Software · head to head
Fluentd vs Azure Monitor
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; Azure Monitor billed per GB ingested across three separate log plans, Auxiliary, Basic and Analytics, so the plan chosen changes the rate as much as the volume does
- They diverge on capability: Fluentd covers Data parsing, Azure Monitor covers Metrics collection.
Where they differ
Only the attributes on which Fluentd and Azure Monitor actually diverge.
| Attribute | Fluentd | Azure Monitor |
|---|---|---|
| Pricing model | open-source | usage-based |
| Founded | 2011 | 2010 |
Identical on both: starting price (Free), free tier (Yes), platforms (Web, Api), 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
- Data parsing
- Filtering and buffering
- Event routing
Only in Azure Monitor
- Metrics collection
- Alerts and notifications
- Custom dashboards
Both cover
- Log collection
- 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 Azure Monitor
- Parsing and transforming log records before forwardingnot Azure Monitor
- Aggregating logs from containers into Elasticsearch, S3 or a SIEMnot Azure Monitor
Azure Monitor
- Collecting logs and metrics from Azure resourcesnot Fluentd
- Alerting on metric thresholds and log queriesnot Fluentd
- Application performance monitoring through Application Insightsnot Fluentd
- Long-term log retention for compliancenot Fluentd
- Querying operational data with KQLnot 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
Azure Monitor
- Billed per GB ingested across three separate log plans, Auxiliary, Basic and Analytics, so the plan chosen changes the rate as much as the volume does
- Only the first 5 GB a month of Analytics logs is free per billing account
- Retention beyond the base period is charged per GB per month, up to 2 years interactive and 12 years long term
- Log queries and search jobs are billed per GB scanned, so investigating an incident costs money
- Alert rules are billed per time series for metrics and by execution frequency for logs
- The pricing page shows placeholders rather than rates until a region and currency are chosen
Pricing, plan by plan
Fluentd
Free- FreeFree
- Log collection
- Data parsing
- Filtering and buffering
Azure Monitor
Free- FreeFree
- Log collection
- Metrics collection
- Alerts and notifications
Which should you pick?
Choose Fluentd if
- You need data parsing.
- You want to start without paying.
- You work on Web, Api.
- You also want filtering and buffering.
Choose Azure Monitor if
- You need metrics collection.
- You want to start without paying.
- You work on Web, Api.
- You also want alerts and notifications.
Questions people ask
- Is Fluentd or Azure Monitor better?
- Neither clearly leads. Fluentd starts at Free and Azure Monitor at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
- Which is cheaper, Fluentd or Azure Monitor?
- Fluentd starts at Free and Azure Monitor at Free.
- Does Fluentd or Azure Monitor 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 Azure Monitor is typically brought in for.
- What can Fluentd do that Azure Monitor cannot?
- Fluentd covers Data parsing, Filtering and buffering, Event routing. Azure Monitor covers Metrics collection, Alerts and notifications, Custom dashboards. Both handle Log collection, API, Webhooks, REST.