It would appear that this is just caused by a race condition with the Kafka Exporter trying to connect to Kafka before it has started up. If I just run docker-compose up and allow the Kafka Exporter to fail, and then separately run the danielqsh/kafka-exporter container, it works:
> docker run -it -p 9308:9308 --network bitnami-docker-kafka_app-tier danielqsj/kafka-exporter
I0103 18:49:04.694898 1 kafka_exporter.go:774] Starting kafka_exporter (version=1.4.2, branch=HEAD, revision=15e4ad6a9ea8203135d4b974e825f22e31c750e5)
I0103 18:49:04.703058 1 kafka_exporter.go:934] Listening on HTTP :9308
and on http://localhost:9308 I can see metrics:
# HELP go_gc_duration_seconds A summary of the pause duration of garbage collection cycles.
# TYPE go_gc_duration_seconds summary
go_gc_duration_seconds{quantile="0"} 8.82e-05
go_gc_duration_seconds{quantile="0.25"} 8.82e-05
go_gc_duration_seconds{quantile="0.5"} 8.82e-05
go_gc_duration_seconds{quantile="0.75"} 8.82e-05
go_gc_duration_seconds{quantile="1"} 8.82e-05
go_gc_duration_seconds_sum 8.82e-05
go_gc_duration_seconds_count 1
# HELP go_goroutines Number of goroutines that currently exist.
# TYPE go_goroutines gauge
go_goroutines 20
# HELP go_info Information about the Go environment.
# TYPE go_info gauge
go_info{version="go1.17.3"} 1
# HELP go_memstats_alloc_bytes Number of bytes allocated and still in use.
# TYPE go_memstats_alloc_bytes gauge
go_memstats_alloc_bytes 3.546384e+06
# HELP go_memstats_alloc_bytes_total Total number of bytes allocated, even if freed.
# TYPE go_memstats_alloc_bytes_total counter
go_memstats_alloc_bytes_total 4.492048e+06
# HELP go_memstats_buck_hash_sys_bytes Number of bytes used by the profiling bucket hash table.
# TYPE go_memstats_buck_hash_sys_bytes gauge
go_memstats_buck_hash_sys_bytes 1.448119e+06
# HELP go_memstats_frees_total Total number of frees.
# TYPE go_memstats_frees_total counter
go_memstats_frees_total 6512
# HELP go_memstats_gc_cpu_fraction The fraction of this program's available CPU time used by the GC since the program started.
# TYPE go_memstats_gc_cpu_fraction gauge
go_memstats_gc_cpu_fraction 1.6141668631896834e-06
# HELP go_memstats_gc_sys_bytes Number of bytes used for garbage collection system metadata.
# TYPE go_memstats_gc_sys_bytes gauge
go_memstats_gc_sys_bytes 4.835688e+06
# HELP go_memstats_heap_alloc_bytes Number of heap bytes allocated and still in use.
# TYPE go_memstats_heap_alloc_bytes gauge
go_memstats_heap_alloc_bytes 3.546384e+06
# HELP go_memstats_heap_idle_bytes Number of heap bytes waiting to be used.
# TYPE go_memstats_heap_idle_bytes gauge
go_memstats_heap_idle_bytes 2.686976e+06
# HELP go_memstats_heap_inuse_bytes Number of heap bytes that are in use.
# TYPE go_memstats_heap_inuse_bytes gauge
go_memstats_heap_inuse_bytes 5.07904e+06
# HELP go_memstats_heap_objects Number of allocated objects.
# TYPE go_memstats_heap_objects gauge
go_memstats_heap_objects 4687
# HELP go_memstats_heap_released_bytes Number of heap bytes released to OS.
# TYPE go_memstats_heap_released_bytes gauge
go_memstats_heap_released_bytes 1.736704e+06
# HELP go_memstats_heap_sys_bytes Number of heap bytes obtained from system.
# TYPE go_memstats_heap_sys_bytes gauge
go_memstats_heap_sys_bytes 7.766016e+06
# HELP go_memstats_last_gc_time_seconds Number of seconds since 1970 of last garbage collection.
# TYPE go_memstats_last_gc_time_seconds gauge
go_memstats_last_gc_time_seconds 1.6412358823440428e+09
# HELP go_memstats_lookups_total Total number of pointer lookups.
# TYPE go_memstats_lookups_total counter
go_memstats_lookups_total 0
# HELP go_memstats_mallocs_total Total number of mallocs.
# TYPE go_memstats_mallocs_total counter
go_memstats_mallocs_total 11199
# HELP go_memstats_mcache_inuse_bytes Number of bytes in use by mcache structures.
# TYPE go_memstats_mcache_inuse_bytes gauge
go_memstats_mcache_inuse_bytes 9600
# HELP go_memstats_mcache_sys_bytes Number of bytes used for mcache structures obtained from system.
# TYPE go_memstats_mcache_sys_bytes gauge
go_memstats_mcache_sys_bytes 16384
# HELP go_memstats_mspan_inuse_bytes Number of bytes in use by mspan structures.
# TYPE go_memstats_mspan_inuse_bytes gauge
go_memstats_mspan_inuse_bytes 71536
# HELP go_memstats_mspan_sys_bytes Number of bytes used for mspan structures obtained from system.
# TYPE go_memstats_mspan_sys_bytes gauge
go_memstats_mspan_sys_bytes 81920
# HELP go_memstats_next_gc_bytes Number of heap bytes when next garbage collection will take place.
# TYPE go_memstats_next_gc_bytes gauge
go_memstats_next_gc_bytes 5.283728e+06
# HELP go_memstats_other_sys_bytes Number of bytes used for other system allocations.
# TYPE go_memstats_other_sys_bytes gauge
go_memstats_other_sys_bytes 1.499625e+06
# HELP go_memstats_stack_inuse_bytes Number of bytes in use by the stack allocator.
# TYPE go_memstats_stack_inuse_bytes gauge
go_memstats_stack_inuse_bytes 622592
# HELP go_memstats_stack_sys_bytes Number of bytes obtained from system for stack allocator.
# TYPE go_memstats_stack_sys_bytes gauge
go_memstats_stack_sys_bytes 622592
# HELP go_memstats_sys_bytes Number of bytes obtained from system.
# TYPE go_memstats_sys_bytes gauge
go_memstats_sys_bytes 1.6270344e+07
# HELP go_threads Number of OS threads created.
# TYPE go_threads gauge
go_threads 8
# HELP kafka_brokers Number of Brokers in the Kafka Cluster.
# TYPE kafka_brokers gauge
kafka_brokers 1
# HELP kafka_exporter_build_info A metric with a constant '1' value labeled by version, revision, branch, and goversion from which kafka_exporter was built.
# TYPE kafka_exporter_build_info gauge
kafka_exporter_build_info{branch="HEAD",goversion="go1.17.3",revision="15e4ad6a9ea8203135d4b974e825f22e31c750e5",version="1.4.2"} 1
# HELP process_cpu_seconds_total Total user and system CPU time spent in seconds.
# TYPE process_cpu_seconds_total counter
process_cpu_seconds_total 0.11
# HELP process_max_fds Maximum number of open file descriptors.
# TYPE process_max_fds gauge
process_max_fds 1.048576e+06
# HELP process_open_fds Number of open file descriptors.
# TYPE process_open_fds gauge
process_open_fds 12
# HELP process_resident_memory_bytes Resident memory size in bytes.
# TYPE process_resident_memory_bytes gauge
process_resident_memory_bytes 1.703936e+07
# HELP process_start_time_seconds Start time of the process since unix epoch in seconds.
# TYPE process_start_time_seconds gauge
process_start_time_seconds 1.64123574422e+09
# HELP process_virtual_memory_bytes Virtual memory size in bytes.
# TYPE process_virtual_memory_bytes gauge
process_virtual_memory_bytes 7.35379456e+08
# HELP process_virtual_memory_max_bytes Maximum amount of virtual memory available in bytes.
# TYPE process_virtual_memory_max_bytes gauge
process_virtual_memory_max_bytes 1.8446744073709552e+19
# HELP promhttp_metric_handler_requests_in_flight Current number of scrapes being served.
# TYPE promhttp_metric_handler_requests_in_flight gauge
promhttp_metric_handler_requests_in_flight 1
# HELP promhttp_metric_handler_requests_total Total number of scrapes by HTTP status code.
# TYPE promhttp_metric_handler_requests_total counter
promhttp_metric_handler_requests_total{code="200"} 3
promhttp_metric_handler_requests_total{code="500"} 0
promhttp_metric_handler_requests_total{code="503"} 0
Update
A more reliable way to do this is to use a wrapper script in order to perform an application-specific health check as described in https://docs.docker.com/compose/startup-order/. With the following directory structure,
.
├── docker-compose.yml
└── kafka-exporter
├── Dockerfile
└── run.sh
the following Dockerfile,
FROM bitnami/kafka-exporter:latest
COPY run.sh /opt/bitnami/kafka-exporter/bin
ENTRYPOINT ["run.sh"]
and the following run.sh,
#!/bin/sh
while ! bin/kafka_exporter; do
echo "Waiting for the Kafka cluster to come up..."
sleep 1
done
and the following docker-compose.yml,
version: '2'
networks:
app-tier:
driver: bridge
services:
zookeeper:
image: 'bitnami/zookeeper:latest'
environment:
- 'ALLOW_ANONYMOUS_LOGIN=yes'
networks:
- app-tier
kafka:
image: 'bitnami/kafka:latest'
environment:
- KAFKA_CFG_ZOOKEEPER_CONNECT=zookeeper:2181
- ALLOW_PLAINTEXT_LISTENER=yes
networks:
- app-tier
kafka-exporter:
build: kafka-exporter
ports:
- "9308:9308"
networks:
- app-tier
entrypoint: ["run.sh"]
myapp:
image: 'bitnami/kafka:latest'
environment:
- KAFKA_CFG_ZOOKEEPER_CONNECT=zookeeper:2181
- ALLOW_PLAINTEXT_LISTENER=yes
networks:
- app-tier
Upon running docker-compose build && docker-compose up, I can see from the logs that after ~2 seconds (on the third attempt) the Kafka Exporter starts successfully:
> docker logs bitnami-docker-kafka-kafka-exporter-1 -f
I0104 16:05:39.765921 8 kafka_exporter.go:769] Starting kafka_exporter (version=1.4.2, branch=non-git, revision=non-git)
F0104 16:05:40.525065 8 kafka_exporter.go:865] Error Init Kafka Client: kafka: client has run out of available brokers to talk to (Is your cluster reachable?)
Waiting for the Kafka cluster to come up...
I0104 16:05:41.538482 16 kafka_exporter.go:769] Starting kafka_exporter (version=1.4.2, branch=non-git, revision=non-git)
F0104 16:05:42.295872 16 kafka_exporter.go:865] Error Init Kafka Client: kafka: client has run out of available brokers to talk to (Is your cluster reachable?)
Waiting for the Kafka cluster to come up...
I0104 16:05:43.307293 24 kafka_exporter.go:769] Starting kafka_exporter (version=1.4.2, branch=non-git, revision=non-git)
I0104 16:05:43.686798 24 kafka_exporter.go:929] Listening on HTTP :9308
