Posts Tagged ‘s3’

Using AWS Athena to query S3 Server Access Logs.

Written by mannem on . Posted in EMR || Elastic Map Reduce

S3 server access logs can grow very big over time and it is very hard for a single machine to Process/Query/Analyze all these logs. So, we can use distributed computing to query the logs quickly. Ideally we might think of Apache Hadoop/Hive/Spark/Presto etc to process these logs. But, the simplicity of AWS Athena service as a Serverless model will make it even easier. This article will guide you to use Athena to process your s3 access logs with example queries and has some partitioning considerations which can help you to query TB’s of logs just in few seconds.

The server access log files consist of a sequence of new-line delimited log records. Each log record represents one request and consists of space delimited fields. The following is an example log consisting of six log records.

This article is based on the Log format of access logs specified here https://docs.aws.amazon.com/AmazonS3/latest/dev/LogFormat.html. The field’s and its format may change and DDL QUERY should be changed accordingly.

Sample Data:

Data Format considerations:

On first look, the data format appears simple , which is a textfile with space filed delimiter and newline(/n) delimited. However, there is a catch in this data format, the columns like Time , RequestURI & User-Agent can have space in their data ( [06/Feb/2014:00:00:38 +0000] , "GET /gdelt/1980.csv.gz HTTP/1.1" & aws-cli/1.7.36 Python/2.7.9 Linux/3.14.44-32.39.amzn1.x86_64) which will mess up with the SerDe parsing .

For RequestURI & User-Agent field, the data is enclosed in quotes with spaces inside it. This can be parsed by any SerDe’s that support Quotes. Unfortunately, Athena does not support such SerDe’s like org.apache.hadoop.hive.serde2.OpenCSVSerde which does has quotes feature.

The org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe included by Athena will not support quotes yet.

A custom SerDe called com.amazon.emr.hive.serde.s3.S3LogDeserializer comes with all EMR AMI’s just for parsing these logs. A query like the following would create the table easily. However, this SerDe will not be supported by Athena.

Looking at these limitations, the org.apache.hadoop.hive.serde2.RegexSerDe only seems like the feasible option. Writing RegEx for your log structure was bit time consuming , but I was able to write it with the help of ELB log structure example and http://regexr.com/ .

I used the following Regex for the S3 server access logs :

([^ ]*) ([^ ]*) \\[(.*?)\\] ([^ ]*) ([^ ]*) ([^ ]*) ([^ ]*) ([^ ]*) \\\"([^ ]*) ([^ ]*) (- |[^ ]*)\\\" (-|[0-9]*) (-|[0-9]*) ([-0-9]*) ([-0-9]*) ([-0-9]*) ([-0-9]*) ([^ ]*) (\"[^\"]*\") ([^ ]*)$

Also found at : http://regexr.com/3erct , where I removed some extra escape chars like \’s. In DDL , we need to add these escape characters like in following DDL.

([^ ]*) – matches a continuous string. Because the number fields like ‘time’ can return ‘-‘ character , I did not use ([-0-9]*) regex which is used for numbers. Because of same reason , I had to use STRING for all fields in DDL. We can use presto string functions to convert strings for appropriate conversions and comparison operators on DML

\\[(.*?)\\] or \\\[(.*?)\\\] – is for Time field – For a string like [06/Feb/2014:00:00:38 +0000], it will match and give a string like 05/Dec/2016:16:56:36 +0000 which is easier for querying between times.

\\\"([^ ]*) ([^ ]*) (- |[^ ]*)\\\" – is for Request-URI field – removes the quotes and splits the "GET /mybucket?versioning HTTP/1.1" into three groups.

(\"[^\"]*\") – is for User-Agent – matches the whole string with quotes.

(-|[0-9]*) – is for HTTPstatus which is always a number like 200 or 404 . If you expect a ‘-‘ string, you can use ([^ ]*) instead,

CREATE TABLE DDL :

Where s3://s3server-accesslogs-bucket/logs/ is the bucket and prefix of you access logs.

Once you create the table, you can query this table for specific information :

Example Queries :

Any field can be set to “-” to indicate that the data was unknown or unavailable, or that the field was not applicable to this request.

Caveats :

1. From time to time, AWS might extend the access log record format by adding new fields to the end of each line.The DDL/RegEx must be written to handle trailing fields that it does not understand.

Partitioning considerations :

Overtime, the logs in your target prefix(s3://s3server-accesslogs-bucket/logs/) can grow big. This is especially true if you have this same bucket/prefix for other buckets access logs. If you enable logging on multiple source buckets that identify the same target bucket, the target bucket will have access logs for all those source buckets, but each log object will report access log records for a specific source bucket.

Amazon S3 uses the following object key format for the log objects it uploads in the target bucket: TargetPrefixYYYY-mm-DD-HH-MM-SS-UniqueString . So, it basically creates multiple files with a bunch of logs in the S3 bucket.

Querying can be slower if there are large number of small files in textformat.

To speed things up, we need at-least one of these options to consolidate these logs.
1. PARTITIONING – can work on subset of files instead of going through all files.
2. CONVERT TO a COLUMNAR STORAGE – like ORC or PARQUET For faster query performance
3. ENABLE COMPRESSION – Snappy or GZ
4. BLOOM FILTERS

Unfortunately, we cannot do this by just defining a DDL. We need to copy/move out text based data-set with the above options enabled. One option to use of AWS EMR to periodically structure and partition the S3 access logs so that you can query those logs easily with Athena. At this moment, it is not possible to use Athena itself to convert non-partitioned data into partitioned data.

Here’s a example to convert Non partitioned s3 access logs to partitioned s3 access logs :

Continuing the Partitioning for incoming logs :

Note that above discussion talks about one time creation of all partitions. When you want to automatically add partitions to Athena with new files and coming to your S3 access logs with new request days on your log bucket, you will need to have a ‘batch job on schedule’ or a ‘trigger mechanism’ to do this.

Batch job on schedule :

Note that our source s3 access logs are dumped into one single directory. Each file name is like 2016-12-05-17-17-06-5D51435906E10586. Since we run our batch jobs after the above one-time-bulk-job, on the daily(or frequent) batches, we need to avoid the files that we already processed by previous one-time-job. For this , we can rely on the filename itself to get a list of newly generated files and then use an ETL to convert these files to partitioned data. We can also maintain a manifest file for the list of files already processed and the files which need to be processed etc. Managing all that is left beyond this blog. There’s multiple ways to do ETL. One way is to run an AWS Data Pipeline with EMR, on schedule, and run the hive queries on the new data.

/

Trigger based solution :

If you run a partition job on every S3 PUT or bunch of PUTS , you can use AWS Lambda which can trigger a piece of code on every S3 object PUT. You can get Metadata about that put and Handle that on your Lambda code accordingly to fireoff an ETL etc to do the partitioning. AWS Lambda should come with AWS SDK and you make all types of AWS API calls with proper permissions.
http://docs.aws.amazon.com/lambda/latest/dg/with-s3.html
http://docs.aws.amazon.com/lambda/latest/dg/with-s3-example.html

Other Input Regex’s :

CloudFront
'^(?!#)([^ ]+)\\s+([^ ]+)\\s+([^ ]+)\\s+([^ ]+)\\s+([^ ]+)\\s+([^ ]+)\\s+([^ ]+)\\s+([^ ]+)\\s+([^ ]+)\\s+([^ ]+)\\s+[^\(]+[\(]([^\;]+).*\%20([^\/]+)[\/](.*)$'
ELB access logs
'([^ ]*) ([^ ]*) ([^ ]*):([0-9]*) ([^ ]*):([0-9]*) ([.0-9]*) ([.0-9]*) ([.0-9]*) (-|[0-9]*) (-|[0-9]*) ([-0-9]*) ([-0-9]*) \\\”([^ ]*) ([^ ]*) (- |[^ ]*)\\\” ?(\”[^\”]*\”)? ?([A-Z0-9-]+)? ?([A-Za-z0-9.-]*)?$'
Apache web logs
'([^ ]*) ([^ ]*) ([^ ]*) (-|\\[[^\\]]*\\]) ([^ \"]*|\"[^\"]*\") (-|[0-9]*) (-|[0-9]*)(?: ([^ \"]*|\"[^\"]*\") ([^ \"]*|\"[^\"]*\"))?'

You may also like:
Using Athena to Query CloudTrail logs.
Parsing AWS Cloudtrail logs with EMR Hive and Spark

SqlActivity & RedshiftCopyActivity fails ? Use shellCommandActivity instead

Written by mannem on . Posted in Data Pipelines

There are several limitations of SQLActivity and RedshiftCopyActivity. If the psql/sql commands are too complex, these activities fail to prepare the statements correctly and will throw out some errors which cannot be easily rectified. So, you always have the option to use shellCommandActivity to run your complex script.

This article guides you to create a shell Script and corresponding Data-Pipeline template to run your complex script directly(part 1)or when present in S3(Part 2 ). As the true purpose of Data-Pipelines is automation, The script can also take arguments that you can reference using placeholders.

PART 1:

The following shell script takes arguments referenced in ScriptArguments object of the ShellCommandActivity. Its runs COPY command to copy files from S3 to PostgreRDS. Another example shows a copy from S3 to Redshift.

Run a PSQL command to copy from S3 to PostgreRDS

Run a PSQL command to copy from S3 to Redshift

A sample Pipeline template to copy from s3 to RDSPostgres

You may use a similar definition to copy from S3 to Redshift.


PART 2:

If your script is in S3 and you wanna pass arguments to your script:

Ex: insert into :v1 select * from source where source.id = :v2; -> s3://YourBucket/event_data_yyyymm.sql

$1 -> S3File location
$2 -> Password for Redshift
$3 -> Table Name
$4 -> condition value

A snippet of Definition for ShellCommandActivity can be :

Using a single hive warehouse for all EMR(Hadoop) clusters

Written by mannem on . Posted in EMR || Elastic Map Reduce

As the EMR/Hadoop cluster’s are transient, tracking all those databases and tables across clusters may be difficult. So, Instead of having different warehouse directories across clusters, You can use a single permanent hive warehouse across all EMR clusters. S3 would be a great choice as it is persistent storage and had robust architecture providing redundancy and read-after-write consistency.

For each cluster:

This can be configured using hive.metastore.warehouse.dir property on hive-site.xml.

You may need to update this setting on all nodes.

On a single hive session:

this can be configured using a command like set hive.metastore.warehouse.dir ="s3n://bucket/hive_warehouse"

or initialize hive cli with the following invocation -hiveconf hive.metastore.warehouse.dir=s3n://bucket/hive_warehouse

Note that using above configuration, all default databases and tables will be stored on s3 on path like s3://bucket/hive_warehouse/myHiveDatabase.db/

Running complex queries on redshift with Data-pipelines

Written by mannem on . Posted in Data Pipelines, Redshift

Sometimes AWS Data-Pipelines SQLActivity may not support complex queries. This is because Data-Pieplines SqlActivity passes this script to JDBS executeStatement(Prepared statement). This script is supposed to be idempotent. So here’s an alternative to run psql/sql commands using Data-Pipelines.

Suppose you have the following psql command,

select 'insert into event_data_' ||to_char(current_date,'yyyymm')|| '_v2 select * from stage_event_data_v2 where event_time::date >= '''||to_char(current_date, 'YYYY-MM')||'-01'' and event_time::date <= '''||last_day(current_date)||''';';

and it should output,

insert into event_data_201511_v2 select * from stage_event_data_v2 where event_time::date >= '2015-11-01' and event_time::date <= '2015-11-30';

This is a valid command in psql and can be successfully executed with workbenches and psql shell.

But using Data-pipelines, executing the above command will throw and error:

ERROR processing query/statement. Error: Parsing failed

This is because the script appears to be changing(not idempotent) when it is executed.

If you have a complex redshift commands and wish to performing operations against Redshift that involve custom logic. You could rather write a program in your favorite language and run it
using ShellCommandActivity. This is a quite valid way of interacting with Redshift.

There are several ways to do this. I am including a shell script and its Data-pipelne template as a reference here.

Sample shell command:

Sample Data-pipelines template:


-------------------------------------------------
Some info on the script and Data-pipeline:

1. This script file has 2 arguments (Arg 1 is the sql script that you need to execute , Arg 2 is the Redshift password). These arguments are provided in Data-pipeline shellCommandActivity object using scriptArgument field.

2. The script outputs its result to v2.sql and uploads to s3 bucket (with -t tuples only option), so that you can run the script later.

3. The Data-pipeline template uses the *myRedshiftPass parameter id to hide the password from DataPipelines.
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