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Fluentd vs Grafana Loki

Fluentd logo

Fluentd

Software

Open Source Data Collector for Unified Logging

From
Free
Rated
-
Full reviewWebsite
Grafana Loki logo

Grafana Loki

Software

Log Aggregation for Grafana Stack

From
Free
Rated
-
Full reviewWebsite

The short version

  • Each has a real cost: Fluentd fluentd needs more than 60 MB of memory at runtime, against roughly 450 KB for Fluent Bit; Grafana Loki grafana Cloud Logs Pro plan includes only 30-day retention; retention beyond 30 days requires Enterprise plan with minimum $25,000 annual commitment
  • They diverge on capability: Fluentd covers Log collection, Grafana Loki covers Log aggregation.

Where they differ

Only the attributes on which Fluentd and Grafana Loki actually diverge.

Attributes where Fluentd and Grafana Loki differ
AttributeFluentdGrafana Loki
Pricing modelopen-sourcefreemium
PlatformsWeb, ApiSelf-hosted (open source), Managed (Grafana Cloud Logs), Enterprise (self-managed with support)
Founded20112014

Identical on both: starting price (Free), free tier (Yes), user rating (Not yet rated), category (Unknown).

What each one covers

Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.

Only in Fluentd

  • Log collection
  • Data parsing
  • Filtering and buffering
  • Event routing

Only in Grafana Loki

  • Log aggregation
  • Label-based indexing
  • LogQL language
  • Cost-effective

Both cover

  • API
  • Webhooks
  • REST
  • Web support
  • Api support

What people use each for

The jobs each tool is most often brought in to do.

Fluentd

  • Unified log collection and routing from many sources to many destinationsnot Grafana Loki
  • Parsing and transforming log records before forwardingnot Grafana Loki
  • Aggregating logs from containers into Elasticsearch, S3 or a SIEMnot Grafana Loki

Grafana Loki

  • Cost-sensitive organisations deploying Kubernetes and Prometheus ecosystemsnot Fluentd
  • Teams needing index-free log aggregation for high-volume environmentsnot Fluentd

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

Fluentd

  • Fluentd needs more than 60 MB of memory at runtime, against roughly 450 KB for Fluent Bit
  • Fluentd is built as a Ruby gem and depends on other gems, so a Ruby runtime is required
  • Its capability comes from over 1,000 external plugins rather than built in functionality, so each added input or output is a separate dependency
  • The Fluent Bit documentation states that cloud providers have switched from Fluentd to Fluent Bit for performance and compatibility and calls Fluent Bit the next generation solution

Grafana Loki

  • Grafana Cloud Logs Pro plan includes only 30-day retention; retention beyond 30 days requires Enterprise plan with minimum $25,000 annual commitment
  • Open-source version requires self-hosting all infrastructure including storage and scaling

Pricing, plan by plan

Fluentd

Free
  • FreeFree
    • Log collection
    • Data parsing
    • Filtering and buffering

Grafana Loki

Free

No published plan breakdown. See the Grafana Loki review.

Which should you pick?

Choose Fluentd if

  • You need log collection.
  • You want to start without paying.
  • You work on Web, Api.
  • You also want data parsing.
Fluentd review

Choose Grafana Loki if

  • You need log aggregation.
  • You want to start without paying.
  • You work on Self-hosted (open source), Managed (Grafana Cloud Logs), Enterprise (self-managed with support).
  • You also want label-based indexing.
Grafana Loki review

Questions people ask

Is Fluentd or Grafana Loki better?
Neither clearly leads. Fluentd starts at Free and Grafana Loki at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Fluentd or Grafana Loki?
Fluentd starts at Free and Grafana Loki at Free.
Does Fluentd or Grafana Loki run on more platforms?
Fluentd runs on Web, Api. Grafana Loki runs on Self-hosted (open source), Managed (Grafana Cloud Logs), Enterprise (self-managed with support).
Can I use Fluentd for free?
Both have a free tier, so you can try either at no cost before committing.
What is Fluentd best used for?
Fluentd is most often used for unified log collection and routing from many sources to many destinations, parsing and transforming log records before forwarding, aggregating logs from containers into elasticsearch, s3 or a siem. Of those, unified log collection and routing from many sources to many destinations and parsing and transforming log records before forwarding are not what Grafana Loki is typically brought in for.
What can Fluentd do that Grafana Loki cannot?
Fluentd covers Log collection, Data parsing, Filtering and buffering, Event routing. Grafana Loki covers Log aggregation, Label-based indexing, LogQL language, Cost-effective. Both handle API, Webhooks, REST, Web support.
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