20:17 UTC 2024 x86_64 gigafips (none))" fd_limits="(soft=1048576, hard=1048576)" vm_limits="(soft=unlimited, hard=unlimited)" ``` ### `le` and `quantile` label values In Prometheus v3, the values of the `le` label of classic histograms and the `quantile` label of summaries are normalized upon ingestion. In Prometheus v2 the value of these labels depended on the scrape protocol (protobuf vs text format) in some situations. This led to label values changing based on the scrape protocol. E.g. a metric exposed as `my_classic_hist{le="1"}` would be ingested as `my_classic_hist{le="1"}` via the text format, but as `my_classic_hist{le="1.0"}` via protobuf. This changed the identity of the metric and caused problems when querying the metric. In Prometheus v3 these label values will always be normalized to a float like representation. I.e. the above example will always result in `my_classic_hist{le="1.0"}` being ingested into prometheus, no matter via which protocol. The effect of this change is that alerts, recording rules and dashboards that directly reference label values as whole numbers such as `le="1"` will stop working. Ways to deal with this change either globally or on a per metric basis: - Fix references to integer `le`, `quantile` label values, but otherwise do nothing and accept that some queries that span the transition time will produce inaccurate or unexpected results. _This is the recommended solution._ - Use `metric_relabel_config` to retain the old labels when scraping targets. This should **only** be applied to metrics that currently produce such labels. ```yaml metric_relabel_configs: - source_labels: - quantile target_label: quantile regex: (\d+)\.0+ - source_labels: - le - __name__ target_label: le regex: (\d+)\.0+;.*_bucket ``` # Prometheus 2.0 migration guide For the Prometheus 1.8 to 2.0 please refer to the [Prometheus v2.55 documentation](https://prometheus.io/docs/prometheus/2.55/migration/).