couchbase-fluent-bit

Summary

The Couchbase Fluent Bit image is an image based on the official Fluent Bit image with some additional support for the following:

Dynamic configuration reload - changes to the configuration are watched for and when detected trigger a restart of Fluent Bit to pick up the new configuration.
Rebalance report pre-processing - the rebalance reports produced by Couchbase need some additional pre-processing before they can be parsed by Fluent Bit.
SHA1 LUA hashing implementation and redaction support included (but not enabled by default).

This image is intended to be used as a sidecar with a Couchbase Autonomous Operator deployment to automatically stream various couchbase logs. The log streaming can be dynmically configured per namespace/Couchbase cluster via a standard Kubernetes secret which is mounted then as the configuration directory.

At this time, the image is only officially tested on Kubernetes in conjunction with the Couchbase Autonomous Operator. However, nothing has been added to the image that explicitly prevents it from being run in non-Kubernetes environments. Fluent Bit itself supports various deployment options so refer to its documentation for details.

To help provide the capability in this image we make use of other OSS:

Logs supported

Refer to the official documentation for all possible logs output by Couchbase Server.

This image is used to parse and send the following logs to standard output by default:

analytics_debug.log
audit.log
babysitter.log
couchdb.log
debug.log
eventing.log
fts.log
goxdcr.log
http_access.log
http_access_internal.log
indexer.log
json_rpc.log
mapreduce_errors.log
memcached.log
metakv.log
ns_couchdb.log
projector.log
prometheus.log
Rebalance reports
reports.log

It will also handle the logs like info.log, error.log that are a subset of the full debug.log - there is no point parsing all these logs as it will duplicate the information.

The definition of "parse" here means to turn the unstructured, possibly multi-line log output into structured data we can filter, mutate & forward to any supported Fluent Bit endpoint. For the purposes of this image, we essentially chunk up the log lines into timestamp, level and message - message can be over multiple lines. As an example (taken from tests/logs/memcached.log.000000.txt): 2021-03-09T17:32:01.859344+00:00 INFO Couchbase version 6.6.0-7909 starting. Will become (taken from tests/logs/memcached.log.000000.txt.expected): [1615311121.859344000, {"filename":"/fluent-bit/test/logs/memcached.log.000000.txt","timestamp":"2021-03-09T17:32:01.859344+00:00","level":"INFO","message":"Couchbase version 6.6.0-7909 starting."}] This is a structured stream made up of various fields which can be sent to any supported output (multiple potentially and/or different to other logs):

"timestamp":"2021-03-09T17:32:01.859344+00:00"
"level":"INFO"
"message":"Couchbase version 6.6.0-7909 starting."

Every log is tagged individually to form its own stream within the log shipper. The tag format is couchbase.log.<name>. Each stream can be managed independently so refer to the official Fluent Bit documentation for full details on the extensive capability and configuration available.

Other logs than the list above may be supported by the provided parsers as well.

Technical Overview

This image is essentially the official Fluent Bit image with an entrypoint watcher process that handles both restarting Fluent Bit on config change and pre-processing the rebalance reports.

Parsing

For the purposes of this implementation, parsing is very simple as we’re not trying to extract any more information than the simple timestamp, log level and log message. A few of the logs (http and JSON format ones - audit & rebalance reports) can have some extra fields extracted as it is straightforward but any significant processing is left for the consumer to manage.

The intention is to keep it as simple as possible and produce a structured log stream that can be filtered or consumed with further processing downstream as required.

For those logs with multiline output, the parser should capture everything up to the next log statement. In some cases this includes large content (e.g. Java thread dumps) but this is all treated as part of the log message for the consumer to work with.

The parsers are provided in conf/parsers-couchbase.conf along with default configuration for each log file in conf/couchbase/in-*.conf. We use a separate config file per input type/parser configuration (log file type) to make is simpler to reuse for a custom configuration either in testing or by end users.

Rebalance reports and dynamic configuration

The official version of Fluent Bit does not support dynamic changes to its configuration: if you change the log shipping configuration then you have to restart it. We cannot restart the pods without triggering rebalance.

The rebalance reports have a bit of an issue with the default tail plugin: they are a file with no new lines. The full JSON dump of the report is all over a single line which can be quite large (not for a log file but for a single line in a log file). The tail plugin works on a per-line basis so cannot handle the reports as they currently are. Additionally there is the question of which timestamp to use as the “log” timestamp - a rebalance report can have multiple ones using common tags.

We have solved both these problems by forking the Kubesphere solution (a fork from the official image) to resolve the dynamic configuration issue. This watches for config file changes and then restarts Fluent Bit to pick up the new configuration but all within the container. We can extend this to handle the rebalance reports: we watch for them, when we see one we copy it to a temporary location with any pre-processing we want done and then Fluent Bit reads the copy. We copy it for these reasons rather than updating in place:

No change to the original log or anything reliant on it (e.g. rotation).
The logging sidecar deliberately has no write access to the log volume so it cannot modify any logs.
The log timestamp can be collected from the rebalance report name which includes the time it was created.

Whilst Fluent Bit is restarting, no logs will be shipped out of the container. We could re-parse logs but this would then lead to duplicate entries from previously parsed logs. The intention is that reconfiguration is an asynchronous un-common operation so the temporary potential loss of logs is acceptable.

Interestingly as part of this work, we discovered that the exec plugin is not usable in a container without /bin/sh, i.e. all the official ones including the debug variant with busybox. The original intention was to use this to process the log file but that was impossible: even with a compiled binary it still must be invoked via /bin/sh.

Redaction

Log redaction in flight has been demonstrated and is tested but will not be provided by default.

A tutorial is provided on how to configure this if required so refer to the Couchbase Autonomous Operator documentation for that. There may be a performance impact to redaction in flight and it will also complicate debugging of problems if the logs are auto-redacted within the cluster.

To simplify usage we build everything required into the container image: this is a minimal image so has no support for hashing out of the box. we therefore include the LUA implementation from: https://github.com/mpeterv/sha1 . Lua provides the best approach to dealing with redaction anyway so attaching a Lua hashing library made the most sense.

Similarly any other log mutation could be done that is supported by Fluent Bit. Using a LUA script provides a lot of flexibility but there are plenty of other simpler plugins to modify the content or destination of a log. The recommendation when using LUA parsing is to dedicate a worker thread to it.

Specific parser information

Each of these sections references the specific parser set up in conf/parsers-couchbase.conf.

couchbase_json_log_nanoseconds and couchbase_rebalance_report

These are both JSON parsers so support a full JSON extraction/forwarding. There is no need to match lines in a legacy way with a regex.

couchbase_http

The HTTP parsers reuse the default Fluent Bit Apache2 regex with some minor changes. This means they do not provide a simple triplet of timestamp, level, message but instead include various fields from the message instead.

couchbase_simple_log_mixed

Some of the logs (FTS and eventing in the default configuration) provide a mixed timestamp output which is difficult to parse in one go.

2021/03/09 17:32:15 cbauth: ...
2021-03-09T17:32:15.303+00:00 [INFO] ...

Instead the timestamps are extracted via a generic parser and then could be run through an additional stage to parse it in the appropriate format. This may not be required if it is acceptable as per the default configuration to use local time, i.e. the time at which Fluent Bit tails that line in the log.

couchbase_erlang_multiline

The multi-line erlang parser originally parsed everything after the square bracket as the message. Unfortunately the regex parser does not seem to like a new line immediately after the bracket - with some text first then a new line it works fine. Therefore the message includes everything after the timestamp, this guarantees we get all multiline output and also anything else after timestamp.

Usage

The official Couchbase Autonomous Operator documentation provides full details on using this with Kubernetes including additional tutorials on consuming logs with Loki or sending to Azure, S3, etc.

The image is basically identical to the official Fluent Bit image and can be used in the same fashion. If the capabilities listed above are not required then the official Fluent Bit image can be used as well.

This image is only intended to be used with Kubernetes although it may be usable as a standalone Docker image either for a containerised or on-premise deployment but this is not an officially supported configuration.

An example local configuration running three Couchbase nodes using docker-compose:

version: "3.9"
services:
    couchbase-server1:
        container_name: db1
        image: couchbase:7.0.1
        ports:
          - "8091-8096:8091-8096"
          - "11210-11211:11210-11211"
        volumes:
          - log-volume:/opt/couchbase/var/lib/couchbase/logs/:rw
    couchbase-server2:
        container_name: db2
        image: couchbase:7.0.1
        expose:
            - "8091-8096"
            - "11210-11211"
    couchbase-server3:
        container_name: db3
        image: couchbase:7.0.1
        expose:
            - "8091-8096"
            - "11210-11211"
    log-streamer:
        container_name: logging
        image: couchbase/fluent-bit:1.1.0
        depends_on:
            - couchbase-server1
        environment:
            - COUCHBASE_LOGS=/opt/couchbase/var/lib/couchbase/logs
        volumes:
          - log-volume:/opt/couchbase/var/lib/couchbase/logs/:ro
volumes:
    log-volume:

The volume could be replaced with a bind mount for an on-premise Couchbase Server deployment - and the container could be run directly with a container runtime rather than docker-compose (as per Testing example below.) Couchbase Server will need configuration when it starts up above - it currently does not support a declarative model to auto-provision the containers on startup.

Note that this image copes with multi-line input logs but the default output to standard output will still be over multiple lines for these same messages. This means if you are collecting this information with a Daemonset (e.g. another Fluent Bit or PromTail) reading the container logs (from standard output) then you will need to capture multi-line output. It will all be inside a standard msgpack Fluent Bit record format though so can be parsed that way.

A full example local Loki stack deployment (Loki+Grafana - configured) is also provided in the tools/loki-stack directory, this can be run via a simple docker compose up command. The Grafana instance will then be exposed via localhost:3000. This also supports a blog post showing how to do this in detail: https://blog.couchbase.com/using-fluent-bit-for-log-forwarding-processing-with-couchbase-server/

Configuration

Environment variable	Description	Default
COUCHBASE_FLUENT_BIT_CONFIG	The directory containing the Couchbase (or other) configuration files, primarily used for dynamic output configuration.	/fluent-bit/etc/couchbase
COUCHBASE_LOGS	The directory in which to find the various Couchbase logs we are interested in.	/opt/couchbase/var/couchbase/logs
COUCHBASE_LOGS_BINARY	The Fluent Bit binary to launch.	/fluent-bit/bin/fluent-bit
COUCHBASE_LOGS_CONFIG_FILE	The config file to use when starting Fluent Bit.	/fluent-bit/config/fluent-bit.conf
COUCHBASE_LOGS_DYNAMIC_CONFIG	The directory to watch for config changes and restart Fluent Bit.	/fluent-bit/config
COUCHBASE_LOGS_REBALANCE_TEMPDIR	The temporary directory for out pre-processed rebalance reports.	/tmp/rebalance-logs
COUCHBASE_K8S_CONFIG_DIR	The location where DownwardAPI pushes pod meta-data to load as environment variables.	/etc/podinfo
MEM_BUF_LIMITS_ENABLED	Whether memory buffer limits should be enabled on the input plugins	false
LOKI_HOST	The hostname used by the Loki output plugin (if enabled).	loki
LOKI_MATCH	The set of matching streams to send to Loki.	no-match (prevents any)
LOKI_PORT	The port used by the Loki output plugin (if enabled).	3100
ES_HOST	The hostname used by the Elasticsearch output plugin (if enabled).	elasticsearch
ES_MATCH	The set of matching streams to send to Elasticsearch.	no-match (prevents any)
ES_PORT	The port used by the Elasticsearch output plugin (if enabled).	9200
ES_INDEX	The index used by the Elasticsearch output plugin (if enabled).	"couchbase"
ES_HTTP_USER	The username for API access used by the Elasticsearch output plugin (if enabled).
ES_HTTP_PASSWD	The password for the user defined by `ES_HTTP_USER` for the Elasticsearch output plugin (if enabled).
SPLUNK_HOST	The hostname used by the Splunk output plugin (if enabled).	splunk
SPLUNK_MATCH	The set of matching streams to send to Splunk http event collector.	no-match (prevents any)
SPLUNK_PORT	The port used by the Splunk output plugin (if enabled).	8088
SPLUNK_TOKEN	The token used by the Splunk output plugin (if enabled).	abcd1234
HTTP_PORT	The port used for the HTTP server run by Fluent Bit (enabled by default).	2020
STD_MATCH	The set of matching streams to send to standard output.	couchbase.log.*

Be careful to make sure you have enough file descriptors configured to use this functionality, particularly for local development with something like Kubernetes-In-Docker(KIND).

CAO and K8S labels

The Couchbase Autonomous Operator (CAO) automatically pushes all pod labels & annotations into the container via the DownwardAPI. These are then loaded as environment variables by the Couchbase watcher process so this can be a very useful way to pass configuration into a container.

In addition, any variables that start with the fluentbit.couchbase.com/ have some additional processing applied: the prefix is removed and everything left is upper-cased plus special characters replaced with underscores.

fluentbit.couchbase.com/loki_host: loki.monitoring will therefore provide LOKI_HOST=loki.monitoring.

User-defined labels and annotations can be specified with CAO via the pod template.

Memory buffer limits

By default, memory buffer limits are disabled. However, it is possible to enable them by setting MEM_BUF_LIMITS_ENABLED to true. When enabled the watcher will estimate the memory limits by using the total number of input and output plugins and using the estimating guide from Fluent Bit. This can be useful in situtation where memory is restricted — for instances preventing the container from being OOMKilled in Kubernetes.

Output plugin dynamic enabling

By default we only output to standard output but other output plugins are included they just do not match any existing streams. It is possible to enable matching of streams to output plugins via the <PLUGIN>_MATCH environment variable. For example to enable sending all logs to Loki, set LOKI_MATCH="*". Refer to the default configuration to see which output plugins are enabled.

The major benefit of this for CAO deployments is we only need to have user-defined labels like so to set up Loki usage:

      pod:
        metadata:
          annotations:
            fluentbit.couchbase.com/loki.match: "*"
            fluentbit.couchbase.com/loki.host: loki.monitoring

Building

This repository is set up to be built by the internal Couchbase process with a Makefile. This can be easily reused though to build locally either by installing the relevant tools or using a Golang container to build the source.

Testing

A set of automated tests are provided to verify changes against for sanity checks and some regression testing too of known input and expected output. New sets of input data can be used as well by running the container with the logs (input) and expected output using a volume mount:

docker run --rm -it --mount type=bind,source=<directory>,target=/fluent-bit/tests/logs <test container name>

The directory should be made up of matching pairs of logs and expected output in the following format: <name>.log --> <name>.log.expected. The container will run the Couchbase Fluent Bit image against each log file in turn with some basic sanity checks and produce an output file named <name>.log.actual. The tests/run-tests.sh script will then iterate over all expected output to compare it against actual output.

To help with verifying new output, a simple NodeJS tool is provided in tools/log-verifier. This can be run locally or as an image against the files to check, when run as an image the file will need mounting into the container and passing as an argument.

For the Red Hat variant we make best effort to verify Fluent Bit however the only supported usage is of the tail input plugin to stdout output plugin pipeline used in the default configuration for the Couchbase Autonomous Operator. The Red Hat test container includes the unit tests which can be run manually as required to verify changes.

Feedback

Please use our official JIRA board to report any bugs and issues with the logging component. We also encourage you to use the Couchbase Forums for posting any questions or feedback that you might have.

Support

As indicated above, Couchbase only supports the use of this image when used with the Couchbase Autonomous Operator. Specificially, the default configuration provided by the operator and the ability to provide a custom configuration is supported. Best efforts are made to confirm that custom configurations will work with various plugins but any issues with the custom configuration, plugins or other components are outside of the supported scope.

Compatibility matrix for CAO

CAO = Couchbase Autonomous Operator CFB = Couchbase Fluent Bit

CAO Version	1.0.0	1.0.1	1.0.2	1.0.3	1.0.4	1.1.0	1.1.1	1.1.2	Next (1.2.0)
2.2.0	X	X	X	X	X
2.2.1	X	X	X	X	X	X	X	X	X
Next (2.3.0)					X	X	X	X	X

Release tagging and branching

Every release to DockerHub will include a matching identical Git tag here, i.e. the tags on https://hub.docker.com/r/couchbase/fluent-bit/tags will have a matching tag in this repository that built them. Updates will be pushed to the main branch often and then tagged once released as a new image version. Tags will not be moved after release, even just for a documentation update - this should trigger a new release or just be available as the latest version on main.

The branching strategy is to minimise any branches other than main following the standard GitHub flow model.

Releases

A quick summary of each release is given below to help understand the changes. For full details have a look at the diff of the tags and associated commits for each: https://github.com/couchbase/couchbase-fluent-bit/releases/tag/

main - in progress for next relase (1.2.0)
- Updated Fluent Bit to 1.8.14.
- Resolved issue where Loki labels were being set incorrectly
- Updated compatibility matrix
- Added in Elasticsearch and Splunk output plugins
- Changed output Record couchbase.server to couchbase.server.server to support Elasticsearch outputs
1.1.2
- Updated to Go 1.17.1 - this relates to the internal Watcher code layered on top of Fluent Bit.
- Additional configuration variables now available for Loki output and the HTTP server.
- New support for enabling output plugins via environment variables fed in from Kubernetes labels or annotations.
- Updated to Fluent Bit 1.8.8.
1.1.1
- Updated to Fluent Bit 1.8.7.
- Updates to support on-premise usage with rotated memcached logs.
- Resolve issue with missing version information in the output.
- Updated loki stack example to handle changes to user security preventing log file reading.
- Added support for mapreduce_errors.log parsing.
- Added test for rebalance output being present.
- Added level_numeric field for a numeric value for the log level to simplify querying downstream.
1.1.0
- Updated to Fluent Bit 1.8.2.
  - Matching change in versions here, 1.0.4 --> 1.1.0.
- Added version information into records.
- Ensures log level is always one of DEBUG, INFO, WARN, ERROR, UNKNOWN and maintains the original value if not one of these as original_level, e.g. "original_level":"audit","level":"UNKNOWN".
- Splits Path_Key (filename) into path & file keys to make it easier to filter on downstream, e.g. "file_path":"/fluent-bit/test/logs","file":"eventing.log","filename":"/fluent-bit/test/logs/eventing.log".
- Tested against Couchbase Server 7.0.0, added parsing for new prometheus.log.
1.0.4
- Switch to using record_modifier for common info so missing variables do not trigger an exit, just an error.
- Removed Fluent Bit tests from running on every RHEL build: issue with reliability so only run manually now on version change.
- Git version information now included in log output.
- Log entire environment at launch.
- Supports redaction of the log key as well now for un-parsed logfiles.
- Simple example showing how to implement a file-transfer service with the forward plugin.
- Updated to Fluent Bit 1.7.8.
1.0.3
- Disables auto-run of Fluent Bit unit tests during RHEL builds due to timing issue making them unreliable: fluent/fluent-bit#3520
- Added run-as numeric USER to support security improvements.
- Copyright headers added to all source files along with CI checks to confirm it on every build.
- Resolved race condition in unit tests for restarting.
1.0.2
- Major refactor to move from single main.go file to Go module across packages with unit tests as well for each sub-component.
- Update to Fluent Bit 1.7.4.
- Linting and other CI improvements.
- Addition of extra common information as extra keys when run with the operator (pod and couchbase cluster information).
- Additional filters from observability work to standardise log levels for easy use with Grafana, along with example output configuration and supporting documentation.
- Optional filter to pick up examples of common problems, purely an initial example so not used by default.
- Reduced refresh interval to pick up new log files to 10 seconds - previously was 60 seconds.
- Enabled HTTP server by default to support metrics and healthchecks if required - on port 2020.
- Explicit non-root USER support.
1.0.1
- Minor licensing updates to pass Red Hat certification checks.
1.0.0
- Initial release containing the various watchers and parsers.
- Based on Fluent Bit 1.7.3.

License

Licensed under the Apache License, Version 2.0

See LICENSE for further details.

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