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Update VictoriaLogs FQA section to replace VictoriaMetrics with VictoriaLogs. - [x] My change adheres [VictoriaMetrics contributing guidelines](https://docs.victoriametrics.com/contributing/).
133 lines
8.3 KiB
Markdown
133 lines
8.3 KiB
Markdown
---
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sort: 6
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weight: 6
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title: FAQ
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menu:
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docs:
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identifier: "victorialogs-faq"
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parent: "victorialogs"
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weight: 6
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title: FAQ
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aliases:
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- /VictoriaLogs/FAQ.html
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- /VictoriaLogs/faq.html
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---
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## What is the difference between VictoriaLogs and Elasticsearch (OpenSearch)?
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Both Elasticsearch and VictoriaLogs allow ingesting structured and unstructured logs
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and performing fast full-text search over the ingested logs.
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Elasticsearch and OpenSearch are designed as general-purpose databases for fast full-text search over large set of documents.
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They aren't optimized specifically for logs. This results in the following issues, which are resolved by VictoriaLogs:
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- High RAM usage
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- High disk space usage
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- Non-trivial index setup
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- Inability to select more than 10K matching log lines in a single query
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VictoriaLogs is optimized specifically for logs. So it provides the following features useful for logs, which are missing in Elasticsearch:
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- Easy to setup and operate. There is no need in tuning configuration for optimal performance or in creating any indexes for various log types.
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Just run VictoriaLogs on the most suitable hardware - and it automatically provides the best performance.
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- Up to 30x less RAM usage than Elasticsearch for the same workload.
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- Up to 15x less disk space usage than Elasticsearch for the same amounts of stored logs.
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- Ability to work with hundreds of terabytes of logs on a single node.
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- Very easy to use query language optimized for typical log analysis tasks - [LogsQL](https://docs.victoriametrics.com/victorialogs/logsql/).
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- Fast full-text search over all the [log fields](https://docs.victoriametrics.com/victorialogs/keyconcepts/#data-model) out of the box.
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- Good integration with traditional command-line tools for log analysis. See [these docs](https://docs.victoriametrics.com/victorialogs/querying/#command-line).
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## What is the difference between VictoriaLogs and Grafana Loki?
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Both Grafana Loki and VictoriaLogs are designed for log management and processing.
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Both systems support [log stream](https://docs.victoriametrics.com/victorialogs/keyconcepts/#stream-fields) concept.
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VictoriaLogs and Grafana Loki have the following differences:
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- Grafana Loki doesn't support high-cardinality log fields (aka labels) such as `user_id`, `trace_id` or `ip`.
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It starts consuming huge amounts of RAM and working very slow when logs with high-cardinality fields are ingested into it.
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See [these docs](https://grafana.com/docs/loki/latest/best-practices/) for details.
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VictoriaLogs supports high-cardinality [log fields](https://docs.victoriametrics.com/victorialogs/keyconcepts/#data-model).
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It automatically indexes all the ingested log fields and allows performing fast full-text search over any field.
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- Grafana Loki provides very inconvenient query language - [LogQL](https://grafana.com/docs/loki/latest/logql/).
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This query language is hard to use for typical log analysis tasks.
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VictoriaLogs provides easy to use query language for typical log analysis tasks - [LogsQL](https://docs.victoriametrics.com/victorialogs/logsql/).
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- VictoriaLogs performs typical full-text queries up to 1000x faster than Grafana Loki.
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- VictoriaLogs needs less storage space than Grafana Loki for the same amounts of logs.
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- VictoriaLogs is much easier to setup and operate than Grafana Loki.
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## What is the difference between VictoriaLogs and ClickHouse?
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ClickHouse is an extremely fast and efficient analytical database. It can be used for logs storage, analysis and processing.
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VictoriaLogs is designed solely for logs. VictoriaLogs uses [similar design ideas as ClickHouse](#how-does-victorialogs-work) for achieving high performance.
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- ClickHouse is good for logs if you know the set of [log fields](https://docs.victoriametrics.com/victorialogs/keyconcepts/#data-model) beforehand.
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Then you can create a table with a column per each log field and achieve the maximum possible query performance.
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If the set of log fields isn't known beforehand, or if it can change at any time, then ClickHouse can still be used,
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but its' efficiency may suffer significantly depending on how you design the database schema for log storage.
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ClickHouse efficiency highly depends on the used database schema. It must be optimized for the particular workload
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for achieving high efficiency and query performance.
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VictoriaLogs works optimally with any log types out of the box - structured, unstructured and mixed.
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It works optimally with any sets of [log fields](https://docs.victoriametrics.com/victorialogs/keyconcepts/#data-model),
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which can change in any way across different log sources.
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- ClickHouse provides SQL dialect with additional analytical functionality. It allows performing arbitrary complex analytical queries
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over the stored logs.
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VictoriaLogs provides easy to use query language with full-text search specifically optimized
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for log analysis - [LogsQL](https://docs.victoriametrics.com/victorialogs/logsql/).
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LogsQL is usually much easier to use than SQL for typical log analysis tasks, while some
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non-trivial analytics may require SQL power.
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- VictoriaLogs accepts logs from popular log shippers out of the box - see [these docs](https://docs.victoriametrics.com/victorialogs/data-ingestion/).
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ClickHouse needs an intermediate applications for converting the ingested logs into `INSERT` SQL statements for the particular database schema.
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This may increase the complexity of the system and, subsequently, increase its' maintenance costs.
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## How does VictoriaLogs work?
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VictoriaLogs accepts logs as [JSON entries](https://docs.victoriametrics.com/victorialogs/keyconcepts/#data-model).
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It then stores every field value into a distinct data block. E.g. values for the same field across multiple log entries
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are stored in a single data block. This allow reading data blocks only for the needed fields during querying.
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Data blocks are compressed before being saved to persistent storage. This allows saving disk space and improving query performance
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when it is limited by disk read IO bandwidth.
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Smaller data blocks are merged into bigger blocks in background. Data blocks are limited in size. If the size of data block exceeds the limit,
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then it is split into multiple blocks of smaller sizes.
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Every data block is processed in an atomic manner during querying. For example, if the data block contains at least a single value,
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which needs to be processed, then the whole data block is unpacked and read at once. Data blocks are processed in parallel
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on all the available CPU cores during querying. This allows scaling query performance with the number of available CPU cores.
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This architecture is inspired by [ClickHouse architecture](https://clickhouse.com/docs/en/development/architecture).
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On top of this, VictoriaLogs employs additional optimizations for achieving high query performance:
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- It uses [bloom filters](https://en.wikipedia.org/wiki/Bloom_filter) for skipping blocks without the given
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[word](https://docs.victoriametrics.com/victorialogs/logsql/#word-filter) or [phrase](https://docs.victoriametrics.com/victorialogs/logsql/#phrase-filter).
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- It uses custom encoding and compression for fields with different data types.
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For example, it encodes IP addresses as 4-byte tuples. Custom fields' encoding reduces data size on disk and improves query performance.
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- It physically groups logs for the same [log stream](https://docs.victoriametrics.com/victorialogs/keyconcepts/#stream-fields)
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close to each other. This improves compression ratio, which helps reducing disk space usage. This also improves query performance
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by skipping blocks for unneeded streams when [stream filter](https://docs.victoriametrics.com/victorialogs/logsql/#stream-filter) is used.
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- It maintains sparse index for [log timestamps](https://docs.victoriametrics.com/victorialogs/keyconcepts/#time-field),
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which allow improving query performance when [time filter](https://docs.victoriametrics.com/victorialogs/logsql/#time-filter) is used.
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## How to export logs from VictoriaLogs?
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Just send the query with the needed [filters](https://docs.victoriametrics.com/victorialogs/logsql/#filters)
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to [`/select/logsql/query`](https://docs.victoriametrics.com/victorialogs/querying/#querying-logs) - VictoriaLogs will return
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the requested logs as a [stream of JSON lines](https://jsonlines.org/). It is recommended specifying [time filter](https://docs.victoriametrics.com/victorialogs/logsql/#time-filter)
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for limiting the amounts of exported logs.
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