When using memcached with docker, how can I set the max item size?
I know the following can be done e.g. -m 64 to set the storage limit:
docker run --name my-memcache -d memcached memcached -m 64
I also know that in a Linux box the following can be done to set item max size limit:
MAXITEMSIZE=5m
The entry point script in the memcached image will pass on command line options
docker run --name my-memcache -d memcached -I 10m
If you want to make the option default to something and be configured by the MAXITEMSIZE environment variable you could create an image FROM memcached and copy a new entry point script in.
FROM memcached
COPY docker-entrypoint.sh /usr/local/bin/
The script needs to cater for when a user doesn't run memcached and when they specify the -I option manually.
#!/bin/sh
set -ue
# first arg is `-f` or `--some-option`
if [ "${1#-}" != "$1" ]; then
set -- memcached "$#"
fi
if [ "$1" = "memcached" ]; then
shift
MAXITEMSIZE=${MAXITEMSIZE:-1m}
set -- memcached -I "$MAXITEMSIZE" "$#"
fi
exec "$#"
Related
I am trying to import a pipeline into streamsets, during container start up, by using the Docker CMD command in Dockerfile. The image builds, but while creating the container there is no error but it exits with code 0. So it never comes up. Here is what I did:
Dockerfile:
FROM streamsets/datacollector:3.18.1
COPY myPipeline.json /pipelinejsonlocation/
EXPOSE 18630
ENTRYPOINT ["/bin/sh"]
CMD ["/opt/streamsets-datacollector-3.18.1/bin/streamsets","cli","-U", "http://localhost:18630", \
"-u", \
"admin", \
"-p", \
"admin", \
"store", \
"import", \
"-n", \
"myPipeline", \
"--stack", \
"-f", \
"/pipelinejsonlocation/myPipeline.json"]
Build image:
docker build -t cmp/sdc .
Run image:
docker run -p 18630:18630 -d --name sdc cmp/sdc
This outputs the container id. But the container is in the Exited status as shown below.
docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
537adb1b05ab cmp/sdc "/bin/sh /opt/stream…" 5 seconds ago Exited (0) 3 seconds ago sdc
When I do not specify the CMD command in the Dockerfile, the streamsets container spins up and then when I run the streamsets import command in the running container in shell, it works. But how do I get it done during provisioning itself? Is there something I am missing in the Dockerfile?
In your Dockerfile you overwrite the default CMD and ENTRYPOINT from the StreamSets Data Collector Dockerfile. So the container only executes your command during startup and exits without errors afterwards. This is the reason why your container is in Exited (0) status.
In general this is good and expected behavior. If you want to keep your container alive you need to execute another command in the foreground, which never ends. But unfortunately, you cannot run multiple CMDs in your docker file.
I dug a little deeper. The default entry point of the image is ENTRYPOINT ["/docker-entrypoint.sh"]. This script sets up a few things and starts the Data Collector.
It is required that the Data Collector is running before the pipeline is imported. So a solution could be to copy the default docker-entrypoint.sh and modify it to start the Data Collector and import the pipeline afterwards. You could to it like this:
Dockerfile:
FROM streamsets/datacollector:3.18.1
COPY myPipeline.json /pipelinejsonlocation/
# Replace docker-entrypoint.sh
COPY docker-entrypoint.sh /docker-entrypoint.sh
EXPOSE 18630
docker-entrypoint.sh (https://github.com/streamsets/datacollector-docker/blob/master/docker-entrypoint.sh):
#!/bin/bash
#
# Copyright 2017 StreamSets Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
set -e
# We translate environment variables to sdc.properties and rewrite them.
set_conf() {
if [ $# -ne 2 ]; then
echo "set_conf requires two arguments: <key> <value>"
exit 1
fi
if [ -z "$SDC_CONF" ]; then
echo "SDC_CONF is not set."
exit 1
fi
grep -q "^$1" ${SDC_CONF}/sdc.properties && sed 's|^#\?\('"$1"'=\).*|\1'"$2"'|' -i ${SDC_CONF}/sdc.properties || echo -e "\n$1=$2" >> ${SDC_CONF}/sdc.properties
}
# support arbitrary user IDs
# ref: https://docs.openshift.com/container-platform/3.3/creating_images/guidelines.html#openshift-container-platform-specific-guidelines
if ! whoami &> /dev/null; then
if [ -w /etc/passwd ]; then
echo "${SDC_USER:-sdc}:x:$(id -u):0:${SDC_USER:-sdc} user:${HOME}:/sbin/nologin" >> /etc/passwd
fi
fi
# In some environments such as Marathon $HOST and $PORT0 can be used to
# determine the correct external URL to reach SDC.
if [ ! -z "$HOST" ] && [ ! -z "$PORT0" ] && [ -z "$SDC_CONF_SDC_BASE_HTTP_URL" ]; then
export SDC_CONF_SDC_BASE_HTTP_URL="http://${HOST}:${PORT0}"
fi
for e in $(env); do
key=${e%=*}
value=${e#*=}
if [[ $key == SDC_CONF_* ]]; then
lowercase=$(echo $key | tr '[:upper:]' '[:lower:]')
key=$(echo ${lowercase#*sdc_conf_} | sed 's|_|.|g')
set_conf $key $value
fi
done
# MODIFICATIONS:
#exec "${SDC_DIST}/bin/streamsets" "$#"
check_data_collector_status () {
watch -n 1 ${SDC_DIST}/bin/streamsets cli -U http://localhost:18630 ping | grep -q 'version' && echo "Data Collector has started!" && import_pipeline
}
function import_pipeline () {
sleep 1
echo "Start to import pipeline"
${SDC_DIST}/bin/streamsets cli -U http://localhost:18630 -u admin -p admin store import -n myPipeline --stack -f /pipelinejsonlocation/myPipeline.json
echo "Finished importing pipeline"
}
# Start checking if Data Collector is up (in background) and start Data Collector
check_data_collector_status & ${SDC_DIST}/bin/streamsets $#
I commented out the last line exec "${SDC_DIST}/bin/streamsets" "$#" of the default docker-entrypoint.sh and added two functions. check_data_collector_status () pings the Data Collector service until it is available. import_pipeline () imports your pipeline.
check_data_collector_status () runs in background and ${SDC_DIST}/bin/streamsets $# is started in foreground as before. So the pipeline is imported after the Data Collector service is started.
Run this image with sleep command:
docker run -p 18630:18630 -d --name sdc cmp/sdc sleep 300
300 is the time to sleep in seconds.
Then exec your script manually within the docker container and find out what's wrong.
I am trying to find a "global" solution for injecting an SSH key into a container. I know that there are several solutions including docker build kit and so on...but I don't want to build an image and inject the SSH key. I want to inject the SSH key by using an existing image with docker compose.
I use the following docker compose file:
version: '3.1'
services:
server1:
image: XXXXXXX
container_name: server1
command: bash -c "/root/init.sh && python3 /root/my_python.py"
environment:
- MANAGED_HOST=mserver
volumes:
- ./init.sh:/root/init.sh
secrets:
- id_rsa
secrets:
id_rsa:
file: /home/user/.ssh/id_rsa
The init.sh is as follows:
#!/bin/bash
eval "$(ssh-agent -s)" > /dev/null
if [ ! -d "/root/.ssh/" ]; then
mkdir /root/.ssh
ssh-keyscan $MANAGED_HOST > /root/.ssh/known_hosts
fi
ssh-add -k /run/secrets/id_rsa
If I run docker compose with the parameter command
bash -c "/root/init.sh && python3 /root/my_python.py", then the SSH authentication to the appropriate remote host ($MANAGED_HOST) is not working.
An agent process is running:
root 8 1 0 12:50 ? 00:00:00 ssh-agent -s
known_hosts is OK:
root#c67655d87ced:~# cat /root/.ssh/known_hosts
BLABLABLA ssh-rsa AAAAB3BLABLABLA....
and the agent is running, but the private key is not added:
root#c67655d87ced:~# ssh-add -l
Could not open a connection to your authentication agent.
Now, if I log in the container (docker exec -it server1 /bin/bash) and run the commands from init.sh one by one from the command line, then the SSH authentication to the appropriate remote host ($MANAGED_HOST) is working?!?
Any idea, how I can get it working by using the docker compose?
It should be enough to cause the file $HOME/.ssh/id_rsa to exist with appropriate permissions; you don't need an ssh agent running.
#!/bin/sh
if ! [ -d "$HOME/.ssh" ]; then
mkdir "$HOME/.ssh"
fi
chmod 0700 "$HOME/.ssh"
if [ -n "$MANAGED_HOST" ]; then
ssh-keyscan "$MANAGED_HOST" >> "$HOME/.ssh/known_hosts"
fi
if [ -f /run/secrets/id_rsa ]; then
cp /run/secrets/id_rsa "$HOME/.ssh/id_rsa"
chmod 0400 "$HOME/.ssh/id_rsa"
fi
# exec "$#"
A typical pattern is to use the Dockerfile ENTRYPOINT to do first-time setup tasks like this. That will get passed the CMD as arguments, and the commented exec "$#" line at the end of the file runs that as a command. You'd set this up in your image's Dockerfile like:
FROM XXXXXX
...
# Script must be executable on the host, and must start with a
# #!/bin/sh "shebang" line
COPY init.sh /root
# MUST use JSON-array form
ENTRYPOINT ["/root/init.sh"]
# Can use any Dockerfile syntax
CMD ["python3", "/root/my_python.py"]
In your specific example, you're launching init.sh as a subprocess. The ssh-agent setup sets some environment variables, like $SSH_AUTH_SOCK, but when these run as a subprocess they don't get propagated back out to the host process. You can use the standard POSIX shell . builtin (the bash source builtin is equivalent, but non-standard) to cause those environment variables to be set in the context of the parent shell:
command: sh -c ". /root/init.sh && exec python3 /root/my_python.py"
The exec replaces the shell wrapper with the Python script, which you generally want. This will also wind up being the parent process of ssh-agent, which could potentially surprise your process if it happens to exit.
I need to set some environment variable for all users and processes inside docker container. It should be set at container start, not in Dockerfile, because it depends on running environment.
So the simple Dockerfile
FROM ubuntu
RUN echo 'export TEST=test' >> '/root/.bashrc'
works well for interactive sessions
docker run -ti test bash
then
env
and there is TEST=test
but when docker run -ti test env there is no TEST
I was trying
RUN echo 'export TEST=test' >> '/etc/environment'
RUN echo 'TEST="test"' >> '/etc/environment'
RUN echo 'export TEST=test' >> /etc/profile.d/1.sh
ENTRYPOINT export TEST=test
Nothing helps.
Why I need this. I have http_proxy variable inside container automatically set by docker, I need to set another variables, based on it, i.e. JAVA_OPT, do it system wide, for all users and processes, and in running environment, not at build time.
I would create a script which would be an entrypoint:
#!/bin/bash
# if env variable is not set, set it
if [ -z $VAR ];
then
# env variable is not set
export VAR=$(a command that gives the var value);
fi
# pass the arguments received by the entrypoint.sh
# to /bin/bash with command (-c) option
/bin/bash -c $#
And in Dockerfile I would set the entrypoint:
ENTRYPOINT entrypoint.sh
Now every time I run docker run -it <image> <any command> it uses my script as entrypoint so will always run it before the command then pass the arguments to the right place which is /bin/bash.
Improvements
The above script is enough to work if you are always using the entrypoint with arguments, otherwise your $# variable will be empty and will give you an error /bin/bash: -c: option requires an argument. A easy fix is an if statement:
if [ ! -z $# ];
then
/bin/bash -c $#;
fi
Setting the parameter in ENTRYPOINT would solve this issue.
In docker file pass parameter in ENTRYPOINT
For reasons such as hardening a Docker image, I want local users not be able to use wget. Since wget is a function of /bin/busybox, removal seems appropriate, even if a little drastic, and would apparently work at for and at runtime.
However RUN rm /bin/busybox will cause go stack traces, when run on top of Kubernetes or locally.
Is there any build time solution?
The example would be
FROM haproxy:1.6-alpine
RUN addgroup -S haproxy && adduser -S -g haproxy haproxy
RUN rm /bin/busybox
COPY haproxy.cfg /usr/local/etc/haproxy/haproxy.cfg
With the HAProxy's default ENTRYPOINT
#!/bin/sh
set -e
# first arg is `-f` or `--some-option`
if [ "${1#-}" != "$1" ]; then
set -- haproxy "$#"
fi
if [ "$1" = 'haproxy' ]; then
# if the user wants "haproxy", let's use "haproxy-systemd-wrapper" instead so we can have proper reloadability implemented by upstream
shift # "haproxy"
set -- "$(which haproxy-systemd-wrapper)" -p /run/haproxy.pid "$#"
fi
exec "$#"
If your /bin/sh is provided by busybox, and your entrypoint uses /bin/sh, then you need to delete busybox only after the entrypoint is started.
A simpler entrypoint definition, which doesn't require a shell, might look something like:
RUN ["rm", /bin/busybox"]
ENTRYPOINT ["haproxy-systemd-wrapper", "-p", "/run/haproxy.pid"]
CMD ["-f", "/usr/local/etc/haproxy/haproxy.cfg"]
I have a very simple Docker container that runs a bash shell script that returns something. My Dockerfile:
# Docker image to get stats from a rest interface using CURL and JSON parsing
FROM ubuntu
RUN apt-get update
# Install curl and jq, a lightweight command-line JSON processor
RUN apt-get install -y curl jq
COPY ./stats.sh /
# Make sure script has execute permissions for root
RUN chmod 500 stats.sh
# Define a custom entrypoint to execute stats commands easily within the container,
# using environment substitution and the like...
ENTRYPOINT ["/stats.sh"]
CMD ["info"]
The stats.sh looks like this:
#!/bin/bash
# ElasticSearch
## Get the total size of the elasticsearch DB in bytes
## Requires the elasticsearch container to be linked with alias 'elasticsearch'
function es_size() {
local size=$(curl $ELASTICSEARCH_PORT_9200_TCP_ADDR:$ELASTICSEARCH_PORT_9200_TCP_PORT/_stats/_all 2>/dev/null|jq ._all.total.store.size_in_bytes)
echo $size
}
if [[ "$1" == "info" ]]; then
echo "Check stats.sh for available commands"
elif [[ "$1" == "es_size" ]]; then
es_size
else
echo "Unknown command: $#"
fi
So basically, I have a Docker container that I will run with --rm to exit immediately after running and returning the value I want. More precise, I run it from another shell script (in the host) with:
local size=$(docker run --name stats-es-size --rm --link $esName:elasticsearch $ENV_DOCKER_REST_STATS_IMAGE:$ENV_DOCKER_REST_STATS_VERSION es_size)
Now I'm running this periodically to gather statistics, once a minute. While it works well in general, I end up getting containers with status Dead about once a day.
Can anybody tell me what I might be doing wrong? Is there some problem with my approach or why do my containers die with a certain frequency?