Omit rare edge case/bad configuration scenarios from README, add warn…

…ing about low values for maximum_message_size_bytes

README.md

@@ -43,13 +43,21 @@ Logster can be configured using `Logster.config`:
 - `Logster.config.enable_js_error_reporting` : enable js error reporting from clients
 - `Logster.config.rate_limit_error_reporting` : controls automatic 1 minute rate limiting for JS error reporting.
 - `Logster.config.web_title` : `<title>` tag for logster error page.
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 - `Logster.config.enable_custom_patterns_via_ui` : enable the settings page (`/settings`) where you can add suppression and grouping patterns.
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 - `Logster.config.allow_grouping` : Enable grouping of similar messages into one messages with an array of `env` of the grouped messages. Similar messages are messages that have identical backtraces, severity and log message.
-- `Logster.config.maximum_message_size_bytes` : set a maximum size for messages. Default value is 10,000. If a message size exceeds this limit, Logster will first remove all occurrences of `gems_dir` (more on this config below) from the backtrace and computes the size again; if the message is still above the limit, Logster will iteratively remove a line from the end of the backtrace until the size becomes below the limit, or one line remains. At this point if the message size is still above the limit, Logster will remove as many as character as needed to bring the size below the limit. However, before all of this if Logster figures out that removing the whole backtrace will not bring the size below the limit, it'll give up early and not attempt to reduce the size at all. So it's not recommended to set this config to a really low value e.g. less than 2000.
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+- `Logster.config.maximum_message_size_bytes` : set a maximum size for messages. Default value is 10,000. If a message size exceeds this limit, Logster will first remove all occurrences of `gems_dir` (more on this config below) from the backtrace and computes the size again; if the message is still above the limit, Logster will iteratively remove a line from the end of the backtrace until the size becomes below the limit, or one line remains; at this point if the message size is still above the limit, Logster will remove as many as character as needed from the remaining line to bring the size below the limit. It's discouraged to set this config to a really low value (e.g. less than 2000) because a message needs a minimum amount of data in order to make sense (the minimum amount varies per message), so the closer the limit is to the mimimum amount of space needed, the more of the backtrace will be removed. Keep this in mind when tweaking this config.
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 - `Logster.config.max_env_bytes` : set a maximum size for `env`. Default value is 1000. In case `env` is an array of hashes, this limit applies to the individual hashes in the array rather than the whole array. If an `env` hash exceeds this limit, Logster will take the biggest subset of key-value pairs whose size is below the limit. If the hash has a key with the name `time`, it will always be included.
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 - `Logster.config.max_env_count_per_message` : default value is 50. Logster can merge messages that have the same backtrace, severity and log message into one grouping message that have many `env` hashes. This config specifies the maximum number of `env` hashes a grouping message is allowed to keep. If this limit is reached and a new similar message is created and it needs to be merged, Logster will remove the oldest `env` hash from the grouping message and adds the new one.
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 - `Logster.config.project_directories` : This should be an array of hashes that map paths on the local filesystem to GitHub repository URLs. If this feature is enabled, Logster will parse backtraces and try to construct a GitHub URL to the exact file and line number for each line in the backtrace. For a Rails app, the config may look like this: `Logster.config.project_directories = [{ path: Rails.root.to_s, url: "https://github.com/<your_org>/<your_repo>" }]`. The GitHub links that are constructed will use the `master` branch. If you want Logster to use the `application_version` attribute from the `env` tab so that the GitHub links point to the exact version of the app when the log message is created, add `main_app: true` key to the hash.
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 - `Logster.config.enable_backtrace_links` : Enable/disable the backtrace links feature.
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 - `Logster.config.gems_dir` : The value of this config is `Gem.dir + "/gems/"` by default. You probably don't need to change this config, but it's available in case your app gems are installed in a different directory. An example where this config is needed is Logster [demo site](http://logster.info/logs/): [https://github.com/discourse/logster/blob/master/website/sample.rb#L77](https://github.com/discourse/logster/blob/master/website/sample.rb#L77).
 
 ### Tracking Error Rate