How to see all the logs

Question

I have a small app on heroku. Whenever I want to see the logs I go to the command line and do

heroku logs

That only shows me about 100 lines. Is there not a way to see complete logs for our application on heroku?

Quaint

Answer 1

Update (thanks to dawmail333):

heroku logs -n 1500

or, to tail the logs live

heroku logs -t 

Heroku log documentation

If you need more than a few thousand lines you can Use heroku's Syslog Drains

Alternatively (old method):

$ heroku run rails c
File.open('log/production.log', 'r').each_line { |line| puts line }

Statement

This is now not working on cedar stack. Has anybody found a new alternative? – Clie

Just use heroku logs -n 1500, it's the best method available on Cedar. If you need more lines than that, you need a syslog drain: devcenter.heroku.com/articles/logging#syslog_drains – Slavonic

This is a useful tip too for Asset Pipeline issues: heroku logs -n 2000 | grep 'precompiled' – Tumefaction

It's actually heroku run rails c. Updated! – Statement

When you execute a one-off dyno with heroku run, the time spent executing the command will accrue usage. Does anyone know if realtime log tails also accrue usage of dyno hours? – Lowkey

For the old method, why would you run a rails console instead of just heroku run cat log/production.log? – Mole

I think the old heroku might have had a whitelist of what can be run but don't really remember anymore :) – Statement

This is the correct way, heroku logs --app appname – Viviyan

Does anybody have a way to view these in the Heroku web UI? I don't really want to have to page through with the space bar when I can just drag a scrollbar… – Gurolinick

Answer 2

Logging has greatly improved in heroku!

$ heroku logs -n 500

Better!

$ heroku logs --tail

references: http://devcenter.heroku.com/articles/logging

UPDATED

These are no longer add-ons, but part of the default functionality :)

Standifer

Also, -n can go up to 1500, I assume that Heroku just cuts off anything after that. – Slavonic

Answer 3

Heroku treats logs as time-ordered streams of events. Accessing *.log files on the filesystem is not recommended in such an environment for a variety of reasons.

First, if your app has more than one dyno then each log file only represents a partial view into the events of your app. You would have to manually aggregate all the files to get the full view.

Second, the filesystem on Heroku is ephemeral meaning whenever your dyno is restarted or moved (which happens about once a day)the log files are lost. So you only get at most a day's view into that single dyno's logs.

Finally, on the Cedar stack running heroku console or even heroku run bash does not connect you to a currently running dyno. It spawns a new one specifically for the bash command. This is called a one-off process. As such, you won't find the log files for your other dynos that are running the actual http processes on the one spawned for heroku run.

Logging, and visibility in general, is a first-class citizen on Heroku and there are several tools that address these issues. First, to see a real-time stream of application events across all dynos and all layers of the application/stack use the heroku logs -t command to tail output to your terminal.

$ heroku logs -t
2010-09-16T15:13:46-07:00 app[web.1]: Processing PostController#list (for 208.39.138.12 at 2010-09-16 15:13:46) [GET]
2010-09-16T15:13:46-07:00 app[web.1]: Rendering template within layouts/application
2010-09-16T15:13:46-07:00 heroku[router]: GET myapp.heroku.com/posts queue=0 wait=0ms service=1ms bytes=975
2010-09-16T15:13:47-07:00 app[worker.1]: 2 jobs processed at 16.6761 j/s, 0 failed ...

This works great for observing the behavior of your application right now. If you want to store the logs for longer periods of time you can use one of the many logging add-ons that provide log retention, alerting and triggers.

Lastly, if you want to store the log files yourself you can setup your own syslog drain to receive the stream of events from Heroku and post-process/analyze yourself.

Summary: Don't use heroku console or heroku run bash to view static log files. Pipe into Heroku's stream of log events for your app using heroku logs or a logging add-on.

Pilferage

Answer 4

Well, the above answers are very helpful it will help you to view from the command line. Whereas if you want to check from GUI so you have to log into your Heroku account and then select your application and finally click on view logs

Twinberry

This method only shows you the log output as they occur, starting from the time you click on the "View Logs" option. So it is not useful unless you are just wanting to essentially tail the logs without going into the console. – Altorilievo

is not there any option to see all the logs from this UI itself? – Hargrave

^Bump, have same question as @SunilGarg – Ibsen

Answer 5

Follow on Heroku logging

To view your logs we have:

1. logs command retrives 100 log lines by default.

heroku logs

2. show maximum 200 lines, --num (or -n) option.

heroku logs -n 200

3. Show logs in real time

heroku logs --tail

4. If you have many apps on heroku

heroku logs --app your_app_name

Rabblerouser

Answer 6

Also see individual streams/filters.

E.g tail only your application logs

heroku logs --source app -t

Or see only the router logs

heroku logs --ps router

Or chain them together

heroku logs --source app --ps worker

So good..

Proscenium

To see only logs of my application I do : heroku logs --ps web.1 (with 1 dyno) – Pyonephritis

Answer 7

You can access your log files using Heroku's Command Line Interface (CLI Usage).

If Heroku's CLI is installed and you know your application name (like https://myapp.herokuapp.com/), then you can run the following command:

heroku logs --tail --app=myapp

You can also access the logs in a real-time stream using:

heroku logs --source app --tail --app=myapp

If the logs tell you something like this:

npm ERR! A complete log of this run can be found in:

npm ERR! /app/.npm/_logs/2017-07-11T08_29_45_291Z-debug.log

Then you can also access them using the bash terminal via Heroku CLI:

heroku run bash --app=myapp
less ./.npm/_logs/2017-07-11T08_29_45_291Z-debug.log

Ardent

I get /usr/bin/less: cannot execute binary files – Camus

Answer 8

heroku logs -t shows us the live logs.

Celin

But it will stop after a while. – Encephaloma

Answer 9

Might be worth it to add something like the free Papertrail plan to your app. Zero configuration, and you get 7 days worth of logging data up to 10MB/day, and can search back through 2 days of logs.

Wilcher

Answer 10

My solution is to get complete log the first time the application start, like:

heroku logs -n 1500 > log

then add fgrep -vf to keep it up to date, like:

heroku logs -n 1500 > newlog ; fgrep -vf log newlog >> log

for continuous logging, just iterate it using watch for every x minutes (or seconds).

Manouch

Answer 11

You need to use -t or --tail option and you need to define your heroku app name.

heroku logs -t --app app_name

Actinism

Answer 12

for WAR files:

I did not use github, instead I uploaded directly, a WAR file ( which I found to be much easier and faster ).

So the following helped me:

heroku logs --app appname

Hope it will help someone.

Reviviscence

Answer 13

To see the detailed log you need to put two lines in the production.rb file:

config.logger = Logger.new(STDOUT)
config.logger.level = Logger::DEBUG

and then by running

heroku logs -t

you can see the detailed logs.

Indebtedness

Answer 14

You need to have some logs draining implemented and should be draining your logs there, to see all of the logs (manage historical logs as well):

1. First option - Splunk can be used: you can drain all your logs like:

heroku drains:add syslog+tls://splunk-server.com:514 -a app_name

And then login into your splunk server and search for any number of logs. I am using Splunk and this is working perfectly fine for me.

2. Second option - You can purchase add on to your App, like given below: (I haven't used these options, however these are the available ones).

   • Timber.io
   • Sumo Logic
   • LogEnteries
   • Log DNA
   • Papertrail

You can also have a look at below options: If you want to have your logs in JSON format, as it will help if your are pushing your logs to external system like Splunk/ELK, it would become easy (performance wise also) to search in JSON.

https://github.com/goodeggs/heroku-log-normalizer

It is not having Readme.md, but some explanation is given at https://github.com/goodeggs/bites/issues/20

Lastly

And you can always use below command as mentioned by other users already:

The following command will tail the generating logs on heroku

heroku logs -t -a <app_name>

The following comand will show the 1000 number of lines of logs from heroku

heroku logs -n 1000 -a <app_name>

Note only 1500 latest lines of logs are available and rest of them gets deleted from heroku dyno.

Doolie

Hi, do you use Splunk Cloud? If so, how did you get Heroku to drain? I'm using the HTTP Event Collector and enabled AllowStringQueryAuth to include the HEC token in the URL but no data is coming through. – Enlil

Answer 15

I prefer to do it this way

heroku logs --tail | tee -a herokuLogs

You can leave the script running in background and you can simply filter the logs from the text file the way you want anytime.

Maher

thanks, took me a while to scroll but finally found the solution for me. – Diarchy

Answer 16

heroku logs -t shows us the live logs. heroku logs -n 1500 for specific number of logs

But still I would recommend to use paper trail add-on which have certain benefits and has free basic plan.

Fernando

Answer 17

I suggest using an addon, I use Logentries. To use it, run in your command line:

heroku addons:create logentries:le_tryit

(that command creates the addon for a free account but clearly you can upgrade if you want)

Logentries allows you to save up to 5GB of log volume per month. That info is searchable by their command search within the last 7 days and it has real-time alerts.

So to answer your question, by using this addon you ensure that your logs aren't lost anymore when you reach the 1500 lines that Heroku saves by default. Hope this helps! Have a great day!

Indivertible

Answer 18

If you have multiple app instances you need the following.

heroku logs --tail --app app-name-here

Joannejoannes

Answer 19

You can use heroku logs -n 1500

But this is not a recommended approach(in other word doesn't show you the real picture)

I would suggest you plug some logging tool. ( sumoLogic, paper trail n all ) as an add-on

They all have a free version( with few limitations, though enough for a small app or dev env, which will provide good insight and tool to analyze logs )

Homothermal

Answer 20

I was running into a situation where in my apps' dashboard, when I went to:

More > View logs

I wouldn't get an output, just hung...

So I did a google and found this:

Heroku CLI plugin to list and create builds for Heroku apps.

I installed it and ran:

heroku builds -a example-app /* Lists 10 most recently created builds for example-app, that's where you get the id for the next step*/

Then enter:

heroku builds:output your-app-id-number -a example-app 

And that's it, you should get back what you normally see in the dashboard GUI or locally.

Hope this helps someone like it did me!

Greig

Answer 21

If your code is in python,
You can use the heroku3 pip library to access the logs for your Heroku app. First, you'll need to install the library by running. pip install heroku3

Then, you can use the following code to access your logs: import heroku3

# Connect to the Heroku API
conn = heroku3.from_key('YOUR_API_KEY')

# Get the app you want to access logs for
app = conn.app('YOUR_APP_NAME')

# Access the logs
logs = app.logs().stream()

# Print the logs
for line in logs:
    print(line)

Make sure to replace YOUR_API_KEY and YOUR_APP_NAME with the appropriate values for your app.

Additionally, you can use the heroku logs --tail command in your command line to stream the logs for your Heroku app. Make sure you are logged in and you have the access to the app.

Albertinealbertite

Answer 22

For cedar stack see:

https://devcenter.heroku.com/articles/oneoff-admin-ps

you need to run:

heroku run bash ...

Rania

On Cedar heroku run bash spins up a new dyno to host the bash command. The filesystem on that dyno won't contain any log files from the 'active' web dynos so this approach won't work. – Pilferage