Software · head to head
Fluentd vs ELK Stack
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; ELK Stack the free Basic self managed subscription excludes machine learning, alerting, single sign on via SAML or OpenID Connect, LDAP and Active Directory authentication, field and document level security, searchable snapshots and cross cluster replication
- They diverge on capability: Fluentd covers Log collection, ELK Stack covers Full-text search.
Where they differ
Only the attributes on which Fluentd and ELK Stack actually diverge.
Identical on both: starting price (Free), pricing model (open-source), free tier (Yes), platforms (Web, Api), user rating (Not yet rated), category (Unknown), founded (2011).
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 ELK Stack
- Full-text search
- Data visualization
- Log aggregation
- Time-series analytics
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 ELK Stack
- Parsing and transforming log records before forwardingnot ELK Stack
- Aggregating logs from containers into Elasticsearch, S3 or a SIEMnot ELK Stack
ELK Stack
- Centralised log search and analytics over Elasticsearchnot Fluentd
- Dashboards and visualisation of machine data in Kibananot Fluentd
- Self managing a search and observability cluster on your own hardwarenot 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
ELK Stack
- The free Basic self managed subscription excludes machine learning, alerting, single sign on via SAML or OpenID Connect, LDAP and Active Directory authentication, field and document level security, searchable snapshots and cross cluster replication
- Cross cluster operations require the same subscription tier on every cluster involved
- The 99.95 percent monthly uptime SLA applies only to the Platinum and Enterprise subscription tiers
- Three deployment models are priced on three different bases: resource based for Cloud Hosted, usage based for Serverless and licence based on nodes and RAM for self managed
- Elastic Cloud Serverless does not yet support traffic filtering, cross project search or bring your own key
- The pricing page publishes no rate for any tier
Pricing, plan by plan
Fluentd
Free- FreeFree
- Log collection
- Data parsing
- Filtering and buffering
ELK Stack
Free- FreeFree
- Full-text search
- Data visualization
- Log aggregation
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.
Choose ELK Stack if
- You need full-text search.
- You want to start without paying.
- You work on Web, Api.
- You also want data visualization.
Questions people ask
- Is Fluentd or ELK Stack better?
- Neither clearly leads. Fluentd starts at Free and ELK Stack at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
- Which is cheaper, Fluentd or ELK Stack?
- Fluentd starts at Free and ELK Stack at Free.
- Does Fluentd or ELK Stack run on more platforms?
- Both run on Web, Api, so platform support will not decide this one for you.
- 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 ELK Stack is typically brought in for.
- What can Fluentd do that ELK Stack cannot?
- Fluentd covers Log collection, Data parsing, Filtering and buffering, Event routing. ELK Stack covers Full-text search, Data visualization, Log aggregation, Time-series analytics. Both handle API, Webhooks, REST, Web support.