httpuv
httpuv ships almost nothing, which is what you want from the web server under Shiny
Comparison · DevOps
callr vs httr2
A side-by-side editorial comparison of callr and httr2 — release velocity, themes, recent moves, and the top alternatives to consider.
Shared themes:observabilityopentelemetry
callr vs httr2: at a glance
What is callr?
callr adds OpenTelemetry tracing, making R subprocess work observable across process boundaries
callr runs R code in fresh subprocesses and had been in maintenance for roughly two years — the 3.7.x releases are error-object polish, DLL handling, and Windows fixes. 3.8.0 breaks that pattern with a batch of substantive changes: pseudo-terminal support, carrier::crate() handling, configurable temp directories, honest non-zero exit statuses, and OpenTelemetry instrumentation.
What is httr2?
httr2 is growing production concerns: tracing, throttling and token hygiene.
httr2 is the tidyverse's modern HTTP client and the designated successor to httr. Recent releases have moved past request-building ergonomics into operational concerns — OpenTelemetry traces for every request, throttling that behaves correctly across repeated calls, and a fix for OAuth token caches that were never actually being pruned.
callr vs httr2: editorial side-by-side
callr
0.0DEVOPS
callr adds OpenTelemetry tracing, making R subprocess work observable across process boundaries
◆ Current state
callr runs R code in fresh subprocesses and had been in maintenance for roughly two years — the 3.7.x releases are error-object polish, DLL handling, and Windows fixes. 3.8.0 breaks that pattern with a batch of substantive changes: pseudo-terminal support, carrier::crate() handling, configurable temp directories, honest non-zero exit statuses, and OpenTelemetry instrumentation.
◆ Where it's heading
The package is being repositioned from a convenience wrapper into infrastructure that production R workloads can be operated against. Tracing spans that propagate a W3C traceparent into the child process, plus exit codes that finally reflect failure, are both about making callr legible to systems outside R. The pty and libpath changes point the same way — toward callr hosting long-lived, externally managed sessions.
◆ Prediction
Expect the OpenTelemetry surface to spread to sibling packages in the processx/r-lib process stack, and further work on subprocess failure semantics now that non-zero exits are the default.
httr2
2.5DEVOPS
httr2 is growing production concerns: tracing, throttling and token hygiene.
◆ Current state
httr2 is the tidyverse's modern HTTP client and the designated successor to httr. Recent releases have moved past request-building ergonomics into operational concerns — OpenTelemetry traces for every request, throttling that behaves correctly across repeated calls, and a fix for OAuth token caches that were never actually being pruned.
◆ Where it's heading
The package is maturing into infrastructure for long-running R services rather than interactive scripts. The 1.2.0 lifecycle purge removed deprecated streaming and mocking APIs in favour of a connection-based model, and debugging affordances like httr2_translate() point at users who need to reproduce a failing request outside R.
◆ Prediction
Expect further observability and credential-handling work, with the rlang-driven cache hash change in 1.3.0 likely to surface follow-up issues as existing caches silently invalidate.
Alternatives to callr and httr2
Other DevOps products tracked by Sparkpulse, ranked by recent ship velocity. Each card links to a full editorial trajectory and lets you pivot into a head-to-head comparison with either callr or httr2.
promises
promises drops R6 for plain environments and wires async work into OpenTelemetry
withr
withr rebuilt defer() on base R's own on.exit(), and got much faster for it
htmltools
htmltools spends three releases walking back its own fill-layout opinions
xml2
xml2 relicensed to MIT, then moved its hot accessors from S3 into C
httr
httr's last releases are housekeeping - the package now points users at httr2
Recent activity from callr and httr2
Latest ship moves from both products, interleaved chronologically. ⚡ = editorial spark.
- 1mo agohttr2httr2 1.3.0 fixes OAuth token caches that never expired
- 1mo agohttr2httr2 1.2.3 translates requests into curl commands
- 2mo agocallrOpenTelemetry tracing, pty support, and honest subprocess exit codes ⚡
- 8mo agohttr2httr2 1.2.2 emits OpenTelemetry traces for every request ⚡
- 1y agohttr2httr2 1.2.1 stops escaping colons in paths
- 1y agohttr2httr2 1.2.0 removes deprecated mocking and streaming APIs
- 1y agohttr2httr2 1.1.2 fixes AWS request signing and header checks
- 2y agocallrEnv var to skip copying the client DLL
- 2y agocallrRunning-time fix and fully qualified subprocess calls
- 3y agocallrErrors carry subprocess stdout and stderr again
- 3y agocallrExperimental add_hook() for subprocess startup
- 4y agocallrUncompressed transport by default; revamped error objects
Frequently asked questions
What is the difference between callr and httr2?
Both compete on the same themes — observability, opentelemetry — within DevOps. httr2 is currently shipping more aggressively (velocity 2.5 vs 0.0), with 0 editorial sparks in the last 30 days against 0. See the at-a-glance table above for a side-by-side breakdown of velocity, recent sparks, and editorial themes.
Is callr better than httr2?
Sparkpulse doesn't pick a winner — we score release velocity, not feature parity. httr2 is currently shipping more aggressively (velocity 2.5 vs 0.0), with 0 editorial sparks in the last 30 days against 0. For your specific use case, the alternatives sections above list other DevOps products to evaluate alongside.
What are the best alternatives to callr?
Top callr alternatives in DevOps are ranked by recent ship velocity. Browse the "callr alternatives" section above for the current picks, or visit /alternatives/callr for the full list with editorial commentary on each.
What are the best alternatives to httr2?
Top httr2 alternatives in DevOps are ranked by recent ship velocity. Browse the "httr2 alternatives" section above for the current picks, or visit /alternatives/httr2 for the full list with editorial commentary on each.