Michal Klempa created FLINK-8714:
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Summary: Suggest new users to use env.readTextFile method with 2 arguments (using the charset), not to rely on system charset (which varies across environments)
Key: FLINK-8714
URL:
https://issues.apache.org/jira/browse/FLINK-8714 Project: Flink
Issue Type: Improvement
Components: Documentation
Affects Versions: 1.4.0
Reporter: Michal Klempa
When a newcomer (like me), goes through the docs, there are several places where examples encourage to read the input data using the `env.readTextFile()` method.
This method variant does not take a second argument - character set (see [
https://ci.apache.org/projects/flink/flink-docs-release-1.4/api/java/org/apache/flink/streaming/api/environment/StreamExecutionEnvironment.html#readTextFile-java.lang.String-).] This versoin relies (according to Javadoc) on " The file will be read with the system's default character set. "
This behavior is also default in Java, like in the `java.util.String.getBytes()` method, where not supplying the charset mean - use the system locale or the one which JVM was started with (see [
https://stackoverflow.com/questions/64038/setting-java-locale-settings).] There are two ways to set locale prior to JVM start (-D arguments or set LC_ALL variable).
Given this is something a new Flink user may not know about, nor he wants to spend hours trying to find the environment-related bug (it works on localhost, but in production the locale is different), I would kindly suggest a change in documentation: lets migrate examples to use the two-argument version of `readTextFile(filePath, charsetName)`.
I am open to criticism and suggestions. The listing of readTextFile I was able to grep in docs is:
```
./dev/datastream_api.md:- `readTextFile(path)` - Reads text files, i.e. files that respect the `TextInputFormat` specification, line-by-line and returns them as Strings.
./dev/datastream_api.md:- `readTextFile(path)` - Reads text files, i.e. files that respect the `TextInputFormat` specification, line-by-line and returns them as Strings.
./dev/libs/storm_compatibility.md:DataStream<String> text = env.readTextFile(localFilePath);
./dev/cluster_execution.md: DataSet<String> data = env.readTextFile("hdfs://path/to/file");
./dev/batch/index.md:- `readTextFile(path)` / `TextInputFormat` - Reads files line wise and returns them as Strings.
./dev/batch/index.md:- `readTextFileWithValue(path)` / `TextValueInputFormat` - Reads files line wise and returns them as
./dev/batch/index.md:DataSet<String> localLines = env.readTextFile("file:///path/to/my/textfile");
./dev/batch/index.md:DataSet<String> hdfsLines = env.readTextFile("hdfs://nnHost:nnPort/path/to/my/textfile");
./dev/batch/index.md:DataSet<String> logs = env.readTextFile("file:///path/with.nested/files")
./dev/batch/index.md:- `readTextFile(path)` / `TextInputFormat` - Reads files line wise and returns them as Strings.
./dev/batch/index.md:- `readTextFileWithValue(path)` / `TextValueInputFormat` - Reads files line wise and returns them as
./dev/batch/index.md:val localLines = env.readTextFile("file:///path/to/my/textfile")
./dev/batch/index.md:val hdfsLines = env.readTextFile("hdfs://nnHost:nnPort/path/to/my/textfile")
./dev/batch/index.md:env.readTextFile("file:///path/with.nested/files").withParameters(parameters)
./dev/batch/index.md:DataSet<String> lines = env.readTextFile(pathToTextFile);
./dev/batch/index.md:val lines = env.readTextFile(pathToTextFile)
./dev/batch/examples.md:DataSet<String> text = env.readTextFile("/path/to/file");
./dev/batch/examples.md:val text = env.readTextFile("/path/to/file")
./dev/api_concepts.md:DataStream<String> text = env.readTextFile("file:///path/to/file");
./dev/api_concepts.md:val text: DataStream[String] = env.readTextFile("file:///path/to/file")
./dev/local_execution.md: DataSet<String> data = env.readTextFile("file:///path/to/file");
./ops/deployment/aws.md:env.readTextFile("s3://<bucket>/<endpoint>");
```
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