Posts - Page 187 (page 187)
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3 min readTo make an asynchronous Redis subscriber call, you can use the redis-py library in Python which provides support for asynchronous programming. You can create a subscriber instance and then use the subscribe method to specify the channel you want to subscribe to. A callback function can be defined to handle messages as they are received. To run the subscriber asynchronously, you can use the asyncio library in Python and run the subscriber in an event loop using the run_forever method.
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6 min readTo import data from Redis to ClickHouse, you can use the ClickHouse's built-in functionality for importing data from various data sources, including Redis. One common approach is to use the ClickHouse Redis Engine to connect to the Redis server and import data into ClickHouse tables. This can be done by setting up a ClickHouse table with the appropriate storage engine, configuring the connection parameters for the Redis server, and executing the necessary SQL statements to import the data.
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7 min readIn Redis, you can add multiple values to a single key by using data structures such as lists or sets.For lists, you can use the LPUSH or RPUSH commands to add values to the beginning or end of the list respectively. For example, you can use the LPUSH command to add multiple values to a list key like this: LPUSH key value1 value2 value3Alternatively, you can use sets which allow you to store unique values.
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5 min readIn order to store multiple sessions in Redis, you can generate a unique session ID for each user session and use this ID as the key to store the session data in Redis. This way, you can easily retrieve the session data by referencing the session ID. Additionally, you can set an expiration time for each session to automatically clear out expired sessions and free up memory in Redis.
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4 min readThe "evicted_keys" value in the output of the Redis INFO command represents the number of keys that have been evicted due to the maxmemory limit being reached. This typically occurs when Redis runs out of memory and needs to remove some keys to free up space for new data. Keeping an eye on the "evicted_keys" count can help monitor memory usage and performance of the Redis database.[rating:ce821fa8-0cbe-48d4-a522-252e94dac366]How to recover data from evicted keys in redis.
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7 min readTo use Python logging with a Redis worker, first import the logging module in your script. Then, set up a logger with the desired level of logging and format. Next, create a Redis connection using the redis-py library and specify the hostname and port of your Redis server.In your worker function, use the logger to log messages at different levels based on the actions performed by the worker. For example, you can use logger.debug() to log debug messages, logger.
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5 min readTo store unique visits in Redis, you can use a Redis set data structure. Each unique visitor can be stored as a member in the set. You can add a visitor to the set using the SADD command and check if a visitor is already in the set using the SISMEMBER command. This way, you can keep track of unique visits without duplicates. You can also use Redis commands like SCARD to get the total number of unique visits stored in the set.
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3 min readTo get only the first occurrence of a pattern in a bash script, you can use the grep command with the -m option followed by the number 1. This option tells grep to stop reading the input file after the first match is found. For example, you can use the following command: grep -m 1 "pattern" filename This command will search for the pattern in the specified file and output only the first occurrence of the pattern. You can then use this output in further processing within your bash script.
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3 min readTo concatenate a string to a comma-separated element in bash, you can use the following syntax: myString="hello" myElement="apple,banana,orange" myElement="$myElement,$myString" echo $myElement In this example, we first have a string "hello" stored in the variable myString and a comma-separated element "apple,banana,orange" stored in the variable myElement.
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3 min readIn Bash, the asterisk (*) is known as a wildcard character that can be used for pattern matching in file and directory names. When the asterisk is used in a command, it represents any sequence of characters or none at all.For example, if you want to list all files in a directory that start with "test", you can use the command "ls test*". This will match all files that start with "test" followed by any characters.
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4 min readTo replace * with #* in Bash, you can use the following command: echo "original string" | sed 's/\*/#*/g' This command uses the sed command to search for instances of * and replace them with #* in a given string. The s command in sed stands for substitute, and the g at the end of the command tells sed to make the substitution globally (i.e., for all instances of * in the string).
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7 min readIn bash, you can use a combination of commands such as awk or grep to print a line when a certain text pattern changes. One way to achieve this is by using the awk command with the print function to output the lines that match the desired text pattern.For example, if you have a file with lines containing different text patterns, you can use the following command to print a line when the text pattern changes: awk 'a!=$0{print}{a=$0}' filename.