feat(llmobs): track prompt caching for bedrock converse api

[lievan]

Tracks number of tokens read from and written to the prompt cache for bedrock converse api

https://docs.aws.amazon.com/bedrock/latest/userguide/prompt-caching.html

Bedrock returns cacheWrite/ReadInputTokenCount or cacheWrite/ReadInputTokens (not exactly sure why there are two names, but I believe they are the same)

We map these to cache_write/read_input_tokens keys in our metrics field.

Checklist

• [x] PR author has checked that all the criteria below are met
• The PR description includes an overview of the change
• The PR description articulates the motivation for the change
• The change includes tests OR the PR description describes a testing strategy
• The PR description notes risks associated with the change, if any
• Newly-added code is easy to change
• The change follows the library release note guidelines
• The change includes or references documentation updates if necessary
• Backport labels are set (if applicable)

Reviewer Checklist

• [ ] Reviewer has checked that all the criteria below are met
• Title is accurate
• All changes are related to the pull request's stated goal
• Avoids breaking API changes
• Testing strategy adequately addresses listed risks
• Newly-added code is easy to change
• Release note makes sense to a user of the library
• If necessary, author has acknowledged and discussed the performance implications of this PR as reported in the benchmarks PR comment
• Backport labels are set in a manner that is consistent with the release branch maintenance policy

[github-actions[bot]]

CODEOWNERS have been resolved as:

releasenotes/notes/bedrock-p-cache-0b73a062953ecfcf.yaml                @DataDog/apm-python
tests/contrib/botocore/bedrock_cassettes/bedrock_converse_prompt_caching.yaml  @DataDog/ml-observability
tests/contrib/botocore/bedrock_cassettes/bedrock_converse_stream_prompt_caching.yaml  @DataDog/ml-observability
ddtrace/contrib/internal/botocore/services/bedrock.py                   @DataDog/ml-observability
ddtrace/llmobs/_constants.py                                            @DataDog/ml-observability
ddtrace/llmobs/_integrations/bedrock.py                                 @DataDog/ml-observability
ddtrace/llmobs/_integrations/utils.py                                   @DataDog/ml-observability
tests/contrib/botocore/bedrock_utils.py                                 @DataDog/ml-observability
tests/contrib/botocore/test_bedrock_llmobs.py                           @DataDog/ml-observability

[github-actions[bot]]

Bootstrap import analysis

Comparison of import times between this PR and base.

Summary

The average import time from this PR is: 283 ± 4 ms.

The average import time from base is: 287 ± 4 ms.

The import time difference between this PR and base is: -3.7 ± 0.2 ms.

Import time breakdown

The following import paths have shrunk:

ddtrace.auto 2.151 ms (0.76%)

ddtrace.bootstrap.sitecustomize 1.465 ms (0.52%)

ddtrace.bootstrap.preload 1.465 ms (0.52%)

ddtrace.internal.remoteconfig.client 0.689 ms (0.24%)

ddtrace 0.687 ms (0.24%)

ddtrace.internal._unpatched 0.036 ms (0.01%)

json 0.036 ms (0.01%)

json.decoder 0.036 ms (0.01%)

re 0.036 ms (0.01%)

enum 0.036 ms (0.01%)

types 0.036 ms (0.01%)

[pr-commenter[bot]]

Benchmarks

Benchmark execution time: 2025-07-01 19:59:00

Comparing candidate commit 4fed7b97651bc7c440191d1998efc2946b219319 in PR branch evan.li/bedrock-prompt-caching with baseline commit 5fb2a8af26edfab9d0b1cccd04174361aa481473 in branch main.

Found 0 performance improvements and 5 performance regressions! Performance is the same for 542 metrics, 3 unstable metrics.

scenario:iastaspects-replace_aspect

• 🟥 execution_time [+651.659ns; +755.892ns] or [+13.666%; +15.852%]

scenario:iastaspectsospath-ospathbasename_aspect

• 🟥 execution_time [+787.550ns; +859.076ns] or [+18.436%; +20.110%]

scenario:iastaspectsospath-ospathjoin_aspect

• 🟥 execution_time [+923.493ns; +1006.824ns] or [+15.064%; +16.424%]

scenario:iastaspectsospath-ospathnormcase_aspect

• 🟥 execution_time [+386.273ns; +440.924ns] or [+10.978%; +12.531%]

scenario:iastaspectsospath-ospathsplit_aspect

• 🟥 execution_time [+1.016µs; +1.094µs] or [+20.870%; +22.465%]